Changes in breast cancer incidence and surgical treatment in Baden-Württemberg (Germany) during the COVID-19 pandemic.

The COVID-19 pandemic affected the diagnostics and treatment of breast cancer. Numerous studies reported an early decline in breast cancer (BC) incidence during the COVID-19 pandemic. Less evidence is available on changes in medical care. Reports from individual patients have provided anecdotal evidence for a shift from breast-conserving surgery to mastectomy to reduce the number of visits to radiation units during the pandemic. This study aimed to explore changes in BC incidence and surgical treatment in the south of Germany. Using data from the Baden-Württemberg Cancer Registry, the age-standardized incidence of BC (ICD-10 C50 and D05) (women) in 2018-2021 was investigated overall and by age and stage using standardized incidence ratios. Among pre-operative stage I/IIA BC patients, differences in the time to surgery and type of surgery were investigated using negative binomial and logistic regression models. The incidence of invasive BC decreased significantly from 170.9 per 100,000 women in 2018/2019 to 159.7 in 2020 and increased to 169.2 in 2021. This decrease resulted from a lower incidence around April 2020 and was also observed for non-invasive BC. In 2021, incidence of invasive BC was still decreased by 8% in women aged 80 + years. Surgical treatment was analyzed in 22,708 BC patients with a pre-operative stage ≤ IIA. The median time to surgery was 33 days in 2018/2019, 32 days in 2020 and 36 days in 2021. The proportion of mastectomies increased from 16.1% in 2018/2019 to 17.1% in 2020 and 17.3% in 2021 (adjusted odds ratio and 95% confidence interval (2021 vs. 2018/2019): 1.13 (1.03-1.24)). The adjusted increase was strongest for patients aged 50-59 years (1.34 (1.09-1.64)) and those with high-grade tumors (1.27 (1.07-1.51)). While the early return to pre-pandemic age-standardized BC incidence rates is promising, missed cases have not been caught up until 2021. Furthermore, the decreased incidence in elderly women in 2021 warrants further attention. In early-stage BC, a slightly greater rate of mastectomies was observed, although such a change was not recommended. This result underlines the importance of good communication of adapted treatment guidelines in such exceptional circumstances.