Patients can now opt to have ovarian tissue removed before therapy to be re-implanted afterwards.
They can have their eggs stimulated with daily hormone injections, but this delays cancer treatment for two or three months.
Independent experts not directly involved in this work praised it as important, but also cautioned that there is much more to do before lab-grown human eggs could be safely be made ready for fertilization with sperm.
While the feat has previously been achieved for mouse eggs, and has given rise to live young after fertilisation, the process has proved tricky in humans. Human eggs had also been grown in laboratory conditions - but only from a relatively late stage of development. But this study has for the first time been able to develop an egg in the laboratory from its earliest stage to full maturity, scientists say.
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Decades of work have finally shown that scientists can grow eggs to maturity outside of the ovary, under strict laboratory conditions such as controlled oxygen levels, hormones, proteins that mimic growth, and the substance in which eggs are cultivated.
But Professor Simon Fishel, founder and president of leading IVF treatment providers CARE Fertility, said further research was needed to establish whether eggs developed using the method could be healthy. "The next step would be to try and fertilise these eggs and then to test the embryos that were produced, and then to go back and improve each of the steps". Women are born with ovaries containing immature eggs that only fully develop after puberty.
The scientists are now working on testing whether the eggs can be fertilized and produce healthy embryos.
"Being able to fully develop human eggs in the lab could widen the scope of available fertility treatments", she said.
He said: 'This study demonstrates that there is much laboratory research to be undertaken before we can be encouraged to believe that we will achieve healthy normal eggs for clinical purposes in vitro developed follicles derived from human ovarian cortical tissue'.