(ChemotherapyAdvisor) – Endometriosis increases risk for specific histologic subtypes of ovarian cancer, results of an international collaborative study published in The Lancet Oncology online February 22 have found.

The investigators pooled data from 13 ovarian-cancer case-control studies from the Ovarian Cancer Association Consortium and assessed the association between self-reported endometriosis and risk of ovarian cancer. The analysis included 13,226 controls and 7,911 women with invasive ovarian cancer and an additional 1,907 women with borderline ovarian cancer.

Of these, 818, 738, and 168 women, respectively, reported a history of endometriosis, which was associated with a significantly increased risk of clear-cell (OR=3.05), low-grade serious (OR=2.11), and endometrioid invasive ovarian cancers (OR=2.04). No association was found between endometriosis and risk of mucinous (OR=1.02) or high-grade serous invasive ovarian cancer (OR=1.13) or borderline tumors of either subtype (serious, OR=1.20; mucinous, OR=1.12).

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“Future efforts should focus on understanding the mechanisms that might lead to malignant transformation of endometriosis so as to help identify subsets of women at increased risk of ovarian cancer,” the investigators noted.