Photo Credit: Nemes Laszlo
A recent study evaluated the impact of circulating plasma cells (PCs) in patients with primary multiple myeloma (MM) on bortezomib-containing induction therapy. This prospective study, conducted from 2015 to 2018 across 44 centers, included 3,220 patients aged 24 to 90 years, with a median age of 63. Disease staging at diagnosis showed that 50% were at Stage III per the ISS system. Researchers assessed circulating PCs at diagnosis through peripheral blood smear analysis and examined the overall survival (OS) in relation to the presence and proportion of these cells.
Circulating PCs were detected in 207 patients (6%), with varying proportions: 1–4% in 62%, 5–20% in 21%, and over 20% in 17%. The remaining 3,013 patients showed no circulating PCs at diagnosis. Analysis revealed that the presence of circulating PCs significantly reduced OS. Patients without detectable PCs had a 5-year OS of 42%, compared to 25% in those with circulating PCs (P<0.05). Median OS was notably lower in patients with circulating PCs, at 21 months versus 48 months for those without.
Interestingly, no significant differences in OS were observed based on the proportion of circulating PCs. Median OS was 22 months for patients with 1–4% circulating PCs, 16 months for those with 5–20%, and 20 months for those with more than 20% (p>0.05). However, platelet count emerged as a significant prognostic factor among patients with circulating PCs. Those with platelet counts exceeding 100,000/μl had a median OS of 24 months, compared to 12 months for those with counts below 100,000/μl (P<0.05).
The study underscores the adverse prognostic impact of detecting circulating PCs in MM patients, regardless of their quantity. The findings highlight the need for a revision of diagnostic criteria for primary plasma cell leukemia, advocating for a reduction in the threshold of circulating PCs from 5% to 1%.
