Efficacy of Lenalidomide in Patients with Multiple Myeloma Previously Treated by Melphalan-Prednisone and Thalidomide
Authors: Michel Jessica , Revuz Sabine , Tardy Stéphanie , Fouquet Guillemette , Roussel Murielle , Balasanu Oana , Bologna Serge , Bonmati Caroline , Perrot Aurore , Ranta Dana , Feugier Pierre , Attal Michel , Leleu Xavier , Facon Thierry , Hulin Cyrille 
Published: October 2019

Abstract
Abstract 4075

Introduction.
The association of Melphalan-Prednisone and Thalidomide (MPT) is approved as first-line treatment in elderly patients with Multiple Myeloma (MM). This treatment demonstrated significant benefit in terms of overall survival (OS) and Progression Free Survival (PFS) as opposed to MP alone. Lenalidomide (Len), used in combination with Dexamethasone (Len/Dex), is recommended to treat patients with relapsed MM who received a prior therapy. Len is an oral immunomodulator similar to Thalidomide (T). Both these drugs have identical activity but their safety profiles are different. So, in case of successive use of MPT and Len/Dex, it is legitimate to think that the efficacy of Len is affected by the previous use of T, probably because of the resistance to Len developed by relapsed or refractory patients. Therefore, we carried out a retrospective, multicentric study in order to assess the efficacy and safety of Len in patients with relapsed MM previously treated by MPT.

Method.
Our survey included 64 elderly patients with symptomatic MM from three French hematology centers. All the patients showed a relapsed MM treated with first-line treatment of MPT. Len was administered at first or second relapse. The main objective was to assess the efficacy of Len in terms of response rate, OS and PFS. Another objective was to evaluate the tolerance to Len and MPT treatments and to identify the predictive factors of efficacy of Len like the response rate, the duration of remission after MPT treatment and the line number of treatment before using Len.

Results.
The median age of patients at diagnosis was 73.5 years old and the sex ratio was 1. The M-protein was IgG for 64% of patients, IgA for 20%, light chains for 14% and IgD for 2%. Concerning the International Staging System, 35% of patients were stage I, 28% were stage II and 37% were stage III. MPT was administered with a 100mg/d thalidomide dose to 83% of patients. The median duration of T treatment was 13 months [range: 0.1 – 29.5]. The overall response rate (ORR) was 90% with 53% of partial response (PR), 27.5% of very good partial response (VGPR) and 9.5% of complete response (CR). Five patients stopped T because of progression on therapy, 36 because of toxicity out of which 26 because of peripheral neuropathy and 2 thromboembolic events. The median response duration after MPT was 25.5 months. Len was administered at first relapse to 47 patients (73.5%) and at second relapse for the others (n=17). The second-line treatment for these 17 patients was bortezomib-based regimen treatment. The daily dose of Len was 15 to 25 mg, always associated with low dose of Dex, for 83% of patients. Ten cycles of Len/Dex were administered on average. For 23/64 patients, the Len/Dex treatment is going on, 21/41 patients stopped because of progression and 17/41 because of toxicity (hematologic toxicity: 8/17, thromboembolic events: 2/17, general and gastrointestinal disorder: 7/17). The Len ORR was 78% (CR: 3.5%, VGPR: 27.5%, PR: 47%). The median SSP after initiation of Len is 12.8 months. The median OS after initiation of Len is 43 months and the OS rate is 58% at 3 years. Since the diagnosis, No predictive factor has a significant impact on the efficacy of Len. No second primary malignancies were reported.

Conclusion.
Our study shows that the efficacy and safety of Len is satisfactory, even after a Thalidomide treatment. The ORR and median PFS are similar to published data. There is no increase of toxicity for patients on Len, especially concerning thromboembolic events.
With the development of new drugs like Carfilzomib, Pomalidomide and Eculizumab, the perspective of treatment increased as well as the number of lines. The choice of therapeutic sequences must be taken into account. In this study, we show that the MPT – Len/Dex sequence is effective and safe for elderly MM patients.

Disclosures:
Roussel: celgene: Honoraria; janssen: Honoraria. Attal:celgene: Membership on an entity's Board of Directors or advisory committees; janssen: Membership on an entity's Board of Directors or advisory committees. Leleu:celgene: Honoraria; janssen: Honoraria. Facon:onyx: 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; millenium: Membership on an entity's Board of Directors or advisory committees. Hulin:celgene: Honoraria; janssen: Honoraria.