By Mitzi Baker
Childhood Cancer Late Effects
New research highlights pediatric cancer survivors’ risk of second cancers
By Mitzi Baker
Treatment of childhood cancer has been an ever-improving success story. But ironically what destroys the cancer can leave the survivor with a greater chance of developing a second cancer. A study in the June 2 issue of the Journal of the National Cancer Institute provides the longest-running follow-up of former childhood cancer patients yet, helping to illuminate the actual long-term risks of second cancers among these survivors.
Epidemiologist Jørgen Olsen, the director of the Institute of Cancer Epidemiology in Copenhagen, Denmark, and his team analyzed data from national cancer registries in Denmark, Finland, Iceland, Norway and Sweden. The researchers looked at more than 47,000 survivors ranging in age from birth to 79—essentially every person diagnosed with childhood cancer in these five countries.
Statistically, Olsen says, the research team would have expected 356 cases of new cancers if the childhood cancer survivors’ risk was the same as that of the general population. But the researchers observed 1,180 new cancers—or 824 more than would be expected—among the survivors. The second cancers appeared most frequently in the brain (262 out of 1,180 cancers), the breast (148 cancers) and the digestive organs (123 cancers).
The study findings indicate that childhood cancer survivors, overall, are more than three times as likely to develop a new primary cancer as the general population—an increase in risk that drops with age. In absolute terms, this translates into less than 10 percent of survivors between 10 and 19 soon developing a second cancer and about 20 percent of pediatric cancer survivors in their 60s—a population in which cancer is more frequently diagnosed—developing a second cancer. “Although more common in survivors, cancer is still a relatively rare outcome, indicating that survivors should not be too concerned,” Olsen says. But, he adds, being aware of their higher risk will hopefully increase the chances of early detection and treatment for those who eventually do develop a second cancer.
The results confirm previous research indicating that pediatric cancer survivors are generally at increased risk of second cancers. The big contributions of the new research are the large number of patients included in the study and the long follow-up, which shows that the higher risk persists into middle age and beyond, says pediatric oncologist Daniel Green, whose research at St. Jude Children’s Research Hospital in Memphis, Tenn., includes work on the long-term effects of treatment for childhood cancer. Green was not involved with the new study.
“The bottom line is that the cancer-causing effects of treatment for childhood cancer persist through life, though the risk is highest in the decades directly after treatment,” says Anne Lown, an epidemiologist at the University of California, San Francisco, and the Public Health Institute in Oakland, Calif., who also was not involved in the study. “However, the devil is in the details: A survivor’s own risk will vary greatly depending on gender, age, primary cancer diagnosis and the type of treatment received.”
Green agrees. “This study doesn’t include information on [treatment] exposure, and that’s what you need to clear up: which groups [of patients] have the highest risk,” he says.
A pediatric cancer survivor has to consider his or her own personal cancer history to make the current study’s findings relevant, says Lown. For instance, between the ages of 40 and 79, survivors of some cancers face barely any increased risk for a second cancer, according to the study, while survivors of brain cancer may have more than 10 times the risk of someone who didn’t have cancer as a child. In addition, it’s known that survivors who have had high doses of radiation to the chest and abdomen should undergo regular screenings due to the subsequent cancers they are more likely to develop, particularly breast cancer in women, says Green.
Importantly, the new study found an increased cancer risk among childhood survivors despite a reduction in radiation dosage in Nordic countries in the 1970s and 1980s. Previous studies based on the same data suggested that chemotherapy drugs may play a critical role in causing secondary cancers in survivors—possibly by enhancing the carcinogenic effect of radiation. Green and Olsen are both involved in further research that could help determine the long-term effects of different types and doses of treatment.