HEALTH

Refined therapies cut risk of second cancers, St. Jude study shows

Tom Charlier
USA TODAY NETWORK – Tennessee

Confirming an effect long suspected but never before proven, a study based at St. Jude Children's Research Hospital found that the reduced use of radiation in treating young cancer patients radically cuts the chances they'll develop second cancers years or decades after surviving their first.

A study based at St. Jude Children's Research Hospital found that the reduced use of radiation in treating young cancer patients radically cuts the chances they'll develop second cancers years later.

In findings published Tuesday in the prestigious Journal of the American Medical Association, researchers concluded that only 1.3 percent of patients treated for cancer in the 1990s developed second malignancies within 15 years — a 38 percent decline from the 2.1 percent of kids treated during the 1970s. During that time, the percentage of child cancer patients treated with radiation fell from 77 to 33, and the individual doses of radiation used also dropped.

The findings build on earlier studies showing the benefits of the less-toxic treatments that accompanied advances in fighting childhood cancer. During the 1960s and '70s, when research in the field was in its relative infancy and survival rates were low, doctors sometimes used so much radiation that the kids who survived the disease experienced lasting physical and cognitive effects as well as late-developing problems such as second cancers.

The study is particularly important given that 84 percent of the kids who contract cancer now survive the disease over the long term. The U.S. is home to around 400,000 people who survived childhood cancer.

The research sprang from the long-term Childhood Cancer Survivor Study funded by the National Cancer Institute and headed by Dr. Greg Armstrong, a member of St. Jude's department of epidemiology and cancer control. Armstrong said that while researchers long assumed that reduced use of radiation would lower the risk of second cancers, the study confirmed the relationship.

He called second malignancies the "most ominous late effect of pediatric cancer treatment," saying they often resulted from more primitive therapies.

"The goal in the 1970s was simply to cure," Armstrong said. "Once we achieved those high cure rates ... we realized it wasn't enough. We want to set them (patients) up for a long life."

Still, the advancements in pediatric cancer treatment haven't completely eliminated the risk of second malignancies. While survivors who had been treated during the 1970s were six times more likely to develop cancer than others their age and gender, those cured in the 1990s were still four times more likely.

The most common second malignancies were breast and thyroid cancers. In fact, girls who receive chest radiation for Hodgkin's lymphoma run about a 30 percent chance of developing breast cancer by age 50, Armstrong said.

Radiation remains a necessary tool in treating some cancers, he said, but its use has diminished as researchers learned how to distinguish the types of malignancies for which it is most needed.

According to the NCI, about half of all cancer patients, including adults, receive some type of radiation therapy during the course of their treatment.