Background: The COVID-19 pandemic has disrupted US healthcare delivery and led to delays in life-prolonging therapy for some conditions. Its impact on diagnosis and timely care delivery for patients (pts) with cancer is unknown. We assessed the pandemic’s impact on time from advanced diagnosis to systemic treatment initiation (TTI) for pts with newly diagnosed advanced solid cancers. Methods: We performed a controlled interrupted time series analysis using the nationwide Flatiron Health electronic health record-derived de-identified database, which originated from ̃280 US cancer clinics. The study sample included pts ≥ 18 years diagnosed with advanced solid cancers from Jan 1-Jul 31 in 2019 or in 2020, excluding a 30-day period (Mar 8-Apr 7) encompassing the start of most state stay-at-home orders. We used Cox proportional hazards models to estimate standardized predicted probabilities of TTI within 30 days of advanced diagnosis before (Jan-Mar) and during (Apr-Jul) the pandemic in 2020, compared to historical controls in 2019, adjusted for age, sex, race, insurance, performance status, and cancer type. Interactions by cancer type and race examined heterogeneity of effects. Results: The study included 12,977 pts (median age 69 yrs [IQR 61-77]; 47.4% female; 59.4% non-Hispanic white). At the time of analysis, fewer advanced cancer diagnoses were recorded in 2020 (Jan-Mar 2,409; Apr-Jul 3,027) than in 2019 (Jan-Mar 2,910; Apr-Jul 4,631). Compared to Apr-Jul 2019, pts diagnosed with advanced cancer during the COVID-19 period were more likely to have de novo (vs recurrent) disease (67.3% vs 56.8%). In adjusted models, the COVID-19 period was associated with an increased probability of treatment within 30 days (adjusted difference-in-differences +5.2 percentage points [ppts]). TTI improvements were not observed for pts with advanced breast cancer or Black pts, but effect differences across subgroups were not statistically significant (Table). Conclusions: Among pts diagnosed with advanced cancer, the COVID-19 pandemic was associated with shorter time to systemic therapy initiation. These treatment patterns may reflect the fewer advanced cancer diagnoses and higher proportion of de novo cancers observed during this period. Longer follow-up and data maturity are needed to understand the impact of the pandemic on clinical outcomes.

*p=0.043.