New developments in post-transplant maintenance treatment of multiple myeloma.

Treatment of multiple myeloma (MM) has evolved significantly over the past two decades with high-dose chemotherapy and autologous stem cell transplant (ASCT), incorporating novel therapies such as proteasome inhibitors (PIs) and immunomodulatory drugs (IMiDs) during induction and post-transplant maintenance therapies. We reviewed the evolution of maintenance therapy from traditional chemotherapy, interferon (IFN), and prednisone to the current use of thalidomide, lenalidomide, and bortezomib in the post-transplant maintenance setting. Based on existing literature, either thalidomide or lenalidomide can be recommended for maintenance therapy post-transplant resulting in improved progression- free survival (PFS) and overall survival (OS). Thalidomide is less tolerated than lenalidomide and does not improve survival in patient subgroups who had achieved at least a very good partial response (VGPR) or who had chromosome 13 deletion. Thalidomide maintenance may be even detrimental in patients with high-risk cytogenetics. Alternatively, lenalidomide maintenance improves PFS in all subgroups of patients including those achieving at least a VGPR and those with high-risk cytogenetics, and improves OS in one other study. Bortezomib maintenance improves PFS and OS as part of induction and maintenance when compared to thalidomide maintenance and it is uncertain as to whether this improvement was due to bortezomib used during induction. The future research in maintenance therapy may include incorporation of current novel agents and testing new oral agents such as pomalidomide, or ixazomib or antibody therapy with elotuzumab.