Background Clinical trials are an important therapeutic option for cancer patients (pts). Although financial burden in cancer treatment is well-documented, the financial burden associated with clinical trials is not well understood, especially for pts with lower income. Methods We conducted a survey regarding economic burden and financial toxicity in cancer pts who had been on Phase I clinical trials for ≥1 month. Financial Toxicity Score (FTS) was assessed using the validated COmprehensive Score for Financial Toxicity (COST) survey (scale 0-44, lower scores indicate worse toxicity). Pts also reported monthly out-of-pocket (OOP) medical and non-medical expenses. We applied multivariable logistic regression to analyze risk of financial toxicity, and unanticipated expenses. Results Early-phase clinical trial pts (N=213, median age = 59y; 59% female; 74% White, 45% w/ annual income ≤$60K; 54% had employer sponsored insurance; 37% had Medicare; 50% lived >300 miles from the clinic; 37% required air travel) had a median FTS of 20, with interquartile range of 12. Median monthly OOP costs for non-medical expenses was $1075, and for medical expenses was $475. Median total monthly OOP costs was $1750. 55% and 64% of pts reported that actual medical and non-medical expenses were higher than expected, respectively. Worse financial toxicity (≤ median FTS) in pts was associated with yearly household income <$60K (OR: 2.7, P=0.008), having medical costs higher than expected (OR: 3.2, P=0.024), participation on ≥1 Phase I clinical trial prior to their current trial (OR: 2.2, P=0.028), and living >100 miles away from the clinical trials hospital (OR: 2.3, P=0.043). 29% of pts received partial/full reimbursement of clinical trial-related travel costs from study sponsor/other/insurance. Racial/ethnic minority (OR: 2.6, P=0.008) and pts who were unemployed or not working outside the home (OR: 2.4, P=0.023) were more likely to report that actual medical costs were much higher than expected. 53% of pts used savings and 19% borrowed money from friends/family or had a personal fundraiser to pay for treatment. Conclusions Among cancer pts participating on clinical trials, economic burden is high, and most of pts’ OOP costs were on non- medical expenses. Financial toxicity is disproportionally higher in pts with lower income and those who travel farther, and unexpected medical costs were more common among minorities. OOP costs can be substantial and are often unexpected for pts. Future work should focus on methods to reduce disparities in clinical trial participation, including the role of reimbursement of trial-related expenses.

Citation Format: Ryan W. Huey, Goldy C. George, Penny Phillips, Revenda White, Filip Janku, Daniel D. Karp, Aung Naing, Sarina Piha-Paul, Vivek Subbiah, Apostolia M. Tsimberidou, Shubham Pant, Timothy A. Yap, Jordi Rodon, Funda Meric-Bernstam, Ya-Chen Tina Shih, David S. Hong. Patient-reported out-of-pocket costs and financial toxicity during early- phase oncology clinical trials [abstract]. In: Proceedings of the AACR Virtual Conference: Thirteenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2020 Oct 2-4. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(12 Suppl):Abstract nr PO-208.