Early Detection of Ovarian Cancer

Abstract

Despite advances in therapy, ovarian cancer remains the most deadly of the gynecological cancers. Less than 30% of women with advanced stage disease survive long-term. When diagnosed in stage I, up to 90% of patients can be cured with conventional surgery and chemotherapy. At present, only 25% of ovarian cancers are detected in stage I due, in part, to the absence of specific symptoms and to lack of an effective screening strategy. Early detection of ovarian cancer might significantly improve the overall survival rate of women with ovarian cancer if 1) most cancers are clonal and unifocal, arising in the ovary rather than in the peritoneum, 2) metastatic disease results from progression of clinically detectable stage I lesions, and 3) cancers remain localized for a sufficient interval to permit cost-effective screening. Given the prevalence of ovarian cancer, strategies for early detection must have high sensitivity for early stage disease (> 75%), but must have extremely high specificity (99.6%) to attain a positive predictive value of at least 10%. Transvaginal sonography (TVS), serum markers and a combination of the two modalities have been evaluated for early detection of ovarian cancer. Among the serum markers, CA125 has received the most attention, but lacks the sensitivity or specificity to function alone as a screening test. Greater specificity can be achieved by combining CA125 and TVS and/or by monitoring CA125 over time. Two stage screening strategies promise to be cost effective, where abnormal serum assays prompt TVS to detect lesions that require laparotomy. Accrual has been completed for a 200,000 woman trial in the United Kingdom that will test the ability of a rising CA125 to trigger TVS and subsequent exploratory surgery. Given the heterogeneity of ovarian cancer, it is unlikely that any single marker will be sufficiently sensitive to provide an effective initial screen. Sensitivity of serum assays might be enhanced by utilizing a panel of biomarkers. Candidate biomarkers have been discovered through empirical development of monoclonal antibodies, studies of gene expression, cloning of gene families and proteomic techniques. The development of technologies that measure multiple serum markers simultaneously, linked to the creation of statistical methods that enhance sensitivity without sacrificing specificity hold great promise.