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Cancer pain is usually caused directly by neoplastic injury to pain-sensitive structures. For this reason, primary antineoplastic therapy, including radiation, chemotherapy, and palliative surgery, should be considered part of an analgesic strategy in some cases. When therapy directed at the tumor is inappropriate, is not feasible, or is ineffective, symptomatic analgesic therapies become the overriding concern. Opioid-based pharmacotherapy is the mainstay approach, but adjunctive anesthetic, surgical, psychiatric, and physical modalities may be essential in some cases (See Chapter 46, Anesthetic Interventions in Cancer Pain). Pharmacologic approaches may be systemic or regional (anesthetic). This chapter addresses only systemic pharmacologic analgesics.

The World Health Organization (WHO) proposed a three-step approach to the selection of drugs for the treatment of cancer pain (Fig. 45-1).1 The first step, for mild pain, utilizes non-opioid analgesics and adjuvant drugs. Adjuvant drugs can be either nontraditional analgesics (so-called adjuvant analgesics) or drugs added to manage the side effects of the primary analgesics. For more intense pain, an opioid is added. Some opioids are used conventionally for moderate pain and others are used for severe pain. This approach is designed to be simple to understand and useable around the world. Uncontrolled field testing has found the WHO guidelines effective for 70% to 100% of patients with cancer.2

Figure 45-1

The three-step analgesic ladder for cancer pain treatment. (Reproduced by permission of WHO, Cancer Pain Relief. 2nd ed. Geneva, World Health Organization, 1996.)

Pain is often underrecognized in cancer patients. Cleeland et al surveyed outpatients with metastatic cancer and physicians from 54 treatment centers.3 They found that 42% of 597 patients with pain were not receiving adequate analgesia by the WHO guidelines (Fig. 45-1). Insufficient pain relief was particularly common among minorities, women, and the aged. An important barrier to effective pain management was a discrepancy between the patient’s and physician’s assessments of the extent to which pain was interfering with daily activities. The data underscore the importance of accurate pain assessment in providing adequate cancer pain relief.

The assessment should allow inferences about the pain mechanisms, identification of the pain syndrome (See Chapter 44, Cancer Pain Syndromes), and classification of the relationship between the pain and the disease. The clinician must also assess the functional impact of the pain and psychosocial comorbidities. It is essential to accept the patient’s report of pain at face value. Pain should be assessed frequently and systematically, especially when a new pain is reported or a new analgesic treatment is initiated. The location, intensity, and quality of the pain, aggravating and relieving factors, and the patient’s emotional and cognitive response to pain should be noted.

Pain Measurement Tools

Although there is no quantitative biochemical or neurophysiologic test for pain, tools have been devised to assess pain intensity 4 (See Chapter ...

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