Childhood cancer survivors have a persistent and high risk for a second primary cancer throughout their lives, says a new study published in the May 26 online issue of the Journal of the National Cancer Institute.
Previous studies established that second primary cancer risk after treatment in childhood is higher than that in the general population, but follow-up was restricted to a few decades and the incidence in long-term survivors was rarely investigated. This study presents data for incidence of second cancers among childhood cancer patients in the Nordic countries over a full age range, from birth to age 79.
In the study, Jørgen H. Olsen, M.D., of the Institute of Cancer Epidemiology, Danish Cancer Society, in Copenhagen, Denmark, and colleagues studied a cohort of 47,697 people who were diagnosed with cancer prior to the age of 20, from 1943 to 2005. Members of the cohort were followed for subsequent primary cancers listed in registries, and the age-specific risk pattern of the survivors was compared with that of the national populations using country and sex standardized incidence ratios (SIRs).
The researchers found that the observed incidence rate of new primary cancers was higher than the expected rates, and the relative risk of second primary cancers was statistically significantly increased in all age groups. A total of 1,180 second primary cancers were observed in 1,088 persons, yielding a SIR of 3.3, with the brain as the most common site. They also found that the relative risk for second primary cancers in male survivors was statistically significantly higher than in female survivors.
"This study quantified long-term temporal patterns of increased risk of cancer at specific sites in survivors of childhood cancer," the authors write. "The results may be useful in the screening and care of these individuals."