Exercise Training in Childhood Cancer

Inclusion criteria: * First/initial diagnosis of a primary oncologic disease according to the International Classification of Childhood Cancer (ICCC), requiring chemotherapy and/or radiation therapy or First/initial diagnosis of a relapsed oncologic disease according to the International Classification of Childhood Cancer (ICCC), requiring chemotherapy and/or radiation therapy or First/initial diagnosis of a secondary oncologic disease according to the International Classification of Childhood Cancer (ICCC), requiring chemotherapy and/or radiation therapy * Planned or started anti-cancer treatment (chemo- and/or radiotherapy) at one of the recruiting centres of the FORTEe trial * The patient is assessed by the treating team (pediatric oncologist, exercise professional etc.) as suitable to participate in the trial, e.g. due to medical or psychological reasons. * Existing informed consent (or assent) to participate in the study * The patient (and the legal guardian) has/have sufficient knowledge of the respective national or English language so that it is possible to carry out the informed consent as well as interviews (in age-appropriate language). * The patient is not in a terminal phase of the disease. Exclusion criteria: * Oncologic disease (primary/relapsed/secondary) according to the International Classification of Childhood Cancer (ICCC), requiring neither chemotherapy nor radiation therapy or solely requiring surgery * Reasons that already exist or are foreseeable at…