Abstract P5-08-13: Frequency of low bone mineral density in young women with breast cancer and associated factors
Authors: Mesa-Chavez Fernanda , Chavarri-Guerra Yanin , Ruiz-Cruz Sandy , Cabrera-Galeana Paula , del Rio-Martinez Christopher Jesus , Bermudez-Barrientos Carmen Guadalupe , Moreno-Jaime Brizio , Samayoa-Mateos Abigail , Vega-Morales David , Villarreal-Garza Cynthia 
Published: March 2023

Abstract
Background: Young women with breast cancer (YWBC) may experience bone mineral density (BMD) loss due to the effects of cancer treatment on estrogen levels. Studies assessing BMD in breast cancer (BC) patients have had a limited representation of young women. This study aimed to analyze the frequency of low BMD and its associated factors in this specific age group.
Methods: This retrospective, multicenter study included women ≤40 years diagnosed with stage 0-III BC, treated with chemotherapy (CT) and/or endocrine therapy (ET) between 2010-2020, and with no documented bone metastases during follow-up. The protocol was conducted in 5 BC referral centers in Mexico. Demographic, clinical and treatment data were collected, as well as bone dual-energy X-ray absorptiometry (DEXA) results. Low BMD was defined as T-score &lt;-1.0 or Z-score ≤-2.0 at the lumbar spine (L1-L4) or femoral neck.
The frequency of low BMD was analyzed with descriptive statistics. Binary logistic regression using complete case analysis was conducted to calculate odds ratios (OR) and 95% confidence intervals (95%CI) of experiencing low BMD according to demographic, clinical and therapeutic factors.
Results: In total, 716 YWBC met inclusion criteria. Median age at BC diagnosis was 36 years (21-40); 708 (99%) women were premenopausal at diagnosis. Most were married (355; 50%), had higher education (381; 53%), were unemployed (433; 61%), and were non-smokers (552; 77%). Body mass index (BMI) was &lt; 18.5 kg/m2 (underweight) and ≥25.0 kg/m2 (overweight/obese) in 14 (2%) and 392 (58%) cases, respectively. The most common BC subtype was hormone receptor (HR) positive/HER2 negative (371; 52%), followed by triple negative (168; 24%), HR positive/HER2 positive (122; 17%) and HR negative/HER2 positive (55; 8%). Patients were mostly diagnosed with stage II (346; 48%) or III (276; 39%) disease. As for treatment, CT in 667 (93%), ET in 468 (65%), anti-HER2 therapy in 168 (24%), and radiotherapy was administered in 562 (79%) cases.
DEXA scans were documented in 213/716 (30%) patients. In total, 286 DEXA results were available. The time elapsed from the start of the first systemic treatment to the DEXA result was 0-12 months in 42 cases (15%); 13-36 months in 103 (36%); 37-60 months in 72 (25%); and &gt;60 months in 69 (24%). Overall, 133/213 patients (62%; 95%CI 56-69%) had at least one low BMD report after the start of CT or ET. T-scores and Z-scores in each period are detailed in the Table. No fractures were recorded in any case after BC diagnosis. The only variable associated with at least one low BMD result was BMI ≥25.0 kg/m2 (OR, 1.88; 95%CI, 1.04-3.40). The described demographic, clinical and treatment factors were not significantly associated with low BMD.
Conclusion: This study showed a suboptimal frequency of bone DEXA monitoring in YWBC. A considerable proportion of YWBC experienced low BMD after initiation of CT and/or ET; and a significant association was found between obesity/overweight at BC diagnosis and subsequent low BMD. These data reflect the importance of requesting DEXA scans in young patients on a regular basis and promoting the maintenance of an adequate body weight, in line with international recommendations. Further studies evaluating the degree of BMD loss and its determinants would contribute to establish the optimal periodicity to monitor BMD in relation to BC therapy, allow timely offering of interventions to reduce bone morbidity, as well as improve the quality and life and survivorship of this young group of patients.
Table. DEXA T-scores and Z-scores.
Citation Format: Fernanda Mesa-Chavez, Yanin Chavarri-Guerra, Sandy Ruiz-Cruz, Paula Cabrera-Galeana, Christopher Jesus del Rio-Martinez, Carmen Guadalupe Bermudez-Barrientos, Brizio Moreno-Jaime, Abigail Samayoa-Mateos, David Vega-Morales, Cynthia Villarreal-Garza. Frequency of low bone mineral density in young women with breast cancer and associated factors [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-08-13.