Impact of pretransplant minimal residual disease in patients with multiple myeloma and a very good partial response or better receiving autologous hematopoietic stem cell transplantation

Background: The prognostic significance of minimal residual disease (MRD) status before autologous hematopoietic stem cell transplantation (autoHCT) in patients with multiple myeloma (MM) has not been clearly elucidated.

Methods: Retrospective single-center study of adult MM patients who achieved ≥very good partial response (VGPR) after induction therapy from 2015 to 2021 received upfront autoHCT and had available pretransplant MRD status by next-generation flow cytometry. The cohort was divided into pretransplant MRD-negative (MRDneg) and MRD-positive (MRDpos) groups.

Results: A total of 733 patients were included in our analysis; 425 were MRDneg and 308 MRDpos at autoHCT. In the MRDpos group, more patients had high-risk cytogenetic abnormalities (48% vs. 38%, respectively; p = .025), whereas fewer patients achieved ≥CR before autoHCT (14% vs. 40%; p < .001). At day 100 after autoHCT, 37% of the MRDpos versus 71% of the MRDneg achieved ≥CR, and at best posttransplant response 65% versus 88% achieved ≥CR, respectively. After a median follow-up of 27.6 months (range, 0.7-82.3), the median PFS was significantly shorter for patients in the MRDpos group compared to the MRDneg group: 48.2 months (95% confidence interval [CI], 0.3-80.5) versus 80.1 months (95% CI, 0.5-80.1), respectively (p < .001). There was no significant difference in overall survival between the two groups (p = .41). Pretransplant MRDpos status was predictive of shorter PFS in multivariate analysis (hazard ratio, 1.80; 95% CI, 1.31-2.46; p < .001). The impact of pretransplant MRD status was retained in most of the examined subgroups.

Conclusions: In patients achieving ≥VGPR to induction, pretransplant MRDpos status was associated with a lower CR rate after autoHCT and a shorter PFS.