The Impact of Assisted Reproduction Technology on Breast Cancer Risk for Women With Infertility: Current Insights and Future Perspectives

Breast cancer is the most frequently diagnosed malignancy among women worldwide. Because assisted reproduction technology (ART) commonly involves controlled ovarian stimulation (COS) and temporary increases in circulating estradiol and progesterone, its possible effect on long-term breast cancer risk remains an important clinical question. This narrative review, supported by a structured literature search of MEDLINE/PubMed, Scopus, and Web of Science from January 2003 to March 2026, summarizes 31 primary observational studies with a cumulative reported sample exceeding 7.1 million participants, with follow-up extending beyond three decades in some cohorts. Most studies found no significant association between ART and breast cancer incidence. Signals of increased risk were reported in selected subgroups, including women undergoing multiple stimulation cycles, women starting treatment at younger or older ages, and some women with prolonged clomiphene citrate (CC) exposure. The review also considers evidence concerning letrozole, postpartum breast cancer risk, tumor subtype, and fertility preservation in women with breast cancer. Overall, the available evidence does not demonstrate a meaningful increase in breast cancer risk attributable to ART itself. However, substantial heterogeneity, the predominance of older treatment protocols, and the lack of long-term incidence data for contemporary letrozole-based treatment limit definitive conclusions. Prospective studies using current ART protocols and long-term, subtype-specific follow-up are needed.