Correlation Between Blast Percentage In Myelofibrosis And Outcomes: A Single-Center Experience.

e18562 Background: Patients with accelerated phase (AP) myelofibrosis (MF; >10% blasts [BL] in bone marrow [BM] or peripheral blood [PB]) have shorter overall survival (OS) than those in the chronic phase (<10% BM/PB BL). However, outcomes of patients with “lower” BM/PB BL (1-9%) are not well described. Methods: Clinical characteristics and OS of 1099 patients with MF who presented to MD Anderson Cancer Center between years 1984 – 2013 were retrospectively evaluated. Kaplan-Meier analysis and Cox regression models were used for calculations and comparisons. Results: PB and BM BL were available for 1038 (94%) patients at presentation. Five percent had AP, 10% had 5-9% BM or PB BL; 45% had < 5% BM BL and 1% (n=282), 2% (n=110), 3% (n=47) or 4% (n=27) PB BL; and 40% had < 5% BM BL and 0% PB BL (normal range). OS was similar among patients with 5-9% BM or 4-9% PB BL and those in AP (P>0.05). OS was also similar among patients with BL in the normal range and those with <5% BM and 1-3% PB BL (p>0.05). By grouping patients with similar OS, we have identified 2 groups with distinctive OS of 54 and 27 months, respectively (Table; p<0.001; HR = 1.81 [95%CI 1.5-2.2]). Five-year leukemia free survival was 65% for those in AP, 76% for ≥ 5-9% BM or ≥ 4-9% PB blasts, and 91% for < 4% BM or ≤ 3% PB BL (P<0.001). Clinical characteristics were similar for patients in the AP and with ≥ 5-9% BM or ≥ 4-9% PB blasts. Both groups had significantly higher leukocytes, lower hemoglobin and platelet levels, and were more likely to be transfusion dependent, have systemic symptoms, and unfavorable karyotype than patients with ≤ 4% BM or ≤ 3% PB blasts. There was no significant difference in age, splenomegaly, BM fibrosis grade, or distribution of JAK2, MPL and CALR mutations among these groups. Conclusions: Patients with ≥ 4% PB or ≥ 5% BM BL have OS that appears to be the same as those with >10% BL, suggesting that these patients may require a more aggressive treatment approach. [Table: see text]