An Italian clinical trial has shown that patients with newly diagnosed multiple myeloma (MM) who received a transplant of their own stem cells (an autologous stem cell transplant) and a second stem cell transplant from an “HLA-matched” sibling (an allogeneic stem cell transplant) had superior survival outcomes compared to patients who received two autologous stem cell transplants.

Published in the March 15 New England Journal of Medicine, the trial involved 162 consecutive patients with newly diagnosed MM who were under age 65 and had at least 1 sibling. Patients with a sibling whose blood cells expressed genetically identical surface antigens, human-leukocyte antigens - known as an HLA match - were offered the option of the autologous-allogeneic treatment regimen. The chances of a sibling being an HLA match are one in four.

Both patient groups received the same initial chemotherapy regimen at conventional dosing followed by high-dose myeloablative chemotherapy and an autologous stem cell transplant. Those with an HLA-matched sibling received radiation and an allogeneic stem cell transplant using the siblings’ cells (60 patients); those without an HLA-identical sibling received another round of high-dose chemotherapy and a second autologous stem cell transplant (59 patients). Of these patients, 58 receiving allogeneic transplant and 46 receiving double autologous transplants completed treatment.

Allogeneic stem cell transplants, while they are considered to have greater curative potential because they have a stronger antitumor cell effect, have been associated with high treatment-related mortality rates. Combined regimens like the one used in the Italian trial that employ “reduced-intensity” chemotherapy or radiation before the allogeneic transplant “have lowered transplant-related mortality to approximately 15 percent,” lead author Dr. Benedetto Bruno of the University of Turin and colleagues explained. But it has been unclear whether they offer a survival advantage.

In the trial, there was little difference in treatment-related mortality between the two groups; however, survival outcomes clearly favored those in the autologous-allogeneic transplant group - a 67-percent improvement in overall survival and a 53-percent improvement in event-free survival.