Abstract PO2-17-02: Can body mass index be a complete pathological response predictor in breast cancer patients submitted to neoadjuvant chemotherapy? A real-world data trial

Abstract Background: Breast cancer is a prevalent disease, and Its incidence has increased annually worldwide. The prognosis depends on several factors, such as patient characteristics, tumor characteristics and treatment efficacy. In this scenario, neoadjuvant chemotherapy (NAC), previously used only to make surgical approach possible in advanced cases, has been increasingly used in more aggressive initial tumors such as HER 2 positive and triple negative and, in these tumors, the presence of pathological complete response is directly correlated with survival and the disease-free interval. Obesity is very common in Brazil and in the world, and its incidence grows annually. There is a direct relationship between the risk of breast cancer and obesity, especially in postmenopausal women. Justification: Many authors suggest that obese patients are less likely to achieve this pathological complete response (pCR). Real-world data is important to evaluate how patients behave in the real world, only 5% of the patients are enrolled in clinical trials. Most of the clinical trials have strict inclusion and exclusion criteria that ends up selecting a patient that almost doesn't exist in the real world. Objective: To correlate complete pathological response with Body Mass Index (BMI) and, secondarily, to evaluate the relationship between overall and disease-free survival with BMI. Methods: This was a retrospective observational study that has evaluated patients with invasive breast cancer in two Brazilian hospitals. Clinical and pathological characteristics were extracted from the database, being eligible the patients diagnosed with invasive breast cancer, stages I to III, and who underwent neoadjuvant chemotherapy (NAC). Patients were categorized using the World Health Organization (WHO) definition: BMI 18.5 to 25 kg/m2: normal weight; BMI 25 to 30 kg/m2: overweight; BMI ≥30kg/m2: obesity. pCR was defined as the absence of breast and axillary invasive tumor. The t test or chi-square test were used to individually analyze the association of each variable between the groups with and without RPc. Univariate and multivariate analyzes to calculate odds ratios (OR) and 95% confidence intervals (CI) of the independent variables BMI, age, clinical stage, histological type, and subtype of cancer, correlated with pCR. where p value 0.05 was considered statistically significant. Results: 1,779 records were included in the analyses, with a mean age of 50 years at diagnosis and a mean BMI of 28.08 kg/m2. Most patients had stage III cancer (68.1%) at diagnosis and the invasive carcinoma nonspecial type was predominant (95.2%). Immunohistochemistry allowed us to divide the groups into Luminal A like (12.4%), Luminal B like (31.1%), HER2+ like (25.3%) and triple negative like (31.2%). After NAC, 1461 had residual disease and 390 (22.3%) had a pCR. Regarding stages, 2% of the patients were in stage I, 30% in stage II and 68% in stage III. No correlation was found between BMI categories and pCR (p=0.7607). In the multivariate analysis, the results were also not significant for the correlation between the BMI categories after adjusting for age, clinical stage, tumor histology and subtype of breast cancer. We observed, however, that the most aggressive types of cancer were predictors of pathologic complete response. The estimated average overall survival (OS) was 102 months for those of normal weight, 99 months for the overweight ones and 101 months for the obese ones. As for recurrence-free survival, the data were immature. Conclusion: This study with Brazilian real-world data found no correlation between BMI and pCR after NAC and BMI and OS in patients with breast cancer. As an additional finding, most patients were obese or overweight at diagnosis (69%) and public policies should be encouraged to act in this scenario. Trials considering stratification of patients between different regions of the country or specific subtype of cancer can elucidate this finding. Citation Format: Fernanda Grace Bauk Richter, Andre Mattar, Marcelo Antonini, Juliana Real, Luis Henrique Gebrim, Reginaldo Coelho Lopes. Can body mass index be a complete pathological response predictor in breast cancer patients submitted to neoadjuvant chemotherapy? A real-world data 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 PO2-17-02.