## CA-125 in Ovarian Cancer **Key Point:** CA-125 is the most widely used tumor marker for epithelial ovarian cancer, elevated in 80–90% of advanced-stage disease and used for surveillance and treatment monitoring. ### Clinical Applications #### Diagnosis & Staging - Elevated in 50% of stage I and 90% of stage III–IV epithelial ovarian cancer - Not used alone for diagnosis (lacks specificity) - Baseline level correlates with tumor burden and prognosis #### Monitoring & Recurrence - **Most important use:** Detecting biochemical recurrence before clinical symptoms - Serial measurements more valuable than absolute values - Rise of >2× baseline suggests recurrence or progression - Used in conjunction with imaging for treatment decisions #### Limitations - **Not specific:** Elevated in benign gynecologic conditions (endometriosis, menstruation, fibroids) - **Not sensitive in early disease:** Only 50% sensitivity in stage I cancer - Cannot be used for screening in asymptomatic women **High-Yield:** CA-125 is part of RECIST criteria for ovarian cancer response assessment and is essential for long-term surveillance post-chemotherapy.
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