This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Prostate Cancer, Subject name: Surgery
70 year old man with prostate cancer was given radiotherapy. The recurrence of the cancer is monitored biochemically by 
Select and explain. 
A. Androgens only, B. Prostate specific antigen and carcino-embryonic antigen, C. Prostate specific antigen only, D. ALP and CEA
C: Prostate specific antigen only
Answer: C: Prostate specific antigen only 
Explanation: Ans. (c) Prostate specific antigen onlyRef: Bailey & Love 26th ed. /1341* The most common presentation of advanced prostate cancer is a patient with a rising PSA level in whom initial local therapy has failed. Generally, after a radical prostatectomy, the PSA level should be less than 0.2 ng/ mL and, after radiation therapy, less than 0.5 ng/mL. Other important prognostic indicators include PSA velocity, time to PSA nadir, time to PSA recurrence, and pattern of PSA recurrence.* PSA levels for all men with prostate cancer who are having radical treatment should be checked at the earliest 6 weeks following treatment, at least every 6 months for the first 2 years and then at least once a year thereafter.