Most patients with advanced cancer, and up to 60% of patients with any stage of the disease, experience significant pain. The WHO estimates that 25% of all cancer patients die with unrelieved pain.

The cause of cancer pain should be treated whenever possible. By doing so, one can frequently achieve rapid, lasting pain relief and may prevent the problems associated with untreated progressive disease, such as spinal cord compression and pathologic fracture. Also, the need for pain medications may be diminished, thus reducing side effects and drug interactions.

Although pain can be relieved adequately in most cancer patients, it is undertreated for a multitude of reasons. The problem is not trivial, as unrelieved pain is known to be a risk factor for suicide in cancer patients. Current efforts are being directed toward standardizing pain treatment and separating issues of pain treatment from those of substance abuse.

The effective management of cancer patients with pain is best accomplished with coordination of the services of multidisciplinary professionals, community volunteers, and the family.

Pathophysiology

Pathophysiologic classification of pain forms the basis for therapeutic choices. Pain states may be broadly divided into those associated with ongoing tissue damage (nociceptive) and those resulting from nervous system dysfunction in the absence of ongoing tissue damage (non-nociceptive or neuropathic).

Damage to the nervous system may result in pain in an area of altered sensation. Such pain is typically described as burning or lancinating. Patients may report bizarre complaints, such as painful numbness, itching, or crawling sensations. The postamputation phenomenon of phantom pain (pain referred to the lost body part) may be disabling.

Psychological factors
Psychological factors may affect the reporting of pain. Chronic unrelieved pain has psychological consequences, but this does not support a psychiatric basis for the pain complaint. “Psychogenic pain” or somatoform pain disorder is rare in cancer patients.

Pain syndromes
Cancer pain syndromes vary by tumor type and are related to patterns of tumor growth and metastasis. Pain may also be related to antineoplastic therapy or may be unrelated to either the neoplasm or its treatment.

Elements of management

Elements of cancer pain management include a proper medical evaluation, psychosocial assessment, formulation of the pain “diagnosis,” and consideration of pharmacologic and nonpharmacologic treatments. Ongoing care is needed to monitor the efficacy of analgesics and the evolution of different symptoms during treatment or disease progression.

The steps in medical decision-making are to:

• determine whether primary antineoplastic therapy is indicated for palliation,

• tailor pharmacologic analgesic therapy to individual needs,

• consider concurrent nonpharmacologic analgesic methods, and

• monitor response and modify treatment accordingly (Figure 1).

The patient is the focus of care, although family members and others often participate in treatment decisions and require emotional support.