Comparison of MRD Detection in Autografts in Multiple Myeloma between Novel High-Sensitivity Euroflow-NGF and NGS

Background: Autologous stem cell transplantation (ASCT) remains the gold-standard treatment for multiple myeloma (MM). To date, we have reported the prognostic value of minimal residual disease (MRD) detection in autografts in an ASCT setting using EuroFlow next-generation flow (NGF) and next-generation sequencing (NGS) (Takamatsu et al., ASH 2018, 2020). The main problem with NGF is its lower sensitivity (2 × 10 -6) compared with that of NGS ( Methods: We reanalyzed 11 autografts in which the MRD were negative on NGF but positive (n = 7) or negative (n = 4) on NGS (Takamatsu et al., ASH 2018, abstract #258) using 5-20 mL of autografts with NGF to increase the sensitivity of MRD detection. Additionally, we enrolled 9 patients with newly diagnosed MM, from whom 5-20 mL of apheresed autografts were cryopreserved. We included 20 patients with newly diagnosed MM. The median age at ASCT was 60 (range, 45-67) years, and the patients included 12 men and 8 women at International Staging System I (n = 3), II (n = 13), and III (n = 4), 6 of whom harbored high-risk chromosomal abnormalities, including t(4;14) (n = 3), t(14;16) (n = 1), del17p (n = 1), and t(4;14) and del 17p (n = 1). All patients received bortezomib-based chemotherapy for induction followed by melphalan at a dose of 200 mg/m 2 for conditioning before ASCT. Three patients received consolidation therapy with carfilzomib-lenalidomide-dexamethasone (n = 2) or bortezomib-lenalidomide-dexamethasone (n = 1), and 18 patients received lenalidomide (n = 16), thalidomide (n = 1), or thalidomide and lenalidomide (n = 1) maintenance. Frozen autografts (n = 20) were thawed for MRD assessment using NGF and NGS. The NGF method was based on a previous report (Flores-Montero et al., Leukemia 2017). NGS-based MRD assessment was performed using Adaptive's standardized NGS-MRD assay (Seattle, WA) (Ching et al., BMC Cancer 2020). The NGF method was modified to increase the sensitivity of MRD detection by capturing up to 6 × 10 7 cells. Results: Frozen autografts were used in this study; therefore, we performed a sensitivity test using a dilution of frozen/thawed primary MM cells in an autograft with NGF. The sensitivity test revealed a strong correlation between 5 × 10 -7 and 1 × 10 -4 MRD levels (Figure 1A; r = 0.999, P Conclusion: The modified EuroFlow-NGF method may be used to assess MRD in frozen/thawed autografts, and its sensitivity may increase up to 5 × 10 -7, which is comparable to that of NGS. Figure 1 Figure 1. Disclosures Yamashita: Janssen: Honoraria; Bristol-Myers Squibb: Honoraria; celgene: Honoraria; Takeda: Honoraria. Nakao: Novartis Pharma: Honoraria; Symbio: Consultancy; Kyowa Kirin: Honoraria; Alexion Pharma: Research Funding. Takamatsu: Adaptive Biotechnologies, Eisai: Honoraria; SRL: Consultancy; Bristol-Myers Squibb: Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding.