Plasma Cell Leukaemia. Experience from Tertiary Referral Centres in Abu Dhabi

Plasma cell neoplasms range from an indolent disease (MGUS) to highly aggressive and relatively rare Plasma Cell Leukaemia (PCL). The diagnostic criteria for PCL is well established and includes plasmacytosis of greater than 20% of total white cell count or an absolute plasma cell count of greater than 2 X 10⁹/L in peripheral blood. It is classified as either primary (pPCL) if there is no antecedent history of Multiple Myeloma (MM) or secondary (sPCL) arising as a leukemic event of MM. The median survival of PCL remains poor despite the use of novel agents and stem cell transplant. Here we report our experience with PCL.

Method:

Retrospective review of the medical records of patients with plasma cell dyscrasia identified through the tumour registry between January 2008 and March 2016. Eight patients were identified with diagnosis of PCL.

Results:

The median age was 53.5 years (range 34-77 years), male to female ratio was 5:3. There were four cases of sPCL while the other four patients had pPCL. The median time for transformation in sPCL was 199 weeks (range 163 to 244 weeks).

All 4 patients with sPCL had received treatment with novel agents including bortezomib and IMIDS (lenalidomide/thalidomide) as part of their myeloma therapy. At the time of transformation two patients were unfit for any therapy while the other two patients were re-induced with bortezomib, lenalidomide and dexamethasone (RVd) with no response. None of the four patients had undergone autologous stem cell transplantation (due to unavailability of hematopoietic stem cell transplant facilities in UAE as well as socioeconomic reasons). The median survival after diagnosis of sPCL was 5.4 weeks (range 4-11 weeks).

Patients with pPCL were treated with RVd (n=3) and VMP N=1. One patient also had an autologous stem cell transplant. Patients with primary PCL had a better median survival of 37 weeks (range 14 - 133 weeks) with one patient alive and under therapy 14 weeks after diagnosis.

Conclusion:

Plasma cell leukaemia remains a disease with extreme poor prognosis and an overall mortality of 88 per cent in our experience. Interestingly two patients with pPCL were noted to have evidence of plasma cell disorder (elevated total protein) a median of 8 months before the diagnosis of pPCL. Whether these two cases truly represent pPCL or 2ndry event because of under diagnosis of MM remains speculative at best. One of the above two patients also had a diagnosis of chronic myeloid leukaemia on Imatinib and was in a major molecular remission. Patients with primary plasma cell leukaemia tend to do relatively better as compared to secondary plasma cell leukaemia where the transformation is catastrophic with a very short median survival. The difference in survival between pPCL and sPCL is most likely because the sPCL has a more resistant disease due to previous treatment and clonal evolution of their disease.

Second generation novel agents including carfizlomib and the monoclonal antibodies daratumomab and elotuzumab should be evaluated in the induction and maintenance strategy to improve the outcome of PCL.