Pain in patients who are long-term survivors of cancer is an increasingly important topic. Currently more than 3.5% of the population in the United States are cancer survivors, and this rate is rising annually.3,4 Chronic pain syndromes are surprisingly common in this patient population. Currently, about 50% of patients with head and neck cancer will become long-term survivors, and 17% of these persons report substantial chronic pain.⁵ Twenty percent of breast cancer survivors younger than 40 years who are treated with surgery, radiation, and chemotherapy report significant pain years after treatment has been completed, and this pain appears to interfere with quality of life.^6,7 Approximately 30% of long-term survivors of lung cancer report substantial pain related to their illness.⁸ In addition, hip and sacral pain related to prior treatment with radiation is seen in 30% of long-term gynecologic cancer survivors.⁹ Chemotherapy-induced neuropathic pain is also an increasingly important long-term problem for cancer survivors.¹⁰ Of particular importance is emerging information suggesting that inadequately treated acute pain may predispose long-term cancer survivors to chronic pain syndromes.¹¹

Current Status of Cancer Pain Management

Studies from hospices and from World Health Organization demonstration sites suggest that 85% of patients with cancer pain can have their pain palliated with use of oral opioids. A wide array of effective options exists for the remaining 15% of patients. These options include parenteral, transdermal, transmucosal, intranasal, or intraspinal opioids, glucocorticoids, antiinflammatory and adjuvant medications, antineoplastic therapies, and anesthetic and neurosurgical procedures.

Although proper use of available therapeutic approaches should result in excellent pain control in nearly 95% of patients with cancer pain, this pain remains grossly undertreated throughout the world. In most countries, the lack of availability of oral opioids is a major contributing factor.¹² Even in countries such as the United States and the United Kingdom, where a wide range of opioid analgesics and routes of administration are readily available, studies suggest that cancer pain is undertreated. A survey of oncologists highlights their reluctance to assess pain routinely and to prescribe appropriate analgesics. These findings prompted the creation of cancer pain initiatives in most states and the development of cancer pain guidelines and algorithms.^13–18 In addition, to improve the overall management of pain in the United States, The Joint Commission has set new standards for pain management that are required for continued accreditation.¹⁹

Barriers to the Provision of Adequate Analgesia

Many reasons have been cited for the inadequate treatment of patients with cancer pain in developed nations. Some of these reasons relate directly to health care providers, including:

• Failure to appreciate the intensity of the pain their patients are experiencing

• Reluctance to evaluate the etiology of the pain

• Lack of training in pain management

• Excessive concern regarding the regulatory oversight of opioid prescribing

One major barrier to the provision of adequate analgesia in patients with cancer is the failure of health care providers to appreciate the intensity of patients’ pain. This barrier occurs because pain is entirely subjective and can only be experienced and quantified by the patient. There are no pathognomonic findings on physical examination, and results of laboratory studies can be normal. Assessment of pain is further complicated by the complexities surrounding death and dying and the possibility that patients with chronic, severe pain might not appear or act uncomfortable. In one study examining health care provider perceptions of patient pain, pain intensity was quantitatively assessed using a visual analog scale (VAS) in 103 consecutive patients admitted to the solid-tumor service of a large cancer center.²⁰ Each patient’s primary care nurse, house officer, and oncology fellow rated his or her perceptions of their patient’s pain intensity using the same pain rating instrument as the patient. The results (Fig. 40-1) demonstrate a lack of correlation between the patient’s and the health care provider’s perception of patient pain. Furthermore, the concordance between patient and health care provider pain intensity scores was highest when patients had no pain and lowest when the patients were experiencing severe discomfort. Similar results have been obtained in studies of patients with cancer and their next of kin and in patients with burns.

Figure 40-1 Correlation of health care provider and patient perceptions of patient pain. VAS, Visual analog scale, (Data from Grossman SA, Sheidler VR, Swedeen K, et al. Correlation of patient and caregiver ratings of cancer pain. J Pain Symptom Manage 1991;6:53. Copyright U.S. Cancer Pain Relief Committee.)

Health care providers might be unaware of the pain their patients are experiencing for many reasons. Because pain is entirely subjective, its presence and intensity must be communicated to health care providers by patients. Patients, however, might not discuss their pain if they expect cancer to be painful or if they are concerned about opioid addiction, tolerance, or adverse effects or about diverting their physician’s attention from treating the tumor or the intensity with which the oncologist is treating the tumor. In addition, patients might be reluctant to admit to themselves or others that their pain has worsened, knowing that this admission could signify progression of the cancer. Health care providers also contribute to the lack of communication by neglecting to emphasize their interest or abilities in controlling pain and by failing to use validated pain assessment tools. Serial numeric pain ratings in the medical record encourage the necessary dialogue between patients and health care providers about pain management issues.

These issues are greatly magnified in children, the elderly, or persons with a history of drug abuse. Children have special difficulty in communicating pain intensity, and their unique pain management needs have been relatively neglected. Special pain assessment tools are required, and the child’s age and developmental level must be considered when planning assessment or interventions. Many elderly patients also find it difficult to communicate their discomfort to health care professionals, have multisystem disease, and are especially sensitive to the adverse effects of analgesics.21–24 Persons with cancer and a current or prior history of drug abuse often have difficulty finding health care providers who believe their reports of pain and who will provide the high doses of analgesics required by these opioid-tolerant individuals.²⁵

Another barrier to the provision of adequate analgesia relates to the training of medical professionals. The principles of cancer pain management receive little attention in academic centers and relevant scientific societies. Medical school courses and textbooks typically focus on diseases rather than symptoms, and pain management issues are infrequently highlighted at rounds, educational conferences, or in the formal curriculum of those training to care for patients with cancer. These circumstances leave many health care professionals eager to concentrate on medical problems they feel competent to handle. In addition, the scarcity of research abstracts on cancer pain at the scientific meetings of physician oncologic societies reinforces the notion that pain control is a topic of limited importance. The lack of training and emphasis on cancer pain management is evident in many ways, including physicians’ lack of opioid-prescribing skills, failure to evaluate the etiology of cancer pain, and excessive concerns regarding the regulatory oversight of opioid prescribing. These difficulties in calculating equi-analgesic doses have prompted the development of software to facilitate opioid conversions.²⁶

Many physicians and nurses consider “cancer pain” a diagnostic entity that requires opioids without a formal evaluation of the etiology of the pain. Although this approach can provide relief, it is often ineffective and can lead to indefensible medical practices. For example, progressive back pain in a patient with metastatic lung cancer can occur as a result of a postobstructive pneumonia or tumor invasion of the esophagus, liver, spleen, pleura, pericardium, rib, vertebrae, intercostal nerves, brachial plexus, leptomeninges, or epidural space. Each of these diagnostic possibilities can be associated with a different therapeutic approach or sense of urgency. To provide opioids without evaluation would be an error in such a patient with an impending epidural cord compression. Furthermore, many common cancer pain syndromes might be better treated with therapies tailored to a patient’s individual pain problem. These therapies may include local radiation, nerve blocks, glucocorticoids, anticonvulsant agents, or surgery to maximize analgesia, minimize adverse effects, and improve quality of life.

Physicians, pharmacists, and nurses caring for patients with cancer must be willing to prescribe, dispense, and administer the opioids in doses required to alleviate their pain. However, drug enforcement agencies often discourage opioid prescribing in an attempt to reduce the illegal diversion of these drugs. Some health care professionals with limited knowledge and experience react to the perceived threat of investigation by law enforcement agencies with dramatic decreases in opioid prescribing, potentially compromising the appropriate treatment of patients with cancer pain.27,28

Evaluation of the Patient with Pain

A comprehensive assessment of cancer pain is the first important step toward optimal pain relief. This evaluation should provide the clinician with sufficient information to carry out the following tasks:

• Estimate the severity of pain

• Form a clinical impression regarding the etiology of the pain

• Determine the need for further diagnostic studies

• Formulate therapeutic recommendations that take into account the patient’s overall medical and psychosocial status (Box 40-3)

Box 40-3 Components of a Comprehensive Assessment of Cancer Pain

I Detailed History of Current Pain Problem

A Catalogue of pain (number and locations)

B Information for each pain

1. Intensity (0-10)

2. Locations and radiation

3. Onset and changes over time

4. Temporal pattern (e.g., constant or intermittent) and quality (e.g., burning)

5. Exacerbating and relieving factors

6. Associated neurologic or vasomotor abnormalities

7. Other associated factors

8. How the pain interferes with the patient’s life

9. Current therapeutic modalities (e.g., schedule, efficacy, and adverse effects)

10. Prior therapeutic modalities (e.g., schedule, efficacy, and adverse effects)

II Oncologic History

A Histologic

B Presentation: date, stage, and sites of involvement

C Antineoplastic therapies: dates, types, doses, toxicities, and response to each therapy

D Current sites of disease: stable, responding, or progressive

E Patient expectations and goals

III Medical History—May be Affected by Pain Therapies

A Coexisting diseases

B Medications and allergies

C Substance abuse history

D Other constitutional symptoms (e.g., anorexia, fatigue, sedation and other changes in mental status, nausea, vomiting, dysphagia, dyspnea, constipation, urinary and sexual function, depression, dry mouth, ability to take medications by mouth, and presence of a central venous catheter)

IV Personal and Social History

A Background: age, education, employment, marital status, place of residence, religious affiliation, and cultural and ethnic background

B Current status: functional status, caregivers and their health and availability, support system

V Physical Examination

VI Review of Additional Information

A Medical records, radiologic/laboratory studies

B Family members and physicians and/or nurses who know the patient and his or her illness

VII Differential Diagnosis

VIII Recommendations Regarding Workup and Therapy

IX Reassessment

As with any serious medical condition, the assessment of cancer pain requires a detailed history, physical examination, and review of available records, laboratory data, and imaging studies. The special challenges associated with the assessment of cancer pain include the entirely subjective nature of pain, the complex multisystem involvement in patients with advanced malignancies, and the ever-changing clinical situation in this patient population.

A detailed pain history is the cornerstone of the assessment. Obtaining this history can be a complex process, because 75% of patients with advanced cancer have several concurrent painful sites and nearly one third have four or more separate pain problems.¹⁹ Each distinct pain must be identified and characterized. Pertinent information should include its intensity, location, radiation, how and when it began, how it has changed over time, and what makes it better or worse. The quality of each pain, its temporal pattern, whether it is associated with neurologic or vasomotor abnormalities, how it interferes with the patient’s life, and an account of the successes and failures of current and prior therapeutic modalities also provide valuable insight.

Many instruments have been developed to aid in pain assessment. These instruments attempt to characterize and quantify the quality and/or intensity of a patient’s pain and represent the best available means to document the discomfort and to follow the results of therapy serially. Each instrument has its shortcomings, but several have been validated in patients with cancer pain and incorporated into clinical practice. Most instruments contain a variant of the unidimensional visual analog scale and a schematic representation of the body for patients to indicate where their pain is located. The McGill Pain Questionnaire is comprehensive but too awkward and time-consuming for most oncology patients in a clinical setting.²⁹ The Wisconsin Brief Pain Inventory, which can be completed in 15 minutes, provides information on the characteristics, severity, and location of the pain, its interference with normal life functions, and the efficacy of prior therapy. The Memorial Pain Assessment Card can be completed in less than a minute and features scales for the measurement of pain intensity and pain relief.³⁰ It is also designed to provide insight into global suffering or psychological distress. The Hopkins Pain Rating Instrument is a validated plastic version of the visual analog scale that obviates the need for the paper, pencil, ruler, and measurements associated with the standard visual analog scale.³¹ This instrument simplifies repeated pain intensity measurements, making it easier to reassess the efficacy of therapeutic endeavors on a continuing basis.³²

A complete oncologic history is also essential, because 90% of cancer pain is related to the malignancy or cancer treatment. The histology, presentation, stage, sites of involvement, and natural history and the history of surgery, radiation, chemotherapy, and hormonal treatments will help shape a therapeutic approach. In addition, it is important to note whether the malignancy is responding to therapy, stable, or progressing. A general medical history is also helpful, because pain treatments can affect coexisting medical problems, exacerbate constitutional symptoms, interact with other medications, or be contraindicated because of allergies. For example, a patient with painful bone metastases and severe peptic ulcer disease would not be an ideal candidate for potent antiinflammatory agents. Opioids can be problematic in patients with severe benign prostatic hypertrophy or severe obstructive pulmonary disease and carbon dioxide retention. Likewise, knowledge that a patient tolerates food or fluids poorly by mouth, has an indwelling venous access device, or admits to substance abuse might influence decisions about the best way to control that patient’s pain. The patient’s age, functional status, social support, education, residence, health insurance, finances, and religious and cultural background might also figure prominently in planning therapy. A careful neurologic and physical examination also provides important clues as to the etiology of the pain. Added insight can come from a review of available laboratory and imaging data, from medical records, and from discussions with family members and physicians who are familiar with the patient and his or her illness.

The history, physical examination, and review of other available data should provide the clinician with sufficient information to formulate a differential diagnosis for each of the patient’s distinct pains and to make recommendations regarding the workup and therapy for each. Based on this initial impression, analgesic therapy should be initiated. The nature of the treatment prescribed might depend on the clinician’s judgment regarding the origin of the pain. Somatic, visceral, neuropathic, and sympathetically maintained pain are each approached somewhat differently (Table 40-1). Prompt institution of therapy reassures patients that their pain will receive immediate attention, ensures patient comfort for diagnostic studies, and can provide information on the accuracy of the clinician’s assessment. Excellent pain relief suggests an accurate initial diagnosis and appropriate therapy, whereas suboptimal control might prompt a new treatment approach or a search for a different etiology of the pain.

Table 40-1

Classification of Cancer Pain

Type	Characteristics	Examples	Primary Therapies
Somatic	Constant, aching, gnawing, often well localized	Bone metastases	Treatment of tumor, antiinflammatory agents, analgesics
Visceral	Constant, aching, often associated with nausea	Pancreatic cancer	Treatment of tumor, analgesics, nerve blocks
Neuropathic	Paroxysmal shocklike pain on top of a burning, constricting sensation	Plexopathy or postherpetic neuralgia	Treatment of tumor, analgesics, TENS, nerve blocks
Sympathetically maintained	Severe burning, squeezing, or constricting with local edema	Reflex sympathetic dystrophy	Sympathetic blockade, physiotherapy, adjuvant analgesics