Impact of chemotherapy dose capping on treatment intensity and survival in early breast cancer patients with high body surface area

This study evaluates treatment intensity, tolerability, and survival outcomes in early breast cancer patients with high body surface area (BSA) receiving capped chemotherapy doses. We retrospectively analyzed 730 patients with early breast cancer who received neoadjuvant or adjuvant chemotherapy with anthracycline/cyclophosphamide and taxane-based regimens at the University Hospital Tübingen between 2014 and 2021. Institutional policy capped dosing at BSA 2.0 m 2 . To identify patients with clinically relevant dose reduction (≥ 5%), we classified those with BSA > 2.1 m 2 as the high-BSA group. We assessed relative dose intensity (RDI), adverse events leading to treatment modifications, and survival outcomes using Kaplan–Meier analyses and Cox proportional hazards regression. Among 730 patients, 61 (8.4%) had BSA > 2.1 m 2 . High-BSA patients received significantly lower median RDI (83.9% vs. 92.6%, p < 0.001). Consistent with reduced dose intensity, treatment tolerability was good: blood and lymphatic system disorders (8.2% vs. 24.5%, p = 0.006) and gastrointestinal disorders (0.0% vs. 11.1%, p = 0.002) occurred less frequently, and fewer patients required subsequent dose reductions (37.7% vs. 58.3%, p = 0.008). Despite this favorable tolerability profile, 5-year overall survival (85.5% vs. 94.3%, p = 0.015) and disease-free survival (74.3% vs. 91.0%, p = 0.008) were inferior in the high-BSA group. This association persisted in multivariate analysis (OS: HR 3.25; DFS: HR 2.17), though obesity-related effects could not be separated due to collinearity. In this cohort with consistent dose capping at BSA 2.0 m 2 , patients with high BSA represent an at-risk population with reduced chemotherapy intensity, inferior survival, but good treatment tolerability. Lower rates of blood and lymphatic system disorders and gastrointestinal disorders and fewer dose reductions suggest these patients may have tolerated full weight-based doses. While the contributions of obesity-related prognostic factors and potential underdosing could not be separated, these findings support ASCO guideline recommendations against routine dose capping in curative settings.