Menstrual cycle and timing of breast surgery in premenopausal node-positive breast cancer: results of the International Breast Cancer Study Group (IBCSG) Trial VI

Timing of breast cancer surgery, menstrual phase, and prognosis: Systematic review and meta-analysis

BACKGROUND

For over 25 years, there has been a debate revolving around the timing of breast cancer surgery, menstrual cycle, and prognosis.

METHODS

This systematic review synthesizes and evaluates the body of evidence in an effort to inform evidence-based practice. A keyword and reference search was performed in PubMed and Web of Science to identify human studies that met the inclusion criteria. A total of 58 studies (48 international and 10 U.S.-based) were identified. We provided a narrative summary on study findings and conducted a meta-analysis on a subset of studies where quantitative information was available.

RESULTS

Findings from both qualitative and quantitative analyses were inconclusive regarding performing breast cancer surgery around a specific phase of the menstrual cycle.

CONCLUSION

Based on the Institute of Medicine criteria, evidence is insufficient to recommend a change in current primary breast cancer surgery practice based on menstrual phase.

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

BACKGROUND

It is controversial whether surgery during different menstrual phases (a kind of host milieu may influence biological characteristics of micrometastatic foci) affects clinical outcomes.

METHODS

Survival 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.

RESULTS

The 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.

CONCLUSION

Surgery performed during the follicular phase provides a more favorable prognosis compared with the luteal phase.

The Relationship between Surgery and Phase of the Menstrual Cycle Affects Survival in Breast Cancer

PURPOSE

The impact of time of surgery based on the menstrual cycle is a controversial issue. Two decades after the first interest in this topic, a number of studies with conflicting results have not helped to resolve this problem. This study aimed to prospectively evaluate the impact of timing of surgery based on the menstrual cycle on survival rates of breast cancer patients, and various clinical and hormonal classifications of the menstrual cycle were compared in order to determine the phase of the menstrual cycle which showed the highest degree of surgical survival.

METHODS

Premenopausal breast cancer patients treated with curative surgery between 1998 and 2002 were prospectively included in this study. Patients were divided into different groups according to the first day of their last menstrual cycle using three different classifications (clinical, Hrushesky, Badwe), and were also grouped according to their serum hormone levels. Serum levels of follicle stimulating hormone, luteinizing hormone, estrogen, and progesterone were measured on the day of surgery.

RESULTS

Ninety patients were included in the study. Median follow-up time was 90 months. Nineteen patients (21.1%) had loco-regional recurrence and/or distant metastases while 12 patients (13.3%) died during follow-up. Five-year (78.6% vs. 90.6%) and 10-year (66.7% vs. 90.6%) disease-free survival (DFS) rates of patients in the clinically defined follicular phase were significantly decreased compared to luteal phase. On the other hand, hormonally determined phases of the menstrual cycle and grouping of patients according to clinical classifications did not show an impact on prognosis.

CONCLUSION

In the current study performing surgery in the follicular phase of the menstrual cycle decreased DFS in premenopausal patients. According to these results, performing surgery during the luteal phase of the menstrual cycle might have a beneficial effect on survival.

Timing of breast surgery in premenopausal breast cancer patients

BACKGROUND

The majority of women diagnosed with breast cancer undergo a multidisciplinary treatment with surgical intervention and radiotherapy or chemotherapy, or both. The importance of timing of tumour removal in relation to the menstrual cycle and its influence on disease-free survival and overall survival has been studied by researchers since 1989 but still remains speculative.

OBJECTIVES

To determine if surgery performed either during the follicular or luteal phase of the menstrual cycle affects the overall and disease-free survival of premenopausal breast cancer patients.

SEARCH STRATEGY

We searched the Cochrane Breast Cancer Group Trials Register (January 2009), Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2009, Issue 1), MEDLINE (1966 to January 2009), EMBASE (1974 to September 2006) and the WHO International Clinical Trials Registry Platform (ICTRP) search portal (July 2010). We checked references of articles and communicated with authors.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing breast surgery during the follicular phase of the menstrual cycle with the luteal phase in premenopausal women. Prospective non-RCTs or observational studies were considered if randomised studies were lacking.

DATA COLLECTION AND ANALYSIS

Three authors independently extracted data and assessed trial quality.

MAIN RESULTS

Completed randomised trials were not found. There is one trial that is currently ongoing in Italy; the results have yet to be published.Two prospective observational studies had data on recurrence-free survival. One study reported an odds ratio for recurrence rate at one year (where > 1 favours the luteal phase) of 0.86 (95% confidence interval (CI) 0.69 to 1.08); 0.87 at two years (95% CI 0.69 to 1.09); 0.95 at three years (95% CI 0.75 to 1.21); 1.12 at four years (95% CI 0.87 to 1.43); and 1.12 at five years (95% CI 0.87 to 1.43). Another study reported a hazard ratio for overall survival of 1.02 (95% CI 0.995 to 1.04, P = 0.14) and for disease-free survival of 1.00 (95% CI 0.98 to 1.02, P = 0.92) at three years based on the last and first menstrual period. The results were not significant. There was no difference in the recurrence rate whether the surgery was done during the follicular or luteal phase of the menstrual cycle.

AUTHORS' CONCLUSIONS

In the absence of RCTs, this review provides evidence from large prospective observational studies that timing of surgery does not show a significant effect on survival.

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.

Does the timing of breast cancer surgery in pre-menopausal women affect clinical outcome? An update

There is some evidence that breast cancer surgery during the luteal phase in pre-menopausal women is associated with a better clinical outcome, however the evidence for this is still equivocal.

In this paper, after summarizing the normal physiology of the menstrual cycle, we examine how such an association may occur and provide a comprehensive review of the literature in the area.

Preoperative and perioperative chemotherapy with 5-fluorouracil as continuous infusion in operable breast cancer expressing a high proliferation fraction: cytotoxic treatment during the surgical phase

BACKGROUND

Experimental data on perioperative chemotherapy (PeCT) indicate that its initiation might be most useful if administered as close as possible to the time of first 'disturbance of the tumour'. Regimens including 5-fluorouracil (5-FU) as continuous infusion are commonly used in the preoperative setting, especially for large tumours and locally advanced disease. We therefore evaluated the role of PeCT with 5-FU as continuous infusion after preoperative chemotherapy (PreCT), covering the surgical phase and acute wound healing period, in patients with breast cancer too large to attempt breast-conserving surgery upon diagnosis.

PATIENTS AND METHODS

Breast cancer patients, clinical stages T2-T3, N0-N2, M0, and Ki-67 labelling index >/= 20%, were treated every 3 weeks with a maximum of six courses of vinorelbine 20 mg total dose intravenously (i.v.) on days 1 and 3, cisplatin 60 mg/ m(2) i.v. on day 1 and 5-FU 200 mg/m(2)/day as a continuous infusion (ViFuP regimen). Patients who achieved a clinical and radiological objective remission with PreCT were also treated with perioperative 5-FU that was continued until 30 min before, and restarted immediately after surgery, prolonging infusion until 15 days after surgery.

RESULTS

Following preoperative treatment, 39 of 49 evaluable patients [80%; 95% confidence interval (CI) 70% to 90%] had an objective response. Pathological complete remission (pCR) was achieved in 14 (29%) patients. No relevant clinical or haematological toxicity due to PeCT was observed. In 36 patients submitted to PeCT the rate of pCR was 33% (95% CI 18% to 48%). The highest response of the primary tumour to PreCT and PeCT was observed in women with tumours not expressing estrogen and progesterone receptors (pCR 46%; 95% CI 19% to 73%).

CONCLUSIONS

Preoperative therapy can be protracted into the surgical (and wound healing) period without significant additional short-term toxicity. Proper selection of patients according to biological features might improve the therapeutic yield of preoperative therapies.

Upregulation of HER-2/neu by Ovarian Ablation: Results of a Randomized Trial Comparing Leuprorelin to CMF as Adjuvant Therapy in Node-positive Breast Cancer Patients

PURPOSE

HER-2/neu oncogene expression is modulated by an estrogen-sensitive binding site in the HER-2/neu promoter. Utilizing the circulating antigen of HER-2/neu in serum (sHER-2/neu) as a surrogate marker we investigated whether ovarian ablation by adjuvant therapy leads to an upregulation of HER-2/neu in breast cancer patients.

PATIENTS AND METHODS

The analysis was done on sera from premenopausal, node-positive, hormone-receptor positive patients randomized in a multi-center trial. The study was designed with patients receiving either 11.25 mg of leuprorelin s.c. every 3 months over 2 years or CMF chemotherapy for 6 cycles. Sera, available from 80 patients in the leuprorelin arm and from 53 patients in the CMF arm, were collected at 0, 3, 6, 12, 18, 24 and 30 months. sHER-2/neu was measured using a standardized ELISA assay that has an upper limit of normal of 15 ng/ml. sHER-2/neu results were correlated to the levels of LH, FSH and estradiol as indicators of ovarian ablation and to the tumor marker, CA 27.29.

RESULTS

During estradiol deprivation, sHER-2/neu levels increased significantly by more than one third from 8.1 ng/ml to 11.0 ng/ml (p < 0.0001) in both treatment arms. The most pronounced relative increase occurred within the first 3 months (p < 0.001). In only 2.7% (16/587) of sHER-2/neu measurements, the sHER-2/neu results were elevated above 15 ng/ml, confirming the upper limit of normal for breast cancer patients irrespective of their menopausal status. At month 30, the sHER-2/neu level started to decrease in the leuprorelin arm, reflecting reversible castration and estradiol reconstitution. Conversely, CA 27.29 levels did not show a trend over time, indicating that sHER-2/neu changes were of a regulatory nature and were not merely a reflection of increasing residual disease.

CONCLUSION

Our study demonstrates the upregulation of HER-2/neu during ovarian ablation. These results are consistent with data showing that the percentage of HER-2/neu positive tumors, evaluated by standardized immunohistochemistry on the primary tumor, is significantly increased during the follicular phase of the menstrual cycle (Balsari et al., Am J Pathol 155: 1543-1547, 1999). Regulatory processes at the HER-2/neu gene should be considered when prescribing specific therapy for breast cancer.

Lunar phases and survival of breast cancer patients--a statistical analysis of 3,757 cases

The potential influence of lunar phases on human life has been widely discussed by the lay press. The purpose of this study was to find out whether the timing of surgery during particular lunar phases influences the survival of breast cancer patients. It has been postulated that breast cancer surgery performed during the waxing moon, or particularly at full moon, is associated with a poorer outcome. We tested this hypothesis by evaluating the overall survival for 3,757 consecutive patients with invasive breast cancer. All patients underwent either modified radical mastectomy or breast conserving surgery plus radiotherapy, followed by adjuvant cytotoxic or hormonal therapy. The date of definitive surgery was allocated to the lunar phases. 1,904 (50.7%) patients were operated on during the waxing moon and 1,853 (47.3%) during the waning moon. The median follow-up was 74 months (range 1-372 months). The mean age at primary surgery did not differ significantly in the two groups 58.39 (SD 13.14) versus 58.34 (12.75) (p >0.05, t-test). Breast cancer stages at initial diagnosis were evenly distributed according to the lunar phases (p = 0.325; chi-square). Survival curves were plotted according to the method of Kaplan-Meier. No significant differences were observed when timing of surgery was allocated to the lunar phases (p = 0.4841, log-rank). Subgroup analysis of premenopausal patients revealed similar results (p = 0.2950, log-rank; n = 1072). Using multivariate Cox modelling, we found a significant association between the patient's age, stage of disease and survival, whereas no association with survival was observed for the timing of surgery (RR= 1.062; 95% CI, 0.970-1.163; p = 0.1937). No significant differences in overall survival of breast cancer patients were observed when timing of breast cancer surgery during the lunar cycle was considered. Although this was not a prospective randomized trial, the statistical magnitude of the results do not support any recommendations for scheduling patients for surgery at any particular day of the lunar phase.

Timing of breast cancer surgery in relation to the menstrual cycle: an update of developments

It is well-established that hormones have multiple effects on breast cancer. Some, but not all studies indicate that the phase of the menstrual cycle (and hence hormonal status) at the time of breast surgery may influence survival. In this paper we review the literature in this area, explore how it is possible that such an association may occur, and note that randomised studies which unambiguously determined the phase of the cycle at the time of the operation are lacking. We go on to describe an ongoing self-randomised trial designed to address this problem and present preliminary results which show that only about 75% of the women ovulated during the cycle in which the operation took place, and that the established prognostic factor Ki-67 varied with the phase of the cycle in women who ovulated. It is too early to assess the significance of this finding.

Timing of surgery during the menstrual cycle and prognosis of breast cancer

There are conflicting reports on the differential effect of surgery performed during the two phases of the menstrual cycle, namely, follicular and luteal, and prognosis of operable breast cancer. A statistical meta-analysis of the published evidence suggests a modest survival benefit of 15+/-4% when the operation is performed during the luteal phase. Further research in this area might provide a novel avenue to understand the natural history of breast cancer. A spin off from these studies might be the understanding of the importance of events that occur at the time of surgery in determining long term prognosis.

Survival of premenopausal breast carcinoma patients in relation to menstrual cycle timing of surgery and estrogen receptor/progesterone receptor status of the primary tumor

BACKGROUND

Premenopausal breast carcinoma patients who undergo tumor excision during the follicular phase of their menstrual cycle may have a significantly worse prognosis than those whose tumors are excised in other phases of the menstrual cycle.

METHODS

Outcome was determined in a series of 112 premenopausal women with operable breast carcinoma in relation to the timing of surgery within the menstrual cycle and the estrogen receptor (ER) and progesterone receptor (PR) status of their primary tumors as determined by immunohistochemistry.

RESULTS

Those patients with ER positive tumors who underwent surgery in the early and luteal phase of the cycle had a significantly better survival than women with ER negative tumors (chi-square test = 15.56; P < 0.001). This also was true for PR status (chi-square test = 18.21; P < 0.001). After follicular phase surgery, tumor receptor status had no effect on overall survival. Patients with the best prognosis had ER/PR positive tumors excised on Days 0-2 and 13-32 but even those women with ER or PR negative tumors removed during the luteal phase of their menstrual cycle fared better than patients whose tumors were removed during the follicular phase.

CONCLUSIONS

There was a better survival rate for patients with both ER/PR positive and negative tumors treated during the luteal phase of the menstrual cycle. This could be the result of progesterone acting on the surrounding peritumoral normal tissue, thereby exerting a straitjacket effect and improving cohesion of the primary carcinoma. Unopposed estrogen in the follicular phase of the cycle may enable more tumor emboli to escape and successfully establish micrometastases.

Fluctuation of HER2 expression in breast carcinomas during the menstrual cycle

The hormonal milieu at time of tumor surgery seems to have a significant impact on survival in premenopausal breast cancer patients. Indeed, surgery performed during the follicular phase of the menstrual cycle was suggested to correlate with a poor prognosis. To investigate the relationship between prognosis and menstrual cycle at time of surgery, we analyzed the expression of some markers associated with tumor aggressiveness, such as the hormone receptors, HER2, p53, Bcl2, and cathepsin D in breast carcinomas obtained from 198 premenopausal women who underwent surgery during different phases of the menstrual cycle. HER2 overexpression was found to fluctuate in hormone receptor-positive tumors. In actual fact, 20% of the tumors removed during the follicular phase scored HER2-positive, versus 8% of those removed during the luteal phase. Similarly, a number of hormone receptor-positive tumor specimens, obtained from the same patients during follicular and luteal phases, were scored HER2-positive when the sample was removed during the follicular phase and HER2-negative when removed in the luteal phase. Southern blot analysis of the HER2 gene indicated that, in hormone receptor-positive cases, the overexpression of HER2 is often not associated with gene amplification. The finding that overexpression of the HER2 gene, associated with tumor aggressiveness, can fluctuate according to the hormonal milieu may explain the increased survival of patients operated during the luteal phase. It is also relevant to the selection and treatment of patients most likely to benefit from anti-HER2 antibody therapy.

Timing of surgery with regard to the menstrual cycle in women with primary breast cancer

There is sufficient evidence to support both the hormonal influence on the outcome of breast cancer surgery and the SDA hypothesis. The SDA model produces a paradigm shift in the understanding of the natural history of breast cancer. It offers opportunities to try modifying a tumor's biological potential for metastasis (e.g., by tamoxifen, progesterone, antiprotease, or angiostatin) in the neoadjuvant setting. It continues to support the beneficial effects of detection and surgery early in the natural history of disease. It would be worthwhile to plan a trial comparing standard practice (unplanned surgery as the patient enrolls) with surgery during the luteal phase of the menstrual cycle in premenopausal women. Another possibility, based on studies of circulating progesterone, would be to compare primary progesterone treatment (for 4 to 10 days before surgery) with standard practice. Such a trial of primary progesterone is already under way, conducted by the Indian Breast Group. More than 200 patients have enrolled so far. The details of the trial are available from Clinical Research Secretariat, Tata Memorial Centre, Parel, Mumbai, India (e mail: tmho3@bom2.vsnl.in).

International Breast Cancer Study Group trials

The International Breast Cancer Study Group (IBCSG) was established in 1978 as the Ludwig Breast Cancer Study Group. It involved member institutions from Switzerland, Australia, New Zealand, Sweden, Italy, Slovenia, South Africa, Spain, Canada, Hong Kong and at various times from other countries. It has completed seven trials in three generations, and has a further eight trials currently open. Total accrual to December 1997 exceeds 12,000, and more than 9000 of these patients are in active follow-up. Early trials established the pattern of addressing important biological questions and adapting the randomisation to the risk group of the patient. The first two generations of trials demonstrated that combined modality chemoendocrine therapy was superior to endocrine therapy alone or no therapy in node-positive postmenopausal patients; that a single perioperative cycle improved disease-free survival (DFS) in node-negative patients, but was inferior to more prolonged therapy in node-positive patients; and that six conventionally timed cycles of CMF were as effective as seven cycles commenced in the perioperative period. Recently reported trials in node-positive patients showed that three early cycles of CMF chemotherapy added to tamoxifen in postmenopausal patients, while late reintroduction of chemotherapy appeared detrimental, particularly in patients with ER-negative tumors. In premenopausal patients six initial cycles were superior to three, especially in younger patients. Current studies in node-positive patients are addressing the role of a gap between courses of different chemotherapy, and the relative value of the anti-estrogens tamoxifen and toremifene. In node-negative premenopausal patients ovarian suppression with goserelin is being tested either instead of or added to CMF, while the value of initial CMF before tamoxifen is being tested in node-negative postmenopausal patients. For high-risk patients a triple-transplant regimen is being compared with conventional dose therapy. Planning for future trials recognises the need for rapid accrual of large numbers of similar patients, and therefore the need for inter-Group collaboration. The emergence of the Breast International Group as a consortium of European, Australasian and Canadian cooperative Groups is important to the rapid evaluation of new agents and strategies.

Vascular endothelial growth factor in premenopausal women--indicator of the best time for breast cancer surgery?

Timing of surgery in premenopausal patients with breast cancer remains controversial. Angiogenesis is essential for tumour growth and vascular endothelial growth factor (VEGF) is one of the most potent angiogenic cytokines. We aimed to determine whether the study of VEGF in relation to the menstrual cycle could help further the understanding of this issue of surgical intervention. Fourteen premenopausal women were recruited, along with three post-menopausal women, a woman on an oral contraceptive pill and a single male subject. Between eight and 11 samples were taken per person, over one menstrual cycle (over 1 month in the five controls) and analysed for sex hormones and VEGF165. Serum VEGF was significantly lower in the luteal phase and showed a significant negative correlation with progesterone in all 14 premenopausal women. No inter-sample variations of VEGF were noted in the controls. Serum from both phases of the cycle from one subject was added to MCF-7 breast cancer cells; VEGF expression in the supernatant was lower in the cells to which the luteal phase serum was added. The lowering of a potent angiogenic cytokine in the luteal phase suggests a possible decreased potential for micrometastasis establishment in that phase. This fall in VEGF may be an effect of progesterone and should be the focus of future studies.

Menstrual timing of breast cancer surgery

PURPOSE AND DESIGN

This is a critical review of the growing body of data, 32 retrospective studies of the outcomes of 9,665 women published since 1989, relevant to the possibility that the timing of primary breast cancer resection within the menstrual cycle impacts breast cancer recurrence and/or spread and patient survival. This article evaluates and contrasts the adequacy of information and data analysis presented in each publication. The overall purpose of this exercise is to rigorously determine the relative strength of the hypothesis that the menstrual cycle timing of operation impacts outcome and, thereby, to determine whether or not a specific change in the practice of breast surgical oncology can be recommended.

RESULTS

The single most completely reported and thoroughly analyzed series, involving 1,175 young women, indicates that surgical resection timing is likely to be relevant to outcome. Seven additional high-quality studies involving 2,864 women have been most completely reported. While two of these eight find no impact, six (75%) of these studies find that breast cancer outcome is affected by operative timing. Nine of the remaining 24 less-complete studies report a statistically significant effect of operative timing. Among these 15 studies of the fates of more than 5,000 women, the opportune menstrual cycle phase almost invariably includes the putative luteal phase. A large number of retrospective studies of widely varying quality find no outcome difference as a function of resection timing. The adequacy of design of each of four ongoing prospective studies is found lacking.

CONCLUSIONS

Although it is likely that the menstrual cycle phase of operation is relevant to outcome, the nature of the available data cannot allow a clear recommendation of precisely when to operate. It is, therefore, concluded that current retrospective data are inadequate to recommend an immediate change in practice. Prospective studies of this potentially important question are essential. The prospective trials initiated to date will not be able to definitively answer this question because of inadequate chronobiological design. The minimal requirements for adequate prospective study are delineated.