Percutaneous progesterone use and risk of breast cancer: results from a French cohort study of premenopausal women with benign breast disease

Cyclical mastalgia and breast cancer risk: results of a French cohort study

Cyclical mastalgia is a common complaint, with a potentially important relationship to breast cancer risk. In the last decade, case-control studies have reported that cyclical mastalgia could be considered as an independent risk factor for breast cancer. The subjectivity of a retrospectively collected symptom questioned the validity of this finding. We have examined the association between cyclical mastalgia and breast cancer risk in the French cohort study of women with benign breast disease diagnosed in two breast clinics between 1976 and 1979 and followed-up until 1997. The present study was restricted to the women free of any hormonal treatment (n = 247). The mean follow-up was 16 +/- 5 years, and a total of 22 breast cancers occurred during the follow-up. Using a Cox model with duration of cyclical mastalgia as a time-varying variable, the adjusted relative risk of breast cancer increased with the duration of cyclical mastalgia (P = 0.006). The corresponding relative risk for 37 months of cyclical mastalgia was 5.31 (95% confidence interval, 1.92-14.72). We show here that the conclusion still holds when the symptom cyclical mastalgia was collected prospectively in a cohort study, bringing additional evidence that cyclical mastalgia may represent an independent and useful clinical marker of increased breast cancer risk. It might be a confounding factor when assessing the effects of hormonal treatments on breast cancer risk such as hormonal replacement therapy or oral contraceptives.

New evidence regarding hormone replacement therapies is urgently required

Controversies about the safety of different postmenopausal hormone therapies (HTs) started 30 years ago and reached a peak in 2003 after the publication of the results from the Women Health Initiative (WHI) trial and the Million Women Study (MWS) [Writing group for the women's health initiative investigations. Risks and benefits of estrogen plus progestin in healthy postmenopausal women. JAMA 2002;288:321-33; Million women study collaborators. Breast cancer and hormone-replacement therapy in the million women study. Lancet 2003;362:419-27]. The single HT formulation used in the WHI trial for non hysterectomized women-an association of oral conjugated equine estrogens (CEE-0.625 mg/day) and a synthetic progestin, medroxyprogesterone acetate (MPA-2.5 mg/day)-increases the risks of venous thromboembolism, cardiovascular disease, stroke and breast cancer. The MWS, an observational study, showed an increased breast cancer risk in users of estrogens combined with either medroxyprogesterone acetate (MPA), norethisterone, or norgestrel. It is unclear and questionable to what extent these results might be extrapolated to other HRT regimens, that differ in their doses, compositions and administration routes, and that were not assessed in the WHI trial and the MWS. Significant results were achieved with the publication of the WHI estrogen-only arm study [Anderson GL, Limacher M, Assaf AR, et al. Effects of conjugated equine estrogen in postmenopausal women with hysterectomy: the Women's Health Initiative randomized controlled trial. JAMA 2004;291:1701-1712] in which hormone therapy was reserved to women who had carried out hysterectomy. What emerged from this study will allow us to have some important argument to develop.