Children with neuroblastoma, an aggressive cancer of the nervous system, can be treated successfully with less chemotherapy than previously thought, a new study suggests.

Of nearly 500 neuroblastoma patients who received chemotherapy treatments reduced by 40 to 70 percent from the current standard, 96 percent survived over a three-year period. Usually, a 90 percent survival rate is expected for patients at the intermediate stage of this cancer when standard chemotherapy treatment is given.

"This trial will lead to permanent treatment reductions in our protocol for treating this disease and will have a significant impact on the hundreds of children who are diagnosed with neuroblastoma each year," study researcher Dr. Katherine Matthay, chief of pediatric oncology at University of California, San Francisco's Benioff Children's Hospital, said in a statement.

The less chemotherapy given to children, the better, researchers say. Reducing the dose is especially important for young children whose developing bodies are extremely sensitive to the toxic cancer drugs, which are known to cause a host of side effects and increase the risk for later diseases unrelated to the cancer.

In the study, researchers reduced chemotherapy treatments by 40 percent for some patients and 70 percent for others. The reductions depended on the properties of the cancer cells, including their DNA content, the number of copies of certain cancer-causing genes, the rate of cell replication and factors that indicate the maturity of the tumor.

Patients whose tumors were labeled by researchers as favorable received the 70 percent reduction in their chemotherapy doses, and their survival rate was 98 percent. Those whose tumors were deemed "unfavorable" were given a stronger dose of chemotherapy their doses were reduced just 40 percent from the current standard and they showed a 93 percent survival rate.

Neuroblastoma is the most common tumor found in children younger than one year old and usually develops in the tissues of the adrenal glands, located above the kidneys, but can also begin in the chest, abdomen, neck or pelvis.

The cancer, which affects 650 children in the United States each year, is often not detected until it has grown and compressed surrounding organs, or spread to other parts of the body.

The study was published Sept. 30 in the New England Journal of Medicine.