Combination Therapy with BCNU/Etoposide/Melphalan (BEM) as Conditioning Regimen for Autologous Stem Cell Transplant In Multiple Myeloma.

High-dose chemotherapy and autologous stem cell transplant (ASCT) remains an important therapeutic modality for MM patients. Traditionally high-dose single agent melphalan (200 mg/m²; Mel-200) has been used as the conditioning regimen prior to ASCT for MM. We investigated the combination regimen of BCNU, etoposide and melphalan (BEM) in this setting at our center.

All patients who had undergone ASCT for MM utilizing BEM conditioning regimen at Norris Cancer Center, University of Southern California, Los Angeles were eligible. BEM consisted of BCNU 12 mg/kg (actual body weight or ideal body weight whichever was lower) iv on day -5, etoposide 60 mg/Kg iv on day -3, and melphalan 140 mg/m² iv on day -1, prior to stem cell reinfusion on day 0. Overall survival (OS) was defined as time from MM diagnosis to death, or in patients still alive, the date of last follow-up. Progression-free survival (PFS) was defined as time from ASCT to date of relapse, or in patients without documented relapse, date of death or last follow up, whichever was sooner. Survival for patients with different clinical and disease-specific characteristics was explored using logrank test. Response was assessed according to International Uniform Response Criteria for MM.

A total of 44 MM patients underwent ASCT utilizing the BEM conditioning regimen. Of these, evaluable data was available for 42 patients (25 males; 60%, 17 females; 40%) with a median follow up of 27.6 mths. Median age at diagnosis was 54.5 yr (range 34–68) while median time from MM diagnosis to ASCT was 10.5 mths (range 2.8–47.8). MM subtypes included IgA (n=5, 12%), IgG (n=30, 71%) and light chain-only (n=7, 17%). Median bone marrow (BM) plasmacytosis at diagnosis was 42.5% (range 0%-100%). Durie-Salmon (DS) stages included stage I (12%), II (36%) and III (52%), while 4 patients (10%) had renal dysfunction at the time of initial MM diagnosis. Majority of the patients (71%) had lytic bone lesions at the time of diagnosis and 86% (n=36) hade secretory disease. Patients had received a median of 1 prior treatment (range 1–5), while 23 (55%) patients had received novel agents (proteasome inhibitors or IMiDs) prior to the BEM regimen. Response rates prior to and after the regimen are summarized in Table 1. After BEM-ASCT an additional 16 (38%) patients achieved a CR. Median duration of hospitalization and time to engraftment were 19 days (range 15–41) and 10.5 days (range 7–19), respectively. One patient died prior to discharge from the hospital post ASCT (Day 36 post ASCT) for a treatment related mortality of 2%. CR rate post BEM-ASCT was 64% with an ORR of 97%. Relapses have been noted in 25 patients to date. Median OS for all patients was 4.9 yrs (5.6 yrs for patients in CR and 6.6 yrs for patients in PR after BEM-ASCT). Median PFS was 23.9 mths for all patients (25 mths for patients in CR and 21.8 mths for those in PR after BEM-ASCT). No statistically significant differences were noted in OS based on patient gender (p=0.47), age at diagnosis (< or ≥60 yr), MM subtype (p=0.52), DS stage at diagnosis (0.09), patients without lytic bone lesions at diagnosis (p=0.054), secretor status (p=0.2), response status at the time of BEM-ASCT (p=0.9) or prior exposure to novel agents (p=0.62).

BEM is a well-tolerated conditioning regimen prior to ASCT in MM and has efficacy comparable to Mel-200. BEM can be effectively employed in patients where Mel-200 is not feasible. We are particularly intrigued by its ability to deliver high CR rates (64%) compared to <30% (historical control). Very encouraging median OS (4.9 yr) and PFS (23.9 mth) rates were noted which were even better in patients who had a measurable response after this regimen. Further investigations will be needed to optimally define its potential as standard conditioning regimen in MM patients undergoing ASCT.

No relevant conflicts of interest to declare.