Rapid and Excellent Response to Hyper CVAD, Particularly with Thalidomide, in Plasma Cell Leukaemia and Long Term Remissions Following Allogeneic Stem Cell Transplantation.
Authors: Murthy Vidhya , Mwirigi Anne , Ward Susan , Rassam Saad M.B. 
Published: October 2019

Abstract
Abstract 4963
Plasma cell leukemia [PCL] is the most aggressive form of plasma cell neoplasms constituting 2% to 4% of all cases of plasma cell disorders. The presentation may be primary or secondary from an existing multiple myeloma. Approximately 60 to 70% of cases are primary. Immunophenotype of PCL cells differs from the most of other myelomas with more frequent expression of CD20 antigen (50% vs. 17%), and lack CD56 antigen present on the majority of multiple myeloma cells. PCL patients have a higher presenting tumor burden with higher frequencies of anaemia, organomegaly, renal impairment, increased levels of serum lactate dehydrogenase (LDH), β-2 microglobulin and plasma cell proliferative activity. Prognosis of PCL is exceptionally poor with median survival of 6.8 months for patients with primary PCL and 1.3 months for patients with secondary PCL. It responds poorly to conventional myeloma treatment and polychemotherapy approach has yielded some short lived success. Recently, bortezomib has been reported first line in combination with other agents with good initial response. In the UK, bortezomib is not approved as a first line treatment for plasma cell disorders. The Hyper CVAD regimen (fractionated high dose cyclophosphamide and dexamethasone with infusional vincristine and adriamycin) has been developed for acute lymphoblastic leukaemia by the M D Anderson group and has also been shown to be effective in other aggressive B-cell disorders such as mantle cell and Burkitt's lymphoma. There are few single patient anecdotal reports of its efficacy in plasma cell leukaemia. We report three cases of plasma cell leukaemia successfully induced with limited courses of Hyper CVAD chemotherapy and long term remissions achieved with stem cell transplantation.
Two men aged 53 and 56 and one woman aged 40 presented with PCL. All were anaemic (median Hb 8.5 g/dl), had impaired renal function, raised beta-2 microglobulin, creatinine, circulating plasma cells and plasmablasts and almost total marrow replacement by plasma cells. Two had IgG kappa paraprotein and one had light chains only. All had weak CD56 expression and two, where tested, were CD38 positive. Cytogenetic analysis was positive in one patient with t(4,14). All received hydration, bisphosphonate and allopurinol preparation before induction with the Hyper CVAD regimen. Two, given Thalidomide as well, achieved morphological complete remission (CR) after one course of therapy with marked reduction of paraprotein and normalisation of renal function. They received one further course of Hyper CVAD before receiving a Melphalan conditioned autlogous stem cell (ASCT) followed by a reduced intensity conditioning (RIC) sibling allogeneiec transplant in one patient. She remains in CR and full donor chimerism 11 months post SCT. The other is being prepared for ASCT to be followed by a RIC voluntary unrelated transplant. The patient with light chain disease achieved partial response (20% plasma cells in the bone marrow) after one course of Hyper CVAD without Thalidomide but a complete response after the second. He was consolidated with a third cycle, followed by a course of mini BEAM and then a RIC sibling allogeneic SCT. He had an early relapse 12 months following his SCT but responded to a course of donor lymphocyte infusion (DLI) and remains in CR 8.5 years from his SCT.

Discussion
To our knowledge, this is the largest series using this approach in PCL reported in the literature. PCL is a rare but aggressive disease with poor response to conventional therapy and short survival. Hyper CVAD appears to be highly effective in inducing a good response after 1-2 cycles of therapy particularly when combined with thalidomide. It appears that PCL is sensitive to the graft-versus-myeloma effect with long lasting remissions after allogeneic SCT and DLI therapy.

Disclosures
Rassam: Johnson and Johnson: Research Funding.