Clinical Implications of Circulating Tumor DNA in Multiple Myeloma and Its Precursor Diseases

Abstract

Background: Genetic alterations play a pivotal role in multiple myeloma (MM) development and therapeutic resistance. Traditionally, the genetic profiling of MM requires invasive bone marrow (BM) procedures; however, these procedures are associated with patient discomfort and cannot fully capture the spatial and temporal heterogeneity of the disease. Therefore, we investigated the clinical implications of liquid biopsy using targeted deep sequencing.

Methods: We analyzed the genetic profiles of circulating tumor DNA (ctDNA) by targeted deep sequencing from 102 patients, including those with monoclonal gammopathy of undetermined significance (MGUS, N=7), smoldering MM (N=6), and symptomatic MM (N=89).

Results: The number of ctDNA mutations increased with disease progression from MGUS to MM, with averages of 1.0 mutations in MGUS, 1.8 mutations in smoldering MM, and 1.9 mutations in MM, respectively. Shared mutations between BM and ctDNA were more prevalent in MM (68.9%) than in MGUS (25.0%). RAS/RAF and TP53 mutations were significantly enriched in MM ctDNA. Specific mutations were associated with clinical features in patients with MM: hypercalcemia and TET2 (P =0.006), renal insufficiency and NRAS (P =0.012), paramedullary myeloma and TP53 (P =0.02), and extramedullary myeloma and NRAS (P =0.007). TET2 mutations significantly affected 2-yr progression-free survival (hazard ratio=7.11, P =0.003). Serial ctDNA profiling accurately predicted treatment response in patients with MM.

Conclusions: Our findings highlight the potential of liquid biopsy for understanding MM progression and prognosis utilizing a minimally invasive approach, paving the way for its integration into personalized treatment strategies and real-time disease monitoring.

Keywords: Cell-free DNA; Circulating tumor DNA; High-throughput nucleotide sequencing; Liquid biopsy; Myeloma.

Fig. 1. Clonal genomic landscape of ctDNA in plasma cell dyscrasia. (A) Distribution of MM putative driver somatic mutations from next-generation sequencing of ctDNA. (B) Location of KRAS mutations. (C) Location of NRAS mutation. (D) Location of BRAF mutation. (E) Location of TP53 mutation.

Abbreviations: MM, multiple myeloma; SMM, smoldering MM; MGUS, monoclonal gammopathy of undetermined significance.

Fig. 2. ctDNA mutations significantly associated with survival outcomes. (A) APC, NRAS, NIPA2, and TET2 mutations associated with overall survival. (B) NRAS and TET2 mutations associated with progression-free survival.

Fig. 3. Sequential monitoring of mutant clones in a subset of seven patients with MM. (A) MM510 and MM429 had a PFS of more than 12 months, representing a favorable outcome for first-line treatment. The PFS for MM510 and MM429 following first-line treatment was 14 and 13 months, respectively. (B) MM564, MM347, MM514, MM543, and MM233, with a PFS of less than 12 months (10, 11, 9, 11, and 9 months, respectively), had severely adverse first-line treatment outcomes.

Abbreviations: MM, multiple myeloma; PFS, progression-free survival; VTD, bortezomib-thalidomide-dexamethasone; VMP, bortezomib-melphalan-prednisone; Rd, lenalidomide-dexamethasone; VTd+ASCT, bortezomib-thalidomide-dexamethasone+autologous stem cell transplantation.