11070 Background: Financial conflict of interest (FCOI) among authors of clinical practice guidelines is a potential concern for the independence and integrity of guideline recommendations. The National Comprehensive Cancer Network (NCCN) Guidelines policy stipulates limits on physician-industry FCOI among its panelists (<$50,000 overall and <$20,000 from each individual company, annually). Those in violation will be asked to resign. However, COI policies reliant on physician self-report may be difficult to enforce. The increased transparency of FCOI resulting from Open Payments – and the ensuing attention in 2016 on high levels of FCOI among guideline-writing bodies including the NCCN – may have enabled and motivated increased enforcement of existing FCOI policy. We describe trends in FCOI among NCCN Guidelines panelists and in enforcement when violations occur. Methods: We manually extracted NCCN Guidelines panelist names and terms of service for the 20 most prevalent cancers, 2013-22. We manually linked each physician to their Open Payments records, a federal archive of financial transactions from industry to physicians. For each panelist, we included only the categories of industry payments deemed relevant by the NCCN COI policy: ownership payments and some General Payments categories (eg., speaking fees, consulting) but not others (eg., free meals). We measured payments during each full calendar year of service. If a panelist received payments above NCCN limits (“violation”), we assessed whether their term of service continued for at least 1 additional full calendar year (“retained"), inferring that panelists who were retained had not been asked to resign as stipulated. We assessed whether retention post-violation was less likely after 2016. Results: There were 978 eligible physician-guideline pairs. Mean industry payments increased from $6175 in 2014 to $9169 in 2019, then declined to $6492 in 2021 following the COVID-19 pandemic. There were 143 panelist-years in violation of NCCN FCOI limits. Violations occurred among 99 unique panelists; 32 panelists had multiple observed violations. Across the full study period, panelists with a violation were less likely to be retained versus those without a violation (OR 0.21, 95% CI 0.15-0.31). However, likelihood of post-violation retention was lower after 2016 compared to before. 81% were retained during 2014-15 (versus 89% for those without violation, OR 0.55, 95% CI 0.26-1.31) compared to 47% during 2017-20 (versus 89% without violation, OR 0.10, 95% CI 0.06-0.17). Conclusions: Lower retention among panelists receiving excessive industry payments is consistent with NCCN enforcement of its COI policy. Lower post-violation retention after 2016 is consistent with stricter enforcement following that year. However, even in 2017-20, in 47% of violations, the panelist continued to serve, suggesting that enforcement remains incomplete.