Prevalence, detection, and clinical implications of BRAF V600E and NRAS Q61R mutations in multiple myeloma BM-FFPE tissues using digital droplet PCR.

Abstract

Multiple myeloma (MM) exhibits significant genetic heterogeneity with mutations in the MAPK pathway being increasingly recognized as drivers of progression and treatment resistance. This study is the first to employ droplet digital PCR (DD-PCR) on bone marrow formalin-fixed paraffin-embedded (BM-FFPE) tissue to quantify BRAF V600E and NRAS Q61R mutations in MM, and the first such investigation conducted in an Indian MM cohort. Mutations were identified in > 80% of samples. BRAF V600E displayed stage-specific variation, being lowest in intermediate MM and significantly higher in advanced disease (MMII vs MMIII, p = 0.0453). Burden declined after treatment (p = 0.038) and correlated with stage (β = - 36.95, p = 0.0041) and lytic lesions (β = - 25.97, p = 0.0268). NRAS Q61R was enriched in progressive disease (p = 0.02) and showed an upward trend with advancing stage (β = 14.38, p = 0.0686). Higher BRAF and NRAS burdens were associated with reduced 2-year progression-free survival (PFS). We show that DD-PCR applied to BM-FFPE samples is both feasible and informative. However, our study has inherent limitations: DD-PCR measurements can be influenced by sampling biases, droplet variability and FFPE DNA quality. Our single-centre design and small cohort size limit generalizability but demonstrate the potential for DD-PCR to complement sequencing and clinical stratification if validated in larger populations.