Partial Response at Completion of Bortezomib-Thalidomide-Dexamethasone (VTd) Induction Regimen Upfront in Multiple Myeloma Does Not Preclude Response to VTd in Consolidation.

The impact of consolidation on response rates and PFS has recently been demonstrated after induction and autotransplantation upfront in Multiple Myeloma (MM). We further showed that patients in ≥VGPR following the intensification procedure benefited most from consolidation. Question remains as to the benefit of consolidation for patients in PR at completion of induction - feature of partial resistance to the induction regimen. We collected data from 54 newly diagnosed MM treated with VTd-auto-VTd regimen that reached only PR at completion of the induction procedure. Overall, 37 patients (68%) improved depth of response (≥VGPR) at completion of consolidation, including 35% that reached CR and 38% solely related to consolidation. Of patients that remained on PR or improved depth of response after ASCT, 26% and 38% further responded to consolidation, respectively. With a median follow-up of 36 months, improved depth of response translated into lower relapse rate compared with patients remaining in PR, 19% vs. 36%. This difference was more striking in patients that reached CR vs. others, 8% and 38%, respectively (p=0.039). The median TTP was prolonged in patients that improved depth of response after consolidation (p=0.012), with a 3-year TTP of 87% vs. 18% otherwise. In multivariate analysis, lack of improved depth of response to consolidation independently predicted shorten median TTP [OR=4.4, 95%CI=1-21; p=0.039], with elevated LDH and beta2m, and adverse FISH. This study shows that VTd consolidation should be recommended to patients solely on PR at completion of induction with VTd, feature of lower sensitivity to VTd.