More than 40% of older patients with acute myeloid leukemia (AML) can remain in long-term cancer remission through a modified, less aggressive approach to donor stem cell transplantation, according to the results of a phase 2 study published in the Journal of Clinical Oncology (doi:10.1200/JCO.2015.62.7273).

AML is an aggressive, life-threatening blood cancer typically diagnosed in patients older than 60 years. The data represents new hope in a disease where the 5-year survival rate is often less than 10%, despite achieving initial remission.

Previous observational studies have suggested that allogeneic hematopoietic stem cell transplantation can reduce cancer recurrence and, therefore, improve overall survival for patients with AML.

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Patients older than 60 years, however, traditionally have been considered poor candidates and excluded from stem cell transplants due to other prohibitive health conditions or concerns about their ability to tolerate the intensive chemotherapy treatments necessary to eradicate leukemia cells before infusing the body with donor stem cells to rebuild healthy bone marrow.

Steven Devine, MD, director of Blood and Marrow Transplantation at The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute (OSUCCC – James) directed the study. The current study sought to determine whether a modified conditioning regimen for stem cell transplantation could improve long-term cancer remission rates for patients with AML age 59 to 75 years.

The phase 2 cooperative group trial enrolled 114 patients, median age 65 years, at 21 US hospitals between November 2004 and November 2011. The trial was conducted with grant support through the National Cancer Institute’s cooperative group trials network (Alliance for Clinical Trials In Oncology, formerly the Cancer And Leukemia Group B).

This is the first prospective study of this less-intense approach, known medically as reduced-intensity conditioning.

For this study, all patients received reduced-intensity chemotherapy (fludarabine followed by busulfan) prior to transplant, which essentially cut treatment strength by half compared with the traditional high-dose chemotherapy regimens used for younger patients. Patients were also given medications (tacrolimus and methotrexate) to help prevent graft-versus-host disease.

Researchers found that 42% of patients enrolled onto the study remained cancer-free 2 years after stem cell transplantation. Previously published data suggested that not more than 20% of similar patients who underwent conventional chemotherapy regimens would remain cancer free after 2 years.

“This new data offers strong support against using biological age as a limiting factor for stem cell transplantation in AML patients who are otherwise well positioned to tolerate and achieve long-term remission with this approach,” said Devine. “Close to half of the patients treated in this study achieved long-term cancer-free survival after 2 years. These outcomes are similar to what we would expect to see in younger patients and appear to be better results than those that can be achieved with conventional chemotherapy-based approaches typically used in AML patients [older than] 60 [years].”