Validation of previous prognostic models for thrombosis and exploration of modified models in patients with essential thrombocythemia

Objective We examined the prognostic factors to validate previous prognostic models for survival and thrombosis with large-scale data on Japanese patients with essential thrombocythemia (ET). Method We conducted a study in 352 patients with ET to validate previous prognostic models and search for new prognostic factors. Results The International Prognostic Score for essential thrombocythemia (IPSET), the conventional risk classification and the International Prognostic Score for thrombosis in essential thrombocythemia (IPSET-T) were confirmed to be reproducible in Japanese patients. However, no significant difference was observed between the low-risk and intermediate-risk categories according to the revised IPSET-T, which does not allow direct comparison of the four risk groups. We reevaluated the risk using a modified revised IPSET-T, which was derived from the revised IPSET-T by scoring the factors as follows: one point for age > 60 years, two points for past history of thrombosis, two points for JAK2 gene mutation-positive; total points of 0 = very low risk, 1 = low risk, 2 = intermediate risk, 3 and above = high risk, with significantly different thrombosis-free survival. Conclusion The modified revised IPSET-T has been useful for 4-group stratification to predict a population that requires therapeutic intervention, irrespective of the treatment regimens.