A 62-year-old man with hepatocellular carcinoma has AFP of 4,500 ng/mL. He is considered for liver transplant under Milan criteria. Which biochemical characteristic of AFP makes it a reliable marker of hepatocellular carcinoma recurrence post-transplant?

• A AFP is glycosylated with a specific lens culinaris agglutinin (LCA)-reactive fucosylated form (AFP-L3) that indicates malignant hepatocytes
• B AFP has a half-life of 3 days, so post-transplant decline mirrors tumour clearance ✓
• C AFP stimulates T-cell immune surveillance of residual tumour cells
• D AFP crosses the blood-hepatocyte barrier only during malignant transformation

Explanation

Alpha-fetoprotein (AFP) has a serum half-life of approximately 5-7 days. After curative liver transplantation, AFP should decline exponentially following its half-life. If AFP fails to decline as predicted, or rises again, it is a sensitive indicator of tumour recurrence either within the graft or as extrahepatic metastasis. Additionally, the AFP-L3 fraction (LCA-reactive fucosylated isoform) is more specific for HCC versus benign liver disease, though AFP-L3% rather than AFP-L3 absolute value is used clinically. However, the question specifically asks about recurrence monitoring where the half-life principle governs post-transplant surveillance. Both options A and B have merit, but option B directly answers why AFP is reliable for recurrence monitoring.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

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Written and medically reviewed by the StethoPrep medical team.