BREAST-CANCER SURVIVAL AND THE TIMING OF TUMOR REMOVAL DURING THE MENSTRUAL-CYCLE

In a retrospective cohort study of 262 premenopausal breast cancer pat ients treated at the Mayo Clinic between 1965 and 1985, we investigate d whether survival was associated with the timing of tumor removal dur ing the menstrual cycle, Participants were women less than or equal to 50 years old who had not used exogenous hormones, been pregnant, been lactating, or given birth within 6 months of diagnosis, The menstrual cycle day at surgery was used to assign women to group 1 (cycle days 0-7), group 2 (cycle days 8-15), or group 3 (after cycle day 15), Cox proportional hazards analysis adjusting for age at diagnosis, stage, t umor size, grade, and node involvement showed a nonsignificantly worse survival for group 2 than for group 3 [hazard ratio (KR), 1.41; 95% c onfidence interval (CI), 0.89-2.23], Stratification revealed that the association between survival and timing of tumor removal during the me nstrual cycle was slightly stronger among patients with stage II disea se (adjusted HR, 1.56; 95% CI, 0.92-2.63), The association was the sam e among patients with stage II disease and node involvement (adjusted HR, 1.57; 95% CI, 0.82-3.03), Prospective studies using hormone measur ements to define menstrual cycle status more accurately than the repor ted day of the menstrual cycle could provide further insight about the postulated association.