SEER database analysis of incidence, treatment patterns, and mortality of breast cancer during the first year of the COVID-19 pandemic

The COVID-19 pandemic created significant disruptions in the diagnosis and treatment of breast cancer (BC). A population-based study using the SEER database compared incidence of BC, treatment patterns, and mortality during 2020 versus 2018 and 2019. The study included 37,834 patients with ductal carcinoma in situ (DCIS) and 199,594 patients with invasive BC between 2018 en 2020. From 2019 to 2020 the incidence of female DCIS decreased from 36.4 to 31.0 per 100,000 whereas the incidence of female invasive BC decreased for 184.2 tot 166.6 per 100,000. The relative reductions in incidence from 2019 to 2020 were 14.8% for DCIS, 12.1% for stage I, 5.8% for stage II, 2.6% for stage III, and 1.9% for stage IV. Comparing 2020 to 2018-2019 in invasive BC, there were significant changes in treatment patterns, with decreased use of surgery and radiation, and increased use of chemotherapy. The 12-month mortality rates were 4.49%, 4.37%, and 4.57% for 2018, 2019, and 2020, respectively. In the Cox model, there were no significant differences in mortality between patients diagnosed in 2020 versus 2018 and 2019. The authors conclude that during 2020, the incidence of BC decreased significantly and the treatment patterns changed. The impact on BC-specific outcomes requires further follow-up.