Many studies have shown Childhood Cancer Survivors (CCS) are ill-informed about long-term follow-up (LTFU). Massive open online courses (MOOCs) could easily allow a deployment at an international level and make reliable information available for all CCS, wherever they live. The MOOC team (specialists of LTFU care, communication professionals and CCS associations), bringing together nearly 130 people, designed a MOOC named "Childhood Cancer, Living Well, After" including three modules addressing transversal issues (lifestyle, psychological support, fertility problems) and eight modules covering organ-specific problems.

Detailed data on childhood cancer treatments were used during a study of feasibility in spring 2020 to allocate specific modules to each participant. The aim of the present study is to quantify the impact of this MOOC on the CCS knowledge about LTFU adapted to their own medical history, but also to measure how this MOOC can improve the LTFU care of each CCS.

Inclusion Criteria:

• Patient affiliated or entitled to a social security plan,
• Former patient included in the Childhood Cancer Observation Platform (CCOP) for pediatric cancer or leukemia (<15 years of age) between 2000 and 2010 with at least five years free of anticancer treatment
• Availability of computerized and validated treatment data in the Childhood Cancer Observation Platform (CCOP),
• A subject who has received informed information about the study and digitally signed the online express consent for subjects participating in the MOOC, and digitally signed the online express consent to continue for subjects not participating in the MOOC
• A subject who completed an initial COHOPER survey from Childhood Cancer Observation Platform (CCOP) online self-questionnaire
• Subject who has accepted that data collected as part of the COHOPER survey (including french national health data system (SNDS)) may be reused for scientific research purposes and shared with other research teams,

Exclusion Criteria:

• A subject having already been drawn for the START-MOOC1 feasibility study,
• A subject for whom a doubt, validated by the study coordinating physician, persists on the exact treatment received in childhood and does not allow the allocation of specific modules with certainty,
• A subject who has had several cancers and whose anticancer therapies are not all known,
• A subject who has not been treated in one of the participating referral centers,
• Subject having expressed opposition to the french national health data system (SNDS) interrogation following the sending of the information letter or share the data with other research teams,
• Pregnant