BOSTON – An international team of researchers said they have pinpointed three variants of the genetic code that appear to set the stage for aggressive neuroblastoma, the deadliest solid tumor in early childhood.

The finding is not expected to immediately change the way doctors treat the cancer, diagnosed in 700 children in the United States alone each year, they reported in the New England Journal of Medicine.

However, it may lead to new therapies for the tumor, which kills more than 60 percent of its high-risk victims because the cancer often remains undetected until it has spread widely.

Because the chance is less than 1 percent that a neuroblastoma will reappear in a family, there is little point in doing genetic screening for the risk, Drs. Brian Kushner and Nai-Kong Cheung of the Memorial Sloan-Kettering Cancer Center in New York wrote in a Journal commentary.

The research team, led by Dr. John Maris of the Children's Hospital of Philadelphia, pinpointed the genetic defects by screening samples from 1,032 affected children and 2,043 seemingly healthy controls.

They checked their results by looking for the same abnormal code sequence in three independent groups with and without neuroblastoma, including 720 additional patients.

The researchers said little is known about the healthy function of the three genes, all of which appear on the sixth largest chromosome.

“Ultimately, they probably cause subtle changes in gene expression during early development, interacting with other genes yet to be discovered. This suggests that neuroblastoma has complex causes, in which a series of genetic changes may occur at different sites to combine into a 'perfect storm' that results in cancer,” Maris said in a statement.

Neuroblastoma has been difficult to study because different types can behave very differently. Some cases are so mild they can disappear on their own with little treatment.

But the tumor can be very aggressive, so it is responsible for 15 percent of all childhood cancer deaths even though it accounts for just 7 percent of all cases of childhood cancer.

(Editing by Maggie Fox; editing by Mohammad Zargham)