Biology of Hepatocellular Carcinoma

An understanding of the biology of HCC is critical to assist in clinical decision making about surveillance and treatment. Although the molecular biology of HCC remains to be fully elucidated, the close association between cirrhosis and the development of HCC is clear (Miyazawa et al, 2003; see Chapter 8C). Viral hepatitis, chronic alcohol use, and NAFLD are the most common causes of cirrhosis in the Western world (see Chapters 64, 65, and 70A). NAFLD, an unfamiliar diagnosis as recently as the early 1980s, is now present in 17% to 30% of Americans (Farrell & Larter, 2006); that progresses to steatohepatitis in 32% to 37% (Fassio et al, 2004; Harrison et al, 2003; Hui et al, 2003) and then to cirrhosis in 5% to 24% (El-Zayadi, 2008; Hui et al, 2003). The development of cirrhosis in patients with NAFLD is driven by repetitive liver injury from lipid peroxidation, fatty acid toxicity, mitochondrial impairment, and oxidative stress.

Viral infection with HBV and HCV lead to cirrhosis by different mechanisms. HBV induces transgene activation, oncogene transcription, and loss of tumor suppressor genes as a result of viral DNA integration into the host genome (Brechot et al, 1980; Bressac et al, 1990; Di Bisceglie, 2000; Kim et al, 1991). As many as 30% of patients with chronic HBV without cirrhosis will develop HCC (Zhou et al, 2001). HCV does not integrate into the host genome but rather leads to chronic inflammation through continued viral replication (Sherlock, 1994). This rapid hepatocyte turnover in the presence of oxidative stress drives the development of multiple dysplastic nodules.

Unlike what has been found in some other cancers, no sequential progression of genetic defects has been identified that leads to the development of HCC. Instead, a variety of genetic alterations are commonly seen, and they have been broadly grouped into events that occur either early or late in the development of a tumor. Genetic alterations that lead to inhibition of the insulin-like growth factor II receptors are considered early mutations (Yamada et al, 1997). Loss of heterozygosity of a variety of genes, often of tumor suppressor genes such as TP53, is a late event in the development of neoplasia (Buetow et al, 1989; Fang et al, 2000).

Clinically Relevant Aspects of Hepatocellular Carcinoma Pathogenesis

The clinician must understand three aspects of HCC pathogenesis: 1) the influence of cirrhosis on HCC development, 2) arterial recruitment of the tumor, and 3) the tendency for HCC to invade portal vein branches.

First, HCC most commonly develops in the context of cirrhosis, and the biology of HCC is related directly to the environment found in the cirrhotic liver. Repeated insult causes chronic inflammation driven by tumor necrosis factor (TNF)-α; transforming growth factor (TGF)-β and interleukin (IL)-1 from Kupffer cells; endothelial cells; and hepatocytes. This inflammation stimulates nodular regeneration with bridging fibrosis. Rapid cellular turnover in this regenerative environment leads to low-grade dysplastic nodules that do not contain atypia and high-grade dysplastic nodules that do. Eventually, a small percentage of these high-grade dysplastic nodules will go on to develop microscopic foci of HCC before becoming frank carcinoma (Rocken & Carl-McGrath, 2001). Recent evidence suggests that tumor cells may even secrete IL-6 and TNF-α, directly contributing to the inflammatory microenvironment by activating Toll-like receptors (Kim et al, 2009).

Because of the diffuse nature of the injury, multiple tumors can develop at the same time. If a focus of HCC is removed, recurrence most often happens at a distant site (Koike et al, 2000; Fig. 97D.1). This second tumor at the distant site is most likely a second primary tumor. As most of the second lesions are found within a few years of treatment of the primary lesion, the tumor was most likely present when the first tumor was treated but was too small to be detected. The occurrence of synchronous and metachronous lesions in the same organ suggests the entire cirrhotic organ has the potential for neoplastic conversion, much like the genetic defect in the colon in familial adenomatous polyposis, which leads to multiple cancers; this situation is referred to as a field defect.

FIGURE 97D.1 Recurrence of hepatocellular carcinoma after ablation most often occurs at a site distant from the primary tumor, suggesting a second tumor was present at the time of treatment that was too small to be detected.

(From Koike Y, et al, 2000: Risk factors for recurring hepatocellular carcinoma differ according to infected hepatitis virus: an analysis of 236 consecutive patients with a single lesion. Hepatology 32(6):1216-1223.

Secondly, there is a clinically relevant difference in blood supply between foci of HCC and low-grade dysplastic nodules, which derive most of their blood supply from the portal vein. Histopathologic evaluation of high-grade dysplasia and HCC demonstrates the tumor being fed by branches of the hepatic artery that are not paired with the other structures of the portal tract, a process called arterial recruitment, or neoangiogenesis. The resulting hepatic artery dominance in blood supply produces the characteristically hyperdense appearance of HCC that is used to identify tumors during the arterial phase of contrast imaging (Matsui, 2004; Willatt et al, 2008), and it allows for treatment via selective hepatic artery embolization.

Lastly, HCC is known to invade vascular structures, most commonly the portal vein but also hepatic veins and, less commonly, the biliary tree. The development of vascular invasion appears to be a key step in the metastatic potential of the tumor, and the risk of portal venous invasion seems to be directly related to size and differentiation status of the tumor (Esnaola et al, 2002). Venous invasion is such a strong predictor of metastatic disease that tumor size and tumor number can be thought of as surrogate markers for vascular invasion.

The likelihood of microvascular and macrovascular portal venous invasion has implications for treatment decisions; for example, evidence of portal venous invasion on imaging or biopsy rules out transplantation, because the probability of recurrence is unacceptably high. It is this risk of recurrence with large or multiple tumors that resulted in the poor outcomes with early attempts at liver transplantation for HCC, and it is the reason why patients with small tumors are selected for transplantation.

Hepatocellular Carcinoma Screening

HCC presenting as symptomatic disease has a 0% to 10% 5-year survival rate (Llovet et al, 2003), so a screening program that identifies early disease can have a major impact on treatment outcomes. HCC meets the World Health Organization criteria for performing screening (Meissner et al, 2004), and a randomized, controlled clinical trial showed that screening for HCC reduces mortality (Zhang et al, 2004). An effective screening program evaluates patients at risk of developing disease, using a highly standardized and relatively inexpensive test with a high sensitivity. A screening program is used if the cost of screening a large population is less than the benefit of early detection of the disease in a small number of individuals in that population. Several decision-analysis and cost-efficiency models for HCC screening suggest the ability of a screening program to decrease mortality while remaining cost-effective depends on the inclusion of patients with an incidence of HCC of at least 1.4% to 1.5% (Arguedas et al, 2003; Lin OS, et al, 2004; Sarasin et al, 1996). Patients who should be included in a screening program can be found in Box 97D.1. Further information about the incidence of HCC in cirrhosis from nonalcoholic steatohepatitis (NASH), α₁-antitrypsin deficiency, and autoimmune hepatitis is required, but most centers include these patients in their screening population.

Traditionally, the most commonly used serum tumor marker to detect HCC was α-fetoprotein (AFP), a protein produced by normal fetal hepatocytes, and by tumor cells, but not by healthy, mature hepatocytes. AFP has traditionally been used for diagnosing HCC, predicting outcome after resection, and screening for recurrence postoperatively (Tan et al, 2003). The normal range of AFP in the serum is 10 to 20 ng/mL; an absolute value of 20 ng/mL was used commonly as the screening cutoff; however, using this cutoff yields a sensitivity of only about 64%, making it a poor screening test (Sherman et al, 1995). Moreover, normal AFP levels vary widely across ethnic backgrounds (Soresi et al, 2003), and the test has a lower positive predictive value in patients with acute viral hepatitis or cirrhosis from a viral cause (Nguyen et al, 2002; Soresi et al, 2003).

In patients with a liver mass, a concomitant serum AFP greater than 200 ng/mL carries a very high positive predictive value (Sherman et al, 1995), but because of its unacceptably low sensitivity and specificity, the American Association for the Study of Liver Disease (AASLD) recommended that serum AFP no longer be used as a screening tool, although it still plays a diagnostic role (Bruix & Sherman, 2005). Using an absolute value greater than 400 ng/mL is considered diagnostic regardless of the patient’s ethnic background or the cause of their liver disease. Research is ongoing to identify better serum markers for screening, diagnosis, and prognostication, and possible candidate compounds include AFP-L3 and des-γ-carboxy prothrombin (Bruix & Sherman, 2005; Grazi et al, 1995; Izuno et al, 1995; Koike et al, 2001; Marrero et al, 2003; Tsai et al, 1990).

Ultrasound (US) is the most widely used radiologic screening tool. It has a sensitivity of 65% to 85% and specificity over 90% when used as a screening test (Bolondi et al, 2001). Although the performance of US in cirrhotic patients is not as well defined (Bruix et al, 2001; Chen et al, 2002; Larcos et al, 1998; Sherman, 1999), and the test is operator dependent, US remains superior to any widely available serologic screening test. A large, prospective, randomized controlled study done in China suggests that surveillance of high-risk individuals with US and serum AFP testing every 6 months reduces HCC-related mortality by close to 40%, even though patients in that trial were offered only resection but not transplantation. One of the limitations of this study is that screening compliance was only approximately 60%, which may have dampened the reduction in mortality (McMahon, 2009; Zhang et al, 2004). Combined AFP and US surveillance increases sensitivity, but it raises the cost, and using both tests increases the rate of false-positive results from 5% for AFP alone to 7.5% for combined screening (Zhang & Yang, 1999). It is clear that further randomized controlled trials are needed, but based on the available information, the AASLD recommends screening patients at risk for HCC with US alone every 6 to 12 months (Bruix & Sherman, 2005). Evaluation of serum AFP can be added to US in the event of concerns regarding operator influence, but the use of AFP as the lone surveillance tool is discouraged.

Most centers use a 6-month screening interval, but this remains controversial. No evidence suggests that a 6-month interval improves outcome compared with a 12-month interval (Santagostino et al, 2003). The surveillance interval was derived from tumor growth rates, so the interval does not need to be shortened for patients who have a very high risk of developing HCC.

Early HCC can be difficult, if not impossible, to distinguish from cirrhotic nodules by US, but any suspicious nodule less than 1 cm should be evaluated for stability by repeat US at 3- to 6-month intervals for up to 2 years. All 1- to 2-cm nodules should be investigated with a dynamic contrast-enhanced imaging modality—computed tomography (CT), magnetic resonance imaging (MRI), or US—although contrast-enhanced US has not yet been adopted in the United States.

A nodule that is 2 cm or larger and hypervascular with portal venous washout on a single dynamic imaging study, or a 1- to 2-cm nodule on two such confirmatory studies, is treated as HCC. If the results are contradictory, a biopsy of the lesion should be obtained (Bruix & Sherman, 2005). If the lesion is larger than 2 cm and has a typical appearance on a single dynamic imaging study, or if it is found in concert with a serum AFP level above 200 ng/mL, biopsy is not required. Biopsy should be performed on any 1- to 2-cm lesion in any noncirrhotic patient has who has risk factors for the development of HCC. Biopsies should be read by expert pathologists, and patients with negative biopsy results should undergo US or CT scanning every 3 to 6 months and should be rebiopsied if the characteristics of the lesion change (Bruix & Sherman, 2005). Biopsy results that suggest a high risk for progression to HCC include dysplastic nodules, both low and high grade (Hytiroglou et al, 2007); small and large cell change, formerly called small cell dysplasia and large cell dysplasia (International Working Party, 1995; International Consensus Group for Hepatocellular Neoplasia [ICGHN], 2009); and dysplastic foci, defined as atypia outside of a dysplastic nodule (ICGHN, 2009).

Another commonly used radiologic surveillance tool is CT scanning (Kobayashi et al, 1985; Miller et al, 1994; Takayasu et al, 1990). Although the use of CT scanning is becoming commonplace, the radiation exposure to a patient from screening every 6 to 12 months is considerable. The use of CT for diagnosis and staging has been defined, but the performance of CT as a screening test has not been described. Finally, CT scan is the diagnostic test used to confirm HCC, and the screening test should be different from the confirmatory test.

MRI with gadolinium-based or iron oxide–based contrast has not been widely studied as a screening test, but there are reports that this modality is 81% sensitive and 85% specific for HCC compared with 68% and 93% for contrast-enhanced helical CT scanning (Colli et al, 2006). Moderate signal strength on T2-weighted images is specific for HCC, because dysplastic and regenerating nodules are not hyperintense on T2—unless they have infarcted, which can occur. Delayed venous phase hypointensity with concomitant delayed enhancement of the rim of the lesion are also features specific for HCC (Freeny et al, 2003). Similar to CT scanning, characterization of small nodules remains difficult, as MRI is only 50% to 80% sensitive for lesions 2 cm or smaller and only 4% to 33% sensitive for lesions 1 cm or smaller (Willatt et al, 2008); this is due in part to the fact that lesions 1 cm or smaller are frequently isointense on T2 (Krinsky, 2004). It remains to be seen whether contrast-enhanced MRI is cost-effective as a screening tool for HCC, but it may prove to be marginally superior to CT scanning for characterization of known hypervascular lesions.

Indications for Transplantation (See Chapter 97A)

An unlimited supply of organs and money would allow for a liberal policy of transplantation for patients with HCC confined to the liver; but resources are limited, so efforts must be made to allocate organs to those recipients with a high likelihood of long-term survival. Recurrence risk is clearly higher in patients with more advanced disease, and the size and number of nodules in the patient’s explanted liver is directly correlated with the risk of HCC recurrence (Jonas et al, 2001; Mazzaferro et al, 1996).

Based on these observations, selection criteria have been developed. The primary set of selection criteria are the Milan criteria, created to allocate organs to patients with HCC who would have a similar chance for long-term survival as patients without HCC (Mazzaferro et al, 1996; Fig. 97D.3). To allocate scarce organs in such a way that all recipients have an acceptable chance for long-term survival, patients with HCC are currently evaluated for suitability based on three factors: 1) tumor size in centimeters, 2) number of radiologically evident tumors, and 3) evidence of portal venous invasion or extrahepatic disease. These factors are a crude but somewhat effective method for predicting overall tumor biology and subsequent risk of recurrence.

FIGURE 97D.3 Milan selection criteria for transplantation call for either a single lesion 5 cm or smaller or two to three lesions all ≤3 cm, equivalent to T1 and T2, respectively, of the American Liver Study Group modified tumor-node-metastasis classification system.

Preoperative staging, as outlined by UNOS, includes a triple-phase CT scan (Otto et al, 2006) of the abdomen to quantify intrahepatic disease burden, and a scan should be done of the chest to look for extrahepatic disease. This can also be accomplished with an MRI of the abdomen and a noncontrast CT of the chest (Bruix et al, 2003; Maddala et al, 2004). Unfortunately, these imaging modalities—the gold standard for HCC imaging—understage about 20% of patients (Yao et al, 2005) and can sometimes also overestimate actual tumor burden. A review of the HCC imaging literature that included only studies with explant pathologic correlation reported that triple-phase CT scan is only 37% to 75% sensitive at detecting HCC in a cirrhotic liver (Krinsky, 2004), although it remains the gold standard for diagnosis and preoperative staging. Bone scintigraphy was used in the past to locate extrahepatic disease but is no longer used because of low sensitivity and specificity.

In the United States, the modified tumor-node-metastasis (TNM) staging system of the American Liver Tumor Study Group (ALTSG) is used to allocate livers from deceased donors to patients with HCC awaiting transplantation (UNOS, 2004; Table 97D.1) to ensure that all patients who receive an organ have a reasonable chance at long-term survival. The original transplantation criteria from the mid-1990s, the Milan criteria, are equivalent to stage I or II of this TNM classification system. Using these criteria, recurrence is between 4% and 16%, and 5-year survival is 71% to 75% (Hayashi et al, 2004b; Jonas et al, 2001; Llovet et al, 1998, 1999). Patients whose disease falls outside the ALTSG criteria for stage II disease, and thus outside the Milan criteria, may be at higher risk for recurrence.

In February 2002, the Model for End-Stage Liver Disease (MELD) scoring system was implemented. As part of this system, priority was given to patients with TMN stage T1 and T2 HCC in an effort to combat the risk of tumor progression in patients awaiting a transplant. The prioritization was revised in 2004 to no longer include T1 tumors, so that only patients with T2 tumors get priority listing (Wiesner et al, 2004) to prevent overallocation of organs to patients with HCC, and because approximately 30% of patients with presumed HCC (a single lesion ≤2 cm with arterial enhancement) were found to have no tumor in their explant (Wiesner et al, 2004). Currently, the MELD points added to a patient with a T2 lesion are equivalent to a 15% 3-month probability of candidate mortality.

It has been suggested that the Milan criteria are too restrictive and that the size criteria are somewhat arbitrary. Several centers have extended their criteria to include highly selected stage III patients who are expected to have a tolerable rate of recurrence (Duffy et al, 2007; Herrero et al, 2001; Kneteman et al, 2004; Onaca et al, 2007; Roayaie et al, 2002; Yao et al, 2001, 2007). A recent retrospective analysis of 1556 patients undergoing transplantation at 36 centers included 1112 patients with tumor burden exceeding the Milan criteria on posttransplant pathologic review. Of these, 283 patients had no evidence of microvascular invasion with tumor burden up to 7 cm in largest diameter or up to seven nodules, and this subset of patients achieved a 5-year survival of 71%.

The Univerity of California–San Francisco (UCSF) criteria—single tumor smaller than 6.5 cm, maximum of three total tumors with none larger than 4.5 cm, and cumulative tumor size smaller than 8 cm (see Table 97D.1)—represent a modest expansion of the Milan criteria and have been validated at other centers. One such evaluation, a retrospective review of preoperative imaging and explant pathology, looked at 467 transplantations performed over a 20-year period and found similar 5-year survival in patients meeting the Milan criteria and the UCSF criteria by explant pathology (86% vs. 71%) and preoperative imaging (79% vs. 64%). Survival for patients with tumors beyond UCSF criteria was less than 50% at 5 years (Duffy et al, 2007).

This discussion highlights the point that tumor burden is only a surrogate for vascular invasion and microscopic metastatic disease, which along with extrahepatic disease limits the effectiveness of liver transplantation. Formal guidelines for transplantation of patients with disease outside the Milan criteria have not been established, but with many centers reporting equivalent survival of highly selected patients outside the Milan criteria, and with the advent of downstaging, this topic has taken on widespread debate.

Another consideration is the impact of MELD exception points for cancer patients or the selection of patients with liver failure as a result of benign disease. In regions with long waiting times, if patients with tumor burden beyond the Milan criteria are transplanted, organs are taken away from patients with liver failure from other causes. Volk and colleagues (2008) examined the issue of what is the acceptable outcome risk for transplantation of patients with HCC as compared to using the organ in a patient without HCC. On a national basis, the authors found that expansion of the Milan criteria would significantly increase waiting list mortality, unless 5-year posttransplant survival for the expanded criteria recipients exceeded 61%.

The authors also showed a dramatic difference in the effect of a policy change based on transplant region. This regional variability appeared to result from dramatic differences in the risk of death for patients without HCC, because the MELD score at transplantation of non-HCC patients was quite low in some regions. In regions where the risk of death of the non-HCC patients without transplantation is low (low MELD score at transplantation), the HCC criteria could be expanded to allow transplantation in the HCC patients with a posttransplant survival in the HCC patients of 25%, which would mean that patients could have very large tumors or those that number greater than four or five. This is compared with the need for criteria for transplantation in HCC patients that resulted in a posttransplant survival of 70% in regions where there was a greater need for transplantation (higher MELD scores) in the non-HCC population. This wide variation in outcome suggests that changes in national policies would have a variable effect, depending on the region.

Waiting List Screening for Hepatocellular Carcinoma

Patients awaiting transplantation are cirrhotic and are therefore at risk for HCC, so longer wait times can affect survival. The average waiting time for liver transplantation is extremely variable and is based on ABO blood group, progression of liver failure, and geographic location. The mean waiting time in the United States is approximately 4 months, but this varies among regions, ranging from 2 to 7 months; about 50% of patients are transplanted within 3 months. For patients with prolonged waiting times, it is important to screen patients with a CT or MRI scan of the abdomen every 3 to 6 months while they await transplantation.

Pretransplant Management of Patients with Hepatocellular Carcinoma

Unfortunately, controlled trials to evaluate different treatment options for patients awaiting transplantation have not been completed. The sole published series followed patients undergoing surveillance without local therapy and showed a high rate of dropouts from the waiting list because of tumor progression or progression of liver failure over the period of the study (Llovet et al, 1999). This report, combined with the understandable anxiety felt by patients and caregivers observing unhindered tumor progression, compelled most centers to offer cancer-directed treatment for patients awaiting transplantation. Retrospective data would suggest that cancer-directed therapy should be used if the expected waiting time exceeds 6 months (Bruix & Sherman, 2005).

Options for pretransplant locoregional control include TACE, RFA, percutaneous ethanol injection (Hoshida et al, 2008), or some combination of these modalities (see Chapters 83 and 85A). TACE is used by many centers because it offers locally effective treatment with a low risk of complications. Three studies support the argument that TACE may help reduce attrition from the pretransplant waiting list (Maddala et al, 2004; Majno et al, 2007; Millonig et al, 2007). These data include patients with variable waiting times and follow-up periods, but they suggest that pretransplant TACE is associated with a dropout rate of only 2% to 14%, with the possible added benefit of a lower posttransplant recurrence rate (8% to 10%).

A recent decision analysis evaluated the waiting-list time interval associated with the greatest impact of neoadjuvant TACE (i.e., greatest reduction in the dropout rate) and showed the greatest benefit in patients transplanted within 4 to 9 months (Aloia et al, 2007). The authors reported that when waiting time was less than 4 months, waiting-list attrition was similar in treated and untreated patients (20% vs. 34%; P = .08), and when waiting times exceed 9 months, dropout rates reequilibrated (33% vs. 46%; P = .06).

No studies have described percutaneous ethanol injection (PEI) as a sole treatment in patients awaiting a transplantation, although several studies suggest it is a safe and reliable component of multimodal therapy for tumors smaller than 3 cm (Troisi et al, 1998; Veltri et al, 1998; Vilana et al, 1992). PEI uses a small needle that reduces the risk of tract seeding to 0.6%. Some authors have suggested that pretreatment with arterial embolization to disrupt intratumoral septae facilitate the ethanol diffusion and may therefore improve the efficacy of subsequent ethanol injection (Lencioni et al, 1994). PEI requires several sessions when used as primary treatment for unresectable HCC, and prospective evidence supporting it as a neoadjuvant therapy is lacking; as a result, the trend has been toward other treatment methods.

RFTA induces tissue necrosis by delivering heat at the tip of one or several electrodes. Major complications occur in less than 10% of patients, and mortality is less than 1% (Orlando et al, 2009). This strategy is at least as efficacious as PEI for tumors smaller than 2 cm but requires fewer treatments (Livraghi et al, 1999; Lencioni et al, 2003), and randomized controlled trials suggest it improves survival (Lencioni, et al, 2003; Lin SM, et al, 2004; Livraghi et al, 1999).

A recent meta-analysis reported that RFA is superior to PEI in the treatment of small HCC with respect to survival and cancer-free survival at 1, 2, and 3 years; tumor response; and risk of local recurrence (Orlando et al, 2009). Recurrence is more common in patients with tumors larger than 4 cm, and in 95%, it occurs within 6 months and at a site distant from the primary tumor (Curley et al, 2000). This again suggests that tumor size is only a surrogate marker for microscopic metastatic spread and neoplastic potential of the remaining dysplastic nodules.

Given these data, RFA has evolved into the preoperative treatment of choice for tumors larger than 2 cm (Bruix & Sherman, 2005). With the advent of sorafenib, a chemotherapeutic agent that has shown greater activity against HCC than older cytotoxic agents (see Chapter 88), the paradigm may shift to a combination of locoregional therapy and chemotherapy. Trials examining these combinations are underway.

Another strategy is to prioritize, or fast-track, patients to have them receive a transplant as soon as possible without pretransplant treatment. Although this may be the most reassuring strategy for patients, it takes away the ability to observe the tumor biology over time. A subset of patients with newly diagnosed HCC will have very unfavorable tumor biology, and even if transplanted shortly after diagnosis, they are likely to experience rapid recurrence. A reasonable amount of time on the waiting list may in fact be beneficial, allowing tumor biology to unfold such that very aggressive disease will become obvious in short-term follow-up, thereby avoiding a futile procedure.

Patients with small tumors that fall within the Milan criteria have about a 10% risk of recurrence, which corresponds reasonably well to the percentage of patients with tumors that have aggressive histologic characteristics (Jonas et al, 2001). Fast-tracking such patients likely would significantly increase recurrence rates. One series examining this issue showed that recurrence rates were significantly higher in patients who were fast-tracked and in patients who underwent living-donor liver transplantation (LDLT) compared with patients who had longer waiting times (Kulik & Abecassis, 2004).

Patients with small but aggressive tumors are infrequent, but fast-tracking yields unacceptably high recurrence rates in the more common patient, with tumor burden close to the limits of or beyond the Milan criteria (Bismuth et al, 1993; Jonas et al, 2001; Llovet et al, 1999; Mazzaferro et al, 1996). It has also been suggested that fast-track prioritization is not cost-effective (Sarasin et al, 2001). Unfortunately, no stated guidelines have been established, but it appears that even for LDLT, a waiting time of approximately 6 months is appropriate (Bruix & Llovet, 2002).

Downstaging

Two observations have fueled the current debate about the proper selection criteria for transplantation in patients with HCC. First, it is clear that not all tumors of the same size carry the same risk of recurrence. Secondly, it is well documented that some patients outside the Milan criteria will benefit from liver transplantation (Yao, 2008). This has led to efforts to select patients with more advanced disease, but with favorable tumor biology, who might benefit from transplantation (Otto et al, 2006). The process of downstaging disease to within Milan criteria may be a mechanism for identifying such patients. This approach allows treatment of the tumor, and concomitant selection of patients with favorable tumor biology, by excluding patients who do not respond to locoregional ablative therapy, and it allows time for unfavorable biology to manifest.

A prospective intention-to-treat analysis evaluated 61 highly selected patients with tumor stage exceeding T2 who underwent tumor-directed therapy prior to transplantation. The study included patients with one lesion larger than 5 cm but smaller than 8 cm; those with two to three lesions, with one lesion larger than 3 cm but smaller than 5 cm, with a total diameter less than 8 cm; and those with four to five lesions, all smaller than 3 cm with a total diameter less than 8 cm (Yao et al, 2008). An interval of at least 3 months was required between treatment and transplantation. Downstaging was successful in 70% of patients, with the remaining patients dropping out, usually from disease progression. The 1- and 4-year posttransplant survival rates were 96% and 92%, respectively, suggesting that carefully selected patients with disease exceeding the Milan criteria can be downstaged with excellent posttransplant outcome.

It is important to note that the median time between the first treatment and transplantation was 8.2 months, with a range of 3 to 25 months. It is this waiting time that appears to allow tumor biology to manifest; patients with more biologically aggressive tumors dropped out during the waiting period, allowing selection of lower risk patients for transplantation. There are no formal guidelines for downstaging, but the UCSF protocol for downstaging of patients initially exceeding the Milan criteria is included for reference (Box 97D.2).

Technical Aspects of Liver Transplantation in Hepatocellular Carcinoma (See Chapter 98A)

Liver transplantation for HCC presents some technical challenges that need special consideration. The most important consideration is to perform the operation based on well-established oncologic principles, involving clear surgical margins and avoiding tumor seeding during the procedure to ensure the lowest recurrence rate. The tumor should be handled as little as possible, using the so-called no-touch technique, until the lymphovascular pedicle has been ligated. Hepatic artery ligation at the beginning of the hepatectomy can theoretically limit tumor dissemination during the dissection; however, no proof is available to suggest that such an approach lowers the posttransplant recurrence risk.

The transplant surgeon should be aware of prior therapy, because during RFA or biopsy, the needle tract and the diaphragm may be seeded with tumor. If a limited amount of diaphragmatic seeding is identified during the native hepatectomy, it is reasonable to perform a diaphragmatic resection with primary repair at the time of hepatectomy. Primary repair of the diaphragmatic defect is usually sufficient, and tube thoracostomy is not required. Diffuse seeding should preclude transplantation.

Predicting and Screening for Recurrence

The propensity of HCC to recur after surgical therapy has spurred investigations of potential biomarkers that might help improve patient selection. Recently, formalin-fixed tissue was used for genome-wide expression profiling of the normal tissue surrounding a focus of HCC, and a reproducible expression signature was seen that correlated well with survival (Hoshida et al, 2008). Even with the diversity of genetic events that lead to HCC, specific regions of loss of heterozygosity have been identified that could be used to quantify a patient’s risk of HCC recurrence.

Efforts have been made to identify markers of extrahepatic tumor spread to avoid transplantation in the face of unrecognized extrahepatic disease. One attempt has been to find evidence of malignant cells in the bone marrow of patients with HCC as a method to predict recurrence or survival (Sutcliffe et al, 2005), although this practice is not routinely performed.

A recent multivariate analysis of 136 patients undergoing hepatectomy for HCC reported that low AFP mRNA levels identified by real-time quantitative polymerase chain reaction (PCR) correlated with patient survival and disease-free survival (Kamiyama et al, 2006; Lindemann et al, 1992; Pantel et al, 1996). Patients with negative AFP mRNA had 97% survival at 1 year and 91% survival at 3 years versus 86% and 56%, respectively, in patients with positive AFP mRNA (P < .0001). Similarly, 1- and 3-year disease-free survival were 73% and 45% in patients with negative AFP mRNA versus 55% and 26%. Although not widely used, these tests may help quantify risk of recurrence and could have implications for organ allocation and the effectiveness of transplantation for cure.

Unfortunately, evidence-based data regarding posttransplant screening protocols are lacking, and screening all patients with imaging and serum AFP for recurrence does not appear to be cost effective (Roberts, 2005). Alternatively, screening high-risk patients, as defined by adverse histopathologic characteristics in the explanted liver, is a more promising and potentially cost-effective strategy (Roberts, 2005; Ladabaum et al, 2011). Moreover, because 70% to 75% of recurrence occurs within the first 2 years after transplantation, screening during this time period is the most critical and is most likely to have the greatest yield (Regalia et al, 1998; Roayaie et al, 2004).

Once patients experience recurrence after transplantation, therapeutic options are somewhat limited. In approximately 40% of patients, HCC recurs at extrahepatic sites, and chemotherapy is generally ineffective, leading to a median survival of only 8.7 months (Mazzaferro et al, 1996). A subset of roughly 10% of patients with recurrence can be expected to achieve long-term survival after resection (Roberts, 2005). The use of sorafenib in this situation is currently being studied.

Salvage Transplantation

As a way to better maintain the pool of donor organs, some have argued that primary liver resection should be first-line therapy for patients with preserved liver function and solitary HCCs smaller than 5 cm, and salvage transplantation can be offered to patients who experience recurrence that falls within the Milan criteria. In 2003, Poon and Wong evaluated survival and recurrence after resection of potentially transplantable small HCCs. They concluded that in patients with preserved liver function (CTP class A) with small solitary HCCs, primary resection achieved 5-year survival of 70%, comparable to reported survival after primary transplantation for similar size tumors. In order to apply salvage transplantation, screening must be diligent to find those who recur. Screening after resection with US every 3 months would be an important aspect of any treatment strategy using salvage transplantation for treatment of recurrence. The hope is that if patients recur, they will do so with transplantable disease within the Milan criteria.

Two studies have addressed the issue of outcome after salvage transplantation but reached opposing conclusions. The first was a retrospective analysis of 358 patients with cirrhosis and HCC who underwent either transplantation (n = 195) or resection (n = 163, of whom 98 were transplant candidates at the time of therapy); those patients with recurrence after resection underwent salvage transplantation (n = 17). The authors reported lower operative mortality rate (2% vs. 28%), lower recurrence rate (18% vs. 54%), and higher 5-year posttransplant survival (61% vs. 41%) and disease-free survival rates (58% vs. 29%) for patients who underwent transplantation compared with patients who underwent resection and then had salvage transplantation for recurrence (Adam et al, 2003).

The results of this study suggest that resection and salvage transplantation produced worse outcomes, but this was not supported by the second study of 88 patients with disease meeting the Milan criteria who underwent liver transplantation versus 18 who underwent resection followed by salvage transplantation for recurrence (Belghiti et al, 2003). The authors reported no difference in morbidity (51% vs. 56%), 30-day mortality (5.7% vs. 5.6%), 3-year survival (82% vs. 82%), 5-year survival (59% vs. 61%), or recurrence after primary liver transplantation versus salvage transplantation (n = 3 vs. 1).

Reasons for the discordant results could be the differences in time to salvage transplantation, patient selection, or operative technique of liver resection between the studies (27% underwent a transthoracic resection in the latter study). Another issue limiting the comparability of these two studies is that 7 of the 18 patients who underwent “salvage transplantation” in the latter study did not have recurrence but were transplanted for deterioration of liver function or because of pathologic findings in the resection specimen. Also of note, as Adam and Azoulay pointed out in a letter to the editors of the Annals of Surgery, the theoretical transplantability of patients with recurrence after resection seems to be different than the actual transplantability documented by many centers (Adam & Azoulay, 2005). Although Poon and colleagues describe an optimistic rate of patients with recurrence who would theoretically be transplantable after resection (79%), the percentage of patients who have undergone salvage transplantation, documented in the literature, is 1% to 30% (Belghiti et al, 2002; Llovet et al, 1999; Poon et al, 2002).

Reports of recurrence after salvage vary widely, from 5% to 54% (Adam et al, 2003; Belghiti et al, 2003; Lo & Fan, 2004). Currently, the efficacy of resection followed by salvage transplantation for recurrence is limited by the difficulties that attend screening for recurrence, prolonged waiting times, and a shortage of donor organs, but it may be a viable option for patients with hepatitis B without cirrhosis who have a single lesion.

Future Perspectives

Liver transplantation for HCC has proven to offer long-term survival and recurrence-free survival for patients with cirrhosis, but the shortage of donor organs is likely to perpetuate interest in resection and salvage transplantation. Currently, no consensus exists about an optimal method to select patients for transplantation after resection, which may be offered to patients with documented recurrence, but a more proactive strategy might improve outcomes.

One strategy would be to use the well-established histopathologic findings of microvascular invasion or multiple nodules unseen on preoperative imaging (Castells et al, 1993; Ikeda et al, 1993b; Izumi et al, 1994; Llovet et al, 1999; Nagasue et al, 1993; Okada et al, 1994) to select patients who are high risk for recurrence after resection. Identification of these findings in the resection specimen could initiate listing for liver transplantation (Sala et al, 2004). This strategy may select for patients who are at risk for early recurrence to undergo transplantation (Colella et al, 1997; Klintmalm, 1998), thus selecting a population that is likely to recur, even if they do undergo transplantation. The concern with this strategy is that patients whose explant specimens after transplantation demonstrate vascular invasion are at increased risk for development of extrahepatic disease.

Another possible strategy takes advantage of recent advances in gene-expression profiling of fixed liver tissue, from the liver parenchyma away from the tumor, to reliably predict risk of late (de novo) recurrence by quantifying the field defect (Hoshida et al, 2008). Using this technology, gene-expression profiling could theoretically select the population with a field defect that places them at high risk for late recurrence; this group would perhaps be targeted for transplantation, while allowing those with low risk for late recurrence to have resection and be followed (Sherman, 2008). Although this strategy offers some promise, it remains investigational.

Even with the improvements in overall and cancer-free survival in the last 20 years, many areas in the treatment of HCC are in need of randomized controlled trials, such as the areas of preoperative screening, postoperative surveillance, and downstaging protocols. Nontransplant therapies—such as re-resection, RFA, TACE, and PEI—need to be evaluated against salvage transplantation for patients with recurrence. Lastly, therapeutic options for patients with advanced HCC need to be expanded to improve survival.