Multicenter Phase II Trial Addressing Lenalidomide Maintenance in Patients with Relapsed Diffuse Large B-Cell Lymphoma (rDLBCL) Who Are Not Eligible for Autologous Stem Cell Transplantation (ASCT): Efficacy and Safety Results after a Median Follow-up of Five Years

Abstract Background: Lenalidomide (LENA) maintenance is associated with significantly improved outcome in patients (pts) with chemosensitive relapse of DLBCL not eligible for ASCT or experiencing relapse after ASCT. Preliminary results of a multicentre phase II trial (NCT00799513), reported after a median follow-up of 25 months, showed a 1-yr PFS of 70 ± 7% and a 1-yr OS of 81 ± 6%, with good tolerability (Ferreri AJM, et al. Lancet Haematol 2017). However, LENA was ongoing in 41% of pts at time of analysis, and late side effects and events after maintenance completion remained to be defined. Herein, we report efficacy and safety results of the trial after a median follow-up of 56 (range 27-100) months. Methods: HIV-neg pts (age ≥18 ys) with de novo or transformed DLBCL and relapsed disease responsive to conventional rituximab-containing salvage therapy were registered and treated with LENA 25 mg/day for 21 days out of 28, until lymphoma progression or unacceptable toxicity. A protocol amendment in 2015 allowed physicians to interrupt maintenance after a minimum duration of two years. Primary endpoint was 1-year PFS. Simon's two-stage optimal design was used. To demonstrate a 1-yr PFS improvement from 30% (P0) to 50% (P1), 47 pts (one-sided; α 5%; β 80%) were needed. Maintenance would be considered effective if ≥19 pts were progression-free survivors at 1 yr. Cell of origin was assessed by NanoString Technology (n=23) and Hans algorithm (n=39). Results: Between 3/2009 and 12/2015, we recruited 48 pts; 46 of them were assessable (median age 72 ys; range 34-86); 36 pts had de novo DLBCL, 10 had transformed DLBCL. All pts were previously treated with anthracycline- and rituximab-based combination, plus ASCT in 6 pts. Thirty-three pts were enrolled at 1st relapse; salvage therapy contained high doses of cytarabine or ifosfamide in two-thirds of cases, and response was complete in 26 pts and partial in 20. Most pts had unfavourable features: IPI ≥2 in 38 (83%) pts, advanced stage in 35 (76%), extranodal disease in 29 (63%), high LDH level in 21 (46%); 28 (61%) pts were older than 70 ys. Sixteen pts received ≥2 years of LENA (5 received >2 ys), 30 pts interrupted treatment due to progressive disease (PD; n= 17), toxicity (9) or pt refusal (4) (Table). LENA was well tolerated after an average of 18 courses/pt (range 3-82). With the exception of neutropenia, grade-4 toxicities occurred in <1% of courses. Infections were rare, and well controlled with oral antibiotics (grade 1-2 in 9 courses; grade 3 in 3). LENA dose reduction was indicated in 25 pts (transient in 21), and was due to neutropenia (13), rash (7), diarrhoea (3), or neurotoxicity (2). Three (6%) pts died of toxicity during maintenance (intestinal infarction, meningitis and sudden death) and two pts died due to myelodysplastic syndrome (Table). Grade 4-5 toxicity and SAEs were equally distributed according to maintenance duration (Table). At one year from trial registration, 31 pts were still progression free, which was significantly higher than the pre-determined efficacy threshold (n≥19). During the whole observation period, there were 24 events: progressive disease in 21 pts and death of toxicity in 3, with a 1-yr (primary endpoint) and 5-yr PFS of 67 ± 7% and 50 ± 7%, respectively. The duration of response to LENA was longer than response duration after the prior treatment line in 28 (61%) pts, and was twice as long in 21 (46%) of them. Twenty-six pts were disease-free at the last LENA course (Table), 22 of them remain relapse free after a median observation period from maintenance completion of 26 (8-92) months; 3 of the 4 relapses occurred in pts who received <1 yr of LENA (refusal or SAEs). The benefit of LENA was observed both in pts with de novo or transformed DLBCL. According to the Hans' algorithm, the 4-yr PFS was 50 ± 11% for GCB-DLBCL and 42 ± 11% for nonGCB-DLBCL (p= 0.58). Results using the Nanostring technique were consistent with the Hans' algorithm. Overall, 28 (61%) pts are alive, with a 1- and 5-yr OS of 80 ± 6% and 60 ± 8%, respectively. Conclusions: Long-term results of this trial soundly promotes the use of LENA maintenance in pts with chemosensitive relapse of DLBCL not eligible for ASCT or experiencing relapse after ASCT. LENA was well tolerated in this elderly population, without higher toxicity rates in pts treated for ≥2 years, and with enhanced survival figures. These results warrant further investigation of immunomodulatory drugs as maintenance in these high-risk pts. Table. Table. Disclosures Ferreri: Celgene: Research Funding. Zaja:Abbvie: Honoraria; Takeda: Honoraria; Celgene: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Amgen: Honoraria; Janssen: Honoraria; Sandoz: Honoraria. Di Rocco:Janssen: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees. Rusconi:Celgene: Research Funding.