By I. Soussis MD
Women with endometriosis are 1.9 times more likely to develop ovarian cancer, but are at no higher risk for endometrial and cervical cancers, a meta-analysis suggests.
The study, “Impact of endometriosis on risk of ovarian, endometrial and cervical cancers: a meta-analysis,” was published in the journal Archives of Gynecology and Obstetrics.
While endometriosis is considered a benign gynecologic disease, it displays features similar to those seen in malignant tumors, including:
the ability to invade other tissues
a high rate of new blood vessel formation
development of local and distant sites of lesions
These characteristics of endometriosis rendered its classification as behaving similar to tumor-like lesions by the World Health Organization, and growing evidence suggests that the condition may represent an initial stage of tumor progression.
While some studies have associated endometriosis with an increased risk for developing different gynecologic tumors, namely ovarian and endometrial cancers, the results are conflicting.
Therefore, a team of researchers in China performed a meta-analysis to investigate the link between endometriosis and the risk for three gynecological cancers: ovarian, endometrial, and cervical.
Out of 8538 studies retrieved from several databases, they analyzed 25 studies, which included 15 cohort and 10 case-control studies. These studies had been conducted in different countries, including Taiwan, the U.S., Australia, Sweden, Denmark, the Netherlands, Japan, Canada, and Spain, with one study involving joint participation of multiple countries.
The researchers evaluated the risk factor between endometriosis and ovarian cancer in 23 studies, between endometriosis and endometrial cancer in 9 studies, and between endometriosis and cervical cancer in 3 studies.
They found that endometriosis was associated with an increased risk (1.9 times) for developing ovarian cancer. In fact, the ovary is one of the major target organs for the malignant transformation of endometriosis. An integrated analysis of different studies revealed a great overlap between the genetic alterations of both endometriosis and ovarian cancer.
Of note, researchers found that endometriosis increased the risk for developing some subtypes of ovarian cancer: endometrioid and clear-cell type.
No clear evidence supports a link between endometriosis and the risk for endometrial cancer, and endometriosis was not associated with an increased risk for cervical cancer.
Despite the authors’ efforts in making a robust comparison of the different studies using rigorous selection criteria, they were limited to the number of available articles about each cancer type. There were more ovarian cancer studies available, which could have influenced the observations to some extent, the study noted.
“There is insufficient evidence to support the theory of endometriotic lesions as a precancerous lesion,” the researchers wrote.
Their meta-analysis suggests that endometriosis is a potential risk factor for developing ovarian cancer, but additional studies are required to understand further if endometriotic lesions are precancerous.
“If endometriosis is considered a precancerous lesion, the current treatment management needs to be modified,” the researchers concluded, noting that patients with endometriosis need to be closely observed and rechecked regularly to prevent malignant changes.
The association between endometriosis and clear-cell cancer of the ovary and endometrioid ovarian cancer is well established. This meta-analysis confirms it and also clarifies that there is no increased risk between endometriosis and endometrial and cervical cancer.
Women with endometriosis should have life-long regular follow up by their doctors.