Clinical and biological characteristics of breast cancers in post-menopausal women receiving hormone replacement therapy for menopause.

The paradox of an excess breast cancer incidence among current users of hormone replacement therapy (HRT) without excess in breast cancer mortality raises the question of possible differences in the clinical and biological characteristics of cancers in current HRT users compared to non-users. A consecutive series of 129 post-menopausal patients under HRT for at least 6 months, in whom an operable breast cancer was diagnosed from January 1992 to December 1996, were identified retrospectively. In most cases women had received combination HRT (estrogen and progestative) and the mean duration was 60.4 (range: 6-360) months. Breast cancers diagnosed in post-menopausal patients during 1992-1993 at the Institut Curie constituted the reference series. Cancers in patients receiving HRT were smaller: 78% versus 32% T1 and 12 mm in larger diameter versus 29.5 mm. They were also more often diagnosed radiologically (49 versus 33%). A second group of 420 post-menopausal breast cancer patients whose samples had been referred for steroid hormone receptor and flow cytometric analysis in 1992-1996 were used for comparing biological and pathological information. Cancers of patients receiving HRT tended to be more often grade I and rarely grade III in the Scarf Bloom Richardson classification. Percentage of cells in S-phase as measured by flow cytometry was considerably lower in HRT users compared to control (mean 2.4 versus 3.7, median 2.2 versus 2. 6). Lymph node invasion, ploidy, and steroid hormone receptor expression did not differ significantly between the 2 groups. This apparently more favourable phenotype of breast cancers diagnosed in post-menopausal patients receiving HRT compared to unselected non-HRT users was not confirmed when analysis was restricted to breast cancers of less than 25 mm in diameter. If, as expected, the phenotypic information bears out in terms of prognosis, this may contribute to overcome the reticence in prescribing HRT due to the increased risk of breast cancer. However, it is still not clear whether the biologically less aggressive phenotype is related to the hormone treatment or is simply due to early detection.