Background

Median overall survival (OS) for women with high-grade serous ovarian cancer (HGSOC) is approximately four years, yet survival varies widely between patients. There are no well-established, gene expression signatures associated with prognosis. The aim of this study was to develop a robust prognostic signature for overall survival in HGSOC patients.
Patients and methods

Expression of 513 genes, selected from a meta-analysis of 1455 tumours and other candidates, were measured using NanoString technology from formalin-fixed, paraffin-embedded (FFPE) tumour tissue from 3,769 women with HGSOC from multiple studies. Elastic net regularization for survival analysis was applied to develop a prognostic model for 5-year OS, trained on 2702 tumours from fifteen studies and evaluated on an independent set of 1067 tumours from six studies.
Results

Expression levels of 276 genes were associated with OS [false discovery rate (FDR) < 0.05] in covariate-adjusted single gene analyses. The top five genes were TAP1, ZFHX4, CXCL9, FBN1, and PTGER3 (P < 0.001). The best performing prognostic signature included 101 genes enriched in pathways with treatment implications. Each gain of one standard deviation in the gene expression score (GES) conferred a greater than two-fold increase in risk of death [HR = 2.35 (2.02, 2.71); P < 0.001]. Median survival by GES quintile was 9.5 (8.3, --), 5.4 (4.6, 7.0), 3.8 (3.3, 4.6), 3.2 (2.9, 3.7) and 2.3 (2.1, 2.6) years.
Conclusion

The OTTA-SPOT (Ovarian Tumor Tissue Analysis consortium - Stratified Prognosis of Ovarian Tumours) gene expression signature may improve risk stratification in clinical trials by identifying patients who are least likely to achieve 5-year survival. The identified novel genes associated with the outcome may also yield opportunities for the development of targeted therapeutic approaches.