Classification of Cancer Pain Syndromes

Chronic pain occurs in about one-third of all cancer patients and in about three-quarters of those with advanced disease.[1] A major factor in the undertreatment of cancer pain is inadequate pain assessment.[2] Pain assessment provides the basis for inferred pathophysiology that directs diagnostic evaluation and treatment decisions. Pain syndrome identification plays an important role in this process—much of clinical medicine is based on pattern recognition of symptoms and signs, leading to a specific diagnosis and therapeutic strategy.

Provocative maneuvers that reproduce pain are especially valuable. For example, a positive femoral stretch test or reverse straight-leg-raising maneuver can reproduce back pain and lead the clinician to investigate further for a retroperitoneal mass.

Classification of Pain Syndromes

In this issue of ONCOLOGY, Drs. Caraceni and Weinstein provide a comprehensive review of the classification of cancer pain syndromes. Although they describe several classification schemes, syndromic classification including underlying pathophysiology probably provides the most useful clinical information.

Foley’s seminal work in cancer pain syndrome identification is still useful today.[3] For instance, impending epidural spinal cord compression can be recognized by localized spinal pain followed by radicular pain. The inferred pathophysiology is somatic pain due to vertebral body metastasis, followed by neuropathic pain due to infiltration of the adjacent nerve roots. Recognition and appropriate treatment of this syndrome can prevent a neurologic catastrophe.

Similarly, postmastectomy pain usually presents in a highly stereotypical manner. The pain is typical of neuropathic pain with a burning, stabbing component; it is localized to the axilla, upper inner arm, and chest wall, and usually persists beyond the normal healing time of 3 months. Recognition of this pain syndrome as treatment- related pain rather than due to cancer progression provides valuable prognostic information.

A recent retrospective cohort study of postmastectomy pain syndrome challenged the traditional view that this is an uncommon condition, finding a prevalence rate of 29%.[4] Crystallization of pain syndromes as distinct clinical entities provides a basis for large-scale epidemiologic studies to further define the prevalence of disease- and treatment-related conditions. However, this is complicated by the observation that patients often present with multiple pain syndromes that are due to both disease progression and treatment.