Natural History of Rare Tumor Risk Syndromes: A Scoping Review to Inform Cost-Effectiveness Models.

Background: Hereditary cancer syndromes account for approximately 10% of all cancers. Many of these, classified as rare tumor risk syndromes (RTRS), lack comprehensive data on natural history, lifetime cancer risk, and the long-term impact of surveillance. These evidence gaps limit the development of decision-analytic disease progression models and cost-effectiveness analyses needed to support healthcare decision-making. Objective: To map the available evidence on the natural history, cancer risk, and surveillance strategies in selected RTRS to inform disease progression models and future economic evaluations. Methods: A scoping review was conducted on 8 RTRS: Birt-Hogg-Dubé syndrome, familial gastrointestinal stromal tumor, familial melanoma, hereditary diffuse gastric cancer, hereditary leiomyomatosis and renal cell cancer, Li-Fraumeni syndrome, Peutz-Jeghers syndrome, and PTEN hamartoma tumor syndrome. Systematic searches of PubMed, Embase, and relevant gray literature sources were performed between April and June 2026 for studies published since 2010. Results: After screening 16 631 records, 80 studies were included in the review. Findings indicate significant heterogeneity in data availability and surveillance effectiveness. Some RTRS have relatively well-defined surveillance recommendations, whereas others remain poorly characterized. Across studies, cancer incidence was markedly higher and occurred earlier than in the general population, with lifetime cancer risks approaching 100% in certain syndromes. However, only 44% of studies reported follow-up protocols and fewer than 12% compared surveillance with expectant management. Limited data on postdiagnosis survival further complicates economic evaluations of alternative care strategies. Conclusions: The evidence base for RTRS is heterogeneous, particularly regarding longitudinal outcomes and comparative surveillance strategies. These limitations restrict the parameterization of disease progression models and the evaluation of the cost-effectiveness of surveillance strategies, leaving substantial uncertainty about optimal management strategies. Significant evidence gaps remain in the natural history and management of RTRS. This review provides a foundation for future cost-effectiveness analyses by mapping existing evidence and identifying critical knowledge gaps in RTRS care.