Pain Distribution Patients with cancer pain commonly experience pain at more than one site. The distinction between focal, multifocal, and generalized pain may be important in the selection of pain therapy. Focal pains can be distinguished from those that are referred, that is, experienced in a site remote from the lesion. For example, a patient who develops progressive shoulder pain and has no evidence of focal pathology needs to undergo evaluation of the region above and below the diaphragm to exclude the possibility of referred pain from diaphragmatic irritation. Temporal Relationships Cancer-related pain may be acute or chronic.
Acute pain is defined by a recent onset and a natural history characterized by transience.
Chronic pain has been defined by persistence of pain for three months or more beyond the usual course of an acute illness or injury, a pattern of recurrence at intervals over months or years, or by association with a chronic pathologic process. 2 Chronic tumor-related pain is usually insidious in onset, often increases progressively with tumor growth, and may regress with tumor shrinkage. 52 Breakthrough pains are common in both acute or chronic pain states. Spontaneous fluctuations in pain intensity can also occur without an identifiable precipitant. The assessment process provides the data necessary to infer a predominant pathophysiology.