The presence of circulating tumor plasma cells (CTPCs) by next-generation flow independently predicted disease progression in real-world patients with multiple myeloma after treatment, a study recently published in Blood found.
The study included 328 samples from 137 newly diagnosed multiple myeloma patients in the real world after treatment: 274 of the samples were bone marrow and blood samples from the same patients and 54 were follow-up blood specimens.
Overall, 26% of the patients tested positive for CTPCs by next-generation flow, which according to the study researcher, is a similar rate to what is seen with sensitive techniques such as allele-specific oligonucleotide polymerase chain reaction (PCR) and next-generation sequencing.
All patients that were positive for CTPCs were also positive for bone marrow minimal residual disease (MRD). However, a “significant fraction” of cases that were negative for CTPCs were positive for bone marrow MRD and/or serum immunofixation. According to the study researchers, this finding supports the notion that multiple myeloma is a bone marrow disease with greater levels of infiltration of plasma cells into the bone marrow versus the peripheral blood.
The study also showed that CTPCs measured by next-generation flow could be an independent prognostic marker for progression-free survival. Specifically, among the entire cohort, patients who were positive for CTPCs had a significantly higher likelihood of disease progression (hazard ratio [HR], 5.1; 95% CI, 2.9-8.9; P <.0001), as were patients who had a stringent complete response or complete response (HR, 7.4; 95% CI, 3.0-18.2; P <.0001), compared with patients who were negative for CTPCs.
“These results, together with the demonstration that CTPC are systematically detected in blood of MM at diagnosis and at relapse, suggest that detection of blood CTPC rather than a surrogate marker of response, is a strongly reliable predictor of impending (early) disease progression,” the study researchers wrote.
Sanoja-Flores L, Flores-Montero J, Puig N, et al. Blood monitoring of circulating tumor plasma cells by next generation flow in multiple myeloma after therapy [published online October 10, 2019]. Blood. doi: 10.1182/blood.2019002610