Purpose: It has been postulated that breast cancer surgery performed during the follicular phase of the menstrual cycle is associated with poorer outcome.
Patients and methods: We tested this hypothesis by evaluating disease-free survival (DFS) for 1033 premenopausal patients who received definitive surgery either during the follicular phase (n = 358) or the luteal phase (n = 675). All patients were enrolled in a randomized trial conducted between July 1986 and April 1993. All had node positive breast cancer and randomization was stratified by estrogen receptor (ER) status. All patients received at least three cycles of adjuvant cyclophosphamide, methotrexate, and 5-fluorouracil (CMF). The median follow-up was 60 months.
Results: Patients who underwent definitive surgery for breast cancer in the follicular phase had a slightly worse disease-free survival than those operated on during the luteal phase (five-year DFS percentage: 53% versus 58%; hazard ratio, 1.13; 95% confidence interval (CI), 0.94-1.38; P = 0.20). The effect was significantly greater for the subpopulation of 300 patients with ER-negative primaries (P = 0.02 interaction effect; five-year DFS percentages 42% vs. 59%; hazard ratio 1.60; 95% CI, 1.12-2.25; P = 0.008). The effect of timing of surgery diminished for analyses based on lesser surgical procedures, e.g., excisional biopsies. In particular, no effect of timing was observed for fine needle aspiration procedures.
Conclusions: Surgical procedures which are more extensive than a fine needle aspiration biopsy might be associated with worse prognosis if conducted during the follicular phase of the menstrual cycle. This phenomenon was seen predominantly for high risk breast cancer with low levels or no estrogen receptors in the primary tumor.