Till recently, transplantation of haematopoietic stem cells found in the bone marrow has been the only curative option for patients with thalassemia major (genetic inability to produce normal, adult haemoglobin leading to severe anaemia). Since only 30-35% of such patients have a suitable tissue-matched donor in the family, a majority of them rely on regular blood transfusions for survival.
A study carried out at Chennai’s Apollo Speciality Cancer Hospital now gives hope to children who have no related donors. Of the 25 thalassemia major patients who underwent stem cell transplantation at the hospital (from December 2012 to November 2016) from tissue-matched unrelated donors, none rejected the donated cells. The median age of the patients was five years (between one to 14.5 years). Also, a majority of them received stem cells separated from the blood (peripheral blood stem cells) . The results of the study were published in Pediatric Hematology Oncology Journal.
Even when there is perfect tissue match between a donor and recipient, there is a 5-10% risk of rejection of the donated stem cells by the patient’s immune system. Thalassemia patients undergo several blood transfusions and antibodies from several donors remain in the patient’s body and are responsible for rejection.
While 60% of the children suffered from acute graft versus host disease (a complication that arises when the transplanted tissue is genetically different from the host’s) only two patients died due to this; none suffered from chronic, extensive graft versus host disease. “The two patients who died did not have a perfect tissue match,” says Dr. Revathy Raj, Senior Consultant at Apollo Speciality Cancer Hospital and one of the authors of the paper.
The probability of surviving nearly three years after stem cell transplantation was 95%. The study found that as long as high tissue compatibility between a donor and the recipient is maintained, stem cells from unrelated donors can be used for curing thalassemia major.
“Our study found that children who underwent tissue-matched, unrelated stem cell transplantation had the same survival rate as children with a family-matched donor,” says Dr. Raj. “Previously, drugs that caused a lot of damage to the gut and liver were used prior to transplantation. But now we have used newer, liver-safe drugs.”
“Stem cell transplantations from perfectly tissue matched, unrelated donors are done in multiple centres in the country. Results from tissue matched, unrelated donor transplantations are steadily improving and becoming comparable to tissue matched related donors,” says Dr. Vikram Mathews, Professor and Head at the Department of Haematology, CMC Vellore.
Talking about the caveats, Dr. Mathews says: “These results have to be kept with the risk profile of the patients in mind. Good results can be anticipated in the case of young and good-risk patients and should not be generalised to all patients.”
Peripheral blood stem cells from donors were used in 80% (20 patients) of the patients, three children received umbilical cord blood stem cells while only two children received bone marrow-derived stem cells. The study found that no patient suffered from chronic, extensive graft versus host disease though a majority received peripheral blood stem cells.
While all the 25 patients were Indians, 60% of stem cell donors were Indians and the remaining were Caucasians. “The chances of finding perfectly matched Indian donors are now high. We must encourage more people to register to donate stem cells as we have about 10,000 new thalassemia patients each year,” says Dr. Raj. No surgery is required when a person donates stem cells found in the blood (peripheral blood stem cells) and the stem cells in the donor get replaced in a week.