Cancer of the Rectum
Summary of Key Points
Incidence
• Approximately 40,000 new cases of rectal cancer are diagnosed in the United States annually.
• Since 1998, the incidence rate has been decreasing by 2% to 3% per year.
• The peak incidence of rectal cancer is during the fifth decade of life.
• Aspirin and nonsteroidal antiinflammatory drugs have been shown to be effective in the chemoprevention of colorectal cancer by decreasing the risk of adenoma formation as well as the incidence and mortality of colorectal cancer.
Clinical Presentation
Numerous clinical features suggest the presence of rectal cancer, including:
• Located approximately 12 cm from the anal verge
• Rectal bleeding, often bright red and on the surface of the stool
• Subtle changes in bowel habits
• Decreased caliber of stool; mucus in stool
• Sensation of fullness and tenesmus
• Increased straining during defecation
• Synchronous colon cancer (in 2% to 9% of patients with rectal cancer)
Staging and Assessment
• Careful rectal examination yields 67% to 84% accuracy in staging (superficial, mobile, tethered, fixed) and should include pelvic examination for women and prostate examination in men.
• Rigid proctosigmoidoscopy provides the most accurate assessment of distance, size, and position, as well as tethering to surrounding structures.
• Colonoscopy, colonography, or double-contrast barium enema is used to assess for synchronous colon tumors.
• Endorectal ultrasound can assess the depth of invasion and nodal status. Nodal assessment is less reliable.
• Magnetic resonance imaging (MRI) with endorectal coil and ultrasound are useful to stage rectal cancer and are more sensitive and specific than computed tomography (CT) alone. MRI is used to assess locally advanced or recurrent local disease. CT should be performed on all patients to assess intraabdominal spread. CT or chest x-ray is required to evaluate for synchronous lung metastases.
• The liver is the most frequent site of distant spread, followed by lung, retroperitoneum, ovary, and peritoneal cavity.
• Baseline carcinoembryonic antigen (CEA) levels are assessed and followed postoperatively, even if initially normal.
Treatment
• Goals of treatment are cure, local control, and quality of life.
• All retrorectal tumors should be resected, and preoperative biopsy must be avoided.
• Full-thickness local excision is feasible for highly selected patients with T1 mucosal, submucosal, and early invasive cancer, particularly in patients with high-risk comorbidities.
• For T1 to T3 rectal adenocarcinomas, surgical procedures are total mesorectal excision, low anterior resection, low colorectal or coloanal anastomosis with J pouch, and abdominoperineal resection, leaving at least a 2-cm distal margin and clear lateral margins. With surgery, mortality rates are 1% to 7% and morbidity rates are 13% to 46%. The survival rate at 5 years is 74% to 87%.
• Combined therapy cures 50% of N1 patients; 25% of tethered or fixed rectal cancers treated by neoadjuvant chemoradiotherapy are subsequently resected and cured.
• Of patients who die of rectal cancer, 25% fail with pelvic disease only.
1. Imaging features, pros-cons of different strategies. A 68-year-old man presented to his family doctor with rectal bleeding. Physical exam, including a rectal exam were unremarkable. Colonoscopy revealed a mass in the rectum, 9 cm from the anal verge. The mass measured 5 cm and occupied two-thirds of the circumference of the bowel. Remainder of the colonoscopy to the cecum was unremarkable. Biopsy of the mass confirmed moderately differentiated adenocarcinoma. Blood tests revealed a Hgb of 10.8, normal liver function tests, and a carcinoembryonic antigen of 2.1. In planning his treatment, the best next step is:
A Computed tomography (CT) scan of the chest, abdomen, and pelvis
B CT scan of the chest, abdomen, and pelvis, and endorectal ultrasound or magnetic resonance imaging (MRI) of the pelvis
C CT scan of the chest, abdomen, and pelvis, MRI, and endorectal ultrasound
2. Rectal adenocarcinoma selection for neoadjuvant therapy. A 52-year-old woman on routine gynecologic exam was found to have a palpable mobile rectal mass. Colonoscopy revealed a mass 4 cm from the anal verge, and biopsy revealed moderately differentiated adenocarcinoma. CT scan of the chest, abdomen and pelvis revealed no evidence of metastatic disease. Endorectal ultrasound found that the tumor invaded the full thickness of the bowel wall and penetrated into the mesorectal fat posteriorly. Several lymph nodes were seen but were not felt to be suspicious for malignancy. Of the following, the best course of treatment is:
A Low anterior resection (LAR) or abdominoperineal resection (APR) followed by adjuvant chemotherapy and radiation therapy if the nodes are positive
B LAR or APR followed by adjuvant chemotherapy and radiation therapy
C Neoadjuvant chemoradiation therapy, followed by LAR or APR and postoperative chemotherapy if the nodes are positive
D Neoadjuvant chemoradiation therapy, followed by LAR or APR and postoperative chemotherapy for 4 months
E Neoadjuvant chemoradiation therapy and close observation if a clinical complete response is achieved
3. Indications and complications of transanal excision. The following are relative contraindications for transanal excision of a malignant polyp less than 3 cm except:
4. Lateral lymph nodes in rectal cancer. A 56-year-old man with a low rectal cancer had the PET-CT scan seen below. His workup showed no evidence metastatic disease. Because of these findings on his scan, the following is true:
B Optimal management is initial surgical resection, followed by chemotherapy.
C Local recurrence in this population is common.
D A complication of resection of nodal disease is numbness to the medial thigh.
E Overall survival after multimodality therapy is similar to that of patients with stage III disease.
5. Locally advanced disease—pelvic exenteration. A 76-year-old man presented with pelvic pain, change in bowel habits, and on rectal examination, a bulky low fixed rectal cancer. CT scan showed no evidence of metastatic disease. His pelvic MRI is shown below. All of the following are true except:
A Initial treatment should be chemoradiation therapy.
B To remove all disease with negative margins, he will require a pelvic exenteration.
C If he has a good response to chemoradiation therapy, it will be possible to spare the bladder.
D After treatment with chemoradiation therapy and surgery, his 5-year survival is less than 30%.
E If he was found to have metastatic disease, at the time of surgery, debulking is still warranted.
6. Metastatic disease with intact primary. A 46-year-old woman presented with a change in bowel habits, although she was eating a regular diet. She had lost 15 pounds, and was using stool softeners. Workup, including a colonoscopy, revealed a midrectal cancer, and a biopsy confirmed adenocarcinoma. Her CEA was elevated at 215. CT scan of the chest, abdomen, and pelvis showed the primary tumor in the rectum (below) and metastases in the liver. All of the following are true except:
A Resection of the primary tumor and liver can be staged or synchronous.
B Neoadjuvant chemotherapy may improve the change of obtaining an R0 resection.
C Neoadjuvant radiation therapy will improve overall survival.
D Overall 5-year survival, if all disease is resectable, is 20% to 30%.
E If surgery is the initial therapy, patients should receive postoperatively adjuvant chemotherapy.
7. Management of the complete response. A 74-year-old woman presented with a 3-cm low rectal cancer. On endorectal ultrasound, the tumor was staged as a T3N0. CT scan of the chest abdomen, and pelvis showed no evidence of metastatic disease. She underwent chemoradiation, with oral capecitabine. Six weeks following completion of radiation therapy she was examined and showed no evidence of disease on rectal examination. Endoscopy showed a scar at the site of the cancer. The patient does not wish to undergo an abdominoperineal resection, and asks you what other options are available. All of the following are true, except:
A Endoscopic ultrasound sensitivity for node positivity is poor.
B For T3 lesions, local excision with negative margins gives results comparable to transabdominal resection.
C Survival after an APR in a patient who has a pathological complete response is as high as 85%.
D Observation alone, and salvage if the cancer recurs locally, has inferior overall survival compared with APR.
E Local excision in a patient with a limited long-term survival because of intercurrent illness is a reasonable alternative.
1. Answer: B. Treatment depends on the location and stage of the primary tumor (T and N), and presence or absence of metastatic disease (M stage). Metastatic disease is identified by CT scan; PET-CT imaging is not routinely indicated in initial rectal cancer staging. Endorectal ultrasound (ERUS) and MRI are both very sensitive for the T-stage of the tumor, but MRI is very specific for assessment of the circumferential radial margin (CRM). In contrast, lymph node assessment is poor on both ERUS and MRI.
2. Answer: D. Combined multimodality therapy consisting of surgery, chemoradiation therapy, and an additional 4 months of chemotherapy is recommended for most patients with stage II rectal cancer. Preoperative chemoradiation therapy for stages II/III rectal cancer is associated with a significant reduction in local recurrence and acute toxicity compared with postoperative chemoradiation therapy. Overall survival is similar in both groups. In the randomized studies comparing preoperative and postoperative adjuvant therapy, all patients received two cycles of chemotherapy during radiotherapy and four additional cycles of chemotherapy regardless of the surgical pathology results. The role of close observation in patients who have a clinical complete response is being investigated, but is not standard therapy today.
3. Answer: D. T3 tumors, angiolymphatic invasion, tumors with positive margins, and tumors removed in fragments so that margins cannot be assessed are all contraindications for transanal excision.
4. Answer: D. Low rectal cancers can spread to the lateral lymph nodes. Although controversial, the AJCC defines lateral nodes as regional nodes. However, in Japan, where lateral node dissections are commonly part of the operation, positive lateral side wall nodes, when included in the resection, do not appear to have a significant impact on overall survival or local control. Finding positive nodes in low rectal cancers that extend into the external iliac nodes may have an adverse effect on outcome.
5. Answer: C. For patients with T4 disease, as seen here, with invasion into the bladder wall, risk of locoregional recurrence is high. The risk is associated with the close proximity of the rectum to the pelvic sidewalls and the technical difficulties associated with obtaining clear margins. Initial treatment should be preoperative chemoradiation therapy.
With a complete R0 resection, the prognosis is reasonable, and warrants a pelvic exenteration with en bloc removal of the rectum with the bladder. Even if the patient has an very good response to chemoradiation therapy, removal of the bladder will be necessary to optimize local control. For patients found to have metastatic disease at surgery, a colostomy and urinary diversion may be considered, but tumor debulking is discouraged.
6. Answer: C. Patients who present with stage IV disease should be viewed by the multimodality team as resectable, potentially resectable, or unresectable. If the patient is unresectable (all gross disease removed in an R0 resection), then the goal is palliative. If the patient is resectable initially, it is reasonable to offer immediate resection (either synchronously, or as a staged procedure, depending on patients ability to tolerate the procedures), or an initial short course of chemotherapy prior to surgery. If the patient is not initially resectable, but may be resectable if they have a good response to chemotherapy, then neoadjuvant chemotherapy should be administered, followed by surgery after 2 to 4 months of chemotherapy. If the primary tumor is in the rectum, it is important maximize local control in the pelvis. If the disease presents with a fixed rectal cancer, radiation therapy will improve local control, but not overall survival, and should receive radiation therapy prior to surgery. In this situation, a short course of radiation therapy may be reasonable.
7. Answer: C. Patients with stages II/III cancers who have a pathological complete response have an excellent long-term survival. However, for low rectal cancers, the impact of an APR on overall quality of life is significant, and has resulted in interest in alternative treatments. Unfortunately, endorectal ultrasound and MRI do not accurately stage lymph node status, and for T3 lesions, it is as high as 40% to 50% in several series. Pathological complete response rate from chemoradiation therapy is only 15% to 25%, and so observation alone carries a significant risk of local failure, even if the local excision removes mucosal disease. Ongoing studies in England and South American are examining this issue.
