Molecular Imaging News
May 17, 2005
MIBG/I-131 Therapy Yields High Response, Low Toxicity in Children With Relapsed Neuroblastoma
Children’s Hospital of Philadelphia
Attaching a radioactive isotope to a compound that binds to tumor cells, physicians can selectively kill those cells and improve treatment for children with neuroblastoma, a cancer of the peripheral nervous system. Researchers achieved a high number of responses with very few side effects in 167 patients with neuroblastoma using a compound called meta-iodobenzylguanidine (MIBG) bound to iodine-131 .
John M. Maris, MD, a pediatric oncologist at The Children’s Hospital of Philadelphia, reported on a phase 2 trial of MIBG in a presentation on May 17 at the American Society of Clinical Oncology (ASCO) annual meeting in Orlando, FL. Dr. Maris was the principal investigator of the multicenter study, carried out at Children’s Hospital, the University of Michigan, and the University of California, San Francisco.
Neuroblastoma, which accounts for 10 percent of all pediatric cancers, often occurs as a solid tumor in a child’s abdomen or chest. The most aggressive forms of the disease often are resistant to conventional treatment with surgery and chemotherapy.
The treatment makes use of the fact that MIBG selectively concentrates in neuroblastoma tumor cells. MIBG, with a radioactive isotope of iodine-131 attached, is delivered as an intravenous infusion in a special lead-lined hospital room that shields parents and staff members from unnecessary radiation exposure. The MIBG then travels to tumor cells, taking the isotope with it. The cancer cells are killed by the iodine’s radiation.
In Dr. Maris’s study, the patients ranged from four months to 25 years of age; all had neuroblastoma that was resistant to first-line treatment, or had relapsed. The overall response rate to MIBG was 35 percent, with a higher response when the cancer was restricted to bone or bone marrow, and when the MIBG dose was higher. The main toxic effect was on blood cells, with 28 percent of the patients requiring infusions of hematopoetic (blood-forming) stem cells to counteract damage to their bone marrow cells. Other toxic effects were rare.
"MIBG is a promising therapy," said Dr. Maris. "It’s not a cure, but it brings us a step closer to controlling neuroblastoma as a chronic, nonsymptomatic disease."
Dr. Maris is involved in other studies of MIBG as a member of the New Approaches in Neuroblastoma Therapy program, a consortium of 14 universities and children’s hospitals working on novel therapies for high-risk neuroblastoma.
Co-authors of the study Dr. Maris presented at ASCO include Gregory Yanik, MD, of the University of Michigan; Katherine Matthay, MD, of the University of California, San Francisco; and Patricia Brophy, CRNP, of The Children’s Hospital of Philadelphia.