Impact of the COVID-19 pandemic on systemic anti-cancer therapy in patients with breast cancer: a systematic review and meta-analysis

Background: The COVID-19 pandemic caused significant disruptions in oncology services worldwide. Breast cancer care depends on timely and coordinated treatment pathways. This review assessed changes in systemic anti-cancer therapy, including chemotherapy, endocrine therapy, targeted therapy, and immunotherapy. Secondary outcomes included treatment delays, short-term mortality, and hospital admissions. Methods: We conducted a systematic review and meta-analysis following PRISMA guidelines. The protocol was registered with PROSPERO (CRD42024542702). We searched PubMed, Scopus, Web of Science, and CINAHL for studies published between March 2020 and August 2024. We included original studies comparing adult breast cancer patients treated before and during the pandemic. Patients of any stage and sex were eligible. We assessed risk of bias and used a random-effects model to present pooled proportions and odds ratios (ORs) with 95% confidence intervals (CIs). Results: Forty-eight studies were included in the review, and 35 in the meta-analysis. Chemotherapy use increased from 35% before the pandemic to 42% during the pandemic. This rise was driven by an increase in neoadjuvant chemotherapy, from 18% to 22%, while adjuvant chemotherapy remained stable. Endocrine therapy increased from 35% to 42%. Neoadjuvant endocrine therapy rose from 2% to 10%, whereas adjuvant endocrine therapy declined from 46% to 43%. Targeted therapy and immunotherapy showed minimal change. The pooled OR for short-term mortality was 0.81 (95% CI: 0.56-1.15). Hospital admission estimates showed wide confidence intervals, reflecting heterogeneity. Conclusion: The pandemic led to notable shifts in systemic treatment patterns, particularly an increase in the use of neoadjuvant strategies. Short-term mortality did not significantly differ between periods. The study findings should be interpreted with caution due to variability in studies. Health systems require robust pharmaceutical policies and resilient triage frameworks to ensure continuity of cancer treatment during future crises.