Chhabra, Saurabh

Abstract Background: Minimal residual disease (MRD) is a critical prognostic and therapeutic response marker in multiple myeloma (MM). Two main technologies are used for MRD assessment in bone marrow: next-generation flow cytometry (NGF) and next-generation sequencing (NGS), from clonoSEQ. While both methods are FDA-cleared and clinically relevant, they differ in sensitivity, sample handling requirements, and technical differences. Comparative performance in real-world matched samples is understudied. Here we compared the detection rates and concordance between MRD by NGF (flow cytometry) and NGS-based clonoSEQ, using paired bone marrow aspirates collected at the same clinical timepoint. Methods We identified 246 paired bone marrow samples from MM patients, which were evaluated by both flow cytometry (Euroflow, typically sensitivity of 10-5) and clonoSEQ (sensitivity of up to 10-6) on the same collection date.MRD-negativity for clonoSEQ was defined as no detectable clones and below the assay's level of detection (LoD). Continuous variables (clonoSEQ and flow CPS) were analyzed using the Mann-Whitney U test. Categorical variables were assessed using chi-square tests with Yates continuity correction for 2x2. A cox proportional hazards model was used to evaluate the association between overall survival and cytogenetic abnormalities, MRD status, and other clinical covariates including age, sex, treatment type, and disease setting (newly diagnosed, relapsed/refractory). A p-value < 0.05 was considered significant. Results Out of 246 paired bone marrow samples, we identified 173 concordant samples, out of which 26 were concordant positive (clonoSEQ+/NGF+), 147 were concordant negative (clonoSEQ-/NGF-), and 73 were discordant (clonoSEQ+/NGF-). clonoSEQ detected MRD in all cases missed by NGF, including some with relatively high tumor burden, reflecting its higher sensitivity. Among discordant samples, 45 (61.6%) were following treatment of newly diagnosed MM (NDMM) and 28 (38.4%) treatment of relapsed/refractory (RRMM). Among the MRD-positive samples, the concordant group (n=26) showed a mean clonoSEQ count of 11923.5 cells per million (CPM) and a mean NGF CPM of 305.5 (p<0.01). In contrast, the 73 discordant samples had a lower mean clonoSEQ CPM of 156.1. For the 147 MRD-negative samples with concordant results, no residual disease was detected by either assay (CPM = 0 for both). When evaluating sex, race, ethnicity, chromosomal abnormalities, prior treatments to sample collection (immunomodulatory drugs, proteasome inhibitors, CD38 antibodies, CAR Ts/bispecific antibodies), and disease stage (NDMM, RRMM, untreated), patients with t(11;14) were significantly higher in the discordant group (17.9% concordant vs. 32.9% discordant; p = 0.016), while CAR T/bispecific antibody-treated patients were more likely concordant for the tests (27.2% concordant vs. 4.1% discordant; p<0.01). High-risk cytogenetics (t(4;14), t(14;16), gain 1q) were associated with worse survival (HR 6.22, 95% CI 2.02 – 19.2; HR 16.2, 95% CI 3.38-77.1; HR 4.0, 95% CI 1.28 – 12.5, respectively). Discordant MRD status did not impact survival, though only 13/246 patients were deceased (median follow-up approximately 50.6 months).Conclusion: ClonoSEQ demonstrates higher sensitivity compared to NGF for MRD detection in MM, identifying residual disease missed by NGF particularly in t(11;14) cases. Discordance did not affect survival, however, only 13 patients were deceased at the time of last follow up, suggesting longer follow up is needed.

Abstract Introduction Matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS, mass fix) represents a sensitive and specific alternative to electrophoresis and immunofixation for quantifying monoclonal antibodies in patients with multiple myeloma (MM). Here we report real world data utilizing mass fix and compare its test characteristics to a gold standard of minimal residual disease (MRD) quantification utilizing next generation sequencing (NGS). Results All patients who had obtained mass fix and MRD testing by NGS as part of routine clinical care at Mayo Clinic Arizona were screened for this study. In total, 343 pairs of mass fix and NGS testing within 50 days of each other representing 269 unique patients with secretory multiple myeloma were included. Cases of IgD myeloma and those secreting only free light chains were excluded. The threshold of MRD negativity was set at <1x10-6(less than one malignant cell in one million) and was assessed utilizing the clonoSEQ NGS assay. The median age of our cohort is 67, it is 44% female, and primarily Caucasian (88%) with a median follow-up of 7.3 months from testing date. FISH testing was performed in 96% of patients and at least one high risk cytogenetic abnormality (t(4;14), t(14;16), del(17p)) was found in 23% of patients. The t(11;14) translocation was found in 18%, +1q in 26%, and amp(1q) in 6% of evaluated patients. Notably, patients at all stages of treatment or disease status were included in our study. Induction treatment for newly diagnosed MM (NDMM, 133 patients) was mostly daratumumab-containing quadruplet (63%) or triplet drug regimens (36%). Autologous stem cell transplant (ASCT) was performed in 79% of NDMM and 80% of relapsed refractory MM patients (RRMM, 138 patients). Of the RRMM patients, 94% were triple class exposed and 41% were penta-exposed. Overall agreement between NGS and mass fix results was 65% (Kappa statistic: 0.31, 95% CI: 0.22 – 0.41). Most discordant cases were instances of mass fix negativity and NGS positivity (n = 89, 26% of all testing pairs). Only 7% of cases (n= 30) represented mass fix positivity with NGS negativity. Mass fix was able to define therapeutic monoclonal antibody by its unique mass spectrometric profile in 38 of the total test pairs that otherwise would have been considered disease associated. Of the 30 patients testing mass fix positive and NGS negative, 25 (83%) represent post-treatment evaluations. Thus, ongoing mass fix positivity represents monoclonal protein washout kinetics. All of these cases are noted to have declining mass fix levels at last follow up and 40% had undetectable monoclonal protein. The discordant mass fix negative and NGS positive cases were evenly distributed across NDMM and RRMM representing 32% and 20% of test pairs in each group, respectively. Amongst these 89 total test pairs, the median abundance of malignant clone by NGS was 10 cells per million (range 0.06 to 297,895). This is in contrast to 136 concordantly positive test pairs where the median was 2960 cells per million (range 0.353 to 1,017,360). The median monoclonal protein identified (in those with a quantifiable M-spike) was 0.30 g/dL. Receiver operating characteristic curves using NGS as gold standard found the optimal mass fix threshold to be 0.010g/dL (specificity 95%, sensitivity 51%) for NDMM patients and 0.046g/dL (specificity 84%, sensitivity 55%) in RRMM patients. Conclusions Development of a MRD assay based on peripheral blood sampling could greatly improve the ease and speed of obtaining these assessments. Our experience highlights both the great potential and need to identify appropriate clinical contexts for optimal use of mass fix MRD assessment. A significant limitation of our data is that low level monoclonal proteins without a previous reference above a threshold of 20mg/dL are not reported as positive and may account for a significant fraction of discordant cases reported here. All clonoSEQ NGS samples are referenced to a positive control greatly increasing specificity. The currently reported dataset is biased against mass fix as not all test pairs reported are known to have a positive reference. Further delineation of these cases is forthcoming. Previous reports have also noted that mass fix test characteristics can improve with time from treatment which will be assessed with future follow-up.

Background The International Myeloma Working Group (IMWG) defines progression of disease (PD) in multiple myeloma by the increase in serum or urine paraprotein beyond a certain threshold. With more common use of serial bone marrow-based measurable residual disease (MRD) assessment, some patients will evolve with increase in MRD burden without meeting IMWG criteria for PD and no consensus exist on the best approach for this circumstance. Understanding the implication of increasing MRD burden is particularly relevant in patients with NDMM treated with quadruplet therapy (QUAD, consisting of a PI, an IMiD, an anti-CD38 mAb and dexamethasone) and autologous stem cell transplantation (ASCT), since most will reach MRD negativity. Methods We analyzed a large dataset of patients with NDMM patients treated with QUADs + ASCT +/- QUAD consolidation +/- single or dual-agent maintenance and monitored with serial MRD assessment by next-generation sequencing (clonoSEQ®) at end of induction, post ASCT, post consolidation and at least yearly thereafter. The dataset was built from clinical trial participants and from patients receiving standard care under an institutional guideline. MRD progression (MRD-P) was arbitrarily defined as quantitative increase in MRD burden by at least 1 log10 above the nadir. Treatment modification in the event of MRD-P without IMWG-defined PD was at discretion of treating physician. For patients with MRD-P without concomitant PD we describe cumulative incidence of PD after MRD-P. To contextualize the clinical implications of MRD-P, we describe survival free of failure of second line therapy (SFF2T), defined as time from progression event (MRD-P or PD not preceded by MRD-P) until occurrence of IMWG-defined PD or death on second line therapy, regardless of whether second line was initiated due to MRD-P or subsequent IMWG-defined PD. Results Among the 216 patients, 113 (52%) were clinical trial participants, median age was 61 years (IQR 56-68), 21% age 70 or older, 32% were non-White, 57% male, 38% had MM with 1 high risk chromosome abnormality [HRCA, gain/amp 1q, t(4;14), t(14:16), del(17p)], 15% had 2+HRCA. Median duration of follow up is 39.5 months, and 966 MRD datapoints were assessed. Overall, 83% of patients achieved sCR, 78% achieved MRD negativity at 10-5, 68% at the 10-6 threshold, and 56% ceased therapy after confirmed MRD negativity. Forty-nine patients had MRD-P(N=19) or PD not preceded by MRD-P (N=30). Patients with MRD-P or PD not preceded by MRD-P often had 1 or more HRCA (73.7% and 82.8%), International staging system III (36.8% and 30.0%), and high LDH at diagnosis (31.6% and 23.3%). Median time from onset of therapy to MRD-P was 24.4 mo (IQR 12.6-35.8) and to PD not preceded by MRD-P was 23.2 mo (IQR 18.4-29.4). Among the 19 patients with MRD-P, 12 (63%) were on observation at time of MRD-P, 2 were receiving single agent lenalidomide, 5 were receiving a QUAD, 17 (89%) had previously obtained MRD negativity at <10-5 including 10 (53%) who had also achieved MRD negativity at 10-6. Upon detection of MRD-P, 12 (63%) pts changed therapy, all to a monoclonal antibody-containing triplet or quadruplet regimen. Yet, median time from MRD-P to PD was 10.1 months. Patients with MRD-P had 1-year SFF2T of 55.6%, in contrast to 35.0% for patients with PD not preceded by MRD-P. OS 2-year from progression event was 78.0% for MRD-P and 53.9% for PD not preceded by MRD-P. Conclusions In the context of NDMM treated with QUAD + ASCT, MRD-P indicates imminent IMWG-defined PD, and is driven by a thriving plasma cell population unlikely to be controlled by reinstitution of anti-CD38 mAb-based combinations. Outcomes of patients with MRD-P are similar to those of patients with IMWG-defined PD. These findings challenge the paradigm of IMWG-defined PD and paraprotein measurability as minimal parameters for change in therapy and introduction of agents with new mechanisms of action.