Abstract 3163: Peripheral blood circulating multiple myeloma cells (CMMCs) correlate with disease burden and can be used to characterize high-risk cytogenetics in newly diagnosed and smoldering myeloma

Abstract

Abstract There is an increasing interest in the ability to dynamically track disease burden and perform molecular subtyping of patients with plasma cell disorders without invasive bone marrow sampling. Circulating multiple myeloma cells (CMMC) have been detected in elevated numbers in the peripheral blood of patients with plasma cell disorders using flow cytometry or circulating cell enrichment platforms. We developed an automated CELLSEARCH® assay to enrich, enumerate, and perform a triplex FISH assay for t(4;14), t(14;16), and del 17p on CMMC (CD138+CD38+, CD45-CD19-) isolated from a 4 mL peripheral blood sample (Gross, et.al. Blood 2011; 118(21):1825). Here we present the enumeration and cytogenetic profiling of CMMC from separate cohorts of patients across the spectrum of plasma cell disorders. The first cohort consisted of newly diagnosed multiple myeloma patients enrolled in the CoMMpass study (ClinicalTrials.gov Identifier: NCT01454297). One or more CMMC per four ml blood were detected in 684/698 (98%) of newly diagnosed myeloma patients with median CMMC count of 413 per 4 mL of blood. CMMC counts decreased significantly from baseline when a remission was achieved due to treatment (p<0.001). CMMC counts <100 at remission were associated with improved PFS and OS compared to those patients whose CMMC counts were > 100 at remission. CMMC FISH results (n = 57) showed overall agreement of 85%, 91% and 80% with bone marrow FISH results and 81%, 91%, and 95% agreement with bone marrow CNV/RNAseq results for the t(4;14), t(14;16), and del 17p assays, respectively. The second cohort of patients consisted of intermediate/high risk smoldering myeloma patients enrolled in a Phase 2 study of Siltuximab (ClinicalTrials.gov Identifier: NCT01484275). One or more CMMC per 4 mL blood was detected at baseline in 74/79 (94%) of intermediate/high risk smoldering myeloma patients with median CMMC count of 100 per 4 mL of blood. Significantly higher CMMC counts were observed between patients in the placebo arm that progressed versus those without progression (n = 34, p = 0.031). This is in contrast to standard metrics of percentage of bone marrow plasma cells and serum M protein levels where statistically significant differences were not seen between progressors and non-progressors in the placebo arm (p = 0.068 and p = 0.070, respectively). CMMCs were collected from a third cohort of 35 patients across the plasma cell disease spectrum with an emphasis on MGUS and SMM. CMMC counts were associated with the disease burden of patients within this cohort. CMMC may be a useful non-invasive tool for disease monitoring and characterization across the plasma cell disorder spectrum. In myeloma, CMMC may be a useful prognostic marker at remission to delineate those patients at risk for relapse. In SMM, CMMC may be useful for predictive patients at risk of progression to MM. Citation Format: Brad Foulk, Mike Schaffer, Steve Gross, Chandra Rao, Denis Smirnov, Shalini Chaturvedi, Manjula Reddy, Madeline Repollet, Claudia Rojas, Daniel Auclair, Mary DeRome, The MMRF CoMMpass Network, Brendan Weiss, A. Kate Sasser. Peripheral blood circulating multiple myeloma cells (CMMCs) correlate with disease burden and can be used to characterize high-risk cytogenetics in newly diagnosed and smoldering myeloma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3163.