We report the findings on longitudinal body composition changes and overall survival (OS) in young women (≤40 years) with metastatic breast cancer. This research expands on our previous work,1 which explored the relationship between body composition characteristics and OS based on pretreatment CT scans.

Our analysis included 18 women with newly diagnosed stage IV breast cancer, with abdominal CT scans at diagnosis (T1), first disease assessment after initial treatment (T2), and death or last contact (T3). Skeletal muscle index (SMI) and intramuscular adipose tissue-corrected (IMAT-C) measurements were obtained at the third lumbar vertebra level using SliceOmatic Software V.5.0 (Tomovision, Magog, Quebec). Time between scans and the percent changes in body mass index (BMI), IMAT-C and SMI were calculated and normalised to 100 days. OS was defined from cancer diagnosis to death or last contact. Kaplan-Meier methods summarised follow-up time and OS with log-rank tests assessing survival differences. Associations between body composition characteristics and OS were examined using univariate and multivariable Cox proportional hazards regression models. The multivariable models included adjustments for hormone receptor (HR) status, which was chosen a priori as the primary covariate due to the small number of observed events in our sample (online supplemental appendix 1).

[spcare-2024-005328supp001.pdf]

Median age was 34.5 years (range, 25–40). Most were White (n=12, 67%), non-Hispanic or non-Latina (n=14, 78%) and had private insurance (n=11, 61%). Breast cancer subtypes included HER2+ (n=11, 61%), HR+/HER2− (n=5, 28%) and HR−/HER2− (n=2, 11%). 12 (67%) were overweight or obese (defined as BMI of 25–30.0 kg/m2 and ≥30.0 kg/m2, respectively). All received chemotherapy (neoadjuvant n=6, adjuvant n=9 and unspecified n=3), half underwent surgery and most received radiotherapy (n=15, 83%), hormone therapy (n=10, 56%) …