Bethesda Handbook of Clinical Oncology, 2nd Edition
General Principles of Cancer Pain Management
Jason R. Beckrow*
Richard A. Messmann†
*Department of Internal Medicine, Michigan State University, East Lansing, Michigan
†Department of Hematology/Oncology, Michigan State University, East Lansing, Michigan
Inappropriate or inadequate pain management is a considerable problem that results in suffering and decreased quality of life for patients with cancer. Most patients with advanced cancer, and up to 60% of patients with any stage of cancer diagnosis, experience considerable pain. The problem is not trivial, and unrelieved pain is a risk factor for suicide in patients with cancer. This chapter is designed to help clinicians focus on the three major components of any comprehensive pain-management plan: (a) initial patient assessment followed by (b) analgesic therapy, and (c) reassessment. The chapter is not intended to be an exhaustive review of pain management, but it may act as a helpful guide to facilitate an understanding of pain assessment and control.
INITIAL PATIENT ASSESSMENT
The initial assessment of any patient with cancer who is in pain should include a comprehensive history, with documentation of the following:
- The primary cancer diagnosis and current extent of disease: This may help define the etiology of the painful stimuli (e.g., prostate cancer and bone pain).
- Any current or earlier treatment of pain: Is the patient opiate naïve? Earlier analgesic interventions and documentation of outcomes may affect dosing considerations. The type(s) of analgesics being used by the patient as well as the administration route (Is the delivery of the medication optimized?), dose (Is the dose sufficient for analgesia?), schedule (Is there appropriate regularly scheduled “around-the-clock” coverage? Is the dosing interval consistent with the duration of action of the prescribed drug?), and change in effectiveness of current regimen (Is there a tolerance developing to the current regimen?) should be identified.
- Location of pain: Identify the specific area, depth or site from which the pain originates.
- Date of onset: Is this an acute or a chronic problem?
- Quality of pain: Characterization may help elucidate the etiology of pain. Is the pain cramping, burning, aching, dull, or sharp?
- Character of pain: Is the pain waxing or waning? What are the aggravating and alleviating factors? Is it constant or intermittent?
- Intensity and severity of pain: A visual analog scale (VAS) and a numeric scale (see Fig. 37.1) should be used to quantify and document the intensity of pain. The patient's subjective interpretation of the level of pain should be believed. Chronic cancer pain may not be accompanied
by sympathetic stimulation, which is normally manifested as tachypnea or tachycardia, despite severe pain.
FIG. 37.1. Pain intensity scales: (Top) Visual analog scale (VAS). (Bottom) Simple descriptive pain intensity scale.
- Psychosocial evaluation (any concomitant major stresses?): Psychological dependency on prescription or illicit drugs, and on alcohol, should be identified.
- Pertinent medical history should be documented. Physical examination: The physical examination should characterize the manifestations of pain, such as atrophy, muscle weakness, and trigger points. A thorough neurologic examination is essential, especially if neuropathic pain is suspected. Appropriate laboratory and imaging studies should be obtained.
- These baseline findings should be documented in the patient's chart to facilitate future management.
The six principles of pharmacologic pain management modified from the World Health Organization (WHO) report are as follows:
- By the mouth:The oral route is the preferred route whenever possible (for the sake of the patient's convenience and to avoid painful i.m. injections).
- By the clock:Basal analgesic administration should be based on a fixed schedule— “around the clock” (ATC) and not on an “as needed” (p.r.n.) basis. A rationally designed, regularly scheduled ATC dosing avoids the peak-and-trough effect of prn dosing, in which high serum levels of the analgesic correlate with adverse effects such as nausea, pruritus, or somnolence, and low levels correspond to periods of suboptimal analgesia. Patients should not rely on prn analgesics to cover basal pain-control requirements. However, prn analgesics should always be ordered for breakthrough pain control.
- WHO three-step ladder(see Fig. 37.2):
FIG. 37.2. Three-step World Health Organization (WHO) analgesic ladder. (From Cancer pain relief, 2nd ed. Geneva: World Health Organization, 1996, with permission.)
- Step 1: For mild pain, use nonopioid analgesics (see Table 37.1) with or without adjuvant therapy (see Table 37.2), at recommended dose and frequency.
TABLE 37.1. Select Nonopioid Analgesics
TABLE 37.2. Select Adjuvant Therapy
- Step 2: For moderate pain, add a weak opioid analgesic (see Table 37.3) to the nonopioid analgesic, or, alternatively, use a narcotic analgesic combination (see Table 37.4) with or without adjuvant therapy.
TABLE 37.3. Select Opioid Analgesics
TABLE 37.4. Select Opioid Analgesic Combinations
- Step 3: For severe pain, substitute a strong opioid analgesic (Table 37.3) for the weak opioid analgesic, in addition to the nonopioid, with or without adjuvant therapy (Table 37.2).
- If a maximum dose of medication fails to adequately relieve pain, move up the ladder, and not laterally to a different drug in the same efficacy group.
- The initial point of entry into the WHO analgesic ladder should correspond to the patient's level of pain. For example, patients with mild pain may start at Step 1, whereas patients experiencing severe pain would start at Step 3 to attain prompt analgesia.
- Individualized treatment:A comprehensive analgesic regimen requires therapeutic customization to the patient's needs, including careful dose titration and reassessment to eliminate cancer pain and the appropriate management of opioid-related side effects (seeTable 37.5). Once the pain “type” is identified and characterized (e.g., bone, visceral, or neuropathic; see Table 37.6), initiate an appropriate regimen of analgesics by the appropriate route (see Table 37.7).
TABLE 37.5. Management of Opioid-induced Adverse Effects
TABLE 37.6. Treatment of Cancer Pain by Etiology
TABLE 37.7. Selected Routes of Analgesic Administration
- Monitoring:Monitoring is required to ensure that the benefits of treatment are maximized and the adverse effects are minimized.
- Use of adjuvant therapies (Table 37.2):Examples of adjuvant therapies include antidepressants, benzodiazapines, steroids, anticonvulsants, and local anesthetics. Depression often accompanies chronic pain, and tricyclic antidepressants at low doses augment analgesia, whereas full-dose selective serotonin reuptake inhibitors (SSRIs) improve sleep and appetite and elevate mood. Use pain-management consultants (e.g., anesthesia pain-management service). Nonsteroidal antiinflammatory drugs (NSAIDs) are often most efficacious in controlling metastatic bone pain. Gabapentin is effective in controlling neuropathic pain.
GENERAL CONSIDERATIONS ABOUT PHARMACOTHERAPY
Use short-acting opioid analgesics [i.e., shorter acting i.v. or PO morphine sulfate versus long-acting morphine sulfate (MS Contin)] until the patient has attained adequate pain control. Short-acting analgesics may offer advantages over longer-acting formulations in the initial management of acute cancer pain, including (a) ease of dose adjustment and (b) rapid onset of analgesic effect. After attaining effective analgesia, the total daily-dose requirements can be determined, thereby facilitating conversion to long-acting formulations. Be aware that there is wide interpatient variability in the amount of analgesics required for pain control.
Consider using patient-controlled analgesia (PCA), which administers small intravenous or epidural doses of opioids on demand. This modality, often used for treatment of acute varying or postoperative cancer pain, affords a high degree of patient satisfaction and safety. Frequent
evaluation to determine the analgesic effect and the need for dose modification suggests that PCA may be best used through formal consultation of an in-house anesthetist or multimodality “pain-management teams.” Programmable PCA pumps often allow basal or maintenance rates of opioid infusion in addition to bolus dose amounts and “lockout” intervals. Maintenance PCA orders can be initiated after bolus opioid dosing achieves adequate analgesic effect.
Avoid using agents such as meperidine and pentazocine, as well as i.m. injections. Meperidine (Demerol) is metabolized to normeperidine, a metabolite with neuroexcitatory (seizure-producing) effects. The risk of toxicity is increased after prolonged administration (for more than 48 hours) and in patients with renal insufficiency. Pentazocine (Talwin) is not more potent than codeine, with a high incidence of hallucinations and agitation. Oral and subcutaneous routes of ingestion are as efficacious, without the pain and expense of i.m. injections.
ANESTHETIC AND NEUROABLATIVE MANAGEMENT
Referral to an anesthetist or a pain care team may be necessary to implement specific anesthetic blockade, neurolysis, and intrathecal or epidural analgesia. Local anesthetic neural blockade may achieve both diagnostic and therapeutic ends. Diagnostically, the nerve block may help predict the efficacy of neuroablation. Therapeutically, the intervention will provide pain relief and the pain-relieving effect may also outlast the drug effect. Neuroablation involves intentionally destroying the nervous structures implicated in the transmission of pain. Spinal administration of opioids produces analgesia without changes in motor or sensory function. Local anesthetics and/or steroids may be added in patients with refractory pain to enhance analgesia. Implantable intrathecal delivery systems are also available, with promising improvements in rapid and sustained pain relief.
Pain management is a dynamic process that requires frequent reassessment to determine the effectiveness of therapy and to facilitate dose adjustment. Disease progression often requires increasing doses of analgesics, whereas opioid tolerance is often manifested as decreased duration of analgesia.
The appropriate management of opioid-related side effects (Table 37.5), such as constipation or pruritus, is of paramount importance because the mismanagement of these side effects often acts as a barrier that precludes administration of adequate analgesia. Optimization of patient management requires that the clinician be proactive in managing opioid-related side effects and in assessing and reassessing pain related to cancer.
Abraham J. A physician's guide to pain and symptom management in cancer patients. Baltimore, MD: The Johns Hopkins University Press, 2000.
Agency for Health Care Policy and Research. Management of cancer pain guideline panel. Rockville, MD: U.S. Department of Health and Human Services, Public Health Service Agency for Health Care Policy and Research, 1994.
American Association of Hospice and Palliative Medicine. Hospice/palliative care training for physicians: pocket guide to hospice/palliative medicine. Glenview, IL: American Academy of Hospice and Palliative Medicine, 2003.
American Pain Society. Principles of analgesic use in the treatment of acute pain and cancer pain, 3rd ed. Skokie, IL: American Pain Society, 1992.
Arbit E. Management of cancer-related pain. Mount Kisco, NY: Futura Publishing, 1993.
Brisman R. Neurosurgical and medical management of pain: trigeminal neuralgia, chronic pain, and cancer pain. Boston, MA: Kluwer Academic Publishers, 1989.
Brooks PM, Day RO. Nonsteroidal antiinflammatory drugs: differences and similarities [see comments]. N Engl J Med 1991;324:1716–1725 [published erratum appears in N Engl J Med 1991;325:747].
Cleeland CS, Gonin R, Hatfield AK, et al. Pain and its treatment in outpatients with metastatic cancer [see comments]. N Engl J Med1994;330:592–596.
Djulbegovia B, Sullivan DM. Decision making in oncology: evidence-based management. New York: Churchill Livingstone, 1997.
Epps RP, Stewart SC. American Medical Women's Association: guide to cancer and pain management. New York: Dell Publishing, 1996.
Kaiko RF, Foley KM, Grabinski PY, et al. Central nervous system excitatory effects of meperidine in cancer patients. Ann Neurol1983;13:180–185.
Kanner R. Diagnosis and management of pain in patients with cancer. Basel: Karger, 1988.
Magni G. The use of antidepressants in the treatment of chronic pain: a review of the current evidence. Drugs 1991;42:730–748.
McGuire DB, Yarbro CH. Cancer pain management. Orlando, FL: Grune & Stratton, 1987.
McGuire DB, Yarbro CH, Ferrell B. Cancer pain management, 2nd ed. Boston, MA: Jones & Bartlett, 1995.
Mellick LB, Mellick GA. Successful treatment of reflex sympathetic dystrophy with gabapentin [letter]. Am J Emerg Med 1995;13:96.
Parris WCV. Cancer pain management: principles and practice. Boston, MA: Butterworth-Heinemann, 1997.
Pazdur R, Coia LR, Hoskins WJ, et al. Cancer management: a multidisciplinary approach, 7th ed. New York: The Oncology Group, 2003.
Schug SA, Zech D, Dorr U. Cancer pain management according to WHO analgesic guidelines. J Pain Symptom Manage 1990;5:27–32.
Ventafridda V, Tamburini M, Caraceni A, et al. A validation study of the WHO method for cancer pain relief. Cancer 1987;59:850–856.
Waller A, Caroline NL. Handbook of palliative care in cancer. Boston: Butterworth-Heinemann, 1996.
Watson CP. Antidepressant drugs as adjuvant analgesics. J Pain Symptom Manage 1994;9:392–405.