The presence of high numbers of circulating clonal plasma cells (cPCs) in patients with smoldering multiple myeloma (SMM), detected by a slide-based immunofluorescence assay, has been associated with a shorter time to progression (TTP) to MM. The significance of quantifying cPCs via multiparameter flow cytometry, a much more readily available diagnostic modality, in patients with SMM has not been evaluated. This study evaluated 100 patients with a known or new diagnosis of SMM who were seen at the Mayo Clinic, Rochester from January 2008 until December 2013. Patients with ≥150 cPCs (N=9) were considered to have high number of cPCs based on the 97% specificity and 78% PPV of progression to MM within 2 years of cPC assessment. The median TTP of patients with ≥150 cPCs was 9 months compared with not reached for patients with <150 cPCs (P<0.001). Thus, quantification of cPCs via multiparametric flow cytometry identifies patients with SMM at very high risk of progression to MM within 2 years and warrants confirmation in larger studies. In the future, this may allow reclassification of such patients as having MM requiring therapy prior to them enduring end-organ damage.
ASJC Scopus subject areas
- Cancer Research