Diagnosis and treatment of breast cancer in Denmark during the COVID-19 pandemic: a nationwide population-based study

Abstract

Background

The COVID-19 pandemic was a global health crisis with population-wide behavioural restrictions imposed worldwide to reduce transmission of infection and to limit the potential burden on the healthcare systems. We examined whether there was any change in the diagnosis or treatment of breast cancer during the pandemic as compared to previous years.

Material and Methods

The study population comprised all women aged ≥18 years diagnosed with breast cancer in 2015-2021 with data obtained from the clinical quality registry of the Danish Breast Cancer Cooperative Group (DBCG). Data on socioeconomic factors were retrieved from Statistics Denmark. Prevalence ratios (PR) with 95% confidence intervals (CI) were estimated from a generalised linear model (GLM) with a log link for the Poisson family with robust standard errors (SE) of each outcome, using the COVID-19 pandemic period in Denmark as the exposure of interest.

Results

In total, 30,598 breast cancers were diagnosed during the study period. There was a small decrease (4.5%) in the total number of breast cancer cases in 2020 compared with previous years. During the pandemic, a lower proportion of the patients diagnosed with breast cancer had a short educational level (28.5 vs. 26.9%; PR = 0.91; 95% CI: 0.88–0.95), a low income (20.5 vs. 19.0%; PR = 0.90; 0.85-0.95) and fewer than expected in the age group 60-69 years (27.8 vs. 25.3; PR = 0.90; 0.86-0.94) were diagnosed, as compared with the pre-pandemic period. No difference in type of surgery or tumour size was observed. A higher proportion of patients received neo-adjuvant chemotherapy (49.0 vs 55.0%; PR = 1.15; 1.06–1.24), whereas a lower proportion received adjuvant chemotherapy (93.5 vs 85.6%; PR = 0.92; 0.90–0.93) during the pandemic, compared with the pre-pandemic period.

Conclusions

During the pandemic, a small decrease in the number of breast cancer diagnoses was observed particularly among socially disadvantaged groups. Overall, the quality of breast cancer treatment was maintained.

Keywords:

• Breast cancer
• COVID-19 pandemic
• epidemiology
• socioeconomic factors
• treatment indicators

Acknowledgements

We thank the Danish Clinical Quality Program - National Clinical Registries (RKKP) and the Danish Breast Cancer Cooperative Group (DBCG) for giving permission to use data from the DBCG registry for this project.

Author contribution

EHI, HJ, BO, MBH, HM, PC and TBO designed the study. EHI, TBO and HJ acquired the data; HJ analysed the data. All authors contributed to the interpretation of the data. EHI and TBO drafted the article. All authors revised the article critically for important intellectual content and approved the final version of the article to be published. All authors agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

In order to comply with the Danish regulations on data privacy, the datasets generated and analysed during this project are not publicly available as the data are stored and maintained electronically at Statistics Denmark’s research platform, where it only can be accessed by pre-approved researchers. Data can be accessed for research purposes through application to the Danish Clinical Quality Program - National Clinical Registries (RKKP) and Statistics Denmark.

Additional information

Funding

The study was funded by the Danish Cancer Society Scientific Committee (grant number R321-A17417) and the Danish regions.