Long-term results of the phase II trial of the oral mTOR inhibitor everolimus (RAD001) in relapsed or refractory Waldenstrom macroglobulinemia.

Abstract

8043 Background: The mammalian target of rapamycin (mTOR) signal pathway controls cell proliferation and survival. The trial's goal was to determine the anti-tumor activity and safety of single-agent everolimus (TORC1 inhibitor) in patients with relapsed/refractory Waldenstrom macroglobulinemia (WM). Methods: Eligible patients had measurable disease (IgM monoclonal protein >1000 mg/dL with >10% marrow involvement or nodal masses >2 cm), a platelet count ≥75,000 x 106/L, a neutrophil count ≥1,000 x 106/L. Patients received everolimus 10 mg PO daily. Tumor response was assessed after cycles 2 and 6 and then every 3 cycles until progression. Results: 60 pts were treated. The median age was 64 years (range, 43-85). The median number of prior therapies was 3 (range, 1-11). All but two patients (97%) had received prior rituximab based therapy and 64% of patients had received prior alkylator based therapies. The overall response rate (complete response CR+ partial response PR+ minimal response MR) was 73% (95% CI: 60-84%), with a PR of 50% and 23% MR. The median time to progression (TTP), progression-free survival (PFS), and overall survival (OS) for the entire study population is 28 months (mos), (95% CI: 18-not reached (NR)), 22 mos (95% CI: 12 0-NR), and 55 mos (95% CI: 55-NR), respectively. The estimated PFS at 12 and 24 months is 62% (95%CI: 51-75%), and 48% (95%CI: 37-63%), respectively. The 30 patients who achieved a PR responded after a median of 2 months (range, 1-26) of treatment. The median duration of response (DR) for these patients has not yet been reached and 19 of these patients remain in response after a median follow up of 31 months (range, 3-54). All but two patients had a decrease in their serum IgM. Grade 3 or higher related toxicities were observed in 67% of patients. The most common were hematological toxicities with cytopenias. Pulmonary toxicity occurred in 5% of patients. Dose reductions due to toxicity occurred in 63% of patients. Conclusions: Everolimus has high single-agent activity with an overall response rate of 73% and manageable toxicity in patients with relapsed WM, and offers a potential new therapeutic strategy for this patient population.