Surgery for Endometriosis Protects Against Ovarian Cancer

Women with endometriosis who undergo surgery to treat the condition are less likely to have ovarian cancer develop later in life, according to a novel case-control study conducted in Sweden that examined the association between hormonal and surgical treatments of endometriosis and the risk of epithelial ovarian cancer.¹
   
Using the National Swedish Patient Register, the study authors identified women with a primary diagnosis of endometriosis between 1969 and 2007. They then linked their findings to the National Swedish Cancer Register to identify women who also had a diagnosis of epithelial ovarian cancer at least 1 year after the initial diagnosis of endometriosis. There were 220 women identified as having both endometriosis and ovarian cancer (cases) and 416 women with endometriosis only (controls). After the controls were randomly selected, they were matched with cases for year of birth. Data on hormonal and surgical treatments for endometriosis and other reproductive factors were gathered from medical records and analyzed using conditional logistic regression.
   
The study results showed that women who had a one-sided oophorectomy, compared with women who underwent hormonal treatment alone, had a significantly reduced risk of later development of ovarian cancer. In addition, ovarian cancer was significantly less likely to develop in women who underwent radical removal of all visible endometriosis.
   
“Our study suggests that surgical removal of an ovary and removal of visible endometriosis protects women from developing ovarian cancer at a later point,” said Anna-Sofia Melin, MD, lead author from the Karolinska Institute and Karolinska University Hospital, Stockholm.² “For women with endometriosis, the role of hormonal treatment and future ovarian cancer risk remains unclear and further investigation is warranted,” she concludes.
   
More than 5.5 million women in North America have a diagnosis of endometriosis, which occurs when endometrial tissue grows outside of the uterus. Endometriosis can be treated with hormonal therapy or surgery, but neither strategy is curative. An often painful condition, endometriosis can cause infertility in up to 40% of women if left untreated. Previous studies have shown that endometriosis is associated with an increased risk of several cancers, including ovarian cancer, although the overall risk is low.^1,2 The findings of this study add value to previous studies that have linked surgical interventions, such as hysterectomy or tubal ligation, to a reduced risk of ovarian cancer.

Pertinent Points:
- Surgical treatment for endometriosis is protective against the later development of ovarian cancer.
- Hormonal treatments for endometriosis were not associated with a reduction in risk for ovarian cancer.
 

References:

1. Melin AS, Lundholm C, Malki N, et al. Hormonal and surgical treatments for endometriosis and risk of epithelial ovarian cancer. Acta Obstet Gynecol Scand. April 8, 2013. doi: 10.111/aogs.12123. [Epub ahead of print]
2. Endometriosis treatments lower ovarian cancer risk [press release]. Available at: http://www.eurekalert.org/pub_releases/2013-04/w-etl040913.php. Accessed April 11, 2013.