54 Background: Prognostic understanding research has primarily focused on improvements in the accuracy of patient understanding and factors driving such improvements. However, could patients with a terminal prognosis become more inaccurate in their understanding, and what factors predict such change? Methods: In a multi-site prospective study, 184 advanced cancer patients, whom oncologists expected to die within 6 months, were assessed twice (median time 5 weeks apart). Potential predictors were examined at the first assessment: age, gender, education, marital and insurance status, race, ethnicity, geographical region, cancer type, physical and psychological quality of life, and religious beliefs in end-of-life care. The accuracy of prognostic understanding was measured at both assessments using a 4-item index (understanding of terminal illness status, shortened life-expectancy, disease incurability, and advanced stage). Patients with lower prognostic understanding scores at the second assessment compared to the first assessment were categorized as demonstrating more inaccurate understanding. Results: 18.5% ( n = 34) of patients became more inaccurate in their prognostic understanding. Race ( p < .01), geographic region ( p = 0.03), and religious beliefs ( p < .01) emerged as significant correlates. Specifically, being non-white, being from South-Western/Western United States, and holding stronger religious beliefs were associated with higher likelihood of prognostic understanding becoming more inaccurate. Simultaneously examining these three predictors in a logistic regression model showed likely overlap in their predictive ability, with race ( p = 0.45) and geographic region ( p = .32 & .72, dummy coded) becoming non-significant, and religious beliefs retaining marginal significance ( p = .06). Conclusions: Some patients with a terminal prognosis may become more inaccurate in their prognostic understanding, and this may be more likely among those with stronger religious beliefs. The findings additionally raise the potential role of inaccurate prognostic understanding in contributing to the racial, religious, and regional disparities currently found in end-of-life care.