Unopposed oestrogen and survival of breast cancer

Menstrual cycle and surgical treatment of breast cancer: findings from the NCCTG N9431 study

PURPOSE

For nearly two decades, multiple retrospective reports, small prospective studies, and meta-analyses have arrived at conflicting results regarding the value of timing surgical intervention for breast cancer on the basis of menstrual cycle phase. We present the results of a multi-cooperative group, prospective, observational trial of menstrual cycle phase and outcome after breast cancer surgery, led by the North Central Cancer Treatment Group (NCCTG) in collaboration with the National Surgical Adjuvant Breast and Bowel Project (NSABP) and the International Breast Cancer Study Group (IBCSG).

PATIENTS AND METHODS

Premenopausal women age 18 to 55 years, who were interviewed for menstrual history and who were surgically treated for stages I to II breast cancer, had serum drawn within 1 day of surgery for estradiol, progesterone, and luteinizing hormone levels. Menstrual history and hormone levels were used to determine menstrual phase: luteal, follicular, and other. Disease-free survival (DFS) and overall survival (OS) rates were determined by Kaplan-Meier method and were compared by using the log-rank test and Cox proportional hazard modeling.

RESULTS

Of 1,118 women initially enrolled, 834 women comprised the study cohort: 230 (28%) in luteal phase; 363 (44%) in follicular phase; and 241 grouped as other. During a median follow-up of 6.6 years, and in analysis that accounted for nodal disease, estrogen receptor status, adjuvant radiation therapy or chemotherapy, neither DFS nor OS differed with respect to menstrual phase. The 5-year DFS rates were 82.7%, 82.1%, and 79.2% for follicular, luteal, or other phases, respectively. Corresponding OS survival rates were 91.9%, 92.2%, and 91.8%, respectively.

CONCLUSION

When menstrual cycle phases were strictly defined, neither DFS nor OS differed between women who underwent surgery during the follicular phase versus the luteal phase. Nearly 30% of the patients did not meet criteria for either follicular- or luteal-phase categories.

Timing of breast cancer surgery in relation to the menstrual cycle--the rise and fall of a hypothesis

It has been claimed that the timing of surgery in relation to the menstrual cycle can significantly influence the prognosis among premenopausal women with primary breast cancer. The literature on the subject is reviewed. The results are heterogeneous, and the quality of the studies is in general low. Many studies suffer from statistical problems concerning small sample sizes and sub-group analyses. In all, the scientific basis for the hypothesis seems weak.

Perioperative endocrine status and prognosis in early breast cancer

Although the relationship between breast cancer and hormones has been known for almost two centuries, it is only during the last 16 years that evidence suggesting the hormonal profile of the patient at the time of surgery can affect the outcome, came to light. A series of studies investigated the hypothesis that unopposed estrogen (observed during the follicular phase of the cycle) may adversely affect the overall and/or disease-free survival of women operated on at that time. The findings have been, at times, contradictory. The retrospective nature of the studies, poor recording of last menstrual period, small study size, and the possible effect of the timing of the diagnostic procedures (cytology or core biopsy) on the outcome may be responsible for the conflicting results. Despite this, more sophisticated studies based on pathological or hormonal observations/measurements, confirmed the relation of luteal phase surgery to better outcome. Estrogen-induced increased protease activity activates a cascade of proteolysis and allows the more discohesive tumor cells to gain access to the circulation. Moreover, disseminated cells might be able to proliferate easier because of several estrogen-dependent growth factors. Diminished immune function during the follicular phase, because of natural killer cell activity and mononuclear cell phagocytic activity down-regulation may also be implicated in the dissemination of viable tumor cells. Taken together these findings provide a framework for explaining the observation that luteal phase surgery can lead to an improved outcome. By altering the perioperative hormonal milieu it may be possible to reduce deaths from breast cancer in a simple and nontoxic manner.