A window of hope for young girls undergoing chemotherapy for cancer to eventually have their own children has been opened by a multidisciplinary team at Hadassah University Medical Center in Jerusalem's Ein Kerem. Gynecology specialist Dr. Ariel Revel and colleagues are the first in the world to obtain, ripen and freeze eggs for later use from the ovarian tissue of girls as young as five before they undergo chemotherapy, a treatment which usually kills the ova. Using the same technique over the last three years, the Hadassah team treated 18 girls who wanted (or whose parents wanted) to preserve their fertility. Revel, pediatric oncologist Dr. Miki Weintraub, pediatric surgeon Dr. Eitan Gross and pediatric anesthesiologist Dr. Avishag Kedari also proved that even among very young girls, they could extract ova, mature them in the laboratory and then freeze them. They published their initial positive results a few months ago and presented a paper on their findings Tuesday at the 23rd International Conference of the European Society of Human Reproduction and Embryology in Lyon. They will write a long paper for a major fertility journal. "We didn't expect young girls to have eggs that could withstand the process of maturation," he said. Until now, scientists had thought viable ova could be removed only after puberty. "At any age," Ravel said, "when there is concern about any significant damage to the ovary, that's the time to consider freezing it and the freezing the ova." He told The Jerusalem Post by phone from Lyon that his lecture aroused much interest from physicians and scientists around the world. Using the same process used on adult female cancer patients, Revel's team has given hope to girls and young women aged five to 20 to preserve their fertility. Because chemotherapy kills cancer cells, it can also destroy normal body cells. Men produce sperm throughout their lifetime, and after some are destroyed by chemotherapy, the testes recover and can produce sperm again. But girls are born with a limited number of eggs that are not renewable. Women facing chemotherapy who wish to have children later can undergo an oophorectomy (the surgical removal of an ovary), after which the ovary is sliced and frozen under special conditions at a temperature of -197 Celsius. After treatment and recovery, the ovaries can be reimplanted in the woman's body and function normally. In younger girls this is not possible, and the method normally used is to freeze the ovarian cortex, which contains the egg-producing follicles, for transplantation at a later date. But the cortex is often damaged by sub-zero temperatures, so collecting and freezing individual eggs from the follicles - which are more resistant to the damage caused by extreme cold - are more likely to restore fertility in adulthood. Every year Hadassah alone treats dozens of young girls or women who undergo chemotherapy after being diagnosed with Ewing's sarcoma, Wilm's tumor, leukemia, lymphoma or other cancers and who want to have children later. Revel said that the increasing number of children and young women who survive cancer meant that such techniques will become increasingly important in preserving fertility in young patients. Cure rates of cancer in youngsters are higher than in adults and range between 70 percent and 90%. The team was amazed when they found eggs in the follicles of girls as young as five to 10. "We were able to extract oocytes using needle aspiration from very young girls," he said. "For example, we found seven eggs in a five-year-old girl with Wilm's tumor, eight in an eight-year-old girl with Ewing's sarcoma and 17 in 10-year-old girl with Ewing's. We were then able to mature the eggs in vitro and freeze them for use in the future." A total of 167 eggs were found, with an average of 8.5 per patient. "Excluding one patient who asked that the oocytes we had found in her ovaries should be frozen immediately, we matured the 13 others in vitro," said Revel. "A total of 41 were successfully matured, a 32% success rate." Asked how it happened that his was the first team to accomplish this, Revel suggested: "I am not sure that others tried; they didn't think they'd be successful." No eggs have yet been thawed, so the team cannot yet know whether pregnancies will result. "But we are encouraged by our results so far, particularly the young ages of the patients from which we have been able to collect eggs. We believe that no younger patients have ever undergone egg collection, in-vitro maturation, and egg freezing. We are hopeful that the mature eggs can offer these girls a realistic possibility of preserving their fertility."