Two-thirds of female childhood cancer survivors in Canada and the U.S. who were at increased risk of infertility eventually did become pregnant, a new study finds. 

Earlier research indicated that childhood cancer survivors tend to be at increased risk of infertility, but those studies focused on early menopause or ovarian failure from cancer therapies rather than on trying to get pregnant.

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Participants were surveyed when reproductive technologies were less common. (Kacper Pempel/Reuters)

In this week's issue of the medical journal The Lancet, researchers described the findings of their survey of 3,531 cancer survivors and 1,366 female siblings. The survivors were diagnosed before age 21.

Participants were from 26 institutions in Canada and the U.S., including the Hospital for Sick Children in Toronto and the University of Alberta in Edmonton.

Survivors had an increased risk of clinical infertility — more than one year of attempts at conception without success — compared with their siblings, Dr. Sara Barton of Brigham and Women's Hospital in Boston and her co-authors said.

The association was stronger among those aged 24 and under.

Overall, about 16 per cent of women who survived childhood cancer were affected by infertility compared with nearly 11 per cent of the sisters.

Although it took longer on average for survivors to conceive compared with their siblings, 292 of 455 survivors or 64 per cent of survivors who reported clinical infertility eventually became pregnant.

Both groups were equally likely to seek medical treatment for infertility. But survivors were about half as likely to be prescribed drugs to help them become pregnant compared with their siblings, which the study's authors called a cause for concern.

One of the drawbacks of the data is that participants started answering the questions about infertility in 1992, when use of in vitro fertilization was less common and less successful than now, the researchers noted.

Increasing doses of pelvic radiation and alkylating agents, a type of chemotherapy, were strongly associated with infertility, the researchers said.

Preserving fertility is now mainstream, but better identification of those at highest risk could help, Richard Anderson, a professor of clinical reproductive science at the University of Edinburgh, said in a journal commentary accompanying the study.

Anderson suggested cryopreserving or freezing ovarian tissue, which remains experimental.

"Equally valuable is increased and more accurate provision of information, which should emphasize the need to seek early investigation and treatment for infertility," he concluded.

The study was funded by the U.S. National Cancer Institute, American Lebanese Syrian Associated Charities and Swim Across America.