Upfront Autologous Stem Cell Transplantation for Newly Diagnosed Elderly Multiple Myeloma (MM) Patients: A Prospective Multicenter Study

Introduction: Previous trials have shown that autologous stem cell transplantation (ASCT) is superior to conventional chemotherapy in terms of remission rate and PFS in younger MM patients. Concerns about toxicity and potential efficacy of ASCT in older MM patients lead most centers to limit ASCT indications to patients aged <65 years. However, at the era of novel induction regimens, and because of better patient selection and supportive care, ASCT may prove to be a valid treatment option even in older MM patients. Therefore, some investigators are questioning the widely used 65 years age limit.

Patients and Methods: We prospectively analyzed the outcomes of 56 consecutive MM patients who had received ASCT between September 2012 and September 2014 in 6 institutions in France (protocol ClinicalTrials.gov Identifier: NCT01671826). Patients were newly diagnosed MM. For induction therapy, all patients received a bortezomib-based induction regimen (VD, VTD, VCD, or VRD, 4 to 6 cycles) according to center's local guidelines. Mobilization was performed with G-CSF or G-CSF+cyclophosphamide and plerixafor whenever needed. High-dose chemotherapy consisted of either 140 mg/m² or 200 mg/m² Melphalan. A short two months consolidation phase post ASCT was allowed (lenalidomide-dexamethasone, VD, VTD, VCD or VRD). No maintenance treatment was given. Response, disease progression and relapse were defined according to the IMWG uniform response criteria. All patients signed an informed consent form according to the EBMT guidelines.

Results: At time of diagnosis, median age was 67 (range, 64-74) years with 23% of patients being >70 years. There were 30 males and 26 females. The immunoglobulin subtype was IgG (n=29), IgA (n=15), light chain (n=10), other (n=2). The Salmon and Durie stage was III in 89% of cases (n=47), and the ISS score was I (n=18; 35%), II (n=19; 37%), III (n=14; 27%). Patients had high risk cytogenetics features (t(4;14) and/or del17p) in 9 cases (16%). 10% of patients had a serum creatinine level >176 micromol/L. None of the patients underwent hemodialysis. The Sorror comorbidity score was 0 (34), 1 (6), 2 (2), 3 (6), 6 (1), unknown (7). The median age at time of ASCT was 68 years, and the median time from diagnosis to ASCT was 5 months. In an intention to treat analysis, out of 56 patients, 6 patients could not proceed to ASCT because of an early infectious death (n=1), serious comorbidity (n=2), disease refractoriness to induction (n=1), and failure to collect an adequate PBSC graft (n=2). A median of 5.31x10⁶/Kg CD34+ cells could be collected. Disease status at time of ASCT was: CR (n=12; 24%), VGPR (n=19; 38%), PR (n=17; 34%), and SD/non-responding (n=2; 4%). The conditioning regimen consisted of 140mg/m² melphalan in 18 cases (36%) and 200mg/m² in 32 patients (64%). Moreover, 4 patients (8%) received a tandem ASCT. The median time for neutrophils and platelets engraftment was 12 days. The day-100 post ASCT non-relapse mortality was 0% and the 2-year NRM was 4.2% (95% CI:[0.3-18.3]). The overall response rate at day 100 was 96% (CR: 34%, VGPR: 47%, PR: 15%, SD/non-responsive: 4%). At 3 months post ASCT, 82% patients were able to receive the planned post ASCT consolidation treatment. After a median follow-up of 12 months, the estimated progression-free (PFS) and overall survival (OS) rates at 2 years were 76% (95%CI: [61.6-94.1]) and 88% (95%CI: [76.7-100]), respectively. The incidences of infectious complications post ASCT, and response rates were comparable between the two melphalan dose levels (p=0.28). However, in the univariate analysis, the 200 mg/m² melphalan conditioning group showed a better OS rate compared to the 140 mg/m² group (1-year OS: 100% vs. 67%; p=0.012).

Conclusion: These prospective multicenter results indicate that ASCT is a safe and effective treatment modality for elderly, but fit MM patients at the era of novel induction agents. Of note, patients above age 70 did not experience a worse prognosis. Thus, age per se should not be used as an exclusion criterion for ASCT. Longer follow-up data will be presented, but these results already set the frame for a randomized comparison to the non-transplant approaches in this patients' subgroup.