Abstract PO2-10-11: Impact of COVID-19 Pandemic on the Disease Volume, Severity and Clinical Complications at Diagnosis and During First Year of Advanced Breast Cancer: COVID19-ABC Quasi-Experimental Study

Abstract Background: The COVID-19 pandemic affected healthcare systems, tumbling cancer screening programs and increasing fear of infection among medical facilities users. We hypothesized that the pandemic negatively impacted the clinical outcomes of patients (pts) with advanced breast cancer (ABC). The COVID19-ABC study aims to assess the influence of the pandemic on disease volume, severity, and clinical complications at diagnosis and during 1st year of ABC. Methods: Single-center, retrospective, quasi-experimental study with historical control. We included women treated for unresectable/metastatic recurrent or stage IV de novo ABC in a Belgian cancer center. Pts were eligible if ABC was diagnosed between 1/Jun/2020-30/Nov/2021 - pandemic exposure (Exp) cohort - or between 1/Jun/2017-30/Nov/2018 - historical (Hist) cohort. We collected data from medical records for baseline characteristics and study outcomes: proportion of oligometastatic disease (OMD) at ABC diagnosis, and proportion of visceral crisis and disease-related serious clinical events during the 1st month and between 1-12 months after ABC diagnosis. We compared baseline variables between the two cohorts using χ2 test for frequencies and Wilcoxon rank-sum test for continuous variables. We performed a pre-planned subgroup analysis by year of pandemic, immunohistochemistry (IHC) subtype, and recurrent vs de novo ABC. Univariate and multivariate backward stepwise logistic regressions were used to determine the odds ratio (OR) and the 95% confidence interval (CI) of the association of exposure to the pandemic with study outcomes, controlling for confounders. Results: We included 150 pts, 74 in Exp and 76 in Hist cohort. Age and proportion of de novo ABC and triple-negative breast cancer (TNBC) were numerically higher, while comorbidities and Ki67 index were significantly higher among patients in the Exp cohort (Table 1). Pts in the Exp cohort had a significantly higher risk of visceral crisis during the 1st month of ABC (28.4% vs 15.8%; OR 4.24, 95% CI, 1.45-12.39, adjusted for histology grade and recurrent vs de novo), with similar trend between 1-12 months of ABC (19.4% vs 12.7%, OR 1.66, 95% CI, 0.67-4.13). Visceral crisis tended to be more common in patients diagnosed in the 2nd vs 1st year of the pandemic (35.7% vs 26.7%, p=0.50). We observed higher proportions of visceral crisis in the Exp cohort for pts with recurrent ABC (36.5% vs 17.7%, p=0.02), HER2+ (66.7% vs 10.0%, p=0.01), and TNBC (40.0% vs 18.2%, p=0.21) IHC subtypes. The most common indicators of visceral crisis in the Exp cohort were symptomatic brain metastases (33.3%), malignant hypercalcemia (28.6%), and liver metastases with hepatic tests abnormalities (23.8%). OMD at presentation (35.1% vs 36.8%, p=0.83) and disease-related serious clinical events during 1st month (31.1% vs 37.3%, p=0.42) and between 1-12 months (31.9% vs 34.2%, p=0.77) did not differ between cohorts. Conclusion: Our study reports a more clinically severe presentation of ABC during the pandemic compared to historical control. This emerged particularly in recurrences and in more aggressive disease subtypes such as HER2+ and TNBC, suggesting a later diagnosis of ABC during the pandemic. These findings require validation in a larger sample, and longer follow-up is needed to assess survival impact. Table 1. Baseline clinicopathologic characteristics at diagnosis of advanced breast cancer (missing values: 1 for menopausal status, 21 for grade). Citation Format: Diogo Martins-Branco, Véronique Debien, Michel Moreau, Giovanna Pinna, Ottavia Amato, François Cherifi, Guilherme Nader-Marta, Marianne Paesmans, Evandro de Azambuja. Impact of COVID-19 Pandemic on the Disease Volume, Severity and Clinical Complications at Diagnosis and During First Year of Advanced Breast Cancer: COVID19-ABC Quasi-Experimental Study 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 PO2-10-11.