[The German cohort of long-term survivors of childhood cancer. A population-based cohort in the German Childhood Cancer Registry].

Due to the considerably improved prognosis of childhood cancer, research regarding the long-term consequences has become highly valuable. The population-based German Childhood Cancer Registry forms the basis of the long-term follow-up of these patients. The cohort comprises over 25,000 patients (with malignant diseases before their 15th birthday) with a current address and who are neither deceased nor lost to follow-up. The current median age is 21 years and 500 individuals are already over 40 years old. All the long-term survivors are contacted every 5 years at the latest and are asked about possible long-term effects. Due to the continued improvement of the prognosis for childhood cancer over the years, such cohorts of long-term survivors have altered in their composition. Corresponding long-term follow-up studies can therefore not easily be compared to one another. This is illustrated by a nested case control study on the possible relationship between the occurrence of second tumors and the therapy undergone for the initial diagnosis. The cohort of long-term survivors in the German Childhood Cancer Registry is highly valuable both for research on long-term effects in Germany as well as for integration into international projects.