I used to work as a haematology nurse. When male patients were diagnosed with leukaemia, they were offered the choice to "bank" sperm as the treatment would make them infertile in the future. It was often imprtant to start treatment the same day as diagnosis, so there was a very very small window of time in which they could bank their sperm. After just being told they had cancer, and that if they ever wanted kids they had to produce a sample, you can imagine that any help they could get to do it was appreciated!