Clinical Course and Prognosis in Mast Cell Proliferative Disorders: A 17 Year Experience in a Single Center.

In patients (pts) with mast cell (MC) proliferative disorders, the clinical course, prognosis, and outcome vary depending on age, organ-involvement, and the disease-variant. We have retrospectively analyzed the clinical course and outcome in 56 pts with MC disorders refered to the University of Vienna between 1987 and 2004. Using WHO criteria, pts were found to have cutaneous mastocytosis (CM, n=6), indolent systemic mastocytosis (ISM, n=35), aggressive SM (ASM, n=3), mast cell leukaemia (MCL, n=1), SM with associated clonal hematologic non-MC-lineage disease (SM-AHNMD, n=6), and myelomastocytic leukemia (MML, n=5). These groups differed from each other in serum tryptase levels, hemoglobin, platelet counts, and lactate dehydrogenase (p<0.05). By contrast, no significant differences were found in white blood cells, eosinophils, monocytes, or presence of the c-kit mutation D816V. Most pts with ISM showed a stable clinical course without signs of progression or increase in serum tryptase even when monitored for more than a decade. By contrast, in all pts with ASM, MCL, SM-AHNMD, and MML, the neoplasm progressed after a latency period of several months. The median event-free survival was 3.7 months in pts with ASM/MCL, 22.8 months in SM-AHNMD, and 5.0 months in MML. In CM and ISM, the median survival was not reached. The differences in event-free survival among WHO groups were found to be significant (p<0.05). Apart from high grade WHO categories, adverse prognostic variables concerning survival were i. absence of skin-lesions, ii. high percentage (>5%) of MC in bone marrow smears, and iii. splenomegaly. Polychemotherapy resulted in complete remission in MML, but not in ASM or MCL. Interferon-alpha and 2CdA showed cytoreductive effects in some pts with ASM, but did not work in MCL. For the latter group of pts new therapies need to be developed.