Phase II Study of the Combination of Low-Dose Thalidomide, Prednisone, and Oral Cyclophosphamide (TPC Regimen) in the Treatment of Anemia, Splenomegaly, and Constitutional Symptoms Associated with Myelofibrosis with Myeloid Metaplasia (MMM).

Abstract

BACKGROUND: We have previously reported on the therapeutic value of low-dose thalidomide in combination with prednisone (THAL-PRED) for the treatment of both anemia and thrombocytopenia in MMM (Blood 2003; 101:2534), with response rates of 62% and 75% for each cytopenia respectively. Alkylators have long been shown to have palliative benefit in MMM, however are used judiciously as long-term use could increase likelihood of leukemic transformation. Additionally, oral cyclophosphamide has been shown to synergize with thalidomide and steroids in the treatment of myeloma (Garcia-Sanz et. al. Leukemia 2004; 18:856–863). In the current study, we investigated the value of adding oral cyclophosphamide to THAL-PRED for MMM (TPC).METHODS: Study eligibility criteria included a histologically confirmed diagnosis of MMM and either severe anemia (hemoglobin < 10 g/dL) or symptomatic splenomegaly. Protocol treatment was initiated with 50 mg of oral thalidomide (THAL) daily, oral cyclophosphamide (CTX) 25 mg daily for three months, and a three month prednisone taper starting at 0.5 mg/kg/day for the first month followed by a 50% reduction for the second months and a further 50% reduction for the third and final month of treatment with prednisone. Patients with a demonstrable clinical response after three months were able to remain on thalidomide alone as maintenance. Responses were assessed by the International Working Group for Myelofibrosis Research and Treatment (IWG-MRT) criteria for MMM clinical responses (Tefferi et. al. Blood 2006; epub May 2006).RESULTS: 13 patients were enrolled to the trial (median age 73 years, range, 46–80; 7 males). Six patients (46%) completed the planned three cycles (i.e. 12 weeks) of treatment, the remaining seven patients discontinued treatment early for the following reasons: progression (n=3), patient choice (n=2), other medical problem (n=1) and died on study (n=1). After the initial 3 months of treatment, 3/13 (23%) patients evidenced a response (n = 1) or stable disease (n = 2) and continued on an additional three months of THAL alone. At enrollment, nine patients (69%) were anemic (8 of whom (62%) were red cell transfusion dependent). Ten patients (77%) were at least moderately thrombocytopenic (platelet count < 100 x 109//L). Eight patients (62%) had palpable hepatomegaly/splenomegaly, and five patients (38%) had severe constitutional symptoms (night sweats). According to IWG-MRT criteria for MMM the best responses observed from therapy was a CI (clinical improvement) in 2 individuals (one each for anemia (1/9 patients (11%); and thrombocytopenia (1/10 patients (10%)). No clear responses in organomegaly or constitutional symptoms were observed. The regimen overall was well tolerated with toxicities in excess of grade 2 all being related to myelosuppression (anemia (n=2), neutropenia (n=2), and thrombocytopenia (n=3)).CONCLUSIONS: This phase II study of combination therapy with thalidomide-prednisone-cyclophosphamide in patients with MMM strongly suggests that the addition of the alkylator cyclophosphamide largely negates the clinical benefits of THAL-PRED. This observation supports the potential immunologic mechanism of THAL-PRED benefit in MMM, and cautions against potential combinations of immunological and cytotoxic therapy in this disorder.