Comparison of longitudinal CA125 algorithms as a first line screen for ovarian cancer in the general population

Purpose: In the United Kingdom Collaborative Trial of Ovarian Cancer Screening(UKCTOCS) women in the multimodal (MMS) arm had a serum CA125 test (first-line), with those at increased risk, having repeat CA125/ultrasound (second-line test). CA125 was interpreted using the 'Risk of Ovarian Cancer Algorithm'(ROCA). We report on performance of other serial algorithms and a single CA125 threshold as a first line screen in the UKCTOCS dataset. Experimental Design: 50,083 post-menopausal women who attended 346,806 MMS screens were randomly split into training and validation sets, following stratification into cases (ovarian/tubal/peritoneal cancers) and controls. The two longitudinal algorithms, a new serial algorithm, method of mean trends (MMT) and the parametric empirical Bayes (PEB) were trained in the training set and tested in the blinded validation set and the performance characteristics, including that of a single CA125 threshold, were compared. Results The area under receiver operator curve (AUC) was significantly higher (p=0.01) for MMT (0.921) compared to CA125 single threshold (0.884). At a specificity of 89.5%, sensitivities for MMT (86.5%;95%CI:78.4-91.9) and PEB (88.5%;95%CI:80.6-93.4) were similar to that reported for ROCA (sensitivity 87.1%; specificity 87.6%; AUC 0.915) and significantly higher than the single CA125 threshold (73.1%;95%CI:63.6-80.8). Conclusions: These findings from the largest available serial CA125 data set in the general population provide definitive evidence that longitudinal algorithms are significantly superior to simple cut-offs for ovarian cancer screening. Use of these newer algorithms requires incorporation into a multimodal strategy. The results highlight the importance of incorporating serial change in biomarker levels in cancer screening/early detection strategies.

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