SAN ANTONIO — The timing of breast cancer surgery with respect to menstrual cycle phase failed to affect prognosis in two large multicenter prospective observational studies presented at the annual breast cancer symposium sponsored by the Cancer Therapy and Research Center.
This has been a longstanding controversy. Since 1989, roughly two dozen surgical studies have examined the issue. Close to half have reported a survival advantage for breast cancer patients who undergo their surgery during the luteal phase of the menstrual cycle. The remaining studies concluded timing of surgery had no impact upon disease-free or overall survival.
But most prior studies involved a few hundred patients or less, many were single-center retrospective series, and nearly all relied upon patient recall of the last menstrual period, which has the potential for inaccuracy.
To shed light on the issue, investigators from the North Central Cancer Treatment Group conducted a study in which 842 patients undergoing breast cancer surgery at 103 sites were categorized as to menstrual cycle phase both by biochemical determination at time of surgery and by recall of last menstrual period, explained Clive S. Grant, M.D., professor of surgery at the Mayo Clinic, Rochester, Minn.
Five-year disease-free survival in 231 women operated on during the luteal phase was 81.9%, not significantly different than the 82.2% rate among 364 women in the follicular phase or the 79.1% rate in women in an indeterminate menstrual phase. Nor did overall survival differ between the groups.
Biochemical determination of menstrual phase based upon hormone levels at the time of surgery demonstrated that reliance upon last reported menstrual period would have resulted in misclassification of 29% of women, a finding that casts doubt upon the validity of much of the prior work in this area.
In a separate presentation, Richard Sainsbury, M.D., reported on 412 women followed for a median 59 months after undergoing breast cancer surgery in a multicenter study. The 3-year overall survival of 90.7% wasn't affected by timing of surgery in relation to menstrual cycle.
The initial data analysis relied upon patient report of last menstrual period. Hormone levels at the time of surgery were also measured, however, and in the near future the data will be reanalyzed using those measurements to categorize patient menstrual status, according to Dr. Sainsbury, professor of surgery at University of Leeds (England).