Pain is a complex symptom experienced by many cancer patients. It affects most aspects of life, and controlling it well can make a great difference in patients’ perception of their diagnosis. The etiology of pain in cancer patients is very heterogeneous. Finding the cause directs the treatment and improves the chances of good pain control. In general, cancer pain syndromes can be divided into acute and chronic. Acute ones are usually direct consequence of invasive diagnostic or therapeutic procedures, but they can less commonly be related to cancer itself. Chronic ones are more likely to be caused by the neoplastic process or by antineoplastic therapy.
Metastatic disease may invade bone, obstruct a hollow viscus, and compress nerve or spinal cord. Radiation treatment may cause fibrosis of nerve or spinal cord. Chemotherapeutic agents may cause peripheral neuropathy or aseptic bone necrosis and predispose to painful opportunistic infections. Surgical treatment leads to acute postoperative pain and may cause deafferentation pain if major nerves or nerve plexi are cut. In any given patient, one or more of these factors may be in play, and more than 50% of cancer patients with pain have more than one source of pain.1
Primary care physicians and oncologists should be able to recognize and treat most cancer-related pain. They should be able to initiate treatment for the more common causes with opioids and nonopioid analgesics. More than 70% of patients can be treated effectively with simple analgesics and adjuvant drugs. Effective pain relief, without intolerable side effects, is occasionally difficult to obtain with the use of conventional analgesics. When this occurs, consultation with a specialist in pain management may be necessary.
DIMENSIONS OF THE PROBLEM
Based on rates from 2008 to 2010, National Cancer Institute estimates that 40.76% of men and women born today will be diagnosed with cancer of all sites at some time during their lifetimes.2 About half of cancer patients experience pain, most commonly caused by their primary cancer. Pain severity is at least moderate for most patients experiencing cancer-related pain. Pain may also persist in long-term cancer survivors. Cancer-related pain adds to mood disturbance and disability in cancer patients.3
In 1982, Daut and Cleeland found that 36% of 286 patients with nonmetastatic cancer reported pain versus 59% of 381 with metastatic disease.4 In 1994, Cleeland and colleagues found that 67% of 1308 outpatients with metastatic cancer had pain, and 62% of those had severe pain. Thirty-six percent reported disability from pain, and 42% of those with pain reported inadequate analgesia.5 Terminal pain, refractory to escalating opioid administration, is a more challenging problem. Depression, uncontrolled pain, the adverse effects of opioids, and fear of pain may precipitate suicidal thoughts or requests for aid in dying.6,7 Pain also adds to the discomfort experienced by those caring for dying patients.