Frozen ovarian transplants 'safe and effective'
"Ovarian tissue transplants for women who want to have a baby after cancer treatment appear to be safe and are very successful," The Guardian reports after a small Danish study found the technique has around a 1 in 3 pregnancy success rate.
Thanks to improvements in cancer treatments, many young women survive cancer and go on to lead long, normal lives. But many cancer treatments can damage the ovaries, meaning the body doesn't produce eggs and women cannot get pregnant.
To give women a chance of getting pregnant in later years, some doctors now offer to remove all or part of an ovary before cancer treatment so it can be frozen and stored. It can then be transplanted back in pieces later, usually into the remaining ovary.
Of the 32 women in the study who wanted to get pregnant, researchers found 10 were able to do so. None of the women who underwent transplant had a relapse of cancer that was likely to have been caused by the transplant, they say. There have been concerns cancerous cells in the transplanted ovary could spread to the rest of the body.
The research may pave the way for this treatment to become more routinely used in the UK. As yet, it is uncertain whether it would be funded by the NHS, so undergoing this procedure could prove expensive.
Where did the story come from?
The study was carried out by researchers from Copenhagen University Hospital, Odense University Hospital, and Aarhus University Hospital, and was funded by the Child Cancer Foundation in Denmark and the EU interregional project ReproHigh.
It was published in the peer-reviewed journal Human Reproduction on an open-access basis, so it can be downloaded as a PDF for free (PDF, 248kb).
The study was widely reported on by the UK media, accurately for the most part. Several stories jumped from using frozen ovarian tissue to allow women being treated for cancer to have children, to the possible use of the treatment "to delay the menopause for career women wanting to have babies later in life", as the Daily Mail put it. While this could be feasible, the researchers said this was not being contemplated at present – at least not by them.
What kind of research was this?
This retrospective cohort study looked at the results of a group of women who received transplanted ovarian tissue after cancer treatment over a period of 10 years.
Cohort studies of this type can tell us what happened after the treatment was given, but they can't tell us whether the outcomes were caused by the treatment or how the treatment might compare with other available treatments.
What did the research involve?
Over 10 years, a group of Danish women had ovarian tissue frozen before having cancer treatment that might damage their fertility.
Researchers looked at what had happened to the 41 women who chose to have thawed ovarian tissue transplanted back into their bodies. Six women had the treatment to avoid the symptoms of the menopause, and one child did so because she had not successfully started puberty.
The researchers focused on the women who had transplants to help them get pregnant. They wanted to find out how many women had since given birth to children and whether any women had a recurrence of cancer that might have been caused by the transplanted ovarian tissue.
They compared the cancer recurrence rates of women who'd had transplants with women who had not had transplants, although they did not have accurate data for the women who hadn't had transplants – they relied on figures of reported deaths, which may have been different from cancers.
Because not all women who had ovarian transplants wanted to have children, the researchers based their success rates on the pregnancies of 32 women who said they wanted to get pregnant at the time of the transplant.
The researchers also measured how long the ovarian tissue remained active – in other words, how long it continued to release eggs. The research paper does not say how this was measured. The researchers may have asked the women how long they continued to have periods, but this is not stated.
What were the basic results?
Of the 32 women who had ovarian transplants and said they wanted to get pregnant, 10 gave birth to at least one child, giving a result of 31% being able to have a child. Thirteen children were born in total, and one woman was in her third trimester at the end of the study period.
Ten women became pregnant but miscarried or terminated their pregnancies. It is not clear whether any of these women also had a successful pregnancy. Eight of the pregnancies resulting in a child occurred naturally, and six after IVF treatment.
Although three women had recurrences of their cancer, in no case was this thought to be because of the ovarian transplants. The proportion of women with cancer recurrence (7%) was the same among the women who'd had transplants as the estimated proportion among women who didn't have transplants.
The length of time the ovarian tissue remained active varied a lot, from less than a year for four women to more than 10 years for two women. Most (29 of 41 women) transplants lasted between one and seven years. Several women needed two or three transplants.
How did the researchers interpret the results?
The researchers say their findings show ovarian tissue transplants are a "valid method for fertility restoration" and that, "The level of safety appears high, with no relapse [of cancer] due to transplantation of ovarian tissue recorded to date."
Conclusion
This study gives encouraging results about the safety and effectiveness of ovarian transplants to help women have children after cancer treatment. This study is one of the largest to look at results from this treatment over a 10-year period.
However, this type of observational study can only tell us what happened after this treatment. It can't tell us whether some women might have got pregnant naturally without a transplant – five women had functioning ovaries at the time of the transplant, although they were not functioning well.
And we don't know how ovarian transplant compares with other types of fertility treatment, such as extracting and freezing eggs before cancer treatment.
The study also can't tell us whether outcomes such as miscarriage are more common after ovarian transplant than other types of fertility treatment. We need to be cautious about the study's pregnancy success rate of 31%.
Even if you just take the results from the 32 women who said they wanted to get pregnant, that is complicated by other factors. Some women might have got pregnant naturally without treatment. Some women might have changed their minds about wanting to get pregnant.
And some women who did get pregnant had miscarriages or chose to terminate their pregnancies. The researchers say it is "impossible" to provide an exact pregnancy rate for the treatment because of these factors.
Also, 41 women is quite a small group on which to base safety figures. Longer follow-up of all women having this therapy would give more data about the chances of cancer recurrence.
It would be helpful to have reliable cancer recurrence rates for comparable women who did not have an ovarian transplant to be sure rates are not higher for women who have had a transplant.
The study gives us useful information about a type of fertility treatment not often used in the UK, but leaves the above questions unanswered.
