Micrograph showing PMF

ORLANDO, FL—Having a higher grade of bone marrow (BM) fibrosis may confer inferior overall survival (OS) in patients with primary myelofibrosis (PMF), according to a retrospective study.

Investigators found that having a fibrosis grade of 2 or higher at diagnosis was associated with “unique clinical and molecular variables” that suggested a more aggressive disease phenotype.

And the median OS was significantly shorter in patients with higher grades of fibrosis.

However, when the investigators divided patients according to their International Prognostic Scoring System (IPSS) risk group, having a fibrosis grade of 2 or higher was only significantly associated with reduced OS among patients in the low-risk or intermediate-1-risk categories.

Paola Guglielmelli, MD, PhD, of the University of Florence in Italy, presented these findings at the 2015 ASH Annual Meeting (abstract 351*).

Dr Guglielmelli noted that the prognostic significance of BM fibrosis grade in PMF has been debated. So she and her colleagues set out to analyze the prognostic impact of fibrosis in 540 PMF patients from 6 Italian centers belonging to AGIMM (AIRC-Gruppo Italiano Malattie Mieloproliferative).

BM biopsies were obtained at diagnosis and evaluated by local pathologists according to 2008 World Health Organization criteria. The European consensus scoring system was used to grade fibrosis on a scale of MF-0 to MF-3.

Fifty patients were classified as MF-0 (9.3%), 180 were MF-1 (33.3%), 196 were MF-2 (36.3%), and 114 were MF-3 (21.1%).

Patients in the MF-2 and MF-3 groups were significantly more likely to have constitutional symptoms (P<0.0001), splenomegaly ≥10 cm from left costal margin (P<0.0001), a peripheral blast count ≥1% (P<0.0001), a greater risk of anemia (P<0.0001) or thrombocytopenia (P=0.001), and belong to the intermediate-2 or high-risk IPSS categories (P<0.0001).

In addition, patients in the MF-2 and MF-3 groups were significantly more likely to qualify as high-molecular-risk (HMR), which was defined as having at least 1 mutation in ASXL1, EZH2, SRSF2, or IDH1/2 (P<0.0001). The frequency of HMR patients increased progressively according to fibrosis grade: MF-0 (16%), MF-1 (25.6%), MF-2 (33.7%), and MF-3 (44.7%).

Patients with 2 or more HMR mutated genes were preferentially MF-2 or MF-3. None of the MF-0 patients fell into this category, compared to 4.4% for MF-1, 10.2% for MF-2, and 10.5% for MF-3 (P<0.0001).

Survival

The median OS was significantly shorter in patients with higher BM fibrosis grades (P<0.0001). The median OS was 7.2 years in the MF-3 group (hazard ratio [HR]=8.7), 6.7 years in the MF-2 group (HR=7.3), 14.7 years in the MF-1 group (HR=3.9), and not reached in the MF-0 group (reference).

In multivariable analysis, having a BM fibrosis grade of 2 or greater was significantly associated with reduced OS (HR=3.8, P=0.01).

Other variables significantly associated with reduced OS were being in the intermediate-1 (HR=2.9, P<0.0001), intermedicate-2 (HR=10.0, P<0.0001), or high-risk IPSS categories (HR=9.7, P<0.0001); having CALR type 2 mutation (HR=3.4, P=0.010), JAK2/MPL mutation (HR=2.4, P=0.003), or being triple-negative (HR=4.5, P<0.0001); being classified as HMR (HR=2.4, P<0.0001); and having 2 or more HMR mutations (HR=4.3, P=0.009).

Dr Guglielmelli and her colleagues also assessed the impact of BM fibrosis grade according to IPSS risk score.

They found that, for patients in the low/intermediate-1-risk categories, the median OS was not reached in the MF-0 group, was 22.8 years in the MF-1 group (HR=3.9), and was 15.4 years in the MF-2 and -3 groups combined (HR=7.4, P=0.001).

In the intermediate-2/high-risk categories, the median OS was 11 years for the MF-0 group, 3.6 years for the MF-1 group (HR=2.2), and 3.6 years in the MF-2 and -3 groups (HR=2.7, P=0.28).

Dr Guglielmelli therefore concluded that BM fibrosis grade might help refine prognostic stratification for PMF patients in the lower-risk IPSS categories. However, she noted that this study had limitations, and the results should be confirmed with prospective research.

*Data in the abstract differ from the presentation.

BM fibrosis grade may impact OS in PMF