Recent experimental research shows a promising outlook for clinical trials in boys.
Historically, the options for preserving fertility in boys diagnosed with cancer who have not yet hit puberty have been non-existent. While many children will grow up to have their sperm develop normally, others will not, and without sperm to freeze, prepubescent males have been left with no options.
Rod T. Mitchell, MBChB, PhD, is one of a number of researchers trying to change that. As the Professor of Developmental Endocrinology and Principal Investigator at MRC Centre for Reproductive Health, Queen’s Medical Research Institute, University of Edinburgh, and a consultant pediatric endocrinologist at The Royal Hospital for Children and Young People in Edinburgh, Dr. Mitchell is working to establish future clinical trials in humans involving testis grafting to produce sperm.
“Transplantation of tissue is, at the moment, the most promising-looking option,” Dr. Mitchell says.
How It Could Work
The gist of the idea is this: Before prepubertal boys start cancer treatment, tissue is taken from the testis and cryogenically preserved. Then, a decade or three later, when the man is ready to have children, the tissue is grafted back on, and eventually he will begin producing sperm naturally. (Other current research involves using the same tissue to create sperm in vitro but is not quite as far along.)
Studies in rhesus monkeys with testis grafts have proven successful in starting sperm growth and producing healthy offspring. However, ongoing xenotransplantation attempts to replicate this in mice have not yet created sperm.
“One of the theories is that the reason it might not be working yet is just purely because you are putting that tissue from humans into mice, and the host mouse is just not able to support it properly for whatever reason,” Dr. Mitchell says. “I think we’re now at the stage where we actually need to consider setting up clinical trials … and I think we’re on the verge of doing this.”
More Samples Are Needed
One problem in establishing clinical trials in humans is that there simply aren’t enough men who are now old enough, interested in having kids, and infertile.
“We’ve been storing tissue for a relatively short period of time, and not actually that many males have come back wanting the tissue to be used yet,” Dr. Mitchell says.
But physicians can help by encouraging all their eligible prepubertal cancer patients to freeze testis tissue.
“If that’s not offered to a patient before they have their treatment, it’s too late then to do anything,” Dr. Mitchell says. “Can we actually use it to restore their fertility? The answer is not yet. But we’re probably not a long way away.”