Tailoring Oncofertility to Breast Cancer Subtype: A Systematic Review of Fertility Preservation Strategies in Premenopausal Women

Introduction: Breast cancer is the most common malignancy in women of reproductive age, and treatment advances have heightened the importance of fertility preservation (FP) for young patients. Despite heterogeneity across subtypes—hormone receptor-positive (HR+), HER2-positive, triple-negative (TNBC), and BRCA1/2-associated—existing guidelines lack subtype-specific FP guidance. Methods: This systematic review compared FP strategies across subtypes, identified subtype-specific challenges, and proposed pathways toward precision oncofertility care. PubMed, Scopus, and Web of Science were searched following PRISMA guidelines for English-language studies from 2004 to 2024. Results: After screening 1837 records, 19 studies met eligibility criteria (2 RCTs, 17 cohort studies); 11 of 17 non-randomized studies were at low overall risk of bias, and 6 at moderate risk due to confounding. Discussion: COS using letrozole- or tamoxifen-modified protocols was feasible, yielding 8–14 mature oocytes per cycle with reduced estradiol exposure suitable for HR+ disease. Evidence was strongest for HR+ patients; TNBC and HER2+ data were more limited, with some studies noting reduced ovarian reserve. GnRH agonists during chemotherapy reduced ovarian failure rates and improved post-treatment recovery, most consistently in hormone receptor-negative disease. BRCA1/2 carriers showed broadly comparable FP outcomes to non-carriers, though BRCA1-positive patients had modestly reduced oocyte yields in some studies with inconsistent results. Conclusions: Among studies with medium-term follow-up (3–5.5 years), no significant increase in recurrence or mortality attributable to FP was identified; long-term data beyond 5 years remain sparse. Substantial heterogeneity precluded meta-analysis; all synthesis is narrative. Standardized outco reporting and larger prospective subtype-stratified studies are required to establish precision oncofertility recommendations.