17 Background: Financial toxicity (FTox) has been associated with worse health-related quality-of-life (HRQoL), compliance, and even survival in cancer patients (pts). Measuring FTox and understanding its predictors are of paramount importance when planning intervention strategies, the value of care, and healthcare policies. We report FTox and its predictors in a large cohort of thyroid cancer pts and survivors. Methods: Pts with thyroid cancer were surveyed in the North American Thyroid Cancer Survivorship Study. FTox was assessed by the previously validated COmprehensive Score for financial Toxicity (COST), as well as by questions related to financial distress (out-of-pocket costs, loss of income and bankruptcy). Data on sociodemographics, income, type of disease, length of diagnosis (LOD), and prior therapies were collected. Predictors of FTox were assessed in multivariate analyses, controlling for potential confounders, such as HRQoL (as measured by the thyroid cancer-specific City of Hope instrument), type of treatment received, and LOD. Results: 591 pts with thyroid cancer within the past 6 years were surveyed in 2 countries: 553 (93.5%) in the United States (U.S.), and 38 (6.5%) in Canada. Most were women (n = 518 pts, 88%). The median LOD was 857 days (range 105-2176 days), and 430 pts (72.8%) had papillary thyroid cancer. There were 61 pts (10.3%) with Stage IV, and 11 (1.9%) were on tyrosine kinase inhibitors. Overall, 234 pts (39.5%) stated that their out-of-pocket costs were higher than previously thought; 207 pts (35%) felt their disease resulted in loss of income; 44 pts (7.4%) were unable to meet their monthly expenses; and 7 pts (1.2%) declared bankruptcy after diagnosis. The median COST value was 24 (range 0-44). In multivariate analyses, the independent predictors of worse FTox were lower income (p < 0.001), female gender (p = 0.01), lower educational level (p = 0.002), healthcare delivery in the U.S., (p = 0.002), and worse HRQoL (p < 0.001). Conclusions: A significant proportion of thyroid cancer pts experience FTox. We identified pts characteristics (gender, education, income), as well as geographical differences (healthcare delivery in the U.S.) as predictors of FTox.