Multicenter study on the frequency of low bone mineral density in young women with breast cancer and associated factors

Introduction Young women with breast cancer (BC) may experience bone mineral density (BMD) loss secondary to cancer treatment effects on estrogen levels. Studies assessing BMD in BC patients have had a limited representation of young women. This multicenter retrospective study analyzed the frequency of low BMD and associated factors in this age group. Methods Women diagnosed with stage 0-III BC at ≤40 years, treated with chemotherapy and/or endocrine therapy between 2010-2020 at 5 Mexican BC referral centers were eligible. Demographic, clinical and treatment data were collected, as well as bone dual-energy X-ray absorptiometry (DEXA) results. Low BMD was defined as lumbar or femoral neck T-score <-1.0 or Z-score ≤-2.0. Results 1259 patients were included; median age at diagnosis was 36 years (21-40). Overall, 93% received chemotherapy and 65% endocrine therapy (tamoxifen was received at some point by 61%, aromatase inhibitors by 17%, and GnRH agonists/bilateral oophorectomy by 21%). DEXA scans were documented in 254 (20%), of which 163 (64%; 95% Confidence Interval [CI] 58-70%) had a low BMD report. Low BMD was associated with receiving aromatase inhibitors (Odds ratio [OR] 1.92; 95%CI 1.13-3.24), and GnRH agonists/bilateral oophorectomy (OR 2.25; 95%CI 1.21-4.21). Conclusion The suboptimal frequency of BMD monitoring observed displays an alarming disregard for bone health in young patients. Thus, a high proportion of women with low BMD are potentially being missed and precluded from the opportunity to receive timely interventions. Particular focus should be put on BMD monitoring among patients treated with aromatase inhibitors, GnRH agonists or bilateral oophorectomy. Micro Abstract Young breast cancer patients might experience bone mineral density (BMD) loss secondary to estrogen-related treatment effects. Data from 1259 young patients was retrospectively collected at 5 referral centers. BMD was documented in 20%, of which 64% had low BMD, associated with aromatase inhibitors, and GnRH agonists/bilateral oophorectomy. These results highlight the importance of regular BMD monitoring in this young group.