Primary myelofibrosis (PMF) is a myeloproliferative neoplasm whose survival at diagnosis is predicted by the International Prognostic Scoring System (IPSS), which is based on the presence of the following five risk factors: age greater than 65 years, presence of constitutional symptoms, hemoglobin level below 10 g/dL, leukocyte count greater than 25 ×109/L, and circulating blast cells 1% or greater (Cervantes et al, Blood 2009). To allow dynamic prognostication at any time during follow up, we further developed the Dynamic International Prognostic Scoring System (DIPSS), based on the same IPSS-factors, but with different score values (one point for each risk factor, two points for acquisition of anemia) and with a distinct score model (low risk, LR, 0 points; intermediate-1 risk, Int-1R, 1–2 points; intermediate-2 risk, Int-2R, 3–4 points; high risk, HR, 5–6 points) (Passamonti et al, Blood 2010). The DIPSS model was also efficient in the prediction of acute myeloid leukemia (AML) evolution (Passamonti et al, Blood 2010) and in the assessment of survival and non-relapse mortality after allogeneic hematopoietic stem cell transplantation (Scott et al, Blood 2012).
The aim of the present study is to update outcome data of PMF patients included in the original series used to generate the DIPSS model and to assess the DIPSS prediction of survival in PMF patients with a longer follow up. The Institutional Review Board approved the study, and the procedures followed were in accordance with the Declaration of Helsinki.
This study was performed on 520 of 525 regularly followed DIPSS-PMF patients, as five patients have been lost to follow up after the original publication.
Updated median follow up was of 4.1 years (range, 0.1–30.1). At the time of analysis 326 (63%) patients died, of whom 194 due to known causes: 69 AML, 16 non-AML disease progression, 21 bleeding, 17 thrombosis, 33 infections, 38 other. Median survival was 6 years (95% CI: 5.1–6.7). DIPSS stratification allowed different survivals in PMF patients even with a longer follow-up (Figure 1). Hence, to assess the time to DIPSS-category progression, we evaluated the median time spent within each risk group. This estimate revealed that the median time spent in each risk category was: 4.9 years in LR (range, 0–26.7), 2.1 years in Int-1R (range, 0–18.7), 1.7 years in Int-2R (range, 0–13.4), and 0.74 years in HR (range, 0–13.7). To investigate the prognostic role of the DIPSS score on survival, we analyzed the score as a categorical time-dependent covariate in a Cox survival regression model: the hazard ratio of shifting category from LR to Int-1R was 5.0 (95% CI: 2.4–10.6; P <0.001), it was 3.6 when shifting from Int-1R to Int-2R (95% CI: 2.6–4.9; P <0.001), and 2.7 (95% CI: 2.0–3.6; P <0.001) from Int-2R to HR.
The updated analysis shows that the DIPSS model continues to predict survival in patients with PMF.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.