Discontinuation of maintenance therapy in multiple myeloma guided by multimodal measurable residual disease negativity (MRD2STOP)

MRD2STOP is a pragmatic trial evaluating maintenance therapy cessation guided by measurable residual disease (MRD) negativity in multiple myeloma (MM). Eligible patients had previous MRD < 10−5, received ≥1 year of maintenance, and were prospectively confirmed to have undetectable disease by positron emission tomography, bone marrow (BM) flow cytometry (limit of detection [LoD] 10−5), and BM clonoSEQ (LoD 10−6). BM aspirates enriched for CD138+ cells were analyzed by clonoSEQ to achieve MRD 10−7 sensitivity. We evaluated the incidence of disease resurgence and progression-free survival (PFS), stratified by 10−7 status. Forty-seven patients discontinued maintenance after a median of 36 months. Baseline MRD ≥ 10−7 was observed in 19% (9/47). The median follow-up post-discontinuation was 30 months. Disease resurgence (MRD 10 ≥ −6) occurred in 11 patients, including 5 disease progressions. One patient died from a second cancer. The estimated 3-year cumulative incidence of disease resurgence was 20% for patients with baseline MRD < 10−7 compared to 75% for MRD ≥ 10−7 (HR 7.8, 95% CI 2.2-27.6, p = 0.001). Baseline MRD ≥ 10−7 was associated with inferior PFS compared to MRD < 10−7 (HR 10.1, 95% CI 1.6–62.3; 3-year PFS 49% vs 92%). Maintenance discontinuation in patients with MM and MRD < 10−6 led to low rates of disease resurgence. MRD < 10−7 may be a superior cessation threshold, requiring further validation.