Low peripheral blood B lymphocyte count predicts poor outcome in patients with multiple myeloma.

Previous evidence suggested that B lymphocytes may be involved in the progression and prognosis of multiple myeloma (MM). However, the prognostic value of peripheral B lymphocyte counts on MM before and after treatment in the novel agent era was rarely reported. Herein, we conducted a retrospective study in our center to detect peripheral B lymphocyte counts by flow cytometry in 110 patients with MM and explore the relation with survival. The B lymphocyte count was significantly lower in MM patients than healthy controls (p < 0.005). The cutoff value of B lymphocyte count at diagnosis was 49/μl in MM and 94 patients were divided into in high B lymphocyte group. Patients with low B lymphocyte count had a significant shorter progression-free survival (PFS) (p = 0.025) and a trend of unfavorable overall survival (OS) (p = 0.053) at diagnosis and after 4 cycles' induction treatments. Furthermore, Multivariate analysis showed that low B lymphocyte count at diagnosis independent of ISS stage was a significantly inferior marker for predicting PFS (p = 0.027, hazard ratio(HR) 2.281, 95 % confidence interval (CI) 1.098-4.741) and a trend for OS (p = 0.083, HR 2.394, 95 % CI 0.896-6.160). In summary, these results suggested the low B lymphocyte count was associated with poor outcome in MM patients at diagnosis and after treatment in the novel agent era.