Abstract P3-03-20: Breast cancer stage, molecular subtype and survival in patients with obesity: a Brazilian cohort study

Abstract Background Breast cancer (BC) continues to be highly prevalent and lethal among women worldwide. Obesity is an established risk factor for several types of cancer, including BC, particularly in postmenopausal women. Obesity may also be a prognostic factor for BC in all ages, as it increases the risk of surgery complication, decreases the response to chemotherapy, and increases mortality. This study aimed to evaluate if obesity was related to poor prognosis of patients with BC in Brazil. Methods In this retrospective, single center, cohort study, an electronic database from Pérola Byington Hospital (in São Paulo, SP, Brazil) was used to select patients with BC followed between January 2011 and June 2021. All included women had a confirmed diagnosis of BC and were divided in four groups according to BMI categories, defined by weight (kg)/height2 (m): < 18.5 kg/m2: underweight; 18.5 to < 25 kg/m2: healthy weight; 25 to < 30 kg/m2: overweight; ≥30 kg/m2: obese. This study was approved by the local Institutional Review Board. Outcomes The overall survival (OS) was the primary outcome, evaluated by the comparison of the incidence of death from BC among groups. Progression-free disease survival (PFS) was also measured. Statistic methods The descriptive analysis was expressed as continuous variables in summary measures (mean, median, standard deviation, and quartiles), while categorical variables were expressed in frequencies and percentages. The Kaplan-Meier method was used for survival graphs, the Log-rank method to evaluate the difference between the survival curves, and Cox regression to calculate the hazard ratio (HR) and OR for death. The significance level adopted in the tests was 0.05, two-tailed hypotheses considered, and the confidence intervals (CI) constructed are 95%. R version 4.1.1 software was used to carry out all analyses. Results A total of 10,117 patients were screened, 7,424 were included, and 6,992 were considered for the survival analysis. The mean age was 55.12 ±12.47 years at diagnosis and the mean BMI was 27.97 ±5.55 kg/m2. Patients with obesity corresponded to 30.81% of the study population, and 64.82% of them were ≥ 50 years old (postmenopausal), p < 0.001. For each BMI group, most patients were postmenopausal, p< 0.001; without significant difference among groups, p=0.2133. Considering staging by breast (n=6,872), 42.97% of the underweight group were stage III; 41.90% of the healthy weight, 42.79% of overweight, and 39.38% of obese groups were stage II, p < 0.001 (within-group), and p=0.0944 among groups. Molecular subtype did not differ neither within the group (p=0.068) nor among groups, p=0.1155. A total of 6,992 patients were included in the survival analyses, corresponding to 7,090 breasts. During the 10 years-follow up, 265 patients (3.79 %) died from BC. Figure 2 shows the Kaplan–Meier estimates of OS according to BMI, p=0.12. There was no difference in OS according to menopausal status. According to the multivariate Cox-regression analysis results, none of the variables evaluated significantly impacted the OS of patients with BC. BMI did not significantly impact the results. The variables that significantly impacted the chances of pCR were HER2+ and triple-negative compared with luminal A, staging zero compared with I, recurrence, adjuvant therapy, age, and time between diagnosis and surgery. Conclusion In conclusion, obesity did not impact the survival or progression of BC in this retrospective analyses. This study, despite not demonstrating significance in its primary objective, brings important epidemiological data from the Brazilian population with BC not previously published, with high prevalence of overweight and obesity among Brazilian women with BC and highlights the importance of further studies, especially prospective, addressing obesity and BC. Citation Format: ANDRE MATTAR, Larissa Chrispim, Felipe Cavagna, Luiz Henrique Gebrim. Breast cancer stage, molecular subtype and survival in patients with obesity: a Brazilian cohort study. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-03-20.