Kaplan-Meier analysis of survival of PMF patients stratified according to their driver mutation and subdivided according to their IPSS risk. Vertical tick marks indicate right-censored patients. (A) “Lower” IPSS risk subgroup, including patients with low or intermediate-1 IPSS risk: CALR-mutant patients had longer survival compared with either JAK2 (V617F)-mutant (P = .011) or triple-negative patients (P < .001). (B) “Higher risk” subgroup, including patients with intermediate-2 or high IPSS risk: CALR-mutant patients had longer survival compared with the remaining genetic subgroups (maximum P value equal to .023).