Complete Remission after Autologous Stem Cell Transplantation Does Not Impact Relapse or Survival in African Americans with Multiple Myeloma.
Authors: Khaled Yasser , Abidi Muneer H. , Kato Koji , Janakiraman Nalini , Hanbali Amr , Levine John E. , Ferrara James , Mineishi Shin 
Published: October 2019

Complete remission (CR) is now frequently used as a surrogate marker for survival in multiple myeloma (MM), however its utility in African Americans (AA) has not been studied. Limited literature is available regarding outcomes after autologous stem cell transplantation (ASCT) in AA with MM. We evaluated the outcomes of 106 consecutive AA patients who underwent ASCT for MM between 7/1991 and 6/2006 at 3 centers. Melphalan-based conditioning was used in all the patients except 3 who received Busulfan/Cytoxan/TBI. After ASCT 30/105 (28%) evaluable patients were in CR. With median follow up of 47 months, the median progression free survival (PFS) and overall survival (OS) for all the patients was 16 and 51 months respectively. Effects of disease status at and after ASCT (CR v non CR), Age, gender, number of prior treatment regimens, B2M, LDH, plasma cell (%) at diagnosis, time to ASCT, history of prior radiation therapy (XRT), conditioning (TBI v non TBI), cytogenetics (chromosome 13 deletion (Ch13 del) v normal), immunoglobulin subtype and maintenance therapy (yes v no) were analyzed. No pre-transplant characteristic predicted for post-transplant CR. The median PFS in the CR and non CR group was 18 and 15 months respectively (P=0.84). Median OS was 51 months in both groups. In both univariate and multivariate analyses, only history of prior XRT predicted poor PFS (10 v 24 months, P=0.03) and OS (24 v 63 months, P < 0.001). The median time from diagnosis to ASCT was not influenced by prior XRT. Cytogenetic data were available in only 69/106 (65%) patients. Ch13 del was found in 24/69 (35%) patients, consistent with its reported incidence in MM. Patients with Ch13 del (n=24) had PFS and OS of 12 and 37 months while patients with normal cytogenetic (n=39) had PFS and OS of 24 and 57 months (P= 0.42 and 0.057, respectively).

Conclusion: CR after ASCT does not appear to be a surrogate marker for survival in AA patients. A trend toward inferior OS in AA with Ch13 del was observed as expected. The finding of inferior PFS and OS in patients with prior history of XRT was unexpected and merits further investigation in both AA and non AA patients. Cytogenetic, prior treatment toxicity and other biological risk factors should be considered in conjunction with the CR status when assessing the risk of relapse and survival in AA patients with MM.

Disease status at and after ASCT for 106 patients Response Pre-Transplant (%) Post-Transplant (%) Partial remission; PR, Minimal response; MR, Progressive disease PD, not available; NA CR 8 (8) 30 (28) PR 71 (60) 53 (50) MR 17 (16) 19 (18) PD 8 (7) 3 (3) NA 2 (2) 1 (1) Selected Characteristics Characteristic ALL (%) CR group (%) Non CR group (%) P not available; NA, Chromosome 13 deletion; Ch13 del, Radiation therapy; XRT, total body irradiation; TBI Patients, n 106 30 (28) 76 (72) Prior XRT (Y/N) 0.64 Yes 40 (38) 10 (33) 30 (39) No 64 (60) 20 (67) 44 (58) NA 2 (2) 0 (0) 2 (3) Cytogenetics 0.60 Ch13 del 24 (23) 9 (30) 15 (20) Normal 39 (37) 10 (33) 29 (38) Other 6 (6) 2 (7) 4 (5) NA 37 (35) 9 (30) 28 (37) TBI v Non TBI regimen 0.93 TBI 19 (18) 6 (20) 13 (17) Non TBI 87 (82) 24 (80) 63 (83) Number of prior treatment regimens 0.87 1–2 81 (76) 23 (77) 58 (76) > 2 22 (21) 6 (20) 16 (21) NA 3 (3) 1 (3) 2 (3)