Racial differences in pain during 1 year among women with metastatic breast cancer: a hazards analysis of interval-censored data.

Background: Longitudinal tumor-specific studies of cancer pain across the disease trajectory provide insight into the course of pain. Information on pain predictors refines our understanding of patients with greatest distress and need.

Methods: The authors studied 1124 women with metastatic breast cancer and bone metastases, all of whom received standard treatment in an international clinical trial conducted from October 1998 to January 2001. The Brief Pain Inventory (BPI) was administered repeatedly during the course of 1 year. Hazard models were fitted to identify baseline and time-dependent covariates as predictors of pain worsening within cumulative 80-day intervals during the year.

Results: Increased severe pain hazards were associated with non-Caucasian race (hazard ratio [HR] = 2.52; 95% CI, 1.69-3.76), restricted performance status (HR = 1.73; 95% CI, 1.13-2.64), and radiation therapy in a previous interval (HR = 2.86; 95% CI, 1.61-5.09). Estimated cumulative rates for not yet reaching a BPI score of 7 or above ranged from 0.79 (0.72-0.85) in the first interval to 0.64 (0.55-0.74) in the last interval for non-Caucasian women, whereas these rates ranged from 0.91 (0.89-0.93) to 0.84 (0.81-0.87) for Caucasian women.

Conclusions: By using a time-to-event hazards analysis for cancer symptom data, the authors demonstrated that non-Caucasian race predicted poorer pain control among women with metastatic breast cancer. Disparity findings from cross-sectional studies were confirmed. Pain management strategies should take race into account as a risk factor for worsening pain outcomes, and further investigation should seek to uncover and resolve the reasons for this obvious disparity.