Timing of surgery in relation to menstrual cycle does not predict the prognosis in primary breast cancer. Danish Breast Cancer Cooperative Group.

From 1977 to 1989 6488 patients under 50 years with primary breast cancer were registered in the nationwide Danish Breast Cancer Cooperative Group (DBCG). Among these, information on last menstrual period prior to surgery was available in 1635 cases which constitute the study group of the present analysis. The group was representative of all women operated upon during the period with regard to prognostic factors and survival. In the study group time of surgery in relation to last menstrual period was found to have no influence on 5 and 10 years survival.