(AP) — New research shows a painstaking surgical technique can help some men to become fathers after being deemed infertile because of childhood cancer. Young men can bank sperm before cancer treatment if they are told that treatment may render them sterile. For men who had not, surgeons essentially performed tiny biopsies of their testicular tissue to hunt for any pockets of hidden sperm, to be used for in vitro fertilization.

In a study of 73 men, surgeons were able to extract small amounts of sperm in just over a third of them — and 20 children eventually were born, including five pairs of twins. Researchers caution the technique isn’t for everyone. Their research was reported Monday in the Journal of Clinical Oncology.