Body mass index and weight change in relation to triple-negative breast cancer survival

The aim of this study was to evaluate the influence of body mass index (BMI), weight change on triple-negative breast cancer (TNBC) prognosis in a population-based prospective cohort study. The current analysis included 518 participants diagnosed with TNBC in Shanghai Breast Cancer Survival Study. Weight at 1 year prior to cancer diagnosis, at diagnosis, and at 6, 18 and 36 months after cancer diagnosis and height at 6 months after cancer diagnosis were assessed. Disease-free survival (DFS) and overall survival (OS) were evaluated in relation to BMI and weight change using Cox proportional hazard models. Obesity (BMI ≥ 28.0 kg/m²) at 1-year pre-diagnosis was associated with higher risk of total mortality and recurrence/disease-specific mortality, with multivariate hazard ratios (HRs) of 1.79 (95 % CI 1.06–3.03) and 1.83 (95 % CI 1.05–3.21), respectively. The associations between BMI and TNBC prognosis attenuated over time from pre-diagnosis to post-diagnosis. Compared with stable weight (change within 5 %), weight loss ≥5 % at 18- or 36-month post-diagnosis was related with higher risk of total mortality and recurrence/disease-specific mortality. Respective multivariate HRs were 2.08 (95 % CI 1.25–3.46) and 1.42 (95 % CI 0.77–2.63) for OS, and 2.50 (95 % CI 1.45–4.30) and 2.17 (95 % CI 1.14–4.12) for DFS. However, the association of weight loss and OS/DFS attenuated after excluding patients whose weight was measured after recurrence. Weight gain ≥5 % at 18- or 36-month post-diagnosis was associated with a non-significant increased risk of death. The results showed that obesity pre-diagnosis and weight loss post-diagnosis was inversely associated with TNBC prognosis. Emphasis on maintaining stable weight after cancer diagnosis for TNBC patients may be considered.