The optimal cutoff for identification of ultra-high-risk PCL-like multiple myeloma is 2% of CTCs. Kaplan-Meier curves for (A) PFS and (B) OS for transplant-ineligible patients with NDMM (N = 395); and (C) PFS and (D) OS for transplant-eligible patients with NDMM (N = 185) with < 2% (blue line) and 2%-20% (red line) of CTCs. CTC, circulating tumor plasma cell; HR, hazard ratio; NDMM, newly diagnosed multiple myeloma; OS, overall survival; PCL, plasma cell leukemia; PFS, progression-free survival.