Different Treatment Approaches to Blast Phase-Myeloproliferative Neoplasms

CONTEXT:

Transformation to acute myeloid leukemia (AML) occurs in 5-20% of patients with myeloproliferative neoplasms (MPN). Overall survival in blast phase MPN (MPN-BP) is poor, usually in the range of 3 to 6 months, and is not significantly impacted by intensive chemotherapy. Current guidelines favor treatment with a hypomethylating agent (HMA), but survival remains poor, and allogeneic hematopoietic stem cell transplantation (AHSCT) holds the only potential for long term survival.

OBJECTIVE:

To describe the clinical characteristics and overall survival of MPN-BP according to different treatment approaches.

DESIGN:

Single-institution, retrospective analysis of 70 MPN patients that progressed to blast phase, who presented to our institution between 2001 and 2020. Transformation to AML defined as >20% myeloblasts in peripheral blood or bone marrow. We stratified the patients according to initial treatment strategy for AML. Baseline variables were compared between groups. Median overall survival (mOS) was measured from time of AML diagnosis to date of death. Kaplan-Meier plots were created to compare mOS.

RESULTS:

Among 70 MF patients that progressed to AML, initial treatment was: 19 best supportive care (BSC), 25 HMA (20 HMA only and 5 HMA + venetoclax), and 26 intensive chemotherapy (IC) [12 patients received standard "7+3" regimen with daunorubicin/idarubicin and cytarabine, 12 received high-dose cytarabine, cladribine +/- mitoxantrone (CLAG/CLAG-M), and 2 received CPX-351 (Vyxeos)].

Patients receiving IC were younger at time of leukemic transformation than those receiving BSC (median 63.9 years vs 72.9 years; p=0.029) or HMA (median 63.9 years vs. 69.0 years; p=0.026). Additionally, 70% of IC patients had an ECOG performance status of 0 or 1 compared to just 48% of patients receiving either BSC or HMA (p=0.088).

Median OS for the entire cohort (n = 70) was 4.8 months. Compared to patients who received active treatment with HMA or IC, those treated with BSC had shorter survival (0.9 months vs 6.4 months; p=0.001). Median survival between patients treated with HMA and IC was not significantly different (4.5 months vs 9.6 months; p=0.13). Patients treated with IC were more likely to proceed to AHSCT (46% vs 5%; p < 0.001). Between HMA and IC groups, there was no difference in time from MPN-BP diagnosis to treatment (median 0.4 months vs 0.3 months; p=0.644) or total number of lines of treatment for MPN-BP.

Focusing specifically on the role of AHSCT in patients treated with IC, we found that patients who received AHSCT had significantly longer mOS than those patients who did not (18.9 months vs 4.9 months; p=0.002), suggesting the beneficial role of intensive chemotherapy is critically tied to the ability to subsequently undergo AHSCT. Among patients who underwent AHSCT, 1-year and 2-year OS was 51% and 34%, respectively. In contrast, patients not receiving AHSCT had 1-year and 2-year OS of 14% and 2%, respectively.

Independent of age, AHSCT (p=0.008) and receipt of therapy (p=0.017) significantly correlated with longer survival after AML diagnosis. Besides these factors, there were no significant differences in the clinical characteristics between the three groups. Acknowledging the limitations associated with small numbers, we did not note any difference in survival between patients who received HMA vs HMA + venetoclax (p=0.27).

CONCLUSIONS:

In MPN-BP, patients receiving treatment had superior outcomes to those that received BSC. Initial treatment with intensive chemotherapy was associated with non-significant improvement in survival; however, this appears to be critically linked to the receipt of AHSCT. In appropriate patients, intensive chemotherapy may be reasonable in an effort to provide an effective bridge to AHSCT. Still, this study reinforces the poor prognosis associated with MPN-BP and the desperate need for novel therapeutic approaches in this group of patients.

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