Estimating incident and prevalent essential thrombocythemia patients eligible for cytoreductive therapies in the US and Canada

Abstract Introduction: Essential thrombocythemia (ET) is a rare type of myeloproliferative neoplasm (MPN) characterized by elevated platelet counts an elevated risk of thromboembolic events, bleeding and potential progression to myelofibrosis or acute myeloid leukemia. The current treatment landscape for ET remains limited, further complicated by historically non-specific ICD-10 diagnosis codes and ET patients incurring 2.3 times higher medical costs compared to matched controls. This study aimed to estimate the incidence and prevalence of ET patients eligible for National Comprehensive Cancer Network (NCCN) guideline-directed treatments within major U.S. health plans and in Canada. Methods: The literature was assessed systematically to gather epidemiological data on ET prevalence and incidence, determine the distribution of patients according to the revised IPSET-thrombosis risk stratification (rIPSET-T), and identify those eligible for NCCN 1.2025-recommended cytoreductive therapies. Membership data for the eight largest U.S. commercial health plans were sourced from earnings reports, annual filings, and 10-K reports. These data were used in Microsoft Excel to develop model inputs and conduct a base-case analysis estimating the size of the clinically treatment-eligible population potentially receiving NCCN-recommended therapies. Results: Sixteen references were identified across systematic literature searches detailing ET epidemiology, rIPSET-T risk distributions, and the use of NCCN-recommended treatments. For the eight health plans analyzed, the average (median) number of covered lives in the U.S. was 38,725,462 (27,847,800). In Canada, prescription drug coverage is limited to 79%, representing 25,557,474 covered lives in 2024. The analysis identified an average of 426 (SD±362) incident ET patients and 16,915 (SD±14,379) prevalent ET patients across U.S. health plans, while Canada had 281 incident and 11,164 prevalent ET patients. Among these, a mean of 192 (SD±109) incident high-risk and 8,797 (SD±7,479) prevalent intermediate- and high-risk rIPSET-T eligible patients were estimated for U.S. health plans, with corresponding figures for Canada being 127 incident high-risk and 5,806 prevalent intermediate- and high-risk patients. Cytoreductive therapy usage was found to be 72.5%, translating to an average of 128 (SD±109) incident and 5,101 (SD±3,690) prevalent patients for U.S. health plans, and 85 incident and 3,366 prevalent patients in Canada. Conclusion: There is significant variability in the estimates of both incident and prevalent ET populations eligible for NCCN-recommended cytoreductive therapies across U.S. commercial health plans and in Canada, which may influence formulary policy decisions.