As childhood cancer treatments have become more successful, more and more patients are surviving to adulthood. In fact, the National Cancer Institute estimates that one in nearly every 500 adults in the United States between ages 20 and 45 is a survivor of childhood cancer.

With longer survival, there’s more chance that young patients will experience the late effects of their cancer treatments as they get older.

Dr. Leonard Toonkel, chairman of radiation oncology at Mount Sinai Medical Center in Miami Beach, is familiar with childhood cancer treatments. “We think about the side effects all the time, whether it’s children or adults we treat,” he says.

There is good news, however. Progress is being made in detecting and preventing the problems of late effects.

“To treat cancer, you need to use very powerful drugs with powerful side effects. We need to be alert for these expected and unexpected side effects of cancer therapies that might manifest later in life,” says Dr. Gervasio Lamas, chief of the Columbia University division of cardiology at Mount. Sinai Medical Center in Miami Beach.

That has led some doctors to redefine childhood cancer survival, says Dr. Steven Lipshultz, a professor of pediatrics at the University of Miami Miller School of Medicine and a member of the Sylvester Comprehensive Cancer Center.

He and many of his colleagues believe it should be more than not having measureable cancer for five years. “It also should include having the fewest toxicities and late effects of cancer and its therapies,” he says.

Late effects can involve just about every system of the body including the thyroid, heart, brain, lungs, pituitary and hypothalamus, kidneys, bones, lungs and reproductive organs.

They are not easy to study because they can occur 20 to 30 years after the initial cancer. Lipshultz and his colleagues were among the first to recognize the associations between childhood chest radiation therapy and later cardiovascular problems.

“We are just now seeing the first generation of survivors of childhood cancer reaching that age where we can see what some of these late effects are panning out to be,” he says.

That’s because in 1969, only 4 percent of children diagnosed with advanced leukemia were free of leukemia five years later – 96 percent died or had cancer again. Survival rates weren’t much better than they were in the 1940s.

In the early 1970s, children’s cancer specialists throughout the nation decided to work together to improve treatments, developing the cooperative group treatment protocols for childhood cancer.

“What has happened since is one of the biggest miracles in pediatric medicine,” says Lipshultz, who is the George Batchelor Professor of Pediatric Cardiology and the director of the Batchelor Children’s Research Institute.

Now, 80 percent of all children diagnosed with cancer in the United States and 90 percent diagnosed with leukemia are surviving. And those treated in the late 1970s and 80s are just now old enough to experience some of the late effects of their childhood cancer therapies.

Lipshultz and his team have been following this first generation of long-term survivors of childhood cancer. He presented his findings at the annual meeting of the American Society of Clinical Oncology (ASCO), held last month in Chicago.