Reproductive Outcomes After Breast Cancer in Women With vs Without Fertility Preservation

IMPORTANCE: The practice of fertility preservation (FP) in women with breast cancer (BC) is spreading, but long-term reproductive outcomes after FP are largely unknown. OBJECTIVE: To investigate the long-term reproductive outcomes in women who did or did not undergo FP at the time of BC diagnosis. DESIGN, SETTING, AND PARTICIPANTS: A Swedish nationwide cohort study was conducted to investigate the long-term reproductive outcomes of women with BC receiving FP at 1 of the regional FP programs from 1994 to 2017 (n = 425). Population comparators with BC but without history of FP (n = 850) were sampled from regional BC registers, matched on age, calendar period of diagnosis, and county. Data on live births, assisted reproductive technology (ART) use, and mortality were retrieved from population-based registers. Data analysis was performed from January to September 2020. EXPOSURES: History of having received FP compared with no history of FP (unexposed). MAIN OUTCOMES AND MEASURES: The primary outcome was hazard ratios (HRs) of live births and ART treatments following BC in women with vs without FP and the cumulative incidence of these events in the presence of the competing risk of death. RESULTS: Women who had undergone FP (n = 425) had lower parity (302 [71.1%] were nulliparous compared with 171 [20.1%] in the unexposed group), were younger (mean [SD] age, 32.1 [4.0] vs 33.3 [3.6] years), more often had estrogen receptor–positive tumors (289 [68.0%] vs 515 [60.6%]), and were more often scheduled for chemotherapy (399 [93.9%] vs 745 [87.7%]). Of 425 women exposed to FP, 97 (22.8%) had at least 1 post-BC live birth (mean follow-up, 4.6 years), compared with 74 of 850 women (8.7%) unexposed to FP (mean follow-up, 4.8 years). Overall, live birth rates after BC were significantly higher among women with FP (adjusted hazard ratio [aHR], 2.3; 95% CI, 1.6-3.3). The 5-year and 10-year cumulative incidence of post-BC live births was 19.4% and 40.7% among FP-exposed women vs 8.6% and 15.8% among comparators, respectively. Rates of ART use were also higher in the FP group (aHR, 4.8; 95% CI, 2.2-10.7). The all-cause mortality rate was lower in women exposed to FP (aHR, 0.4; 95% CI, 0.3-0.7), with 5-year cumulative incidence of death of 5.3% (95% CI, 3.1%-9.0%) vs 11.1% (95% CI, 8.7%-14.1%) for women with vs without FP. CONCLUSIONS AND RELEVANCE: In this cohort study of Swedish women after a BC diagnosis, successful pregnancy after BC was possible both in women with and without FP at the time of diagnosis, but a significantly higher likelihood of post-BC live births and ART treatments was observed in women who underwent FP, without any negative association with all-cause survival. This information is valuable for health care clinicians responsible for oncologic treatment and reproductive counseling of women diagnosed with breast cancer at reproductive age.