NEW YORK (Reuters Health) Aug 26 - A two-stage ovarian cancer screening strategy has a good chance of catching the cancer early in older average-risk women, researchers reported online today in Cancer.
The approach uses a risk algorithm based on the tumor marker CA125 and transvaginal ultrasound (TVS).
In a large study, the strategy had "excellent" specificity and positive predictive value, according to Dr. Karen Lu from The University of Texas MD Anderson Cancer Center in Houston, Texas, and colleagues.
Right now, there are no established screening strategies for ovarian cancer, and because the disease often causes no specific symptoms, early detection is tough. Most cases women have advanced disease at diagnosis.
Dr. Lu and colleagues tested their two-stage ovarian cancer screening strategy in a study lasting 11 years and involving 4,051 postmenopausal women.
Each woman had an initial CA125 test, after which researchers calculated their risk for ovarian cancer based on the Risk of Ovarian Cancer Algorithm (ROCA). The researchers developed ROCA using data from longitudinal screening trials of postmenopausal women at normal risk for ovarian cancer and a statistical model describing CA125 serial profiles in women subsequently diagnosed with the disease.
"Women with incident cases of ovarian cancer had a baseline level followed by a sharp increase in CA125 values significantly above her baseline, called a change-point CA125 profile, which could not be explained by background CA125 fluctuations," the authors explained. "These thousands of profiles form the basis for the ROCA calculation that determines a woman's risk of having ovarian cancer at that time. For each new woman in the study, the probability calculation of ovarian cancer begins with incidence based on her age, and increases the closer her profile is to the change-point profiles compared with the flat profiles."
Their strategy has women at low risk for ovarian cancer at the outset receiving another CA125 test one year later; those at intermediate risk receive a repeat CA125 in three months; and those at high risk undergo TVS and are referred to a gynecologic oncologist. After every CA125 measurement, ROCA risk is recalculated and a new recommendation is made.
Dr. Lu and colleagues report that an average of 5.8% of women were found to be at intermediate risk for ovarian cancer each year and the average annual referral rate to TVS and review by a gynecologic oncologist was 0.9%.
Ten women underwent surgery based on their ultrasound exams and four had invasive ovarian cancers. All four women with invasive cancer were enrolled in the study for at least three years with low-risk annual CA125 test values prior to rising CA125 levels.
Two of the women had ovarian tumors of low malignant potential, one had endometrial cancer, and three had benign ovarian tumors. This equates to a positive predictive value of 40% for detecting invasive ovarian cancer, the researchers say.
The specificity of the testing strategy was 99.9%, meaning that only 0.1% of women without cancer would be falsely identified as having the disease. Importantly, all of the ovarian cancers detected with this strategy were early stage.
In email to Reuters Health, Dr. Lu noted that having "very few false positives is key for a screening test for ovarian cancer, since we don't want to cause harm by performing unnecessary surgeries based on false positive results. This is especially true for ovarian cancer, as surgery has to be performed in order to determine if cancer is present or not. This contrasts with breast cancer screening, in which a biopsy (still invasive, but certainly less so than a surgery) has to be performed to determine if cancer is present."
This study, Dr. Lu said, provides an "early clue as to how the strategy performs in picking up ovarian cancers (incident cases); although our numbers are small, in all cases the women who were found to be in the study had had normal CA125's for three to five years before their values started to rise. In all four cases they had early stage disease (stage I or II). This contrasts sharply with most ovarian cancers, in which 80% are caught at late stage."
She emphasized that the findings need to be confirmed. "A 200,000 woman study is evaluating this strategy in the United Kingdom with results expected in 2015. This study has enough women to evaluate if this two-stage early detection strategy will decrease deaths from ovarian cancer. I feel strongly that women should not ask their physicians for the CA125 test until we have the results from the larger study."
SOURCE: http://bit.ly/17fMmLi
Cancer 2013.
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