A Prospective Phase II Trial of Lenalidomide and Dexamethasone ( LEN-DEX) in POEMS Syndrome

Background. POEMS syndrome is a rare form of B cell dyscrasia combining a proliferation usually of plasma cells, a polyneuropathy, osteocondensing bone lesions and multiple other clinical signs. The pathogenesis is not well understood but VEGF plays a major role. In patients with one or two sclerotic plasmacytoma and no bone marrow involvement, first line therapy should include radiation. For patients with diffuse sclerotic lesions, bone marrow involvement or absence of any bone lesion and for those who have not demonstrated stabilization of their disease 3 to 6 months after completing radiation systemic therapy is indicated, the most effective being high dose chemotherapy with autologous stem cell transplant (ASCT). Radiation of a single lesion is effective in about every other case and is accompanied by a fairly slow improvement of the neurological symptoms, often after initial worsening. ASCT seems to be accompanied by a number of important complications, in particular engraftment syndrome. Outside these 2 treatments there is no consensus therapy. Lenalidomide (LEN), a drug without serious neurological toxicity, has the advantage of being both anti-angiogenic and cytotoxic to malignant plasma cells (Richardson PG, Blood 2002;100(9):3063-7). We have recently reported a series of 20 French patients with POEMS syndrome treated by LEN with a good efficacy. We now report the first 27 patients of a prospective phase II trial using LEN + dexamethasone (LEN-DEX), 2 cycles preceding radiation or high dose treatment trying to obtain a rapid clinical response and to avoid engraftment syndrome or 9 cycles followed by 1 year LENalone in patients who cannot receive radiation or ASCT.

Methods. Newly diagnosed or relapsing patients with POEMS syndrome who needed to be treated were eligible. Patients who can be treated by local radiation or intensive treatment with stem cell support receive two 28 day cycles of LEN 25 mg PO Days 1-21 and DEX 40 mg PO Days 1,8,15,22 before radiation or intensive treatment (Group 1), the other patients receive 9 cycles of the same LEN-DEX (Group 2) and then 12 cycles of continuous low dose LEN (10 mg). LEN dose was tapered to 10 mg for patients with a creatinine clearance between 30 and 50 ml/min and DEX to 20 mg for patients above 75 years of age and for those who were frail patients. Main eligibility criteria included a diagnosis of POEMS syndrome according to criteria by Dispenzieri et al (Am J Hematol 2012;87(8):804-14), an age of 18 or more, a creatinine clearance above 30 ml/min, no prior treatment with or contraindication to LEN and no uncontrolled thrombosis. Serum and plasma VEGF, serum electrophoresis, immunofixation and free light chain measurements were centrally monitored. Neurologic evaluations were performed using the Overall Neuropathy Limitations Scale (ONLS), the Neurological Impairment Scale (NIS) and the 10 meter walk test (10MWT). The primary endpoint was evaluation of the effectiveness of LEN-DEX combination using biological responses (decrease of monoclonal protein and serum VEGF level) and secondary endpoints were clinical and particularly neurological responses.

Results. Twenty-seven patients have been included in 12 centres, median age was 61 (range 32-75), the median follow-up was 6.6 months (range 2-24). Eighteen patients were in group 1, with radiotherapy in 10 patients and ASCT in 8 patients; 9 patients were in group 2. Nineteen patients were in first line and 8 already treated. Only 2 patients experienced grade 3-4 adverse events due to LEN (cytopenia) and 2 patients had allergic rashes, no thrombotic event occurred. No engraftment syndrome was noted in the 5 patients already treated with ASCT. To date, no patient have died. Evolution of VEGF median values in serum and plasma, M-spike and dFLC levels and evolution of neurological measurements are reported in table 1. Neurological improvement was very rapid in some patients, using ONLS and 10MWT 11/18 evaluable patients had a neurological improvement after 2 cycles with an improvement of 1 or more of the ONLS score and/or change of 0.1 m/s or more in the 10MWT. Only one patient who progressed after nine cycles received another therapy.

Conclusion. This is the first prospective trial of LEN-DEX in POEMS syndrome. This combination seems well tolerated in this disease with a good efficacy on VEGF measurements and rapid neurological improvement in the majority of patients. Updated data will be presented at the meeting.

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