In another study underscoring the daunting risks facing survivors of childhood cancer, scientists at St. Jude Children's Research Hospital report that about 1 in 10 of the survivors will go on to fight second tumors and many will develop third and fourth cancers.
The study, published Monday in the Journal of Clinical Oncology, is the first to enumerate the risks facing adults who survived cancer as children.
It highlights the need for vigilant screening of the survivors, said Dr. Greg Armstrong, an assistant member at St. Jude's department of epidemiology and cancer control and the principal investigator on the study.
"It's hard to know what the future holds for this group, but it is concerning," Armstrong said.
As long-term, overall survival rates for childhood cancer have soared to 80 percent because of research at St. Jude and elsewhere, scientists have shown heightened interest in the myriad health issues confronting the growing population of survivors.
Their primary tool has been the Childhood Cancer Survivor Study, a federally funded project for which St. Jude is the coordinating institution. The 14,358 survivors enrolled in it had been diagnosed between 1970 and 1986, when they were 20 or younger.
The findings reported Monday are from the latest of 170 studies generated by the survivor project. Last year, Armstrong and other researchers reported that survivors of childhood cancer who contract either basal or squamous-cell skin cancer face an almost one-in-five chance of developing a more aggressive type of tumor within 15 years.
The latest study showed that 1,382, or 9.6 percent of the individuals in the survivor project, developed new tumors unrelated to their original cancers. Of that group, 386, or about 30 percent, developed third tumors, while 153 had four or more.
"Now that these childhood-cancer survivors are aging, we're seeing that they are at extremely high risk for a third and fourth cancer," Armstrong said.
The median age of the survivor group was 32, well before the stage in life when rates of prostate, breast and other cancers surge in the general population.
The reasons for the elevated risks likely include the radiation therapy that 70 percent of the survivors' group underwent, Armstrong said. More recent treatment methods rely less on heavy radiation.
But other factors play a role as well, he said. For one thing, survivors afflicted with multiple cancers might be genetically predisposed to the disease, or particularly vulnerable to the effects of radiation.
Armstrong said the study makes all too clear the need for survivors to get frequent cancer screenings. For instance, women who received chest radiation to fight childhood tumors should begin getting regular mammograms by age 25 -- 15 years before those in the general population generally start receiving them.
Additional cancers aren't the only threats facing survivors of childhood tumors. Another recent study led by St. Jude investigators showed that sleep and fatigue problems can sharply reduce the cognitive abilities of survivors.
"The difficulty with the cancer survivors is they're already at risk for neuro-cognitive problems because they've had radiation to the brain and chemotherapy," said Kevin Krull, an associate member of the department of epidemiology and cancer control at St. Jude and the study's corresponding author. "When you add sleep difficulties on top of that, it significantly exacerbates the problem."