Impact of the COVID-19 pandemic on newly-diagnosed breast cancer

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The COVID-19 pandemic resulted in dramatic reductions in use of breast cancer screening and diagnostic services, with screening mammography plunging by up to 99% at the lowest point. Screening and other diagnostic delays have the potential to result in shifts in the population distribution of breast cancer characteristics, resulting in tumors that are larger, higher grade, and more often lymph node positive – all factors associated with increased breast cancer mortality. In observational studies, these effects were more pronounced among Black and premenopausal women, suggesting that pandemic-related changes in the distribution of breast cancer characteristics could worsen existing breast cancer disparities. Despite this emerging evidence, there is little real-world data that quantifies the magnitude of the delay’s effects on the epidemiology of breast cancer. This lack of information inhibits the ability to develop systematic, evidence-based interventions that might reduce excess deaths. Therefore, the objective of this study is to measure the pandemic’s impact on the epidemiology of breast cancer, using data from 3,780 women diagnosed with breast cancer at University of North Carolina (UNC) Medical Center, UNC Rex, and Nash UNC hospitals during the pandemic (March 2020- November 2021), compared to 8,947 breast cancer patients diagnosed at the same hospitals before the pandemic (March 2015-February 2020). The underlying hypothesis is that overall breast cancer incidence declined following the pandemic onset, but that among the breast cancers that were diagnosed tumors with poor prognostic characteristics were over-represented. The hypothesis will be evaluated by pursuing the following specific aims: (1) evaluating pandemic vs. pre-pandemic changes in breast cancer incidence by comparing incidence overall and according to prognostic characteristics (e.g., stage at diagnosis, tumor size, tumor grade, lymph node status, breast cancer subtype); and (2) evaluating pandemic vs. pre-pandemic differences in breast cancer incidence according to indicators of socioeconomic status (e.g., area deprivation index, health insurance status) and patient factors associated with breast cancer survival disparities (age, race/ethnicity). These trends will be evaluated using interrupted time series analysis, a methodologically rigorous approach that allows for the control of pre-pandemic trends while testing for an effect of the intervention. Patient cancer diagnosis and personal information will be obtained from hospital cancer registries, which abstract high-quality, standardized data ~6 months before similar data become publicly available through other sources (e.g., state cancer registry), allowing for the timely identification of changes in breast cancer incidence patterns. Evaluating the pandemic’s impact on the epidemiology of breast cancer will facilitate identification of interventions (e.g., modifications to the diagnostic process, targeting of affected demographic subgroups to decrease loss to follow-up, etc.) to alleviate the impact of pandemic-related delays in care and reduce the number of excess breast cancer deaths attributable to the pandemic.