Link between endometriosis and ovarian-cancer subtypes : The Lancet Oncology
"Previous large epidemiological studies have
attempted to identify benign gynaecological disorders that predispose to
the development of epithelial ovarian cancer. The only disorder that
has been repeatedly1—4 (although not universally5)
associated with this cancer is endometriosis. Results of some of these
studies have suggested a specific link with endometrioid and clear-cell
ovarian cancers, but until now none had the power to allow definitive
subgroup analysis based on a contemporary definition of histological
subtype.
In a study reported in the Lancet Oncology, Celeste Leigh Pearce and colleagues6
assessed self-reported endometriosis data from 13 pooled case—control
studies in the Ovarian Cancer Association Consortium (OCAC). They
confirm that a history of endometriosis is significantly associated with
an increased risk of clear-cell (odds ratio 3·05, 95% CI 2·43—3·84) and
endometrioid (2·04, CI 1·67—2·48) ovarian cancers, and for the first
time show an association with low-grade serous ovarian cancer (2·11,
1·39—3·20). No association was noted between endometriosis and
high-grade serous, mucinous, serous borderline, or mucinous borderline
ovarian cancers.
With more than 23 000
participants (7911 with a diagnosis of ovarian cancer), the main
strengths of this study are its statistical power and its robust
methods. Incidences of reported endometriosis differ substantially
between the pooled studies. Although clinicopathological and genetic
differences between the populations could reasonably be expected,
importantly there was no significant heterogeneity of the association
with histological subtype in the different studies.
The
main truly novel finding is an association between a history of
endometriosis and low-grade serous ovarian cancer. Perhaps surprisingly,
serous borderline tumours (from which invasive low-grade serous ovarian
cancers are believed to arise7)
are not also associated with a history of endometriosis.
