Unfortunately there is no straight answer to this question. Autologous stem cell transplants are more commonly performed, because there is no need to find a matched donor. This makes the process a lot simpler. However, there is a problem. Some cancerous cells might get collected as well and later transfused back into the patient.
Studies show that indeed the chances of recurrence are lower in patients who receive an allogeneic rather than an autologous transplant. There is no risk of collecting cancer cells. Allogeneic stem cell transplants (and bone marrow transplants) however have a higher risk of early complications and graft mismatch. This leads to higher rates of transplant realted deaths in those receiving allogeneic transplants. The improvement in rates of relapse is in many cases offset by the increase in complications.
Current consensus is that alloegenic transplants be reserved for those who have an identical matched HLA sibling - these patients have the least chance of transplant complications.
