Aims: We investigated whether menstrual cycle dependent variations in prognostic factors are detectable in malignant breast tissue.
Methods: Since 1977 the Danish Breast Cancer Cooperative Group has collected population-based information about primary clinical data, treatment regimens and follow-up status on Danish women with breast cancer. Information about last menstrual periods prior to surgery was obtained from files recorded at the time of admission for primary surgery. Included in this study were 1060 patients self-reported to be regularly menstruating and with a menstrual period within 6 weeks of surgery and who were operated in a single-step procedure. None of the patients were current users of exogenous hormones at the time of surgery. Variations of prognostic factors throughout the menstrual cycle were evaluated.
Results: Overall, no significant correlation between endogenous hormone fluctuations and oestrogen receptor (ER) status and progesterone receptor (PgR) status were found. Furthermore, we observed no cycle-dependent variation for mitotic index, lymph node involvement or tumour size.
Conclusions: The classical prognostic factors in breast cancer did not differ significantly throughout the menstrual cycle in the present study.