Detection of which substance is most useful to monitor the course of a patient with testicular cancer?

• A. Alpha-fetoprotein
• B. Carcinoembryonic antigen
• C. Prolactin
• D. Testosterone

Answer: (A)

Tumor markers that reflect how much cancer is present are used to track the course of germ cell tumors in the testis. Alpha-fetoprotein is produced by certain testicular tumor types (like yolk sac tumors and some embryonal carcinomas), so its blood level mirrors tumor burden. Because AFP has a short half-life, levels fall quickly after successful treatment, making serial measurements a sensitive indicator of response, remission, or relapse. While some testicular cancers can elevate other markers like HCG, AFP remains the most reliable marker for monitoring disease activity in many patients, whereas the other substances listed are not used to track testicular cancer progression.