This intersection of oncology and fertility, known as oncofertility, has interested Woodruff since the early 2000s, when she was the director of basic research at Northwestern’s Robert H. Lurie Comprehensive Cancer Center. “I started asking folks about the effects of their cancer drugs on fertility,” she says. That’s when she realized that while young male patients were being offered the option of sperm banking, young female patients were being told to focus on surviving their disease because there were no such options for them. “A lot of the work we were doing in our lab could turn around this disparity,” Woodruff says.
She had found her calling: providing cancer patients, particularly young girls and women like Bott, with fertility preservation options. Thus began what would become the Oncofertility Consortium.
Male fertility preservation is straightforward and immediate: Sperm donation and subsequent freezing, called cryopreservation, has been a widespread practice since the 1970s. For women, though, the process is more limited and more complicated. First, the female must be old enough to have mature eggs, called oocytes. These oocytes are available only in limited quantities at certain times of her monthly cycle, and must be surgically retrieved. The extracted oocytes can then be cryopreserved for later use or combined with sperm in a laboratory to create embryos via in vitro fertilization.
Researchers have been cryopreserving embryos for several decades and cryopreserving oocytes in the past several years, but some female cancer patients lack these options. Pre-pubertal girls can’t yet biologically produce mature oocytes, and some sexually mature women, such as Bott, have aggressive cancers that must be treated immediately. “I definitely didn’t have the [few weeks] to go through the preparation of all the hormones [for oocyte extraction],” Bott says. Instead, she’d need to preserve not her oocytes, but the tissues that produce them. And Woodruff and colleagues are pioneering an experimental procedure to do just this, allowing these girls and women with the fewest options for preserving their fertility to bank on the hope of becoming biological mothers.
A Million to Zero
Infant girls are born with two ovaries each containing about 1 million follicles, cell clusters in which single oocytes are nurtured and matured. These follicles naturally die over time: A girl entering puberty has only about 20 percent of the follicles she was born with. Once a female reaches sexual maturity, her body’s hormones stimulate a monthly cycle in which about 400 follicles die and roughly 20 follicles begin to mature. But during that cycle, only one dominant follicle matures completely to release the oocyte contained within it. “We still don’t really understand why one follicle begins the process of development,” Woodruff says. Ultimately, “We start with a million, and we end with zero,” she says.