e23049 Background: Delays in breast cancer diagnosis and treatment can decrease early screening benefits. This study investigates the relationship between health insurance type and time from cancer screening to biopsy and biopsy to treatment initiation in members of a national health plan diagnosed with breast cancer. Methods: De-identified administrative records of Medicare, Medicaid and Commercial fully insured (C-FI) members with a claim for breast cancer between January 2020 and December 2022 were retrospectively analyzed. Poisson regression modeling determined duration (days) from screening to biopsy and biopsy to treatment initiation by insurance type group controlling for covariates. Between-group differences in duration were estimated by exponentiating the model estimate and converting to a percentage change, which was then applied to the mean days to event. P< 0.05 was considered significant. Results: 29,731 members (C-FI: 5,256; Medicare: 22,304; Medicaid: 2,171) with a diagnosis of breast cancer were evaluated. Mean duration from screening to biopsy was 21.5 days (95% confidence interval [CI]: 20.9-22.0). Insurance type was associated with time from screening to biopsy. Compared to C-FI members, Medicaid members experienced a longer duration between screening and biopsy by +12.6 days (95% CI: 11.7-13.6; P< 0.0001). Compared to C-FI members, Medicare members received biopsies 3.4 days sooner (95% CI: 3.0-3.8; P< 0.0001). Mean duration from biopsy to treatment was 35.4 days (95% CI: 34.9-35.9) with similar differences by insurance type. Compared to C-Fl members, Medicaid members experienced a longer duration between biopsy and treatment by +7.9 days (95% CI: 6.9-9.0; P< 0.0001). Compared to C-FI, Medicare members received treatment 3.6 days sooner (95% CI: 3.0-4.1; P< 0.0001). Conclusions: Health insurance type appears to impact time from breast cancer screening to biopsy and treatment initiation. Medicaid members may experience longer duration for both time from screening to biopsy and biopsy to treatment. Future studies will explore if these variations translate to clinically meaningful health outcomes and identify opportunities to provide additional support for individuals experiencing breast cancer.