The Efficacy of Cladribine (2-CdA) in Advanced Systemic Mastocytosis

Systemic mastocytosis (SM) is a rare clonal disorder with multi-organ involvements and shortened life expectancy. To date, no curative treatment for SM exists. Cladribine (2-CdA) is a purine analogue showing activity against neoplastic mast cells and its use was found to be effective in some patients with SM. Nine patients (six males and three females) with advanced SM at median age of 63 years (range 33-67) who received at least one course of 2-CdA were included in a retrospective analysis. Study patients were classified as having aggressive SM (ASM; n = 7) and SM with an associated hematological neoplasm (SM-AHN; n = 2). The "C" findings were as follows: (1) absolute neutrophil count (ANC) < 1 × 10⁹/l (n = 1) and/or hemoglobin level < 10 g/dl (n = 4) and/or platelet count < 100 × 10⁹/l (n = 4); (2) hepatomegaly with ascites (n = 4); (3) skeletal involvement (n = 2); (4) palpable splenomegaly with hypersplenism (n = 3) and (5) malabsorption with weight loss (n = 5). Treatment consisted of 2-CdA at dose 0.14 mg/kg/day intravenously over a 2-h infusion for 5 consecutive days. Median dose per cycle was 45 mg (range 35-60). Median number of cycles was 6 (range 1-7). Overall response rate (ORR) was 66% (6/9 pts) including three partial responses and three clinical improvements. ORR was 100% and 66% for SM-AHN and ASM, respectively. Median duration of response was 1.98 years (range 0.2-11.2). At the last contact, five patients died, four have little disease activity, but remain treatment- free. 2-CdA seems to be beneficial in some patients with SM, however the response is incomplete.