Abstract PO1-03-02: Impact of Body Mass Index (BMI) on the efficacy of different adjuvant chemotherapy schedules in patients with breast cancer: analysis from the randomized phase III GIM2 trial

Abstract Background: The long-term results of the Italian randomized phase III GIM2 study showed that, in women with node-positive breast cancer (BC), dose-dense (DD) chemotherapy significantly improved both disease-free survival (DFS) and overall survival (OS) compared with standard-interval (SI) chemotherapy. Obesity has been identified as an independent poor prognostic factor in patients with BC, with a potential negative impact on the efficacy and toxicity of systemic therapies. Nevertheless, the specific influence of body mass index (BMI) on the efficacy of different adjuvant chemotherapy schedules (DD or SI) remains a subject of debate. This analysis aimed to investigate this hypothesis in patients enrolled in the GIM2 trial. Methods: GIM2 was a randomized multicentric phase III trial that compared different chemotherapy schedule (DD vs SI) and regimen (FEC-P vs EC-P) in 2091 node-positive early breast cancer patients. BMI (kg/m2) was categorized as follows: 18.5 (underweight), 18.5 to 25 (lean), 25 to 30 (overweight), and ≥ 30 (obese). The primary endpoint was to assess association between BMI and DFS and OS. Survival estimates were compared using the Kaplan-Meier method and log-rank test. Univariate and multivariable Cox proportional hazard models, adjusted for relevant prognostic factors, were used. Results: A total of 1925 patients were included in the present analysis, of whom 31.6% (n=632) were overweight and 19.3% (n=386) obese. Median age was 52 years. Overweight-obesity condition was significantly associated with postmenopausal status, greater representation of T2-T4 tumors with N 2 in both patients in the DD and SI arm. After a median follow-up of 15.0 years (IQR 8.4-16.3), compared to patients with normal BMI, those who were overweight or obese at diagnosis had a higher risk of experiencing a DFS event (Hazard Ratio HR 1.11 95% CI 0.94-1.31 and HR 1.37 95%CI 1.14-1.65, respectively, p=0.003) and OS event (HR 1.11 95% CI 0.89-1.38 and HR 1.59 95%CI 1.26-2.01, respectively, p=0.0003). No significant interaction was found between BMI and treatment schedule in terms of DFS (p for interaction=0.56) nor OS (p for interaction=0.19). At the multivariate analysis, in the DD arm, adjusted HR (aHR) for DFS and for OS were 1.01 (95% CI 0.75- 1.35) and 1.04 (95% CI 0.72-1.52) for obese vs. normal BMI groups, and 0.88 (95% CI 0.68- 1.15) and 0.77 (95%CI 0.54-1.10) for overweight vs. normal BMI groups, respectively. In the SI arm, aHRs for DFS and OS were 1.24 (95% CI 0.94- 1.63) and 1.35 (95%CI 0.96- 1.90) for obese vs. normal BMI groups, and 1.04 (95%CI 0.82- 1.33) and 1.01 (95% CI 0.74-1.40) for overweight vs. normal BMI groups, respectively. Similar results were observed when considering hormone receptor-positive and negative BC separately. Conclusion: In the GIM2 trial, BMI was prognostic but not predictive of different benefit to adjuvant chemotherapy. In high-risk patients, DD schedule should be considered the preferred schedule irrespective of BMI. Citation Format: Francesca Poggio, Eva Blondeaux, Marco Tagliamento, Marta Perachino, Simone Nardin, Benedetta Conte, Sabino De Placido, Mario Giuliano, Valeria Forestieri, Michelino De Laurentiis, Adriano Gravina, Giancarlo Bisagni, Anita Rimanti, Anna Turletti, Cecilia Nisticò, Angela Vaccaro, Francesco Cognetti, Alessandra Fabi, Simona Gasparro, Ornella Garrone, Ylenia Urracci, Maria Grazia Alicicco, Mauro Mansutti, Paola Poletti, Pierpaolo Correale, Claudia Bighin, Fabio Puglisi, Filippo Montemurro, Giuseppe Colantuoni, Luca Boni, Matteo Lambertini, Lucia Del Mastro. Impact of Body Mass Index (BMI) on the efficacy of different adjuvant chemotherapy schedules in patients with breast cancer: analysis from the randomized phase III GIM2 trial abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-03-02.