By Amy Norton
WEDNESDAY, Jan. 13, 2016 (HealthDay News) -- Fewer childhood cancer survivors are dying years later from lingering effects of the treatment that conquered their cancer, a new study finds.
Experts called the report, published in the Jan. 14 issue of the New England Journal of Medicine, "very good news."
"The findings substantiate what experts in the field have hoped would be true," said lead researcher Dr. Gregory Armstrong, of St. Jude Children's Research Hospital, in Memphis, Tenn.
Survival rates from many childhood cancers are high, but survivors still face what doctors call "late effects" -- health problems that develop months to years after the cancer treatment has ended.
Among U.S. children who survived cancer back in the 1970s and '80s, 18 percent died within the next 25 years, Armstrong said.
Sometimes, the initial cancer comes back. Often though, the health issues are related to the very treatment that saved a child's life, Armstrong explained.
Radiation and chemotherapy can damage the heart or lungs, or raise the chances of eventually developing a different type of cancer -- such as cancers of the brain, breast or blood cells. The specific risks vary depending on the cancer treatment, according to the U.S. National Cancer Institute (NCI).
For the new study, Armstrong's team looked at data on more than 34,000 childhood cancer survivors who were originally treated at U.S. and Canadian centers between 1970 and 1999.
Overall, 1,618 survivors died from a late effect of treatment during their follow-up -- which ranged anywhere from five to 38 years. Cancer, heart damage and lung disease were the most common causes.
But children treated for cancer in the 1990s had better long-term survival rates. Over the next 15 years, 2 percent died of a treatment-related cause, compared to 3.5 percent of those treated in the early 1970s.
The overall death rate dropped over time, too: Of children treated for cancer in the early 1970s, 12 percent died over the next 15 years. That fell to 6 percent among children treated in the 1990s.
So what changed? Armstrong said there were important shifts in the way doctors manage common childhood cancers such as acute lymphoblastic leukemia (ALL), Hodgkin lymphoma and Wilms tumor, which affects the kidneys.
In the 1970s, for example, most children with ALL received radiation to the brain, because leukemia cells can travel there. By the 1990s, that was true of only 19 percent of children with ALL.
Over the years, Armstrong explained, researchers have learned that in many cases, they can be less aggressive with certain treatments without dimming a child's chances of surviving the cancer.
That's partly because doctors have gotten better at identifying kids with a low risk of cancer recurrence -- with the help of improved imaging tests, for example.
Before the 1970s, when children developed ALL -- the most common childhood cancer -- they usually died, said Dr. Peter Manley, a pediatric neuro-oncologist at Dana-Farber/Boston Children's Cancer and Blood Disorders Center.
Other childhood cancers also carried a grim prognosis: In the mid-1970s, only about half of U.S. children with cancer survived for five years, according to the NCI, which funded the study.
"So when chemotherapy and radiation regimens were being developed, we were just focusing on the cure," said Manley, who was not involved in the new study.
That focus paid off: These days, over 80 percent of children with cancer are cured, according to the NCI.
Over time, though, the issue of late effects became apparent. "We had to say, wait a second: We're curing these children, but what's happening to them down the road?" Manley said.
Besides cutting back on some older therapies, doctors also have newer treatment options now, Manley noted. These include more precise ways of delivering radiation, and medications that can help protect healthy tissue from treatment-related damage.
In recent years, Manley said, so-called "targeted" drugs -- which zero in on tumor cells and aim to limit damage to healthy cells -- have become available for certain cancers. And more are under development.
"So we're continuing to move forward," Manley said. "We're really thinking about how [treatment] will impact patients' lives 20 years from now."
Still, both Manley and Armstrong stressed that childhood cancer survivors need to stick with their long-term aftercare.
The specifics vary from person to person: A young woman who had chest radiation in childhood may need regular breast cancer screenings, for example. But in general, Manley said, survivors should see their doctor at least once a year.
"It's important that they have that regular follow-up and maintain a healthy lifestyle," he said.
Dr. Nita Seibel, from the NCI's cancer therapy evaluation program, said the study delivered welcome news to those fighting childhood cancers.
"We've learned a lot about watching for late effects, screening for them, and intervening early," Seibel said. "So, it's very important that survivors continue with their follow-up."
Survivors have a 50 percent chance of developing a "significant medical condition" by the age of 50, Seibel added, but researchers continue to look for ways to minimize the long-term side effects of cancer treatments.
The U.S. National Cancer Institute has more on late effects of cancer treatment.