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Description of the Evidence

    continued...

    The UKCTOCS published sensitivity and specificity results from their prevalent screen. The ultrasound screening arm had several levels of screening and possible referral strategies: an abnormal scan resulted in a repeat scan in 6 to 8 weeks, and if still abnormal, a referral was made for clinical assessment. Of 53 total cancers (screen-detected and interval cancers in the following year), 45 were screen positive by ultrasound (two abnormal scans) for a sensitivity of 84.9%. For invasive cancer, the sensitivity was 75%. Specificity of the ultrasound screening arm was calculated to be 98.2%.[12]

    CA-125 concentrations

    CA-125 is a tumor-associated antigen that is used clinically to monitor patients with epithelial ovarian carcinomas.[13,14] Measurement of CA-125 concentrations has been proposed as a potential marker for the early detection of ovarian cancer, either as a single test with a threshold cutpoint or in algorithms examining the change in levels over time. The two randomized trials have included CA-125 either in parallel or sequentially with TVU for multimodality screening. The most commonly reported CA-125 reference value that designates a positive screening test is 35 U/mL, and this was the reference value used in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Screening Trial (NCT00002540) to define an abnormal test result. The measurement of CA-125 levels, in parallel combination with TVU,[15] is the ovarian screening intervention evaluated in the PLCO.[16,17] Elevated CA-125 levels are not specific to ovarian cancer and have been observed in patients with nongynecological cancers [14] and in the presence of other conditions such as the first trimester of pregnancy [18,19] or endometriosis.[20] The sensitivity of the CA-125 test for the detection of ovarian cancer was estimated in two nested case-control studies using serum banks.[21,22] The sensitivity for CA-125 levels of at least 35 U/mL ranged from 20% to 57% for cases occurring within the first 3 years of follow-up; the specificity was 95%.

    A phase II/III biomarker study was conducted to evaluate the sensitivity of several markers of ovarian cancer, including CA-125 concentrations, using specimens collected from ovarian cancer patients at four sites. The estimated sensitivity for early-stage disease (stage I and II ovarian cancer) was 56% (95% confidence interval [CI], 49%–72%) for a cutpoint set to obtain a fixed specificity of 95%. The threshold for the cutpoint for CA-125 at 95% specificity was 24 U/mL. For all cases (56% of cases had stage III or IV disease at diagnosis), the sensitivity was 73% (95% CI, 64%–84%). When the clinical cutpoint of 35 U/mL was used, the sensitivity decreased.[23]

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