The impact of the COVID-19 Pandemic on breast cancer incidence and stage: Results of a retrospective study.

Objective: The study was conducted to determine the impact of the COVID-19 pandemic on the incidence and stage of breast cancer in different age groups.

Methods: This retrospective study analyzed changes in the epidemiological and clinical structure of the cohort of patients treated in the radiotherapy department of the Bydgoszcz Oncology Centre in Poland from 2016 to 2023.

Results: The results of the study showed that in the group of patients under 39 years of age, an increase in the incidence rate was recorded in 2020, and a decrease in 2021 to 2023. A decrease in the incidence rate was also observed in the group of patients aged 40 to 49 years in the period 2021 to 2022 and in the groups 50 to 59, 60 to 69, and >80, from 2020 to 2023. An increase in the incidence rate was recorded in the group of patients aged 70 to 79 years in 2020, 2022, and 2023, and a decrease was observed in 2021. In the group of patients under 40 years of age, the impact of the pandemic on reducing the number of cases of stage I cancer was recorded in 2020, 2022, 2023, stage IIa-in 2020, stage IIIa-from 2020 to 2023, stage IIIb-in 2020. Instead, in 2020, the number of cases of stage IIb and stage IIIc breast cancer increased, and the rate of stage IV cancer detection increased significantly, which remained high throughout the pandemic. In the group of patients over 40 years of age, a decrease in the detection rate of stage I cancer was observed from 2020 to 2023, and stage IIa in 2020. An increase in stage IIIa cancer detection was recorded in 2020, stage IIIb in 2021 to 2023, and a significant increase in stage IV detection from 2020 to 2023.

Conclusion: The results demonstrated that the COVID-19 pandemic has become one of the important factors in the delayed diagnosis of breast cancer.