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By having her eggs frozen before she begins cancer
treatments, a woman can preserve the hope of having a baby.
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ANN ARBOR, Mich. -- A new technique might allow women diagnosed with
cancer the opportunity to have children when chemotherapy and radiation
treatments rob them of their fertility, researchers at the University of
Michigan Comprehensive Cancer Center have found.
By having her eggs frozen before she begins cancer treatments, a
woman can preserve the hope of one day having a baby.
Freezing eggs is one thing; thawing them safely so they can lead to
pregnancy is the challenge. In the past, efforts to freeze a woman's
eggs, or oocytes, have not worked well because the cells are large. When
the egg is thawed, ice crystals cause damage that prevents the egg from
being fertilized.
U-M researchers looked beyond traditional techniques to a method of
freezing cells called vitrification. This cryopreservation technique
allows the eggs to be cooled fast enough that the transformation from
liquid to solid is instantaneous. No ice crystals form and the
consistency resembles a viscous glassy state. Research so far has used
mouse oocytes but U-M expects to make the technology available in the
clinic soon.
"With traditional slow-freeze techniques, just over half the eggs
survive the thawing process. Using vitrification, we are getting 98
percent survival. For a woman with cancer, these are the only eggs she's
ever going to have, so it's important that as many as possible remain
viable," says Gary D. Smith, Ph.D., associate professor of obstetrics
and gynecology, urology, and molecular and integrative physiology at the
U-M Medical School, and director of the Fertility Counseling and Gamete
Cryopreservation Program at the U-M Comprehensive Cancer Center.
Smith will present results of his research on Sunday, May 29, at the
World Congress on In Vitro Fertilization, Assisted Reproduction and
Genetics in Istanbul, Turkey.
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Cancer treatments such as chemotherapy and radiation therapy can cause
damage to a woman's reproductive system and leave her unable to have
children afterward. Some women may regain their reproductive function
after their treatment ends and may be able to conceive on their own,
while others will become infertile. Egg cryopreservation could be
insurance for those women at highest risk of fertility problems after
cancer treatment.
When a woman wishes to become pregnant, the vitrified eggs would be
warmed and then fertilized with male sperm. The fertilized eggs would
then be transferred to the uterus in the same procedure that's used
successfully when couples freeze embryos.
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"This is a very new
technology and it requires education both of patients and
physicians." |
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When eggs are warmed after vitrification, fertilization rates with
conventional IVF are low. Instead, researchers have found, a single
sperm cell must be injected into a single oocyte, a technique called
intracytoplasmic sperm injection, or ICSI. While ICSI is an established
technique used in assisted reproduction, it is more complex and costs
more than traditional methods.
Using mouse oocytes, 80 percent of eggs that had been vitrified
became fertilized with ICSI, with a live birth rate of about 30 percent,
comparable to conventional IVF when eggs are not frozen. The
fertilization and birth rates for vitrified eggs are similar to the
rates for control eggs that were not vitrified.
For egg freezing to work, it must be a mature oocyte, which means a
woman must have 14 days of hormone treatments to stimulate mature egg
production. This could limit its applications for some women.
Researchers question if it is appropriate for women with cancers fueled
by estrogen, such as breast cancer. In addition, the hormone treatments
require delaying the start of cancer therapy, which may not be an option
for every patient.
Guidelines for patients and physicians still need to be established
as the technique begins to be offered in a clinic setting, Smith says.
"This is a very new technology and it requires education both of
patients and physicians," Smith says.
U-M has cryopreserved eggs for one patient; however, the service is
currently not offered while researchers seek approval for a clinical
trial. A specialized clinic in the U-M Comprehensive Cancer Center
provides counseling and information for women considering their
fertility options, and the clinic currently freezes embryos for cancer
patients who have a partner. The clinic also offers counseling and sperm
freezing for male cancer patients. U-M will offer egg vitrification only
to women facing cancer treatments, because the long-term safety of this
technique remains unknown.
"In a woman with cancer, if she is going to lose her reproductive
capacity because of cancer treatments, this is her only choice to have
baby with her own eggs," Smith says. A clinical trial through the U-M
Comprehensive Cancer Center is planned to begin by fall.
Sources
Funding for the research is from the U-M Department of Obstetrics and
Gynecology.
Reference: World Congress on In Vitro Fertilization, Assisted
Reproduction and Genetics, May 26-29, 2005, Istanbul, Turkey
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