The generally low sensitivity of CA 125 for FIGO stage I ovarian cancer diagnosis increases for endometrioid histotype

BACKGROUND: The serum marker CA 125 is still the most widely used biomarker for ovarian cancer (OC) diagnosis in gynecological and oncological setting, but its predictive role in early-stage OC is still debated. The aim of this study was to explore the value of CA 125 in distinguishing between early-stage OC and borderline ovarian tumor (BOT) and to evaluate the accuracy of CA 125 in the detection of early stage OC. METHODS: A retrospective cohort study was performed at the University Hospital of Bologna (Italy) on 1296 consecutive women suffering from OC or BOT (diagnosed at histology) between 1988-2017. Patients for whom CA 125 level was determined preoperatively were included. The positive cut-off level used was >35 U/mL. RESULTS: Of 910 patients, 192 (21.1%) were diagnosed with BOT and 718 (78.9%) with OC. The sensitivity of CA 125 for stage I OC was 54.4 (95% CI: 45.3-63.3) (51.5 for IA, 54.6 for IB, 58.3 for IC), but it increased to 78.0 (95% CI: 63.7-88.0) for stage II. Interestingly, in stage I OC, CA 125 presented a significantly higher sensitivity for the endometrioid histotype 72.4 (95% CI: 52.5-86.5) vs. 49.0 (95% CI: 38.6-59.4), P=0.026. The positive likelihood ratio of CA 125 for early-stage OC compared to BOT was 1.29 (95% CI: 1.06-1.58). CONCLUSIONS: Despite its limited sensitivity for early-stage OCs, CA 125 still represents a useful serum marker to early differentiate between OCs and BOTs. Its sensitivity for stage I OC increases in endometrioid histotype.