Donor stem cells not recommended as part of tandem stem cell transplantation

This study analyzed the results of 5 trials to compare tandem stem cell transplant combinations for newly diagnosed multiple myeloma. Researchers do not recommend a double stem cell transplant, where the stem cells for the first transplant are sourced from the patient and in the second are sourced from a donor. 

Standard treatment for multiple myeloma involves giving high doses of chemotherapy and replacing blood-forming cells destroyed by the cancer treatment with a stem cell transplant. Stem cells (immature blood cells) are removed from the blood or bone marrow of the patient (autologous transplant) or a donor (allogeneic transplant) and are frozen and stored. After the chemotherapy is completed, the stored stem cells are given to the patient through an infusion. While this treatment approach has improved response and survival, many patients experience disease relapse over time.

Studies have shown improved treatment outcomes with tandem transplants compared to a single transplant. This is when two transplants are performed within a given period. Usually both stem cell transplants carried out in tandem are autologous. More high-quality evidence is needed on autologous-allogeneic tandem transplants.

The aim of this study was to analyze recent results on tandem stem cell transplants for newly diagnosed multiple myeloma.

The results of 5 separate studies, involving 1,538 patients, were pooled into a single analysis. All patients were treated with tandem stem cell transplants after high-dose chemotherapy. Patients with a suitable matched donor were offered an autologous stem cell transplant followed by an allogeneic transplant (auto-allo). All other patients underwent a double autologous transplant (auto-auto).

Complete response rates were 65% higher with auto-allo tandem transplants compared to auto-auto tandem transplants. However, no significant differences in overall response rates were observed between the two tandem transplant combinations.

There were no significant differences in treatment-related events such as progression or death. Overall survival (time from treatment until death from any cause) was also similar between the two groups. Mortality rates without confirmed relapse were 3.55 times higher with auto-allo tandem transplants compared to auto-auto tandem transplants. 

Researchers reported higher complete response rates with auto-allo transplants compared to auto-auto tandem transplants. However, overall survival was similar between groups and the auto-allo combination was associated with higher non-relapse related mortality rates. Researchers do not recommend a tandem autologous-allogeneic stem cell transplant outside the setting of a clinical trial.