For Survivors of Childhood Cancer, Walk

Exercise could improve the life expectancy of adults who survive cancer as children, even if the activity begins years after treatments end, according to an inspiring new study.

But the study also finds that many survivors rarely, if ever, move much.

In one of the most stirring success stories of modern medicine, many childhood cancers are now treatable, including types that once would have been fatal.

But there can be costs associated with these advances. Some of the standard treatments for cancer, such as chemotherapy and radiation, are known to weaken the heart or increase the risks for subsequent tumors, including in children.

As a consequence, young people who survive cancer tend to die, on average, about 10 years earlier than unaffected adults of the same age, epidemiological studies show. In some cases they die from recurrences of their original malignancies, but more often from early heart disease or new cancers.

Exercise is known, of course, to reduce the risk that someone will develop or die from heart disease. It also can lessen the incidence of a number of types of cancer.

But whether physical activity likewise may affect and extend the life spans of people who survived childhood cancers has not been known.

So, for the new study, which was published this month in JAMA Oncology, researchers at Memorial Sloan Kettering Cancer Center in New York, St. Jude Children’s Research Hospital in Memphis and other institutions turned to a singular resource, the Childhood Cancer Survivorship Study.

This is a large database of health information about adults from the United States and Canada who are at least five years away from a diagnosis of any type of cancer found before they turned 21. When these participants first join the study, they complete a variety of medical tests and questionnaires and then, in subsequent years, repeat the testing occasionally.

Now, the researchers winnowed the database to find participants who had answered a specific question about their current physical activity habits. That question asked them whether and how often they had exercised in the past week at an intensity that made them “sweat or breathe hard (e.g., jogging, basketball, etc.)?”

The researchers wound up with answers and health information from 15,540 men and women. Additionally, more than 5,600 of these participants answered a follow-up question eight years or so later about their ongoing exercise routines.

The researchers divided these participants into groups, based on whether, at the start of the study, they said that they briskly exercised often, occasionally or almost not at all.

The researchers also looked into deaths, cross-referencing data from the National Death Registry, to see whether in the 10 or 15 years after people had joined the study, any had passed away.

And, although most of the men and women were still relatively young at that point — few were past age 50 — more than 1,000 had died. About 100 of these deaths were the result of recurrences of people’s original childhood cancers. But most of the rest were the result of other health problems, particularly heart disease.

Exercise was associated with differences to that trajectory, though. Deaths were most common among the adults who said that they seldom exercised. Nearly 12 percent of them passed away during the follow-up period. But only about 7 percent of the men and women who often exercised passed away. (The researchers controlled for factors such as body mass index and the types of cancer treatments people had completed.)

Based on these numbers, the scientists determined that the sweet spot for exercise, in terms of improving longevity among people who had survived cancer as children, seems to be about an hour of brisk walking almost every day.

The odds were particularly encouraging for people who had been infrequent exercisers but ramped up their workouts over the years, the researchers found. Their risk for premature death was about 40 percent lower than for participants who had been and continued to be physically inactive.

The inactive were in the majority, however, representing about 70 percent of the total.

“Exercise certainly appears to be beneficial” for people who have survived a childhood cancer, said Lee Jones, chief of the exercise oncology service at Memorial Sloan Kettering, who oversaw the study, perhaps because it can both strengthen hearts and lessen the chances of a new cancer.

But those possibilities are speculative. This study did not examine how exercise may improve longevity. It also is observational and cannot prove that exercise actually caused survivors of childhood cancer to live longer, only that there was an association between more exercise and longer life spans.

It is also possible, Jones said, that the healthiest people exercised more than those who were in worse condition and their robust health increased their life spans, not exercise itself.

He and his colleagues are in the middle of experiments with cancer survivors that they hope will better tease out the role of exercise.

But for now, he said, if you or a loved one have had cancer, “I’d strongly recommend talking with your physician about exercise.”