Overview
What OCAC Is
The Ovarian Cancer Association Consortium (OCAC) is a forum of investigators of case-control studies of ovarian cancer, formed in April 2005. Its aim is to combine data from many studies to provide a reliable assessment of the risks associated with genetic variants. OCAC has established itself as essentially the only functional venue for large-scale validation of ovarian cancer susceptibility polymorphisms.
Scale
OCAC participants are enrolled in 65 studies from 16 countries, making it one of the largest collaborative cancer genetics efforts in the world. The most recent large-scale GWAS meta-analysis analyzed over 22 million variants across 398,238 women, drawing on OCAC, the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA), and the UK Biobank.
Genotyping Infrastructure
OCAC has conducted GWAS using two major custom genotyping platforms.
Key Discoveries
The first GWAS of EOC susceptibility was published in 2009, reporting the identification of the 9p22.2 risk locus. Since then, a total of 37 common SNP loci associated with EOC risk at genome-wide significance (P < 5×10⁻⁸) have been identified. More recently, 40 genomic regions associated with EOC have now been identified through GWAS, with 19 of these regions most strongly associated with the high-grade serous histotype (HGSOC).
A 2025 study — the largest HGSOC GWAS to date — identified eight novel variants associated with HGSOC risk, including a TP53 3'-UTR SNP (rs78378222-T) with a relative risk of 1.44 per allele. A polygenic score built from 64,518 variants showed an odds ratio of 1.46 per standard deviation.
Histotype Specificity
A key finding from OCAC GWAS work is that most risk loci are histotype-specific rather than pan-EOC. The association at each identified locus varies considerably by histotype, and most loci appear to predispose to one histotype or specific combinations of histotypes — this is biologically important given that high-grade serous, clear cell, endometrioid, mucinous, and low-grade serous cancers are now understood to be distinct diseases.
Functional Follow-up
In integrative multi-omics analyses, OCAC data combined with transcriptome-wide association and colocalization analyses identified 86 candidate susceptibility genes in known EOC risk regions, with the goal of identifying credible causal risk variants.
Polygenic Risk Scores
OCAC data have been instrumental in developing polygenic risk scores (PRS) for ovarian cancer, with potential clinical applications for risk stratification, particularly in combination with BRCA1/2 carrier status.
Notes
Subtype-stratified GWAS are particularly valuable. Related consortium CIMBA maintains BRCA1/2 carrier OV datasets in EGA.