LAUSR

Introduction Second AutoSCT has been demonstrated to be beneficial in pts with relapsed multiple myeloma (rMM), in clinical trials. The optimal conditioning regimen for pts who receive a second transplant has not been currently established. We report our experience using an alternative conditioning regimen (ACR) with either bortezomib with high-dose melphalan (Bor.mel) or carmustine with high-dose melphalan (BCNU.mel), versus single-agent HDM in pts receiving a second AutoSCT for rMM. Methods Data was retrospectively collected and analyzed from all pts who received Bor.mel, BCNU.mel (dosing previously reported), and HDM (melphalan 140 mg/m2 or 200 mg/m2 IV) as conditioning prior to second AutoSCT for rMM at our institution. Demographics, disease risk status at initial diagnosis, disease status prior to and response to second AutoSCT, transplant related adverse events and outcomes were analyzed. Fisher's exact test was used to compare response rates between groups. Results Between 2012-2016, 82 adult pts received a second AutoSCT (50 HDM pts, 32 AC pts). The median age was 59 years in the HDM arm and 56 years in the ACR arm. The ACR arm had more high risk pts [7 (22%) vs 2 (4%)]; however, the majority of pts in both arms had standard risk rMM. All patients received HDM as conditioning with first AutoSCT. A complete remission at day 100 was observed in 19 (38%) HDM pts vs 11 (34%) ACR pts; VGPR in 23 (46%) HDM vs 12 (38%) ACR; PR 3 (6%) HDM vs 7 (22%) ACR; SD 1 (2%) HDM vs 1 (3%) ACR; and PD in 2 (4%) HDM vs 1 (3%) ACR. Two patients in the HDM arm were not evaluable at day 100 (1 death, 1 lost to follow up). There was a trend towards more favorable response (stringent CR + CR + VGPR) in patients that received HDM compared to ACR (p = 0.073). Adverse effects were similar between the two groups. The median time to neutrophil (12 days HDM vs 13 days ACR) and platelet engraftment (18 days HDM vs 18 days ACR) were similar. At last follow up, 42 (51.2%) pts were alive, 18 (36%) in the HDM arm and 24 (75%) in the ACR arm. Of the 40 pts that died, cause of death was progressive disease in 8 pts (4 pt in each group), infection related in 5 pts, other causes in 2 pts, and unknown in 25 pts. Conclusions Second autologous stem cell transplant is an effective option for relapsed and refractory multiple myeloma. Based on our analysis, HDM in second AutoSCT was associated with a more favorable response (sCR + CR + VGPR) compared to ACR, however; there were a higher percentage of high risk pts and fewer patients in the ACR arm. Further evaluation with a more robust population size in each group is warranted in addition to evaluating other alternative regimens to determine if a change in conditioning regimen with second autografts would provide better outcomes.