Age and platelet count are IPSS-independent prognostic factors in young patients with primary myelofibrosis and complement IPSS in predicting very long or very short survival

Objectives: The current study was designed to identify International Prognostic Scoring System (IPSS)-independent prognostic factors in young patients with primary myelofibrosis (PMF). The study also examined the overall risk profile of long-term (>15 yr) and short-term (<5 yr) survivors. Methods: Study patients were selected from the Mayo Clinic database for PMF, and study eligibility included age <60 yr, minimum follow-up of 5 yr and availability of IPSS-relevant variables at time of diagnosis. Results: A total of 148 consecutive patients met the above-stipulated criteria. To date, 89 (60%) patients have died; 48 (32%) died within 5 yr of their diagnosis (short-term survivors). Median follow-up of patients who are alive was 9 yr (range 5-28) with a >15-yr survival documented in 16 patients (long-term survivors). Multivariable analysis identified unfavorable IPSS category (intermediate-2/high risk), age >50 yr and platelet count <100 × 10⁹/L as independent predictors of inferior survival (P < 0.01). Median survival in the absence of all three risk factors was approximately 18 yr and was shortened to 7 and 1.6 yr in the presence of 1 or ≥2 risk factors, respectively (P < 0.01). Among long-term survivors, 69% were age ≤50 yr, 100% had favorable IPSS profile and 100% displayed platelet count ≥100 × 10⁹/L; the corresponding figures for short-term survivors were 29%, 50% and 65% (P < 0.01). Conclusions: Age and platelet count are IPSS-independent predictors of survival in young patients with PMF, and they complement the IPSS in identifying patients with very long or very short survival.