Variation in guideline decision-making: a cross-sectional study of oncology compendium panels.

Introduction: Clinical practice guidelines influence coverage policy, utilization management, and health care spending. In oncology, some function as drug compendia that guide Medicare coverage of off-label therapies, yet little empirical work has examined their governance. Methods: We conducted a cross-sectional descriptive study using publicly available documentation to evaluate responses to 75 standardized external change requests submitted to 26 National Comprehensive Cancer Network disease-site panels concerning pembrolizumab or nivolumab dosing. Requests concerning subcutaneous formulations served as a comparator. We characterized request disposition, review timing, transparency, scope interpretation, and financial conflict-of-interest (FCOI) context. Results: By March 6, 2026, 10 of 75 dosing-related requests (13%) had been adopted, 51 (68%) rejected or determined to be outside panel scope, and 14 (19%) remained pending (median time to decision, 190 days). In contrast, requests concerning US Food and Drug Administration-approved subcutaneous formulations were adopted in 52 of 53 cases (98%) and reviewed substantially more rapidly (median, 11 days). Public documentation incompletely described panel deliberations, voting, participation, and management of FCOIs. Conclusions: Standardized requests revealed operational heterogeneity and limitations in publicly available documentation within a Centers for Medicare & Medicaid Services-recognized compendium, identifying opportunities to strengthen transparency and governance in coverage-relevant decision-making.