Socio-demographic, treatment-related, and health behavioral predictors of persistent pain 15 months and 7-9 years after surgery: a nationwide prospective study of women treated for primary breast cancer.

The purpose of this study was to investigate and report prevalence and risk factors for persistent pain in breast cancer patients at 15 months and 7-9 years post surgery. A nationwide inception cohort study including 3343 women treated for primary breast cancer between 2001 and 2004, who returned a questionnaire 3 months post surgery. Socio-demographic and clinical information was obtained from registries. Questionnaire data on pain and health behaviors were obtained 15 months and 7-9 years post surgery. A total of 1905 women were eligible for analysis. At 15-month post surgery, 32.7 % reported pain "almost every day" or more frequently. At 7-9 years post surgery, the prevalence decreased to 20.4 %. Socio-demographic (young age, lower education, lower income, lower occupational status), treatment-related (being lymph node positive, axillary lymph node dissection (ALND), post-menopausal endocrine treatment), and health behavioral factors (smoking ≥ 10 cigarettes/day, obesity (BMI ≥ 30 and < 35), comorbidity, poor physical function) were significantly associated with pain at 15 months. Being physically active and moderate alcohol intake (<3 units/day) were negatively associated with pain. At 7-9 years post surgery, only ALND (OR:1.41, p = 0.03), post-menopausal endocrine treatment (OR:1.62, p = 0.01), poorer physical function (ORs:2.00-2.40, p = 0.003), and weight training (h/week) at 15 months (OR:1.10, p = 0.008) were significant predictors of pain when adjusting for age and pain 15 months post surgery. No socio-demographic predictors remained statistically significant. Younger age, lower socio-economic status, more invasive surgery, endocrine treatment, and adverse health behaviors emerged as risk factors for persistent pain. The influence of risk factors changed over time, suggesting a complex course of pain development and maintenance.