Autotransplants for Multiple Myeloma (MM) – An Update of the Arkansas Experience Since 1989 In Almost 4000 Patients with Special Emphasis on Third and Further Transplants.
Authors: Nair Bijay , Anaissie Elias J. , Waheed Sarah , Alsayed Yazan , Sexton Rachael , Petty Nathan , van Rhee Frits , Hoering Antje , Barlogie Bart 
Published: October 2019

Abstract
Abstract 1352

Background:
The Arkansas program has emphasized high hematopoietic progenitor cell (HPC) yields since its inception in 1989, in order to enable further high-dose therapy for relapse, rescue patients from hematopoietic compromise due to extensive cumulative genotoxic or novel agent dosing, and provide a fall-back option in the case MDS develops. Here we are examining the overall outcome data among 3888 patients undergoing HPC-supported therapy since 1989.

Patients and Methods:
Patients were grouped according to whether they received front-line Total Therapy (TT) protocols (TT-P, n=1452), non-TT protocols for previously treated MM (non-TT-P, n= 1155) or non-protocol therapies (non-P, n=1281). Overall survival (OS) and event free survival (EFS) were measured from the 1st high-dose therapy (Tx-1) intervention and examined in the context of baseline variables present prior to Tx-1, the aforementioned 3 treatment groups, and intervals between successive Tx interventions.

Results:
OS/EFS from Tx-1 was longest with TT-P (5-yr estimates, 67%/52%) followed by non-TT-P (5-yr estimates, 43%/30%) and non-P (5-yr estimates, 36%/27%) (p<0.0001, p<0.0001). Among all 3888 patients, 2773 (71%) received Tx-2 including 2385 (86%) within 6 months of Tx-1; 405 (10%) received Tx-3 including 140 (35%) within 2yr of Tx-2; 58 (1.5%) received Tx-4 including 44 (76%) within 2yr form Tx-3; 12 (0.3%) received Tx-5 all within 2yr from Tx-4; and 3 patients had Tx-6. When examined in the context of the 3 different treatment groups, 1157/1231 (94%) of the TT-P group had Tx-2 within 6mo, 51/169 (30%) had Tx-3 within 2yr of Tx-2, 51/169 (30%) had Tx-4 within 2yr of Tx-3, and 7/7 (100%) had a Tx-5 within 2 yr of Tx-4. Among 1155 non-TT-P patients, 646/822 (79%) had Tx-2 within 6mo of Tx-1, 37/129 (29%) had Tx-3 within 2yr of Tx-2, 14/18 (78%) had Tx-4 within 3yr of Tx-3, and all 4 (100%) receiving Tx-5 had done so within 2yr of Tx-4. Among 1281 non-P patients, 582/720 (81%) had received Tx-2 within 6mo of Tx-1, 52/107 (49%) had received Tx-3 within 2yr of Tx-2, 7/10 (70%) had received Tx-4 within 2yr of Tx-3, and 1 patient received Tx-5 within 2yr of Tx-4. KM plots from Tx-3 were similar among the 3 treatment groups with median OS of 16mo for TT-P, 14mo for non-TT-P and 11mo for non-P (p=0.13); median EFS were 7, 8, and 6 months (P=0.17). Timely application within 6mo resulted in superior OS and EFS from Tx-2 (OS: 79 v 23 months, EFS: 48 v 14 months; both P<0.0001). Multivariate Cox analyses examining post-Tx EFS and OS revealed TT-P superiority from Tx-1 and Tx-2 over non-TT-P and non-P; Tx-2 within 6mo of Tx-1 provided superior post-Tx-2 EFS and OS; while benefit from Tx-3 was not apparent until at least 2yr had elapsed since Tx-2. CA within 1 year of Tx-1 adversely affected EFS and OS from Tx-1, Tx-2 and Tx-3. Other adverse baseline parameters included low albumin for EFS and OS post-Tx-1; and B2M >=3.5mg/L for EFS and OS post-Tx-1 and post-Tx-2.

Conclusions:
We confirm that front-line TT-P provides superior clinical outcomes in comparison with back-up/salvage non-TT-P and non-P Tx, emphasizing the benefit from planned upfront protocol therapy. Timely application of Tx-2 within 6 months of Tx-1 extended both EFS and OS from Tx-2, validating our concept of maximum tumor cyto-reduction and avoiding MM re-growth. Tx-3 was useful when applied beyond 2yr from Tx-2, in support of the notion that longer disease control prior to relapse favorably impacts subsequent salvage Tx.

Disclosures:
No relevant conflicts of interest to declare.