[Breast cancer in women of childbearing age: Issues surrounding the role of hormones].

Breast cancer affects 5% of women of childbearing age, accounting for 30% of cancer cases in this population. These cancers are often more aggressive with a less favorable prognosis in younger women. Hormonal exposure plays a key role in the development of this cancer, although the specific impact of certain exposures, such as hormonal contraception or ovarian stimulation treatments, remains debated. Studies on the link between hormonal contraception and breast cancer risk present contradictory results. Some suggest a slight increase in risk, particularly after prolonged use, while others find no significant association. Regarding assisted reproductive technology, data show no increased risk of breast cancer after ovarian stimulation. For women with breast cancer, fertility preservation is possible before the implementation of gonadotoxic treatments without significantly impacting the risk of recurrence. Pregnancy after breast cancer, including hormone-dependent cancer, is not associated with a higher risk of recurrence. Lastly, women with BRCA mutations would face an increased risk of reduced ovarian reserve, but fertility preservation, as well as the use of contraception or hormone replacement therapy, can be considered in this high-risk population.