Fludarabine Plus Cyclophosphamide and Rituximab In Waldenström's Macroglobulinemia: Results In 55 Patients
Authors: Leblond Véronique , Compain Laetitia , Levy Vincent , Tamburini Jérôme , Delmer Alain , Vargaftig Jacques , Pégourié-Bandelier Brigitte , Mahe Beatrice , Le Guill Steven , Tournilhac Olivier , Brottier-Mancini Elisabeth , Delarue Richard , Buzyn Agnès , Maigre Michel , Gardin Claude , Choquet Sylvain 
Published: October 2019

Abstract
Abstract 1757
Treatment of Waldenström's Macroglobulinemia relies on alkylator agents, nucleoside analogs and/or monoclonal antibody based therapies. We showed previously that combination of fludarabine and cyclophosphamide yields a 78% response rate (RR). We performed a retrospective study in 55 WM patients (pts) treated with RFC regimen in 10 French centers.
The median age was 65 years (range: 34–79), the median IgM level measured by electrophoresis was 27.3 g/L (range: 6.5–64), the median haemoglobin level was 9.7g/dl (range: 3.7–14), the median platelet count was 174 × 109/L (range: 22–500), the median beta 2 microglobulin level was 3.4 mg/l (range: 1.7–9). In all, 40/55 pts had previously been treated with a median of 2 lines of therapy (range: 1–4), including 24 patients with relapsed disease and 16 patients with refractory disease. RFC regimen was given every 4 weeks and consisted in: Rituximab 375 mg/m2 IV Day 1, Fludarabine 40 mg/m2 per os Day 1 to Day 3, Cyclophosphamide 250 mg/m2 per os Day 1 to Day 3. 55 pts received the first cycle of RFC, and 52 received two or more cycles (median of 4 cycles, range 2–6). Main toxicity was hematological. No toxic death was observed.Response was assessed 3 months after the last RFC cycle according to response criteria agreed by the 3rd International Workshop on WM (Kimby, 2006), but delayed responses with improvement of the response occurring more than 3 months after treatment discontinuation were observed in 15 patients. The best response was evaluated in 51 pts (3 early discontinuation treatments, one progressive disease), including 26 partial responses (PR), 5 minor responses (MR), and 2 stable diseases (SD). Of note 18 very good PR/ near RC (VGPR) were observed (> 90% decrease in M-protein) . The overall response rate was 89%. Long lasting cytopenia was observed in 10 patients. In the untreated group one pt in failure had a Burkitt-like lymphoma, the other 14 pts are alive in response. In the previously treated group, 6 pts relapsed, one developed a large B-cell lymphoma. Three ASCT and 4 allogeneic SCT were performed in six patients. With a median follow-up time of 28 months, median time to treatment failure (TTF) was not reached, even in previously treated patients. There was not significant difference in the TTF duration in patients in VGPR compared with those in PR + MR.The median progression free survival time was not reached. Myelodysplastic syndrome/acute myeloid leukemia (MDS/AML) was observed in two heavily treated patients and 3 pts had a secondary solid cancer. In all, 48 pts are alive, 7 patients died (4 from progressive disease, 2 from secondary cancer, and 1 from Burkitt-like transformation).

Conclusion:
RFC combination even in heavily treated patients with poor prognostic factors gives a very high response rate (89%) with 33% of patients achieving at least a very good partial response with acceptable toxicity. The toxicity on the hematopoietic stem cell reservoir is a major concern. This combination could be offered to relapsed/refractory patients. In first line, the choice of this combination must be discuss, increased incidence of MDS/ AML after purine analogs, and impairment of stem cell mobilization having previously been reported by us and others. Because frequent delayed responses, a long follow-up with periodic electrophoresis is needed to assess the best response after RFC.

Disclosures:
Leblond: ROCHE: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; MUNDIPHARMA: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; GENZYME: Membership on an entity's Board of Directors or advisory committees; CELGENE: Membership on an entity's Board of Directors or advisory committees; JANSSEN: Membership on an entity's Board of Directors or advisory committees. Tournilhac:MUNDIPHARMA: Membership on an entity's Board of Directors or advisory committees; GENZYME: Membership on an entity's Board of Directors or advisory committees; CELGENE: Membership on an entity's Board of Directors or advisory committees. Choquet:ROCHE : Consultancy.