Inclusion Criteria:  Aged 18-39 years at cancer diagnosis Having a histologically and/or cytologically confirmed cancer diagnosis, including leukemia, (non-)Hodgkin lymphoma, testicular cancer, osteosarcoma, Ewing sarcoma, breast cancer, and cervical cancer. Scheduled to start systemic therapy with curative intent. Allowed treatments (concurrent or sequential) are: surgery, radiotherapy, chemotherapy, antibodies.  Exclusion Criteria:  patients who are not able to understand the patient information letter and informed consent form patients who will be treated with immune checkpoint inhibitors or targeted therapy with inhibitors of angiogenesis patients who have been treated with systemic therapy or radiotherapy for a previous malignancy (exceptions: in situ carcinoma of the cervix or uterus and adequately treated basal and squamous cell carcinoma of the skin).