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Classification of Cancer Pain Syndromes

Classification of Cancer Pain Syndromes

The problem of pain among cancer patients is endemic.
Appropriate and effective clinical responses to this problem require that the
physician appreciate the cause of the pain, its underlying mechanism, its
natural history, and its significance.

A woman with breast cancer, who presents with shoulder pain, may have one of
a number of pain syndromes, including postoperative frozen shoulder, paclitaxel
(Taxol)- or bisphosphonate-associated proximal myalgias, radiation or malignant
upper brachial plexopathy, metastases in the bony structures of the shoulder,
impending fracture of the proximal humerus, C4 radiculopathy associated with
epidural encroachment or leptomeningeal metastases, hepatic capsular distension,
or a benign pathology unrelated to the cancer. To arrive at an appropriate
therapeutic plan, the treating clinician must be aware of the range of possible
causes of the pain, their distinguishing clinical features, and the efficient
diagnostic strategies available to isolate the specific cause as quickly and
easily as possible. A lack of awareness of the range of diagnostic possibilities
may result in undertreatment, overtreatment, or sometimes even inappropriate
treatment of the pain.

Since the seminal works of John Bonica,[1] various attempts have been made to
taxonomize cancer pain.[2-5] A taxonomy is a clinically useful classification of
a recognized clinical diversity. By necessity, taxonomies of this ilk must be
open to reevaluation as knowledge and experience expands.

International Survey of Cancer Pain

In this article, Dr. Caraceni expands this process of taxonomic reevaluation
based on his experience and the data accrued from an international survey of
cancer pain characteristics and syndromes.[6] This survey of pain-related data
from 1,095 patients provided an unparalleled picture of the pain experience of
cancer patients. Almost one-quarter of the patients experienced two or more
pains; 93% had one or more pains caused directly by the cancer, and 21% had one
or more pains caused by cancer therapies. When classified by pain mechanism,
nociceptive pains due to somatic injury were the most common (71%). These were
usually caused by bone or joint lesions (42%) or soft-tissue infiltration (28%).
Pain generated by neuropathic pain mechanisms, such as peripheral nerve
injuries, and visceral pain syndromes each occurred in 30% to 40% of
patients.[6]

Aside from identifying points of common understanding, the survey also
identified a lack of convergent understanding regarding the concept of
"breakthrough pain." Among clinicians from various countries reporting
their experiences, there were large differences in the frequency with which
breakthrough pain was diagnosed. This observation suggests the need for an
improved understanding of this phenomenon.

Taxonomy of Pain Syndromes

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