The aging of the population and advances in modern medicine have resulted in chronicity of some illnesses, such as neurodegenerative diseases, cancer, end-stage heart and lung diseases, and renal insufficiency. Western populations are experiencing a progressive increase of median life span, and it is predicted that the percentage of individuals aged 60 years and older will reach 15.2% in the year 2030.[1,2] With aging comes a heterogeneous decline of organ reserves and functional impairment contributing to a decreased adaptability both to disease and its treatment. Elderly patients may experience a number of devastating physical and psychosocial symptoms before they die.[1,3,4]. Distress caused by pain and other symptoms increases suffering further among elderly patients and their primary caregivers, especially when these symptoms are not recognized and treated appropriately.
Pain in cancer patients is not yet treated effectively.[1,4] Multidisciplinary evaluation of malignant disease and its related symptoms, and an interdisciplinary approach to the host's symptoms, including pain, constitute the most effective approach to assessing and treating these patients, so those patients with advanced cancer may have the best possible quality of life. Part 1 of this two-part article highlights important issues in pain management in older patients with cancer, including the pathophysiology of pain and appropriate assessment tools. Part 2, which will appear in next month's issue of ONCOLOGY, will address therapeutic options and their effect on quality of life.
Cancer Pain in Older Patients
Pain is an unpleasant and emotional experience associated with actual or potential tissue damage.[4-9] It has been documented that 25% to 50% of community-dwelling aging individuals experience significant pain, and nearly 50% of severely ill hospitalized patients report having pain.[6,10] Poorly managed pain in older cancer patients not only causes suffering and distress, it increases health-care utilization and drives up costs. Unfortunately, many elders and their caregivers expect pain to be a part of aging and do not report it because they think the health-care professional is too busy to hear about their complaint.[11,12] It is extremely important that health-care providers for patients in the oncology and palliative care setting recognize pain and treat it appropriately.
Assessing and managing pain in the elderly patient with cancer poses significant challenges. In many older persons with cancer, the disease is diagnosed late, understaged, and undertreated.[4,5] Pain is a common symptom in these patients, and is often poorly controlled. Reasons for this undertreatment include not only underreporting, but also patient problems with communication or cognition and inherent bias and/or concern among physicians about using analgesic medications in older patients in the presence of comorbid diseases and/or in the face of increased risk of adverse drug reactions.[1,3,6] Misconceptions and knowledge deficits about opioids, including concerns about tolerance and addiction—on the part of both patients and health-care providers—are other barriers to adequate pain control.
Pathophysiology of Pain
There are two broad mechanisms underlying pain: nociceptive and neuropathic. The first mechanism involves direct stimulation of intact pain receptors and travels along intact neurons; it can be classified as somatic or visceral pain. Somatic pain refers to the activation or stimulation of peripheral nociceptors in cutaneous and deep tissues, as occurs after surgical procedures or from bone metastasis. Neoplastic invasion of bone, joint, muscle, or connective tissue is a major cause of persistent somatic pain.[7,13] Bone pain can be secondary to a complex interaction between osteoblasts and osteoclasts, to changes in the dorsal horn of the spinal cord, or to interaction between cytokines and growth factors secreted by a tumor.[7,14] Visceral pain often is secondary to compression, infiltration, or distension of abdominal or thoracic viscera, such as back pain resulting from carcinoma of the pancreas.
Neuropathic pain is secondary to infiltration, compression, or degeneration of neurons in the central or peripheral nervous system. This type of pain often is described as a burning, tingling, or electrical sensation. Examples include pain due to spinal stenosis or diabetic neuropathy, or as an adverse effect of chemotherapy (eg, vincristine) or radiation therapy.
The management of pain in the elderly must take into account other conditions that can greatly influence how the patient experiences pain, including psychosocial factors, such as culture and beliefs; cognitive impairment; emotional and spiritual distress, such as depression and anxiety; and physical symptoms such as nausea, constipation, sedation/confusion, dyspnea, and asthenia.[1,15-17] Any of these conditions can worsen the pain experience. Patients who experience unrelieved pain have less hope and greater likelihood of depression than patients whose pain is well controlled, tending to present also with sleep and appetite disturbances and worsening of cognitive dysfunction. When assessing and managing cancer pain in elderly persons, it is extremely important to consider all physical, psychosocial, and spiritual factors as well as the physiologic changes that accompany the aging process (Figure 1).
Aging and Changes in Pain Perception
The study of pain perception in the elderly has yielded inconclusive results, but some laboratory studies suggest that greater age brings a higher threshold for painful electrical, thermal, and mechanical stimuli to the skin. No definitive conclusions could be drawn in these studies, however, because of the relatively mild pain caused by the stimuli and because the influence of several other factors that might affect the perception of pain could not be eliminated.[8,18]
On the other hand, it has been suggested that older patients report pain less often than younger patients because of alterations in the sensorineural apparatus. Although nerve conduction appears to be well maintained with age, the numbers of nociceptive receptors in the skin and of afferent fibers decrease with age, altering the perception of pain.[8,20] Farrell and Gibson suggested that aging diminishes the capacity of the nociceptive system to downregulate after sensitization; in their study, a group of 15 older (> 65 years) subjects, after receiving trains of five brief electrical stimuli to the skin over the sural nerve at frequencies ranging between 0.2 and 2 Hz, expressed a greater mean rating of pain intensity on the fifth pulse than after a single pulse at all frequencies of stimulation. That the elderly have reduced perception of pain, especially visceral pain, is evidenced by silent myocardial infarcts and the absence of abdominal pain in peritonitis.[22,23]
Evidence also suggests that elderly patients report less pain because of stoicism, slowness to respond, cognitive impairment, or, among members of some minorities, language barriers. Landi et al showed that age > 85 years and low cognitive performance were predictors of failure to receive analgesics. Data have suggested that the prevalence and intensity of pain are lower in elderly patients with cancer than in younger cancer patients.[8,25]
Vigan et al studied 197 patients with advanced cancer, measuring the mean daily pain intensity and daily opioid consumption as a morphine equivalent daily dose. They concluded that older patients (> 65 years) had similar levels of pain intensity but required lower levels of opioid analgesia than younger adults. Another important consideration is that elderly people can have greater sensitivity to opioids than younger patients; this may be related to a reduction in brain volume (approximately 20%), which occurs between ages 20 and 80, and consequent alteration in the ratio of mu and delta receptors.[8,27]
Physiologic Aging and Pharmacokinetics
The changes in bodily systems experienced by older adults are extremely important to consider in the pharmacologic management of pain. The physiologic changes of aging alter the pharmacokinetics and pharmacodynamics of analgesics, decreasing their therapeutic index and increasing the risks of toxicity and drug-drug interactions. These changes, together with decreased volume of distribution, dehydration, decreased plasma proteins, and multiple comorbid conditions, make the older cancer patient more vulnerable to drug interactions.
In many elderly, polypharmacy plays a role in the increased risk of drug interactions.[2,8] The activity of the cytochrome P450 system (CYP) decreases with age, increasing the risk of interactions due to induction or inhibition of CYP isoenzymes.[1,7,8] CYP is the major system responsible for oxidative metabolism of drugs in the liver and for interactions involving lipophilic drugs. For example, fentanyl and methadone are metabolized primarily by the CYP3A4 isoenzyme and to a lesser extent CYP1A2, CYP2D6, CYP2C9, and CYP2C19.
Another important cause of changes in pharmacokinetics is the progressive decline in glomerular filtration rate that occurs in persons aged 65 years and older,[1,7,8,28] which can lead to accumulation of opioid metabolites. Older cancer patients are at higher risk of nephrotoxicity from medications, not only because of the decline in kidney function, but also because of increased susceptibility to volume depletion due to decreases in hypothalamic vasopressin and thus in thirst.[7,8]
Older patients also experience age-related changes in body fat that can affect the metabolism of medications as well as the absorption of transdermal preparations. It is assumed that the elderly are more sensitive to most medications, especially those with central nervous system effects or anticholinergic properties. As part of a thorough and complete evaluation of an older cancer patient experiencing pain, it is important to consider all of these age-related changes in the body as well as potential medication interactions.
1. Yennurajalingam S, Braiteh F, Bruera E: Pain and terminal delirium research in the elderly. Clin Geriatr Med 21:93-119, 2005.
2. Basso U, Monfardinin S: Multidimensional geriatric evaluation in elderly cancer patients: A practical approach. Eur J Cancer Care 13:424-433, 2004.
3. Mercadante S, Arcuri E: Pharmacological management of cancer pain in the elderly. Drugs Aging 24:761-776, 2007.
4. Dalal S, Del Fabbro E, Bruera E: Symptom control in palliative care—Part 1: Oncology as a paradigmatic example. J Palliat Med 9:391-408, 2006.
5. Stein W, Miech R: Cancer pain in the elderly hospice patient. J Pain Symptom Manage 8:474-482, 1993.
6. World Health Organization: Cancer Pain Relief. Geneva, WHO, 1986.
7. Goldstein N, Morrison S: Treatment of pain in older patients. Crit Rev Oncol Hematol 54:157-164, 2005.
8. Balducci L: Management of cancer pain in geriatric patients. J Support Oncol 1:175-191, 2003.
9. Fine P: Pharmacological management of persistent pain in older patients. Clin J Pain 20:220-226, 2004.
10. Goodlin S, Winzeleberg GS, Teno JM, et al: Death in the hospital. Arch Intern Med 158:1570-1572, 1998.
11. Cleeland CS, Gonin R, Hartfield AK, et al: Pain and its treatment in outpatients with metastatic cancer. N Engl J Med 330:592-596, 1994.
12. Cohen-Mansfield J: The adequacy of minimum data set assessment of pain in cognitively impaired nursing home residents. J Pain Symptom Manage 27:343-351, 2004.
13. Portenoy R, Lesage P: Management of cancer pain. Lancet 353:1695-1700, 1999.
14. Urch C: The pathophysiology of cancer-induced bone pain: Current understanding. Palliat Med 18:267-274, 2004.
15. Bruera E: Research into symptoms other than pain, in Doyle D, Hanks GW, MacDonald N (eds): Oxford Textbook of Palliative Medicine, ed 3, pp 179-185. New York, Oxford University Press, 1998.
16. Hopwood P, Stephens RJ: Depression in patients with lung cancer: prevalence and risk factors derived from quality-of-life data. J Clin Oncol 18:893-903, 2000.
17. Bruera E, Kim HN: Cancer pain. JAMA 290:2476-2479, 2003.
18. Gibson SJ, Helme RD: Age-related differences in pain perception and reports. Clin Geriatr Med 17:334-351, 2001.
19. Edgards R, Fillingim R, Ness T: Age-related differences in endogenous pain modulation: A comparison of diffuse noxious inhibitory controls in healthy older and younger adults. Pain 101:155-165, 2003.
20. Davis MP, Srivastava M: Demographics, assessment and management of pain in the elderly. Drugs Aging 20:23-57, 2003.
21. Farrell M, Gibson S: Age interacts with stimulus frequency in the temporal summation of pain. Pain Med 8:514-520, 2007.
22. Clinch D, Banjeree AK, Ostik G: Absence of abdominal pain in elderly patients with peptic ulcer. Age Ageing 13:120-126, 1984.
23. Wroblewski M, Mikulowshi P: Peritonitis in geriatric inpatient. Age Ageing 20:90-102, 1992.
24. Landi F, Onder G, Cesari M, et al: Pain occurs daily, remains untreated among elderly patients in community settings. Arch Intern Med 161:2721-2724, 2001.
25. Curless R, French JM, Williams GV, et al: Colorectal cancer: Do elderly patients present differently? Age Ageing 23:102-108, 1994.
26. Viganó A, Bruera E, Suarez-Almazor ME: Age, pain intensity, and opioid dose in patients with advanced cancer. Cancer 83:1244-1250, 1998.
27. Fuse PG: Opioid analgesic drugs in older people. Clin Geriatr Med 17:479-485, 2001.
28. Repetto L, Balducci L: A case for geriatric oncology. Lancet Oncol 3:289-297, 2003.
29. Hurria A, Lachs M, Cohen H, et al: Geriatric assessment for oncologists: Rationale and future directions. Crit Rev Oncol Hematol 59:211-217, 2006.
30. Coates A, Gebski V, Signorini D, et al: Prognostic values of quality of life scores during chemotherapy for advanced breast cancer. J Clin Oncol 10:1833-1838, 1992.
31. Miller F: Predicting survival in the advanced cancer patient. Henry Ford Hosp Med 391:81-84, 1991.
32. Schag C, Heinrich R, Ganz P: Karnofsky performance status revisited: Reliability validity and guidelines. J Clin Oncol 2:187-193, 1984.
33. Yates J, Chalmer B, McKegner F: Evaluation of patients with advanced cancer using the Karnofsky performance status. Cancer 45:2220-2224, 1980.
34. Katz S, Ford AB, Moskowitz RW, et al: Studies of illness in the aged. The index of ADL: A standardized measure of biological and psychological function. JAMA 185:914-919, 1963.
35. Lawton MP, Brody EM: Assessment of older people: self-maintaining and instrumental activities of daily living. Gerontologist 9:179-186, 1969.
36. Reuben DB, Siu A: An objective measure of physical function of elderly out-patients. The physical performance test. J Am Geriatr Soc 38:1105-1112, 1990.
37. Charlson M, Pompei P, Ales K, et al: A new method of classifying prognostic comorbidity in longitudinal studies: Development and validation. J Chron Dis 40:373-383, 1987.
38. Miller M, Paradis C, Houck P, et al: Rating chronic medical illness burden in gero-psychiatric practice and research: Application of the Cumulative Illness Rating Scale. Psychiatry Res 41:237-248, 1992.
39. Hickie C, Snowdon J: Depression scales for the elderly: GDS. Clin Gerontol 6:51-53, 1987.
40. Folstein M, Folstein S, McMugh P: Mini mental state: A practical method for grading the cognitive state of patients for the clinician. J Psych Res 12:219-226, 1975.
41. Lawlor P, Nekolaichuk C, Gagnon B, et al: Clinical utility, factor analysis, and further validation of the Memorial Delirium Assessment Scale in patients with advanced cancer. Cancer 88:2859-2867, 2000.
42. Centeno C, Sanz A, Bruera E: Delirium in advanced cancer patients. Palliat Med 18:184-194, 2004.
43. Rooij SE, Schuurmans MJ, van dal Mast RC, et al: Clinical subtypes of delirium and their relevance for daily clinical practice: A systematic review. Int J Geriatr Psychiatry 20:609-615, 2005.
44. Lawlor P, Fainsinger R, Bruera E: Delirium at the end of life. Critical issues in clinical practice and research. JAMA 284:2427-2429, 2000.
45. Lawlor P, Gagnon B, Mancini I, et al: Occurrence, causes, and outcome of delirium in advanced cancer patients: A prospective study. Arch Intern Med 160:786-794, 2000.
46. Inouye S, van Dyck C, Alessi C, et al: Clarifying confusion: The confusion assessment method: A new method for detection of delirium. Ann Intern Med 113:941-948, 1990.
47. Herr KA, Garand L: Assessment and measurement of pain in older adults. Clin Geriatr Med 17:457-478, 2001.
48. Pautex S, Michon A, Guedira M, et al: Pain in severe dementia: Self-assessment or observational scales? J Am Geriatr Soc 56:1040-1045, 2006.
49. Bruera E, Kuehn N, Miller MJ, Selmser P, et al: The Edmonton Symptom Assessment System (ESAS): A simple method for the assessment of palliative care patients. J Palliat Care 7:6-9, 1991.
50. Porzio G, Ricevuto E, Aielli F, et al: The Supportive Care Task Force at the University of L'Aquila: 2-years experience. Support Care Cancer 13:351-355, 2005.
51. Stromgren AS, Groenvold M, Peterson MA, et al: Pain characteristics and treatment outcome for advanced cancer patients during the first week of specialized palliative care. J Pain Symptom Manage 27:104-113, 2004.
52. Chang V, Hwang S, Feuerman M: Validation of the Edmonton Symptom Assessment Scale. Cancer 88:2164-2171, 2000.
53. Bruera E, Moyano J, Seifert L, et al: The frequency of alcoholism among patients with pain due to terminal cancer. J Pain Symptom Manage 10:599-603, 1995.
54. Bruera E, Watanabe S: New developments in the assessment of pain in cancer patients. Support Care Cancer 2:312-318, 1994.