Results
We studied the bone marrow biopsies of 29 patients in total; 14 patients had JAK2-mutated PMF, 5 JAK2-unmutated PMF, and 10 controls with negative bone marrow biopsies. The median age of the whole group was 57 years, with 34% males and 66% females. The main clinical characteristics of the myelofibrosis patients is described in thetable 1. PD-L1 expression and intensity is described intable 2. We have a few examples how the PD-L1 expression and intensity was quantified in the bone marrow biopsies, shown infigures 1-4 .
The average PD-L1 expression score for the JAK2-mutated PMF group was 212.57, the JAK2-unmutated PMF group 187.2, and the control group 121.1. There was a statistically significant difference between the PD-L1 score between the JAK2-mutated PMF group vs the control group (t-value 2.05 and p-value of 0.025) and when we compared the PMF group regardless of the JAK2 status vs the control group (t-value 2.12 and p-value of 0.021). However, there was not a statistically significant difference when we compared the PD-L1 expression between the JAK2 negative vs the control group (t-value 1.02 and p-value 0.162).
Myelofibrosis patients with a PD-L1 score <250 had a median overall survival of 130 months vs PD-L1 score >250 of 64 months (hazard ratio 2.63: 95% CI, 0.82 to 8.4; P=0.09), it was numerically longer but not statistically significant as shown infigure 5 .