Outcome of Patients with Light Chain Multiple Myeloma Compared to IgG/IgA Myeloma after Autologous Stem Cell Transplant
Authors: Sasaki Koji , Shah Nina , Bashir Qaiser , Hosing Chitra M. , Popat Uday R. , Nieto Yago , Parmar Simrit , Shah Jatin J. , Weber Donna , Weissinger Daniel , Thomas Sheeba K. , Orlowski Robert Z. , Champlin Richard E. , Qazilbash Muzaffar H. 
Published: October 2019

Abstract
Introduction:
High-dose chemotherapy followed by autologous hematopoietic stem cell transplantation (auto-HCT) is the standard of care for younger patients with newly diagnosed multiple myeloma (MM). In approximately 15% of MM patients the monoclonal (M) spike consists of k or l light chains only as opposed to heavy + light chains. It remains unclear whether light chain (LC) MM has a different prognosis compared to other monoclonal protein subtypes after an auto-HCT.
Methods:
We retrospectively analyzed 1067 patients with MM who underwent auto-HCT between January 1, 2004 and January 1, 2011 at our institution. We evaluated the outcome of newly diagnosed patients with LCMM and compared it to patients with IgG or IgA MM, who underwent an auto-HCT after induction therapy. Primary endpoints were complete remission (CR), progression-free survival (PFS) and overall survival (OS) from the date of auto-HCT. Kaplan-Meier analysis with the log-rank test was performed for univariate comparison of survival. Cox proportional hazards regression method was used for univariate and multivariate analyses.
Results:
Of 1067 patients who underwent auto-SCT during the period, 223 underwent auto-SCT after relapse, and were excluded. From the remaining 844 who underwent auto-SCT in first remission, we excluded 102 patients (AL amyloidosis 60, POEMS and other plasma cell disorders 10, non-secretory MM 15, IgD 10, IgM 6 and IgE 1) from the analysis. The remaining 742 patients were divided as follows: IgA, 162 patients (22%); IgG, 444 (60%) and LC, 136 (18%). Baseline patient characteristics are described in Table 1. Patients with LCMM were younger and had a higher CR rate to induction. Median follow-up for the entire cohort after auto-HCT was 38 months (range, 0.2-87.0). Post auto-HCT, 28% with IgG/IgA MM and 38% with LCMM achieved a CR (p=0.015). Median PFS was 26.0 months and 27.7 months in IgG/IgA MM and LCMM groups, respectively (p= 0.742). Median OS was not reached and 71.1 months in IgG/IgA MM and LCMM groups, respectively (p= 0.18, Figure 1). Multivariate Cox regression analysis for PFS identified <PR after auto-SCT, non-diploid karyotype, and induction chemotherapy without thalidomide or bortezomib as adverse prognostic factors. Multivariate Cox regression analysis for OS identified presence of hypodiploidy or monosomy 13/del13, higher lactate dehydrogenase pre-transplant, lower hemoglobin pre-transplant, and <PR after auto-HCT as adverse prognostic factors. M protein subtype did not affect PFS (hazard ratio [HR], 1.040; 95% confidence interval [CI], 0.825-1.311; p=0.742) or OS (HR, 1.313; 95% CI, 0.874-1.971; p=0.190).
Conclusions:
Patients with LCMM have a higher CR rate after auto-HCT, but their PFS and OS were similar to patients with IgG/IgA MM.
Table 1. Patient Characteristics Variables, No. (%)/median (range) IgG/IgA myelomaN= 606 Light chain myelomaN= 136 P Median age at transplant, (y) 59 (31-80) 56 (32-78) .004 Age >65 years 138 (23) 23 (17) .134 Male 357 (59) 74 (54) .337 Ethnicity .731 Caucasian 399 (66) 94 (69) African American 99 (16) 22 (16) Mixed 87 (14) 18 (13) Asian 16 (3) 2 (2) Cytogenetic abnormalities at diagnosis by conventional cytogenetics Diploid 180 (30) 36 (27) .159 Hyperdiploid 93 (15) 9 (7) .008 Hypodiploid 27 (5) 11 (8) .082 t(11;14) 4 (1) 3 (2) .092 Monosomy 13 / del 13 44 (7) 9 (7) .789 Other high-risk abnormalities 2 (0) 1 (1) .456 Induction chemotherapy Bortezomib or IMiD-based 507 (84) 123 (90) .046 Pre-transplant evaluation Bone marrow plasma cell, (%) 2 (0-71) 2 (0-50) .136 Bone marrow plasma cell >10% 90 (15) 18 (13) .735 Hemoglobin, (g/dL) 11.3 (4.4-16.0) 10.8 (6.8-15.3) .025 Lactate dehydrogenase, (IL/L) 526 (221-5062) 526 (239-2748) .522 Calcium, (mg/dL) 9.0 (7.6-10.4) 9.0 (7.5-11.0) .055 Creatinine, (mg/dL) 0.9 (0.4-12.5) 0.9 (0.5-9.8) .017 Beta-2 microglobulin (mg/dL) 2.4 (1.1-40.0) 2.8 (1.2-33.8) .001 Time from diagnosis to auto-HCT (month) 8.0 (1.9-174.4) 6.8 (2.4-44.6) .001 Pre-transplant disease status .004 ≥ CR 24 (4) 15 (11) VGPR/PR 545 (90) 109 (80) SD/PD 37 (6) 12 (9) Conditioning regimen .008 Melphalan alone 508 (84) 126 (93) Melphalan-based regimen 98 (16) 10 (7) Final response after transplant .080 ≥ CR 168 (28) 52 (38) VGPR/PR 353 (58) 70 (52) SD/PD 81 (13) 14 (10)
Figure 1. a) Progression-free survival, b) Overall survival in patients with light chain myeloma compared to those with IgG/IgA myeloma Figure 1. a) Progression-free survival, b) Overall survival in patients with light chain myeloma compared to those with IgG/IgA myeloma

Disclosures
Shah: Celgene: Consultancy, Research Funding. Thomas:Novartis, Celgene, Acerta Pharmaceuticals, Idera Pharmaceuticals: Research Funding.