By Tom Ulrich. A version of this story originally appeared in Vector, Children’s science and innovation blog
Thanks to advances in medicine, 75 percent of children currently diagnosed with cancer will live to see adulthood. This is extremely welcome news of course, but with it comes new questions about what adult life holds for survivors of childhood cancers. As science is now discovering, the therapies that are so effective at saving children’s lives can also occasionally lead to problems down the road (called the late effects of cancer treatment.)
Some of the more common concerns surrounding late effects of cancer treatment have to do with its effects on fertility, which can be quite harsh. “There’s a huge segment of the pediatric oncology population that’s at risk for infertility when they grow up,” says Richard Yu, MD, PhD who works on male infertility in Children’s Hospital Boston’s department of Urology.
The problem is hardly gender specific. “It’s as though cancer treatment pushes the ovaries further down the age curve,” says Sara Barton, a fertility specialist at Brigham and Women’s Hospital who collaborates with Lisa Diller, MD clinical director of the Dana-Farber/Children’s Hospital Cancer Center (DF/CHCC). “So while a woman who has survived childhood cancer may be 20 years old, her ovaries act like they’re 35 or 40.”
“Boys are at the same relative risk for infertility due to treatment,” says Yu, “because the same chemotherapy and radiation treatments that affect the ovaries can also wipe out the sperm stem cells in the testes.”
The ideal solution would be to have every child diagnosed with cancer bank their eggs or sperm before treatment, so it could be used later in life if needed. But that’s not always an option, particularly for children who need treatment before they hit puberty. And while there are alternatives to banking that are available for these younger kids – ovarian tissue freezing for girls and testicular tissue preservation for boys – the techniques have yet to be proven effective in the long term and can present their own unique challenges.
For example, the process for freezing ovarian tissue is very costly and is rarely covered by insurance. It also requires two surgeries and carries the risk of reintroducing the cancer later in life if cancer cells are present in the ovaries when the tissue is originally collected.
Both Barton and Yu readily admit that these alternatives require some faith in the future, and are hopeful that technologies for restoring fertility from preserved tissues will have gotten better by the time today’s patient are old enough to worry about infertility. To do their part, both researchers are working hard to improve modern tissue preservation to better ensure fertility rates for pediatric cancer survivors in years to come.
Along with Diller, Barton recently launched a clinical trial to learn if an ovarian marker called anti-Mullerian hormone (AMH) can help doctors tell which girls would benefit from either egg or ovarian tissue banking, and which would not. (In some cases fertility cannot be preserved, even with banking. An indication of who would and wouldn’t benefit from the process could spare unnecessary procedures.)
Focusing on the needs of boys, Yu is looking for new sperm stem cell markers that could help better sort cancerous cells out from healthy ones, thereby improving success rates of fertility preservation and reducing risk of a second exposure to cancer. He is also exploring ideas for growing sperm from stem cells in a lab. By collecting stem cells prior to treatment and using them to produce sperm later, the process would be benefit many boys whose cancer treatment leaves them infertile before they are physically able to produce sperm. “We might even use something like mice, engineered without an immune system, which could act as ‘living incubators’ to generate sperm from the stem cells,” he says.
The fact that technologies for reconstituting fertility are far from ready makes the hunt for better preservation options even more urgent. “It may take 15 or 20 years to develop the techniques to help a child who is 8 years old now,” says Yu. “But if you don’t preserve something now, you run the risk of not being able to do anything for them later, which is where we are now with a large number of adults who survived cancer as children.”