Circulating tumor cells identify a disseminated genomic high-risk phenotype within IMS-IMWG 2025 staging in newly diagnosed multiple myeloma.

The 2025 IMS-IMWG consensus genomic staging (CGS) system has improved genomic risk stratification in newly diagnosed multiple myeloma (NDMM), yet does not capture whether high-risk clones have acquired a disseminated phenotype. We investigated whether circulating tumor cells (CTC) refine CGS and enable longitudinal residual disease monitoring. We retrospectively analyzed 631 MM patients from the NICHE cohort (NCT04645199) who underwent CTC assessment across disease phases. Among 410 patients assessed at diagnosis, CTC were detectable in 63.9% and correlated with both bone marrow plasma cell infiltration and accumulation of high-risk cytogenetic abnormalities. In 359 NDMM patients with adequate follow-up, a cohort-derived CTC threshold of 0.38% independently predicted inferior progression-free survival (PFS) after multivariable adjustment. Importantly, CTC refined prognostic stratification specifically within the CGS high-risk subgroup. Patients with CGS high-risk/CTC-high disease had the shortest PFS, thereby defining a disseminated genomic high-risk phenotype comprising 12.4% (39/314) of evaluable NDMM patients. In follow-up cohorts, detectable CTC were associated with inferior outcomes in 127 patients assessed during non-progressive disease states, whereas combined CTC and bone marrow minimal residual disease assessment stratified outcomes in 120 patients with paired measurements. Overall, CTC-integrated CGS supports minimally invasive baseline risk stratification and longitudinal disease monitoring.