Tumour stage and age relate with body composition in breast cancer patients: cohort study

Background: Body composition influences breast cancer (BC) survival and treatment prognosis, but its impact on disease stage remains unclear. This study investigated the association between body composition parameters and BC characteristics. Materials and methods: We conducted an observational study of 833 BC patients. Body mass index (BMI), fat percentage, fat mass index (FMI), fat-free mass index (FFMI), and total body water (TBW) were assessed using the TANITA Bioimpedance Analyser (No. 17060087). Results: Patients with advanced-stage BC were the youngest, while those with intermediate-stage BC were the oldest (p = 0.003). BMI values varied significantly across stages (p = 0.0268), with early-stage patients having the lowest BMI and intermediate-stage patients the highest. Fat percentage also differed (p = 0.0047), following the same pattern, whereas TBW assessment showed an inverse relationship (p = 0.0031). ANOVA analysis did not show a time × stage interaction for any body composition metric. However, over time, early-stage patients tended to lose weight, whereas intermediate- and advanced-stage patients were more likely to gain weight. Age correlated positively with BMI and fat percentage but negatively with TBW. FMI and FFMI also varied by stage (p = 0.0004 and p = 0.0018, respectively). The lowest FFMI values were observed in early-stage patients, the highest FFMI and lowest FMI in advanced-stage patients, and the highest FMI in intermediate-stage patients. Conclusions: Body composition parameters, including BMI, fat percentage, FMI, FFMI, and TBW, differ significantly across breast cancer stages, with patient age also influencing BMI, fat percentage, and TBW.