Ovarian cancer risk from IVF still lower – Health News – NHS Choices.
This was a large, long-term cohort study that examined the association between ovarian stimulation during fertility treatment and the subsequent risk of developing ovarian cancer. The study was well designed, especially in terms of its selection of an appropriate comparator group and its attempts to account for potential confounders.
In their attempt to control potential confounders the researchers collected information on baseline ovarian cancer risk through a mailed questionnaire, and on treatment factors through medical record examination.
However, data on factors such as family history of cancer, number of pregnancies, use of birth control and lifestyle characteristics were available in only 65.2% of the total cohort. This may bias the results, as there is no way of telling whether those who returned the survey were significantly different from non-respondents. This bias is further enhanced as the two groups did not respond proportionately: 48.7% of the subfertile/non-IVF group responded, compared to 71.1% of the IVF group.
Similarly, medical record data extraction was only conducted for 76% of the women who had received IVF. Given this large body of missing data there is no way of knowing whether or not these 24% of women were significantly different from those whose records were extracted.
Another strength of this study was that it also examined ovarian cancer risk in subfertile women who did not undergo IVF treatment. Studies that compare women receiving IVF to women in the general population are useful, but their results are open to debate as any increased risk seen in women having IVF could arguably be due to whatever was causing their fertility problem, rather than IVF itself. By comparing the ovarian cancer risk profiles of different subfertile groups, the study could potentially allow us to tease out the effects of IVF, and allow us to ignore the influence of infertility itself.
The researchers also consider the possibility that some of the increased risk for borderline ovarian cancer may be due to increased contact with medical professionals during the IVF process. Ovarian cancer is generally detected at a late stage, in part due to its vague or asymptomatic nature during its early stages. The researchers attempted to determine whether medical surveillance accounted for the difference by interviewing the patients’ doctors. They say that, based on the interviews they were able to conduct, increased surveillance is an unlikely explanation for the trend.
The researchers say that they are concerned by their finding which suggests an elevated risk of developing invasive ovarian cancer in the IVF group after more than 15 years of follow-up. However, there are statistical difficulties in conducting such extensive subgroup analyses: the likelihood of finding a statistically significant result purely by chance increases the more the data is broken down into subgroups. In this instance the small number of observed cases in this subgroup (nine cases in the IVF group, 13 in the general population) suggest the result is unlikely to be robust.
It is important to remember that all the increased risks detected in this study were relative to the risk seen in other groups, and not absolute risks. While IVF-treated women may be at double the risk of developing ovarian cancer relative to women not given IVF, this absolute risk is still small. In the Netherlands, for example, the researchers say that only about 45 among every 10,000 women (0.45%) may develop an ovarian malignancy (including borderline malignancy) by age 55 years. The rate for women who had used IVF was estimated to be 0.71%.
Another key point is that at the time the women received IVF (1983-1995), the technique was not as widespread or advanced as it was today. This means that both the specific treatment used and the women involved may not be representative of IVF used in more-recent times.
Overall, this was a well-conducted study but further research is needed in order to confirm the results. Women contemplating using or currently using IVF can discuss the matter with their specialist, while women who are concerned about their past use of IVF can consult their doctor. However, the level of risk identified in this study is low, and the matter should not be seen as a cause for alarm.
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