Background:

We had previously piloted thalidomide treatment in MMM and showed an approximately 20% response in terms of both anemia and splenomegaly (Elliott et al.

BJH 2002;117:288
). Encouraged by this experience, we undertook the current phase II study to explore the therapeutic activity of the more potent as well as less neurotoxic immunomodulatory drug, lenalidomide (CC-5013).

Methods:

The study group comprised a consecutive series of patients with MMM that fulfilled protocol entry criteria that included hemoglobin level ≤ 10 g/dL, platelet count ≥ 100 x 109/L, and neutrophil count ≥ 1 x 109/L. The treatment program consisted of daily oral lenalidomide (10 mg/day) for 3 consecutive 28-day cycles with a plan to continue with additional 3 cycles in case of response.

Results:

i. Pretreatment patient information

Twenty-seven patients (median age, 66 years; range, 40–78) were accrued between March 5, 2004 and June 15, 2005. Median duration of disease prior to protocol treatment was 30 months (range, 1–245). Previous therapy was documented in all but 2 patients. Twenty patients were RBC transfusion-dependent. Baseline median (range) values for palpable spleen size, leukocyte count, platelet count, CD34 cell count, and serum lactate dehydrogenase (LDH) were 16 cm (0–31), 8.4 x 109/L (1.8–84.4), 299 x 109/L (124–831), 166.1 x 106/L (2.8–5176.4), and 778 U/L (267–1725), respectively. Cytogenetic abnormalities were detected in 13 patients (48%). JAK2 V617F mutation analysis was performed in 21 patients and revealed homozygous, heterozygous, and wild-type alleles in 3, 8, and 10 patients, respectively.

ii. Adverse events

Adverse events (any/grade 3 or 4) with definite, probable, or possible attributions to the drug included fatigue (52%/12%), neutropenia (40%/24%), pruritus (36%/0%), thrombocytopenia (28%/8%), anemia (16%/8%), rash (12%/8%), and respiratory distress with hypoxia (8%/8%). To date, 7 deaths have been reported, all occuring after discontinuation of protocol therapy, and none were directly linked to the drug.

iii. Response

The median post-treatment follow up is now 16 months (range 1–17 months). During this period, 6 patients (22%) have experienced either a major (3 patients normalized their hemoglobin level), minor (2 patients became transfusion-independent), or marginal response in anemia. The median time to response and response duration were 2 and 7 months, respectively. Two of the 3 major responders had a baseline der(1;18)(q10;q10) or del(5)(q13q33) cytogenetic abnormality, the latter one of which displayed a major cytogenetic remission. In the patient with der(1;18)(q10;q10), the hemoglobin level increased to a level of 19.1 g/dL from being transfusion-dependent at the start of lenalidomide therapy. Interestingly, the particular patient was homozygous for the JAK2 V617F mutation. Responses were also recorded for palpable splenomegaly (26%), constitutional symptoms (67%), and serum LDH level (70%). Seven patients normalized their LDH.

Conclusion:

Lenalidomide therapy improved anemia in at least 20% of patients with MMM. Some of the responses were spectacular and appeared to be associated with specific cytogenetic abnormalities. The documentation of a positive drug effect on LDH, constitutional symptoms, and splenomegaly in patients not showing early response in anemia suggests the possibility of an even higher response rate with a longer treatment schedule.

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