Aims: Breast cancer care has been affected by the COVID-19 pandemic. This systematic review aims to describe the observed pandemic-related changes in clinical and health services outcomes for breast screening and diagnosis.
Methods: Seven databases (01/2020-03/2021) were searched to identify studies of breast cancer screening or diagnosis that reported observed outcomes before and related to the pandemic. Findings were presented using a descriptive and narrative approach.
Results: Seventy-four studies were included in this systematic review; all compared periods before and after (or fluctuations during) the pandemic. There was heterogeneity in the reported study design: 24% (18/74) of studies were based on cancer screening programs or cancer/imaging registries, 34% (25/74) were a single institutional study, 42% (31/74) used a healthcare/community-based system/network. No study was assessed as being at low risk of bias. A reduction in screening volumes during the pandemic was found with over half of studies reporting reductions of ≥49%. A majority (66%) of studies reported reductions of ≥25% in the number of breast cancer diagnoses, and there was a higher proportion of symptomatic than screen-detected cancers. The distribution of cancer stage at diagnosis in the pandemic showed lower proportions of early-stage (stage 0-1/I-II, or Tis & T1) and higher proportions of relatively more advanced cases than that in the pre-pandemic period, however population rates were generally not reported.
Discussion and Conclusion: This is the first systematic evidence review of the global impact attributed to the COVID-19 pandemic on breast cancer screening and diagnosis. Our study found consistent evidence of substantial reductions in screening volume, and similarly reductions in the number of diagnosed breast cancers and diagnostic mammography volume during the pandemic, particularly at the peak stage. These three observed patterns of changes attributed to the pandemic were generally consistent across countries/regions and across study settings, highlighting that screening participation, referral in symptomatic cancer diagnosis and other cancer diagnostic pathways have all been affected by the pandemic. Lower proportions of early-stage and higher proportions of relatively more advanced cases were reported in the pandemic compared to the pre-pandemic period. Even though the stage distributions might raise concerns about potentially worse long-term outcomes, these results should be interpreted with the caveat that these are the percentage of cases from the diagnosed breast cancers, and do not reflect population rates. As our systematic review includes studies reporting outcomes for early-mid-phase of the pandemic, high-quality studies examining the long-term impact are needed.