PS1318 LONG TERM FOLLOW‐UP OF WALDENSTRÖM MACROGLOBULINEMIA PATIENTS PRIMARY TREATED WITH DEXAMETHASONE, RITUXIMAB, AND CYCLOPHOSPHAMIDE: A SINGLE CENTRE EXPERIENCE

Abstract

Background:Waldenström's macroglobulinemia (WM) is a rare indolent B‐cell lymphoproliferative disorder resulting from the accumulation of monoclonal lymphoplasmacytic cells that secret a monoclonal IgM protein. Current guidelines recommend to treat WM patients not based on the concentration of the paraprotein, but on the presence of signs and/or symptoms of disease. Although the rarity of this disease and the paucity of randomized clinical trials, a precise algorithm of therapy is missing and immunochemotherapy is considered a standard of care for WM patients. The Eighth International Workshop on WM considers DRC regimen (dexamethasone, rituximab, and oral cyclophosphamide) a suitable first line treatment because it's safe, manageable and induces a high rate of responses, at least a partial response in 30%>50% of patients.Aims:To date, only two studies describe the use of DRC regimen in previously untreated and in relapsed WD patients (DIMOPOULOS, JCO 2007; PALUDO, BJH 2017). We therefore described 24 previously untreated symptomatic patients with WM who received DRC outside of clinical trials to provide further insights on efficacy, tolerability and safety of this regimen after a long term follow‐up.Methods:24 patients were treated from 2009 to 2018 with DRC (dexamethasone 20 mg intravenously followed by rituximab 375 mg/m2 intravenously on day 1 and cyclophosphamide 100 mg/m2 orally bid on days 1 to 5 for a total dose of 1.000 mg/m2). This regimen was repeated every 21/28 days (depending on frailty of patients) for 6 cycles. Rituximab 375 mg/m2 intravenously was administered for 2 more cycle as consolidation. Several patients had features of advanced disease such as anemia (75%), hypoalbuminemia (30%), and elevated serum beta2‐microglobulin (45%). They were 6 (25%) low, 11 (46%) intermediate and 7 (29%) high risk patients according to International Prognostic Macroglobulinemia Scoring System for Waldenstrom Macroglobulinemia (GERTZ, AJH 2017).Results:Mean age of patients when they started DRC was 69 years old (range 50–85). No grade 3–4 toxicities were seen; 30% of patients presented grade 1–2 haematological toxicity (prevalent leukopenia and thrombocytopenia). No patient experienced febrile neutropenia. Treatment was well tolerated and all patients but one completed the schedulated treatment; one patient died one month after starting therapy due to acute cardiac failure. On an intent‐to‐treat basis, 91.2% of patients achieved a response, including 8.7% very good partial responses, 69.5% partial responses, 13% minimal responses; 4.4% of patients had a stable disease and 4.4% a progressive disease (Figure 1). The median progression‐free survival was 39 months; the overall survival is not reached (Figure 2 and 3).Summary/Conclusion:Our data confirm that DRC regimen is an active, well‐tolerated treatment for symptomatic patients with WM. Long term follow up of patients treated with DRC showed also a good OS.