e23103 Background: Disruptions to health care during the COVID-19 pandemic raises the possibility of delays in treatment for individuals diagnosed with cancer. It is critical that we evaluate the association between the COVID-19 pandemic and time-to-first treatment (TTFT) to address public and patient anxiety, inform recovery efforts, and identify strategies to reduce the cancer system’s vulnerability to future disruptions. Objective: To examine the association between the COVID-19 pandemic and time from cancer diagnosis to first treatment in Manitoba, Canada. Methods: A retrospective, population-based, quasi-experimental study that included individuals diagnosed with breast, colon, rectal, hematologic, lung, or prostate cancer between January 2015 and December 2021 was performed. Interrupted time series analyses with competing risk models were used to compare TTFT for those diagnosed before and after the start of the pandemic. Time-to-first treatment was calculated from diagnosis date to first treatment date (i.e., chemotherapy, hormone therapy, immunotherapy, radiotherapy, or surgery). Death without treatment was included as a competing risk. Follow-up time was censored at three months post-diagnosis. Sub-hazard ratios (SHR) and 95% confidence intervals (CI) were reported. Higher SHR indicates earlier treatment. The delta restricted mean time-to-treatment (D_RMTT) at three months was calculated to complement SHR values, where negative times indicate earlier treatment. Since observation is standard of care for low-risk prostate cancer and androgen deprivation therapy was widely used to temporize intermediate and high-risk prostate cancer patients, analyses were restricted to stage IV prostate cancer. Results: Time-to-first treatment was shorter for individuals diagnosed with breast cancer during the COVID-19 pandemic period (SHR: 1.40; 95% CI 1.24-1.57; D_RMTT: -6.6 days). Time-to-first treatment was also shorter for individuals diagnosed with colon cancer from April 2020 to June 2021 (SHR: 1.25; 95% CI 1.09-1.42; D_RMTT: -6.5 days) but not from July 2021 to December 2021 (SHR: 0.96; 95% CI 0.81-1.15; D_RMTT: 1.2 days). All other analyses did not demonstrate a statistically significant change in TTFT: rectal cancer (SHR: 1.00; 95% CI: 0.83-1.21; D_RMTT: 0.0 days), hematological cancers (SHR: 0.87; 95% CI: 0.74-1.01; D_RMTT:3.9 days); lung cancer (SHR: 1.09; 95% CI: 0.97-1.23; D_RMTT: -2.3 days); and stage IV prostate cancer (SHR: 1.15; 95% CI: 0.89-1.49; D_RMTT: -4.1 days). Conclusions: The COVID-19 pandemic has not increased the time from diagnosis date to first treatment date for individuals diagnosed with breast, colon, rectal, hematologic, lung, or stage IV prostate cancer in Manitoba, Canada.