Lack of correlation between timing of surgery in relation to the menstrual cycle and prognosis of premenopausal patients with early breast cancer.

In a retrospective cohort of a randomised study of adjuvant endocrine, chemotherapy and chemoendocrine therapy, we investigated the correlation between timing of mastectomy and relapse-free survival (RFS) and overall survival (OS) in 721 premenopausal patients with early breast cancer. The median follow-up was 10.1 years (range: 6.1-19.1 years). We grouped the patients by three kinds of classification according to Badwe, Senie, and Hrushesky. The logrank test after the Kaplan-Meier curves showed that there were no significant differences between the categorised menstrual phase in cycle and RFS or OS, except for RFS using Badwe's classification, where the patients whose timing of operation was in the follicular phase had a better RFS compared with those in the luteal phase. These were confirmed by the Cox proportional hazard model. These results suggest that a positive result might be a chance finding, dependent upon the cut-off levels in the menstrual cycle.