Allogeneic transplantation in multiple myeloma.

Allogeneic transplantation has the potential to cure subgroups of patients with multiple myeloma, but its role is controversial due to high transplant-related mortality. Therefore, myeloablative allogeneic transplantation has fallen out of favor. Allogeneic transplantation using reduced-intensity conditioning (RICallo) has lower transplant-related mortality and may be an option for subgroups of patients. Upfront tandem autologous/RICallo (auto/RICallo) was shown to be superior to single auto or tandem auto/auto in both progression-free and overall survival in two studies with long-term follow-up, while four similarly designed studies with shorter follow-up did not show a significant advantage. All studies included patients less than 70 years of age. No study has shown that the auto/RICallo approach is inferior to auto or auto/auto. There have been indications that poor-risk cytogenetics may be overcome by the auto/RICallo approach. Encouraging results have also been seen in treatment of relapsed patients. Small studies indicate that combining allogeneic transplant with new proteasome inhibitors and immunomodulatory drugs may further improve results. Prospective studies including these drugs for induction, conditioning and post-allogeneic transplant maintenance are warranted and planned. New cell therapies, such as with natural killer cells have shown encouraging results in experimental animals and should be tried in combination with allotransplantation.