Invitation process
Within the web-based LATER study database, we developed a tool to automatically support the invitation process and logistics for the outpatient clinical visit during the period February 2016-February 2020. A tailor-made study invitation was generated to facilitate the informed consent for participation to all eligible survivors according to the outpatient clinic where the survivor was known (Amsterdam University Medical Center (location VUmc), Leiden University Medical Center, Erasmus Medical Center, University Medical Center Groningen, Radboudumc and Princess Máxima Center for Pediatric Oncology). A unique feature of this application is that the program assigned each survivor to the appropriate study arms for all 16 sub-studies, based on the characteristics of the survivor, his/her previous childhood cancer diagnosis and treatment, and the center from which he or she participated. If a survivor agreed to participate, study tests were planned in combination with an already planned outpatient visit. If a survivor did not respond to the initial invitation, the local center sent a reminder or attempted to establish contact to the survivor by phone. To optimize and standardize information for all centres study, manuals were developed concerning the logistics, data collection procedure, and storage of material. The study protocol for all LATER 2 sub-studies were approved by the medical ethics boards of all participating centers.