A 58-year-old woman from Delhi with a history of ovarian cancer (stage IIIC, serous adenocarcinoma) completed platinum-based chemotherapy 6 months ago. She is now asymptomatic on follow-up. Serum CA-125 level is 35 U/mL (normal <35 U/mL), and imaging (CT chest/abdomen/pelvis) is unremarkable. What is the most appropriate clinical interpretation and next step?

Explanation

## CA-125 in Ovarian Cancer Surveillance ### Role of CA-125 as a Tumor Marker **Key Point:** CA-125 (cancer antigen 125) is a high-molecular-weight glycoprotein expressed on epithelial ovarian cancer cells. It is the most widely used tumor marker in ovarian cancer but is neither specific nor sensitive enough to diagnose recurrence alone. ### Interpretation of Normal CA-125 Post-Treatment **High-Yield:** In this patient: - **Baseline CA-125 normalization** after chemotherapy indicates response to treatment and is associated with improved prognosis - **Normal CA-125 + normal imaging** = complete clinical response (CR) - However, **normal CA-125 does NOT exclude microscopic disease or early recurrence** ### CA-125 Kinetics and Recurrence Detection **Clinical Pearl:** CA-125 may rise **before imaging detects recurrence** by 3–6 months. This is why serial CA-125 measurements (trend) are more valuable than a single value. | CA-125 Pattern | Clinical Significance | | --- | --- | | Normalized post-treatment | Good prognostic sign; indicates response | | Progressive rise (>2× baseline) | Suggests recurrence; warrants imaging | | Fluctuating (borderline) | Requires repeat measurement and imaging | | Normal throughout | Better prognosis; lower recurrence risk | ### Surveillance Strategy **High-Yield:** Current guidelines recommend: 1. **Serial CA-125 measurements** every 3 months for 2 years, then every 6 months 2. **Clinical examination** at each visit 3. **Imaging (CT or ultrasound)** when CA-125 rises or symptoms develop 4. **Routine surveillance imaging** is NOT recommended if asymptomatic with normal CA-125 ### Limitations of CA-125 **Warning:** CA-125 lacks specificity: - Elevated in benign conditions: endometriosis, menstruation, peritonitis, pancreatitis - Elevated in other malignancies: gastric, pancreatic, lung, breast cancer - **Sensitivity for recurrence:** ~80% but varies by histology and stage - **30% of patients with recurrent ovarian cancer have normal CA-125** ### Surveillance Algorithm for Ovarian Cancer ```mermaid flowchart TD A[Post-chemotherapy follow-up]:::outcome --> B{CA-125 level?}:::decision B -->|Normal + asymptomatic| C[Clinical exam + serial CA-125 q3mo]:::action B -->|Rising trend >2x baseline| D[Imaging: CT/ultrasound]:::action B -->|Borderline/fluctuating| E[Repeat CA-125 in 4-6 weeks]:::action C --> F{Any symptoms or imaging findings?}:::decision D --> G{Recurrence on imaging?}:::decision E --> H{Confirmed rise?}:::decision F -->|No| I[Continue surveillance]:::action F -->|Yes| J[Investigate further]:::action G -->|Yes| K[Second-line chemotherapy]:::action G -->|No| L[Continue surveillance]:::action H -->|Yes| D H -->|No| I ``` **Key Point:** The goal of surveillance is **early detection of recurrence** when treatment is most effective. CA-125 + clinical assessment + imaging (when indicated) form the backbone of follow-up. [cite:Harrison 21e Ch 105; Robbins 10e Ch 7]