STANFORD -- Female cancer patients and other women at risk of losing their fertility because of medical treatments can now help preserve their childbearing options through a new egg-freezing program at Stanford University Medical Center.
Under the program, women ages 18 to 40 who are undergoing chemotherapy, radiation or surgical removal of the ovaries can choose to have their eggs retrieved before treatment and then stored indefinitely in a freezer for possible future fertilization.
"A lot of people don't realize that there are things we can do that may help future fertility," said Lynn Westphal, MD, Stanford assistant professor of gynecology and obstetrics and director of the medical center's donor oocyte program. "It's something women should know about and have a discussion about before they have chemotherapy or other treatment for their disease. Later on, we may not be able to reverse the damage to the ovaries."
Fewer than 100 women worldwide reportedly have become pregnant as a result of the experimental process in which their eggs were frozen, thawed and then fertilized in the laboratory, said Barry Behr, PhD, assistant professor of gynecology and obstetrics and director of the In Vitro Fertilization (IVF) and Assisted Reproductive Technologies laboratories at Stanford. Few medical centers in the country offer this option, and Stanford has the only program in the Bay Area with an approved research protocol, he said.
Stanford also has made arrangements with Organon, a Dutch, research-based pharmaceutical company, which has agreed to cover the cost of some medications associated with the procedure, Westphal said. This will save patients $2,000 to $3,000 out of a total cost of roughly $10,000 for the entire process.
"That may make a big enough difference for some women that they may decide to do it," she said.
Unlike eggs, sperm have long been frozen and used for preservation of future fertility, in part because the use of sperm presented less of a technical challenge. As sperm are much smaller than eggs, they survive the freezing and thawing process relatively unscathed. But the use of frozen eggs in IVF treatment became a viable option in the mid-1990s with the introduction of a technique called intracytoplasmic sperm injection (ICSI). ICSI involves injection of a single sperm into a single egg in order to achieve fertilization. With ICSI, the chance of success is much higher, with reported fertilization rates approaching 65 percent, Westphal said.
"I think we only figured out recently that frozen eggs don't fertilize well with normal fertilization," Behr said. "But they fertilize reasonably well with ICSI."
That's because the freezing process damages the zona pellucida, the outer shell of the egg, to which the sperm normally must bind before penetrating the egg, he said. With ICSI, the damaged shell is of no consequence, as the sperm is injected directly into the core of the egg, he said.
IVF treatment using frozen eggs, however, is still considered experimental and is being reserved for women undergoing medical treatments that directly affect their fertility, Westphal said. These include patients with cancer, lupus, scleroderma or other diseases that require treatment with chemotherapy or radiation, which are toxic to the ovary. Patients who must have their ovaries removed because of endometriosis or other ailments also can choose to have their eggs frozen before surgery, she said.
"This is meant to help women who are going to have their fertility cut short because of a medical treatment and not for women who are going to delay fertility because of timing," Westphal said. "These women do have a choice, and I would hate for them to delay their childbearing when there are no guarantees that pregnancy will result from their frozen eggs."
The entire process takes about six to seven weeks, as the woman must take a series of medications to prepare for egg retrieval. These include birth control pills and daily injections of gonadotropin-releasing hormone agonists, which help suppress the menstrual cycle. Once the cycle has been suppressed, the patient is given fertility drugs, which help stimulate the ovaries to produce more eggs. The patient then is monitored closely through use of ultrasound to make sure enough egg follicles are developing.
During the egg retrieval, doctors insert a small needle into the vagina to reach the ovaries and aspirate the eggs out. The woman is awake but sedated during the 15-minute process and can go home the same day. Doctors typically retrieve about 12 or 13 eggs, Westphal said.
These eggs then are immersed in a cryoprotective solution and frozen in a liquid nitrogen tank that is stored indefinitely in the IVF lab. Egg freezing is a new practice, so it's not known just how long the eggs can be stored and still produce a viable pregnancy. However, some pregnancies reportedly have resulted from embryos that have been frozen for as long as 10 years, Behr said.
Women also have the option of having a portion of the ovary removed and frozen for future use, Westphal said. No pregnancies have ever been reported from this process, although there was an encouraging first report in the fall of 1999 of a patient who had some ovarian tissue frozen, then thawed and replaced in the body. The ovary did show some signs of function, although the patient has yet to become pregnant, she said.
Advances in freezing techniques also might ultimately improve a woman's chances of getting pregnant. Researchers in December 1999 reported the first pregnancy resulting from a freezing process known as vitrification. This is a process in which the eggs are frozen in a matter of seconds, rather than hours, reducing the amount of exposure time to toxic, cryoprotective solutions, Behr said. Behr is now experimenting with new methods of vitrification, including new vessels for freezing that might improve results.
"We have not frozen any eggs using this method, but I think it's something that has the potential to improve the technique even more," Westphal said.
Women who are interested in the egg-freezing program can contact IVF nurse coordinator Andrea Speck-Zulak, RN, at (650) 498-4721.
The above story is based on materials provided by Stanford University Medical Center. Note: Materials may be edited for content and length.
Cite This Page: