Background: Every year over 300 children and adolescents up to the age of 18 years are newly diagnosed with cancer in Switzerland. Survival after childhood cancer has increased substantially over the last decades and 10-year survival now exceeds 85%. This results in an increasing numbers of childhood cancer survivors - currently around 7,000 survivors in Switzerland. Due to cancer treatment or the cancer itself, a large part of the childhood cancer survivors suffers from late effects. Early diagnosis and intervention can reduce morbidity and mortality due to late effects. Therefore, regular follow-up care, even beyond childhood, is very important, but transition from pediatric to adult follow-up care is a critical point. In Switzerland there are very different aftercare and transition models, although it is unclear which aftercare strategy is the best and meets the needs of survivors. The Aftercare of Childhood Cancer Survivors (ACCS) study aims to fill this gap.

Objectives: The main objective of the ACCS study is to identify the current needs of adolescent and young adult long-term survivors in terms of follow-up care by comparing three different transition practices. The secondary objective is to assess survivors' knowledge on their diagnosis, therapy and follow-up examinations longitudinally.

Methods: ACCS is a multicenter questionnaire-based study, including survivors from three pediatric oncology centers in Switzerland. Eligible survivors who already transitioned to adult care at start of the study once receive a letter explaining the purpose of the study, the study information, the informed consent form, and the questionnaire. The questionnaire asks about cancer knowledge and additionally includes validated scales on cancer worry, self-management skills, ongoing care, and expectations. The survivors send the documents back by a prepaid envelope. Eligible survivors before transition to adult care at start of the study receive a letter explaining the purpose of the study, the study information and informed consent form, and the first questionnaire two to four weeks before the next scheduled follow-up visit. They can either send the documents back before the visit or bring them to the visit. The participants receive three month after the visit a short questionnaire to assess cancer knowledge. Three month after the follow-up visit after transition (15 month after last visit in pure pediatric setting), the participants receive the first comprehensive questionnaire again.

Rationale and significance: There are very different aftercare and transition models in Switzerland, although it is unclear which follow-up care strategy best meets the needs of survivors. The data collected within the ACCS study helps to define which transition and follow-up care strategies and related factors are favoured by adolescent and young adult survivors. Adaption of transition processes to the needs of survivors improve adherence to follow-up care of adult childhood cancer survivors. As late effects increase with increasing time from treatment, adult survivors of childhood cancer are at particular risk to develop late effects and it is important that they continue follow-up care.