Cancer-related pain and disability: a longitudinal study.

Although the cross-sectional association between cancer-related pain and disability is well established, their longitudinal relationship has been less studied.Data from the Indiana Cancer Pain and Depression (INCPAD) trial were analyzed to determine whether baseline cancer-related pain and changes in pain over time predict disability over 12 months.A total of 274 cancer survivors with cancer-related pain were accrued in the INCPAD trial. Data were collected at baseline, one, three, six, and 12 months by interviewers blinded to treatment arm. Disability outcomes included a continuous measure (Sheehan Disability Scale [SDS] score) and a categorical measure (≥14 days in the past four weeks with a ≥50% reduction in usual activities). Predictor variables, operationalized by the Brief Pain Inventory, included baseline pain severity and changes in pain severity scores between each time point. Multivariable analyses were conducted adjusting for treatment group, baseline disability, and selected covariates including depression.Baseline pain severity did not predict disability outcomes at 12 months. However, improvement in pain severity predicted less disability over 12 months both in terms of SDS scores (b=-0.17, t=-5.33, P<0.001) and ≥14 disability days in the past month (odds ratio=0.85; 95% confidence interval, 0.79-0.93; P<0.001).Disability over 12 months in patients with cancer-related pain is predicted by changes in pain severity over time. Results suggest that effective pain management may reduce subsequent disability among cancer survivors.