Primary Plasma Cell Leukemia: Results of a Retrospective Italian Multicentric Survey.

Epidemiological and clinical information on Primary Plasma Cell Leukemia (pPCL) are rarely reported.

To evaluate in patients (pts) with pPCL the clinical features, the prognostic factors, and the efficacy of treatments.

A multicenter retrospective cohort study was carried out between January 2000 and December 2008 in 26 Italian hematology divisions. A total of 128 cases of PCL were collected, and 73 of them (57%) were classified as primary (M/F 43/30).

The median age was 63 years (range 32-86). At diagnosis the median values of peripheral blood plasma cells and bone marrow plasma cell infiltration were 2.7 × 10 9/L (range 0.4-49.9) and 80% (range 37-100), respectively. The median values of hemoglobin, white blood cell count, and platelet counts were 9.1 g/dl (range 4.8-12.9), 13.7 × 10 9/L (range 1.3-56.7), 116 × 10 9/L (range 8-428), respectively. Extramedullary disease was present in ten cases (14%) and included testis, muscular, neuromeningeal, and cutaneous localization. At diagnosis, 64 pts (88%) had at least one CRAB sign, namely 35 pts (48%) had low hemoglobin level, 20 pts (27%) calcium ≥11 mg/dl, 32 pts (44%) creatinine ≥2 mg/dl, and 47 pts (64%) had osteolysis. In 41 pts (56%) cytogenetic study was performed, revealing an unfavourable karyotype in 17 (23%), in 13 of them del(13q-). Seventy-two pts received front-line therapy (1 died early, receiving only support treatments and steroids), that included antracycline-containing regimens in 36 pts (50%), and single alkylating agents in 17 pts (24%, 9 cyclofosfamide and 8 melphalan). In 11 of them Bortezomib (BTZ, n= 7) or Thalidomide (THAL, n= 4) were also employed. Finally, 19 pts (26%) received BTZ (4) or THAL (5) or both (10) as unique treatment. Twenty-one pts (29%) underwent autologous stem cell transplantation (SCT) as part of front-line therapy, followed by allogeneic-SCT in four cases; two additional pts underwent only allogeneic-SCT. A complete or partial remission after front-line therapy was achieved in 20 pts (27%) and 19 pts (26%) respectively (overall response rate 53%). The median overall survival (OS) was 13.1 months (range 0.5-75.8); 30.6 months (range 4.7-75.8) in responder pts and 4.2 months in non-responder ones (range 0.5-75.6, univariable hazard ratio, HR, 0.28, 95% CI 0.11-0.39). In the responder pts the median progression free survival (PFS) was 17.2 months (range 1.4-72.1). Of note, in SCT pts the median OS and PFS were 38.1 months (range 4.8-75.8) and 25.8 months (range 1.4-72.1) respectively, with a significant advantage with respect to non-transplanted pts in OS (median 9.1 months, range 0.5-75.6, HR 0.28, 95% CI 0.16-0.52) and in PFS (median 7.3 months, range 1.7-17.7, HR 0.29, 95% CI 0.04-0.44). The low number of allo-SCTs did not allow a reliable separate statistical analysis. A multivariable Cox proportional hazard regression analysis showed that OS was influenced by lack of initial response (HR 2.62, 95% CI 1.04-6.57), albumin <3 g/dl (HR 3.33, 95% CI 1.64-6.76), and SCT (HR 0.34, 95% CI 0.12-0.98). Pts with hypercalcemia at diagnosis had a shorter PFS (HR 4.0, 95% CI 1.04-15.24); the PFS was favourably influenced by SCT (HR 0.05, 95% CI 0.009-0.28). Overall, the use of BTZ and/or THAL did not influence the OS and PFS.

pPCL is a highly aggressive lymphoprolipherative malignancy, characterized by a poor prognosis and a low response rate to conventional therapy. The use of high-dose chemotherapy followed by autologous or allogeneic-SCT is a very effective therapy leading to 66% increase in the OS and to 95% increase in PFS in respect to non-transplanted pts. Apparently, the use of novel drugs such as BTZ and THAL did not produce a further amelioration in the patient outcome. However, those latter findings should be taken with caution, given the relatively low number of treated pts.

No relevant conflicts of interest to declare.