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,[6] 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.[7] 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.[7] 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.[7]

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.[7]

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,[11] tending to present also with sleep and appetite disturbances and worsening of cognitive dysfunction.[2] 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).