Association of bone marrow plasma cell infiltration pre-auto transplant with adverse outcomes in multiple myeloma.

Abstract

8102 Background: Auto-stem cell transplantation (SCT) has become the standard of care for eligible patients (pts) with multiple myeloma (MM). However, the impact of bone marrow (BM) plasma cell (PC) percentage before SCT is not yet known. Methods: Retrospective review of 1489 MM pts who underwent auto-SCT from 7/8/98 – 12/31/2010 with post-induction, pre-SCT BM biopsy information available. Pts were divided into 2 groups: <10% PC infiltration (“PC low”) and >10% PC infiltration (“PC high”). Progression-free (PFS) and overall (OS) survivals were estimated by the Kaplan-Meier method. Log-rank test was performed to test differences in survival. Results: 1489 pts were studied. 1174 pts had <10% involvement of BM by PCs and 315 had > 10% involvement. For pts in the PC low group, 32% had a CR, 20% had a VGPR, 31% had a PR, 13% had <PR and 3% had progressive disease (PD) after SCT. For pts in the PC high group, 11% had a CR, 14% had a VGPR, 48% had a PR, 21% had <PR and 5% had PD after SCT. Median PFS was significantly shorter for the PC high group vs the PC low group (24.8 vs 29.5 months, p=0.05), as was median OS (52.5 vs 79.4 months respectively, p<0.001). When only pts who had a PR to induction were examined, there was a significant difference in both PFS (24.4 vs 33.2 months, p=0.04) and OS (58.3 vs 81.2 months, p =0.002) for the PC high vs PC low groups, respectively. For the 1299 (87%) pts treated in the era of novel therapeutics (after 2000), the differences between the PC high and PC low groups were maintained for both PFS (24.4 vs 29.5 months respectively (p=0.029)) and OS (54.8 vs 88.4 months respectively, p<0.001). Chemo-mobilization before SCT did not improve PFS or OS but this was done in only 44 (14%) of PC high pts. Conclusions: PC BM infiltration before auto-SCT is associated with a worse outcome. This finding persists in pts with a PR before SCT. Thus BM disease burden may further stratify pts with a PR. Though additional therapy did not significantly change the outcome for pts with high PC burden, this was done only in a minority of pts. Additionally, differences between PC high and PC low groups are maintained despite new salvage agents over the last 10 years. Further prospective study is warranted to determine the true impact of BM PC infiltration.