Global distribution pattern of histological subtypes of epithelial ovarian cancer: a database analysis and systematic review.

Background: Epithelial ovarian cancer is basically a heterogeneous disease with different chemosensitivity and distinct molecular alternations for each histological subtype. In order to assess whether the results of clinical trials can be extrapolated to a new country, it is critical to first examine whether the relative frequencies is homogenous across countries.

Methods: Cancer registry database from a single institution in Taiwan combined with systematic review of the global literature on the relative frequencies of histological subtypes between 2003 and 2012 was provided.

Results: Of 175 titles identified, 41 studies met inclusion/exclusion criteria. Globally, for each subtype, the median value of relative frequencies for serous subtype was 45.0%, with the Philippines (16.0%), Indonesia (22.7%), and Brazil (30.1%) as the three lowest countries and South Africa (68.0%), Greece (71.5%), and India (86.7%) as the three highest countries; for mucinous subtype, 11.4%, Italy (3.0%), Australia (3.4%), and Japan (5.4%) were the three lowest countries, while Indonesia (29.1%), Singapore (30.3%), and South Korea (38.6%) were the three highest countries; for endometrioid subtype, 12.6%, India (1.6%), Greece (5.7%), and Portugal (7.6%) were the three lowest countries, while Taiwan (24.8%), Egypt (25.0%), and Austria (25.5%) were the three highest countries; and for clear cell subtype, 5.3%, Pakistan (1.0%), Iran (2.0%), and Brazil (2.1%) were the three lowest countries while Thailand (16.0%), Taiwan (16.8%), and Spain (18.8%) were the three highest countries.

Conclusions: Relative frequencies of subtypes were not homogenous across countries. This diversity may reflect the geographical and ethnic variations. Globally, epithelial ovarian cancer is a heterogeneous disease with a heterogeneous distribution pattern.