Prognostic effect of menstrual cycle on timing of surgery in premenopausal breast cancer patients

•Surgery performed during the follicular phase provides a more favorable prognosis.•A low hazard ratio flat fluctuation was observed from cutoff days 10 to 22.•The risk went up for DFS and OS when the cutoff days were set at greater than or equal to day 20.•Individual timing of surgical treatment could be taken into account.

BackgroundIt is controversial whether surgery during different menstrual phases (a kind of host milieu may influence biological characteristics of micrometastatic foci) affects clinical outcomes.MethodsSurvival outcomes were compared between patients who underwent surgery during the follicular (cycle days 1 to 14) and luteal (days 15 to 31) phases. A range of cutoff days from day 10 to 22 was used to observe the risk trend.ResultsThe follicular phase was associated with a more favorable prognosis than the luteal phase in disease-free survival (DFS) [hazard ratio (HR) .318, 95% confidence interval (CI) .10 to .99, P = .049] and overall survival (OS) (HR .260, 95% CI .07 to .92, P = .036). Similar results were detected when the cutoff day was set at days 14, 18, and 19 in DFS and days 11, 13, and 14 in OS. A low HR flat fluctuation was observed from cutoff days 10 to 22, and the risk went up thereafter for both DFS and OS.ConclusionSurgery performed during the follicular phase provides a more favorable prognosis compared with the luteal phase.