Pietra, Daniela

Abstract BACKGROUND. In primary myelofibrosis (PMF), survival from time of diagnosis is predicted by the international prognostic scoring system (IPSS), and from time of referral, by the dynamic IPSS (DIPSS) or DIPSS-plus. JAK2/CALR/MPL mutational status and presence and number of other prognostically-relevant mutations (ASXL1, SRSF2, EZH2, IDH1/2) provide IPSS/DIPSS-plus independent prognostic information. The objective in the current study was to revise IPSS, by including mutation-relevant prognostic information. METHODS. The study included 986 PMF patients divided into learning (n=588) and validation (n=398) cohorts. Previously published methods were used to screen for mutations involving JAK2,MPL, CALR, EZH2, ASXL1, IDH1/2 and SRSF2. The clinical variables assessed were those previously identified as being prognostically-relevant by IPSS or DIPSS-plus. The prognostic model (MIPSS) was developed through a stepwise selection process, based on a z-test of the regression coefficients, and its relative quality was measured by means of the Akaike information criterion. RESULTS. In the Italian learning cohort (n=588),median follow-up was 3.6years (95% CI, 0.03-30.8) for alive patients and 196 (33.3%) deaths and 67 leukemic transformations were documented. IPSS risk distribution was low in 26%, intermediate-1 in 30%, intermediate-2 in 24% and high in 20%. Mutational frequencies were approximately 63% for JAK2, 20% CALR, 6% MPL, 7% EZH2, 22% ASXL1, 2.5% IDH1/2 and 9% SRSF2. Constitutional symptoms were recorded in 28.6% of patients, splenomegaly 75% (18% >10cm from LCM) and grade 3 fibrosis 21%. Overall 252 patients were evaluable for karyotype and abnormalities were detected in 35%, including 9.5% unfavorable. Univariate analysis identified the following risk factors for inferior survival: age >60 years, constitutional symptoms, hemoglobin <100g/L, leukocytes >25x109/L, platelets <200x109/L, circulating blasts 1% or greater, splenomegaly >10cm, grade 3 fibrosis, unfavorable karyotype, triple-negativity for JAK2, MPL and CALR (TN), JAK2 or MPL mutation, and mutations in ASXL1, SRSF2, EZH2 or IDH1/2. In multivariable analysis, age >60 years, constitutional symptoms, hemoglobin <100g/L, platelets <200x109/L, TN, JAK2 or MPL mutation, ASXL1 and SRSF2 mutation remained significant; these variables were subsequently assigned the following HR-weighted adverse points: 1.5, 0.5, 0.5, 1.0, 1.5, 0.5, 0.5 and 0.5, respectively. Subsequently, four risk groups with no overlap in the 95% CI of their survival curves were delineated (Figure 1A): low (score 0-0.5); Intermediate-1 (score 1-1.5); Intermediate-2 (score 2-3.5); and high (score 4 or greater). The number of patients in each risk category, median survivals and HR and 95% CI values are included in figure 1A. Akaike information criterion indicated that MIPSS performed better than IPSS in predicting survival (1611.6 vs 1649.0). Leukemia-free survival was also predicted by high (p<0.01) and intermediate 1/2 (p<0.01) risk MIPSS. In the Mayo Clinic validation cohort (n=398), median age 63 years; males 64%,median follow-up for alive patients was 7.5 years and 271 (68%) deaths and 51 (13%) leukemic transformations were documented. DIPSS-plus risk distribution was low in 13%, intermediate-1 18%, intermediate-2 37% and high 32%. Mutational frequencies were approximately 51% for JAK2, 30% CALR, 7.5% MPL, 5% EZH2, 36% ASXL1, 5.6% IDH1/2 and 13% SRSF2. MIPSS performed equally well in this cohort, as illustrated in figure 1B, which includes number of patients in each risk category with their median survival and HR and 95% CI values. Leukemia-free survival in the Mayo cohort was also predicted by high (p<0.01) and intermediate-2 (p=0.04) risk MIPSS. Patients in the Mayo cohort were fully annotated for karyotype, which was MIPSS-independent in its prognostic value for both overall (p<0.01) and leukemia-free (p<0.01) survival. CONCLUSIONS. MIPSS addresses the mutation-relevant prognostic information gap in IPSS and performs equally well in the setting of patients seen at time of diagnosis or referral. Karyotype carries MIPSS-independent prognostic value that is recognized in an alternative GIPSS prognostic model (see accompanying ASH 2014 abstract), which complements MIPSS. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Abstract Background The median survival (OS) of patients with primary myelofibrosis (PMF; 6.5y) is significantly shortened compared to reference population (Cervantes et al, JCO 2012; 30:2981). OS is predicted by the four risk categories of IPSS, Dynamic-IPSS and DIPSS-plus score, nevertheless pts heterogeneity persists within these categories, necessitating improved risk stratification. We recently reported that pts harboring mutations in any one of the prognostically relevant ASXL1, EZH2, IDH1/2 and SRSF2 genes constitute a IPSS-and DIPPS-plus independent Molecular High Risk category (MHR+) characterized by significant reduction of OS and leukemia free survival (LFS) (Vannucchi et al, Leukemia 2013). The aim of this work was to analyze the impact of the number of prognostically relevant mutated genes on OS and LFS in PMF. Patients and methods Two independent cohorts are included, a “test cohort” from Europe, analyzed at diagnosis, and a “validation cohort” from Mayo Clinic, analyzed at any time after diagnosis. Mutation analysis was performed in DNA from whole blood or granulocytes using RTQ-PCR, HRM and direct sequencing; all mutations were confirmed at least twice. The prognostic value of the molecular variables with regard to OS and LFS was analyzed by Cox regression. Test cohort It included 490 pts (median age 61y; males = 301) risk stratified by IPSS into high (n=74, 15%), intermediate-2 (n=93, 19% ), intermediate-1 (n=147, 30%) and low (n=176, 36%). The median follow-up was 3.63y (95% CI, 0.06-28.33); 161 pts died (33.0%), of whom 76 (15.6%) had progressed to acute leukemia after a median of 3.4y (0.04-28.3) from diagnosis. One hundred forty-six pts (29.8%) presented at least one of the four aforementioned mutated genes and were classified as MHR+. The OS of MHR+ pts was significantly reduced compared to patients with no mutations (n=344): 80.7 vs 148.9 mo (HR 2.2, CI95% 1.6-3.03). One hundred twelve (22.8%) pts had 1 mutation and 34 (6.9%) had 2 or more mutations. In univariate analysis presence of 2 or more mutated genes was significantly more detrimental for OS (29.5mo; HR 4.12, IC95% 2.6-6.4) than having 1 mutated gene (84.2mo; HR 1.8, IC95% 1.2-2.5) compared with having no mutations (148.9mo). Multivariate analysis results adjusted for IPSS indicated that having two or more mutations was an independent prognostic factor for OS (HR 2.9, 95% CI 1.8-4.5). Notably, the prognostic relevance of harboring two or more mutations involved both lower (low and intermediate-1; HR 1.87, 95% CI 1.3-2.6) and higher (intermediate-2 and high; HR 1.6, 95% CI 1.2-2.1) categories of IPSS. Also LFS resulted significantly shorter (129mo; HR 3.1, 95%CI 1.9-4.8) in MHR+ pts compared with pts with no adverse mutations (323mo). Having 2 or more mutations correlated with greater reduction of LFS (79.6mo; HR 7.02, CI95% 3.9-12.6) than having one mutation only (133.9mo; HR 2.2, IC95% 1.3-3.7) as compared with no mutations (323.2mo). Multivariate analysis showed that IPSS high risk category (HR 4.5; 95% CI 2.3-8.8) and two or more mutated genes (HR 5.3; 95% CI 2.9-9.8) predicted independently for a significant reduction in LFS. The negative impact on LFS of having 2 or more mutated genes compared to one or no mutations was maintained in the lower (HR 6.4, 95% CI 2.6-15.2) and higher (HR 5.5, 95% CI 2.3-12.8) risk categories. Validation cohort Validation cohort included 262 patients (median age 64 years; males = 167) risk stratified by DIPSS-plus into high (n=89, 34%), intermediate-2 (n=92, 35%), intermediate-1 (n=46, 18%) and low (n=34, 13%). One hundred forty-six pts (56%) displayed none of the four aforementioned mutations, 93 (36%) harbored one mutation whereas 23 (9%) harbored two or more mutations. In univariate analysis, having two or more mutations (HR 3.7; 95% CI 2.2-6.1) was significantly more detrimental for OS than having no mutations, which is more favorable than having one mutation (HR 1.9; 95% CI 1.4-2.7). When adjusted for DIPSS-plus, the presence of two or more mutations retained its significance (HR 2.1; 95% CI 1.3-3.6) and outperformed ASXL1 mutation alone in its prognostic relevance Conclusions Overall, these results show that the number of prognostically relevant mutated genes correlate with OS and LFS in pts with PMF, suggesting that screening for these mutations might help to improve risk stratification. Disclosures: No relevant conflicts of interest to declare.