Late relapses following reduced intensity allogeneic transplantation in patients with multiple myeloma: a long-term follow-up study.

We analysed the long-term outcomes of 60 multiple myeloma patients who underwent reduced intensity allogeneic stem cell transplantation between August 2000 and March 2008. Regimens included fludarabine and melphalan conditioning (flu-mel regimen) for allogeneic haematopoietic cell transplant (HCT) or a planned tandem regimen consisting of high-dose melphalan conditioning for autograft followed by low-dose total body irradiation conditioning for allogeneic HCT (auto-allo regimen). Donors included human-leucocyte-antigen-matched siblings (n = 55) or matched unrelated donors (n = 5). With a median follow-up of 9·8 years, 7-year overall survival (OS) and progression-free survival (PFS) were 60% and 31%, respectively. By multivariate Cox regression analysis, disease status of complete response (CR) or partial response (PR) at transplant and the presence of chronic graft-versus-host disease were significantly associated with improved OS. Only disease status was significantly associated with improved PFS. We noted a surprising number of very late relapses, with six patients (10%) relapsing between 6 and 12 years post-transplant. Among the six late relapse patients, all were transplanted within 14 months of diagnosis, five had normal karyotypes, and five were in CR/PR. Our data provide additional evidence that, while survival may be extended by reduced intensity allogeneic transplant, ultimately, it may not offer a cure.