Radiation and chemotherapy can kill ovarian cells in addition to cancer cells.

    "You're trying many aggressive ways of killing cells," explained program leader Teresa Woodruff of Northwestern University.

    The ovaries are made up of groupings of cells called follicles that each contain a single egg. After puberty, these follicles are periodically selected to mature and eventually ovulate.

    Emergency in vitro fertilization can be performed for some women with cancer whereby the woman is given hormones to induce more than one follicle to provide eggs that can later be fertilized outside the woman's body. But for women whose cancer is at an advanced stage, emergency IVF isn't an option.

    It is also impossible for young girls with cancer to use emergency IVF.

    Woodruff said that for adult survivors of childhood cancer, "fertility is just their number one concern," but no viable option to help them has existed before.

    Woodruff's technique would involve removing one of a woman's ovaries and freezing it. Later, the frozen immature follicles would be extracted and matured in the lab so they could be fertilized.

    Woodruff said few ovaries have been cryopreserved (frozen), and she knows of just one case in which a pregnancy resulted from the previous frozen tissue after it was re-implanted in the woman from which it was removed.

    So far, researchers have only extracted and matured follicles from mice, but the technique has resulted in pregnancies in the mice.

    Woodruff's test program plans to enroll girls between the ages of 4 and 17 and women between the ages of 18 and 41 who cannot undergo emergency IVF. They will have one ovary removed, and 80 percent of it will be frozen for possible future fertilization. The remaining 20 percent will be used by researchers to test ways to extract and develop the immature eggs.

    Woodruff said the technique could eventually be used in place of normal in vitro fertilization.

    Because women lose follicles as they age, the procedure could also be used for young women entering a career requiring long years in school who haven't decided whether they want to have children, but want to preserve immature eggs "before their biological clock ticks off."

    (Agencies)