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Expert reaction to a study in The Lancet Oncology that showed endometriosis increases the risk of certain types of ovarian cancer.
Dr Emily Power, health information manager at Cancer Research UK, said:
“We already knew that a history of endometriosis may be linked to a higher risk of ovarian cancer, and this study tells us which particular types are linked. But more research is needed to understand why. About one in five ovarian cancers in the UK are linked to lifestyle and environmental factors, and women can lower the risk by being a non-smoker.
“Ovarian cancer can be difficult to detect at an early stage, so identifying women who are at higher risk could help doctors to develop more targeted monitoring in the future. And all women should be aware of the signs of ovarian cancer, like pain in the lower tummy, bloating, increased tummy size, difficulty eating or feeling full.
“If these symptoms are new and happen on most days then it’s worth getting them checked out by your doctor.”
Shirley Hodgson, Professor of Cancer Genetics, St George’s University of London, said:
“This is a professional pooled analysis of 13 large case-control studies, which appears to show a clearly increased risk of clear cell, low grade serous and endometrioid carcinoma of the ovary in women with self-reported endometriosis, with no apparent increase of other histological types of ovarian cancer. The different studies all show a similar effect, and the clear discrimination between the different histological subtypes increases the probability that this is a real finding. The problem with self-reported endometriosis leaves some doubt about the completeness of ascertainment of endometriosis in the cohorts, but the significance of the finding seems undisputable. It is important to note that the absolute risk of ovarian cancer remains small and women with endometriosis should not be unduly worried; most sufferers of endometriosis will not get ovarian cancer. The reasons for such an association between endometriosis and clear cell ovarian cancer should now be investigated, as this could possibly lead to the development of preventative treatments in women with endometriosis. The implications for screening in women with endometriosis are difficult, however, as screening for ovarian cancers by ultrasound scans and serum markers is at present not sufficiently sensitive or specific to be used in this context.”
Prof Hani Gabra, Director of the Ovarian Cancer Action Research Centre, Imperial College London, said:
“This is an interesting study which highlights an increase in risk of certain subtypes of ovarian cancer in women who have a history of endometriosis. However, most women with endometriosis will not go on to develop ovarian cancer. It is important that all women should be aware of the signs and symptoms of ovarian cancer and consult their GP if they are concerned.”
Dr Paul Pharoah, Reader in Cancer Epidemiology, University of Cambridge, said:
“The probability that a woman in the UK will develop ovarian cancer in her lifetime is less than 1 in 50. It is well-established that this risk is increased slightly in women with endometriosis to about 1 in 40, but the risk remains small. Endometriosis is a condition that affects around 1 in 20 women during their lifetime.
“There are several different types of ovarian cancer. This study shows for the first time that the increased risk associated with endometriosis is restricted to three of the less common types of common ovarian cancer – lear cell, endometriod and low-grade serous. The risk of clear cell ovarian cancer is increased approximately three-fold, while that of endometrioid and low-grade serous ovarian cancer is increased two–fold. Endometriosis does not increase the risk of the commonest form of ovarian cancer, high-grade serous .
“The lifetime risk of clear cell cancer is about 1 in 500, which increases to 1 in 180 for women with endometriosis. The lifetime risk of both endometriod and low-grade serous ovarian cancer are each about 1 in 400 and these also increases to 1 in 180 in women with endometriosis.
“While these finding are of some biological interest they have limited immediate clinical implications as the increase in risk to women with endometriosis is small. The only well-established intervention to reduce ovarian cancer risk is surgical removal of the ovaries, and this would only be offered to women at much higher risks.”
‘Association between endometriosis and risk of histological subtypes of ovarian cancer: a pooled analysis of case–control studies’ by Celeste Pearce et al.,published in The Lancet Oncology on Wednesday 22nd November.