Improved Survival of Calreticulin-Mutated Patients Compared With Janus Kinase 2 in Primary Myelofibrosis: A Meta-Analysis.

Abstract

Next to janus kinase 2 (JAK2) and myeloproliferative leukemia protein, calreticulin (CALR) is a recently discovered mutation present in > 20% of patients diagnosed with primary myelofibrosis (PMF). Six studies published from December 2013 to December 2014 met the inclusion criteria for the present meta-analysis: 2 of an Asian and 4 of a non-Asian population. We assessed the biologic characteristics at diagnosis and investigated overall survival. The analyses were stratified by ethnic origin (Asian vs. non-Asian). A total of 816 patients with the JAK2 mutation and 307 patients with the CALR mutation were included. The patients with the JAK2 mutation were older than those with the CALR mutation, and no statistically significant difference was noted in the gender distribution of the patients with PMF with the JAK2 versus CALR mutation. Patients with JAK2-mutated PMF had a higher white blood cell count, but no statistically significant evidence was found for a difference in the platelet count or hemoglobin level. No difference was found in thrombosis risk or acute leukemic transformation in those 2 populations. Major differences were found between the Asian and non-Asian populations. The difference in characteristics between JAK2 and CALR was larger in the Asian population than in the non-Asian population (P=.007). Also, in the non-Asian population, those with JAK2 mutation had lower platelet counts than the Asians (P=.06). In the non-Asian population, the patients diagnosed with JAK2-positive PMF had worse overall survival than the patients with CALR-positive PMF, with a combined hazard ratio of 2.43 (95% confidence interval, 1.83-3.22). The results of the present meta-analysis have confirmed the role of the CALR mutation in the diagnosis of, and as a prognostic tool for, PMF. Our results suggest that patients with the CALR mutation will have better overall survival than patients with the JAK2 mutation in a non-Asian population.