Background: High copayments for oral anti-cancer medications (OAMs) can lead to detrimental financial and clinical outcomes for patients. Most patients insured by Medicare and prescribed an OAM reach the catastrophic phase of spending.¹ Financial assistance programs are increasingly used to defray high out of pocket costs, though their ultimate impact on catastrophic spending has not been well-characterized. This study investigated whether receipt of financial assistance reduced likelihood of catastrophic spending for patients prescribed OAMs.Methods: This retrospective, single-institution, cross-sectional study included all patients prescribed an OAM with a >$0 annual copay at an academic integrated Specialty Pharmacy between 1/1-12/31/2021. Data were sourced through a prescribing-level pharmacy database and through a third-party (Vivor/TailorMed) database. A fixed-effects linear regression model was used to identify the impact of financial assistance (binary predictor) on catastrophic spending (binary outcome), defined as spending above $4430/yr based on the average Medicare Part D threshold from 2022 to enter the catastrophic copayments phase. The model was adjusted for demographic and clinical covariates. Results: 1,186 patients were included in the analysis. Average annual copayment on OAMs was $862.50 (SD = $4,673.47) with 5.6% of patients faced catastrophic spending. 37% of patients received some form of financial assistance. Patients who received assistance had significantly lower annual spending on OAMs overall (ß= -$1236; 95% CI: -$1841-658, p<0.001), but assistance was not associated with less catastrophic spending (OR=0.44; 95% CI: 0.14-1.38, p=0.16). Patients who were male, older, retired, insured by Medicare, and had higher annual household income by census tract were more likely to face catastrophic spending. Those who spoke English as a second language and lived in rural settings were less likely to face catastrophic spending. (Table). Conclusions: Financial assistance programs can decrease overall spending on OAMs but may not address financial burden for patients facing catastrophic level spending. Older adults with incomes too high to qualify for safety net or financial assistance programs may be at uniquely increased risk of catastrophic spending. Future studies should evaluate OAM-induced financial toxicity across diverse delivery systems and develop targeted interventions for patients who spend at catastrophic levels.