Individual Differences in Pain Modulation as Predictors of Post-Surgical Pain

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DESCRIPTION (provided by applicant): Pain is a critical yet poorly-understood and under-treated problem in the management of breast cancer. Recent studies have estimated that approximately 50% of women who undergo lumpectomies will experience persistent pain, which is associated with impaired quality of life, significant disability, and, in some studies, cancer-related mortality. To date, studies of women undergoing breast surgery have identified few consistent or strong predictors of who reports long-term treatment-related pain, and to what degree. Though not previously studied in the context of breast cancer treatment, emerging evidence suggests that individual differences in how the central nervous system processes pain may be a powerful contributor to the extent of pain experienced after surgery. The proposed project is a prospective cohort study of women undergoing lumpectomy followed by radiation therapy for treatment of early-stage breast cancer. Pain responses will be evaluated pre-surgically by assessing responses to brief, standardized stimuli (i.e, heat, cold, pressure). Patients will be followed during their acute recovery periods using a combination of electronic diaries and automated telephone calls to assess treatment-related pain, analgesic usage, and pain-related sequelae. This study will determine: (1) whether pre-operative psychophysical testing to evaluate pain responses is useful in predicting acute and longer-term pain outcomes after lumpectomy, and (2) what are the most effective measures of experimental pain responses in predicting treatment-related pain outcomes. We hypothesize that the individuals who show the greatest degree of pain sensitivity and the lowest degree of endogenous pain inhibition will report the most acute pain, require the most analgesics, and report the highest levels of long-term pain and pain-related disability. This work will provide important information on mechanisms and risk factors contributing to the experience of pain following treatment for breast cancer. In addition, the findings may enhance future pain-treatment studies by allowing investigators to target high-risk individuals for clinical trials of analgesics. Finally, results from this research would have general implications for post-surgical pain management; those who showed the most high-risk profiles might benefit from additional pre-emptive or post-operative analgesic interventions, or more intense follow-up for a longer period.