The clinical characteristics and prognosis of patients with primary plasma cell leukemia (pPCL) according to the new IMWG definition criteria

Clinical and cytogenetic characteristics of primary and secondary plasma cell leukemia under the new IMWG definition criteria: a retrospective study

BACKGROUND

Plasma cell leukemia (PCL) is a rare and aggressive plasma cell disorder, exhibiting a more unfavorable prognosis than multiple myeloma. PCL is classified into pPCL and sPCL. Recently, the IMWG has recommended new PCL definition criteria, which require the presence of ≥5% circulating plasma cells in peripheral blood smears. Due to its low incidence, research on pPCL and sPCL is limited.

METHODS

We conducted a retrospective study and analyzed clinical and cytogenetic data of pPCL and sPCL patients. Overall survival (OS) and progression-free survival (PFS) were assessed by the Kaplan-Meier method, and survival distributions were compared using the log-rank test.

RESULTS

This is a small cohort comprising 23 pPCL and 9 sPCL patients. Notably, sPCL patients showed a higher incidence of extramedullary infiltration and a higher percentage of bone marrow plasma cells (p = 0.015 and 0.025, respectively). Although no significant difference was found between the two groups in OS and PFS, a trend emerged suggesting a superior survival outcome for pPCL patients, with a higher cumulative 1-year PFS rate (38.3% vs. 13.3%) and a lower early mortality rate (mortality rate at 3 months: 15% vs. 33%). We also suggested that pPCL patients carrying t(11;14) may have a longer median survival time than individuals with other cytogenetic abnormalities, but this was not confirmed due to the small sample size.

CONCLUSION

Our study revealed clinical and cytogenetic features of pPCL and sPCL patients according to the new diagnostic criteria. The findings suggested a generally better prognosis for pPCL than sPCL and the likelihood of t(11;14) translocation acting as a favorable prognostic factor in pPCL. It is important to note that our study had a limited sample size, which may lead to bias. We hope well-designed studies can be conducted to provide more results.

Improved survival of patients with primary plasma cell leukemia with VRd or daratumumab-based quadruplets: A multicenter study by the Greek myeloma study group

We evaluated the efficacy and prognostic impact of bortezomib-lenalidomide triplet (VRd) or daratumumab-based quadruplets (DBQ) versus previous anti-myeloma therapies, that is, bortezomib standard combinations (BSC) or conventional chemotherapy (CT), in a large cohort of patients with primary plasma cell leukemia (pPCL), including those fulfilling the revised diagnostic criteria, that is, circulating plasma cells (cPCS): ≥5%; 110 pPCL patients (M/F: 51/59; median age 65 years, range: 44-86) out of 3324 myeloma patients (3%), registered in our database between 2001 and 2021, were studied; 37% had cPCS 5%-19%; 89% received novel combinations including DBQ (21%), VRd (16%) and BSC (52%); 35% underwent autologous stem cell transplantation. 83% achieved objective responses. Treatment with VRd/DBQ strongly correlated with a higher complete response rate (41% vs. 17%; p = .008). After a median follow-up of 51 months (95% CI: 45-56), 67 patients died. Early mortality was 3.5%. Progression-free survival was 16 months (95% CI: 12-19.8), significantly longer in patients treated with VRd/DBQ versus BSC/CT (25 months, 95% CI: 13.5-36.5 vs. 13 months 95% CI: 9-16.8; p = .03). Median overall survival (OS) was 29 months (95% CI: 19.6-38.3), significantly longer in patients treated with VRd/DBQ versus BSC/CT (not reached vs. 20 months, 95% CI: 14-26; 3-year OS: 70% vs. 32%, respectively; p < .001; HzR: 3.88). In the multivariate analysis VRd/DBQ therapy, del17p(+) and PLT <100.000/μL, independently predicted OS (p < .05). Our study has demonstrated that in the real-world setting, treatment with VRd/DBQ induces deep and durable responses and is a strong prognostic factor for OS representing currently the best therapeutic option for pPCL.

Validation of the revised diagnostic criteria for primary plasma cell leukemia by the Korean Multiple Myeloma Working Party

The International Myeloma Working Group has recently revised the diagnostic criteria for primary plasma cell leukemia (PCL) to circulating plasma cells (CPCs) ≥ 5% in a peripheral blood smear. The present study validated new criteria in patients with multiple myeloma or PCL diagnosed using the previous diagnostic criteria, who were administered immunomodulatory drugs or proteasome inhibitors as induction therapy. We analyzed the medical records of 1357 patients from eight hospitals in South Korea. The median age of the all patients was 64 years, and 187 (13.8%) had CPCs at diagnosis. Only 79 (5.8%) of the patients had ≥ 5% CPCs. The median overall survival (OS) of patients with CPCs ≥ 5% and ≥ 20% was similar, but had significantly inferior median progression-free survival (PFS) and median OS than those with CPCs < 5% (13.1 vs. 21.5 months, P < 0.001, and 21.5 vs. 60.9 months, P < 0.001, respectively). Primary PCL diagnosed using the revised criteria presented with higher total calcium levels and serum creatinine levels, lower platelet counts and frequent organomegaly and plasmacytoma at diagnosis. Univariate and multivariate analyses demonstrated that the presence of plasmacytoma and elevated serum β2-microglobulin were significantly associated with OS in primary PCL. In conclusion, the revised criterion of CPCs ≥ 5% in a peripheral blood smear is appropriate for PCL diagnosis.