The study, “Risk of Gynecologic Cancer According to the Type of Endometriosis,” was published in the journal Obstetrics & Gynecology.
Endometriosis tissue is also known to produce several hormones and other molecules that help sustain an inflammatory state, factors that can contribute to cancer development and progression.
The association between endometriosis and cancer has been explored in several studies that have shown that endometriosis is linked to a higher risk of ovarian cancer. However, the association with other types of gynecological cancer is unclear.
A research team reviewed the clinical records from the Finnish Hospital Discharge Register of 49,933 women surgically diagnosed with endometriosis between 1987 and 2012. The type of lesions they had were classified, according to the affected tissues, as ovarian (23,210 cases), peritoneal (20,187 cases), and deep infiltrating (2,372 cases) endometriosis. Information on the incidence of gynecological cancers was obtained from the Finnish Cancer Registry.
In line with previous data, the researchers found that endometriosis was associated with an increased risk of ovarian cancer. In particular, these women were found to have a 3.12 times higher incidence of the endometrioid type of ovarian cancer and a 5.17 times higher incidence of the clear cell type than the general female population.
This association was found to be stronger in women with ovarian endometriosis, who were found to have a 4.72 times increased incidence of the endometrioid type and 10.1 times increased incidence of clear cell ovarian cancer. Peritoneal endometriosis was also associated with a twofold increased risk for endometrioid ovarian cancer, while no association was found with deep infiltrating endometriosis.
The risk of cervical, endometrial, or other uterine cancers was no different than that reported in the general population. Endometriosis was also not associated with a higher risk for cancers in other female genital organs, such as the vulva or vagina.
“Acknowledging these risks is important when planning long-term management of women with endometriosis,” the researchers said.
“The excess risk of ovarian cancer among women with ovarian endometriosis translates into two excess cases per 1,000 patients followed for 10 years,” they wrote.