Children can be cured of the most common form of leukemia without undergoing radiation therapy that can cause brain damage, U.S. researchers from St. Jude Children's Research Hospital have reported earlier this week.
In a study of nearly 500 children who were diagnosed with acute lymphoblastic leukemia (ALL), the most common form of pediatric cancer, doctors from St. Jude's treated them only with drugs and did not administer radiation therapy to the brain. In spite of the fact that radiating the skull can help prevent tumors from spreading to the brain, it can also lead to serious learning disabilities in children.
At one point radiation was a routine therapy for acute lymphoblastic leukemia, and it is still administered to 20 per cent of the 3,400 young patients in the United States who are diagnosed with ALL each year in the hope of avoiding a relapse. However, the treatment is also associated with second cancers, stunted growth, hormone imbalances and cognitive problems.
For the purposes of a new study, researchers involved 498 young patients that have been undergoing a treatment at St. Jude and Cook Children's Medical Center in Fort Worth, Texas, between 2000 and 2007. The amount of chemotherapy was personalized for each child, depending in part on how many leukemia cells were present after initial treatment.
In order to find out whether cranial radiation would have made a difference, the investigators compared the results of 71 children, whose conditions previously would have qualified them for brain irradiation, to the outcomes of 56 patients who actually did receive radiation in the past. The results revealed that among 71 patients the 5-year survival rate was 91 per cent, significanlt better, when compared to a group of children who had previously received the radiation therapy for their ALL. For these children, the survival rate was 73 per cent. "These are the best results reported to date," said a principal author of the study, Mary Relling, St. Jude's chair of pharmaceutical sciences.
Relling added that even without radiation therapy, high-risk children in the study had longer remissions, coparedto what these children usually have. Researchers said that these patients may have showed improvements because of many small adjustments to their chemotherapy regimens, which last about 30 months. For instance, stronger steroids were used by doctors at this time than ever before.
Relling said that in the 60s, radiation appeared to be a big advantage in survival at a time when only 20 per cent or even less lived for 5 years, in part because new cancer cells would spread to the central nervous system. Using radiation therapy increased the survival rate to 50 per cent. That was a very noticeable increase in cure rates, and therefore almost every patient with childhood leukemia would get radiation at that time, Relling said. "Then there was a gradual backing away from that," so only kids in the highest-risk group received the therapy, where the risk of recurrence outweighed the risk of serious side effects.
Dr. Barton Kamen, chief medical officer for The Leukemia and Lymphoma Society and a pediatric oncologist, said that while scientists had already been leaning away from brain irradiation, the St. Jude findings appear to be very important and encouraging. However, he said that it is too early to predict whether the patients in the study will experience the well-documented side effects that can follow chemotherapy. "But I think this is a first good step," he concluded.
The study is published in the latest issue of the New England Journal of Medicine.