Brief Summary: The goal of this observational study is to learn how gonadotoxic treatments (chemotherapies, radiotherapies or immunotherapies) affect the fertility status of participants with cancer. The main questions it aims to answer are: * in females, if cancer therapies reduce the Anti-Müllerian hormone (AMH) concentration (ovarian reserve); * in males, if cancer therapies reduce sperm concentration (sperm quality).

Detailed Description: This is an international multicenter prospective exploratory study of fertility related data generated mostly routinely in fertility centers in Switzerland belonging to the Swiss network "FertiSAVE" as well as in fertility centers in Germany and Austria belonging to the German-Swiss-Austrian network "FertiPROTEKT" and further international centers who are interested to participate. Both networks include in total around 200 centers. The data, which are mainly part of the routine clinical care, will be collected by the physicians and added to the REDcap study registry. Patients will be coded by the center to be able to follow them up. Each center will only have access to its own registry data set. Access to the total data set is only permitted for the principal investigator and the specific sub-investigators. Data collection before the start of gonadotoxic treatment will be performed for 5 years. Data collection after the end of gonadotoxic treatment will be performed for 10 years (time points: at 12-15 months, at 5 years and at 10 years).