New screening strategy may detect ovarian cancer at early stages
A new screening strategy for ovarian cancer appears to be highly specific for detecting the disease before it becomes lethal, according to a new study. If verified in an ongoing clinical trial, it could potentially help save the lives of thousands of women each year in the United States alone.
Currently, ovarian cancer has no established screening strategies. The disease often causes no specific symptoms, and so it is difficult to detect in the early stages when it is most responsive to treatment. Therefore, ovarian cancer is highly lethal because most women have advanced disease when they are diagnosed.
Karen Lu, MD, of The University of Texas MD Anderson Cancer Center in Houston, led a team that tested the potential of a two-stage ovarian cancer screening strategy that incorporates changes in a blood protein called CA125, which is a known tumor marker. In their 11-year study, published in Cancer (2013; doi: 10.1002/cncr.26241), 4,051 postmenopausal women initially underwent an annual CA125 blood test. Based on a calculation called the "risk of ovarian cancer algorithm" (ROCA), women were divided into three groups: those who should receive another CA125 test 1 year later (low risk), those who should receive a repeat CA125 in 3 months (intermediate risk), and those who should receive a transvaginal ultrasound and be referred to a gynecologic oncologist (high risk).
An average of 5.8% of the women was found to be of intermediate risk each year, meaning that they should receive a CA125 test in 3 months. The average annual referral rate to transvaginal ultrasound and review by a gynecologic oncologist was 0.9%. Ten women underwent surgery based on their ultrasound exams, with four having invasive ovarian cancers, two having ovarian tumors of low malignant potential, one having endometrial cancer, and three having benign ovarian tumors. This equates to a positive predictive value of 40% for detecting invasive ovarian cancer. The specificity of the testing strategy was 99.9%, meaning that only 0.1% of patients without cancer would be falsely identified as having the disease. Importantly, all of the ovarian cancers were early stage.The findings indicate that the ROCA screening strategy achieves high specificity with very few false- positive results in postmenopausal women. "The results from our study are not practice-changing at this time; however, our findings suggest that using a longitudinal (or change-over-time) screening strategy may be beneficial in postmenopausal women with an average risk of developing ovarian cancer," said Lu." We are currently waiting for the results of a larger, randomized study currently being conducted in the United Kingdom that uses the same risk-of-ovarian-cancer algorithm in a similar population of women. If the results of this study are also positive, then this will result in a change in practice."