Fertility in Young Adults Who Did (Not) Store Testicular Tissue Before a Treatment Leading to Fertility Problems

The goal of this prospective comparative interventional cohort study is to assess the fertility status of young adult men (≥18 years) who received gonadotoxic treatment during childhood for the treatment of cancer or hematological disorders. These treatment protocols are highly gonadotoxic (i.e. they may cause later fertility problems) and therefore these patients have been proposed to store some testicular tissue during childhood as an option to preserve their fertility. The main questions this study aims to answer are (1) the impact of the received gonadotoxic treatment on the later fertility status and (2) the additional impact of a testicular biopsy procedure (performed at a young age to harvest testicular tissue for storage) on the future fertility. Participants will be asked to undergo a physical examination by a fertility specialist, to undergo a scrotal ultrasound, to give a blood sample, and to provide a semen sample. Researchers will compare the patients fertility status between the different received gonadotoxic treatment protocols, between patients who underwent a testicular biopsy procedure at a young age and those who did not, and compare the patients fertility status with the reproductive health of spontaneously conceived young adults.