70 year old man with prostate cancer was given radiotherapy. The recurrence of the cancer is monitored biochemically by
**Core Concept**
The underlying principle being tested is the biochemical monitoring of prostate cancer recurrence, specifically focusing on tumor markers. Prostate cancer is often monitored through various biomarkers, with **prostate-specific antigen (PSA)** being the most significant.
**Why the Correct Answer is Right**
The correct answer is related to the use of **PSA** levels to monitor recurrence. After radiotherapy, the **PSA** level is expected to decrease. An increase in **PSA** levels over time can indicate recurrence of the cancer. This is because **PSA** is produced by prostate cells, and its level can reflect the presence or growth of prostate tissue, including cancerous cells.
**Why Each Wrong Option is Incorrect**
**Option A:** Without specific details on the options, we can infer that any option not related to **PSA** or another direct biomarker for prostate cancer would be incorrect.
**Option B:** Similarly, any option not directly related to biochemical markers of prostate cancer would not be the best choice for monitoring recurrence.
**Option C:** Again, without specifics, if this option does not involve a biochemical marker like **PSA**, it would not be the most appropriate choice.
**Option D:** Assuming this option also does not involve **PSA** or a similar biomarker, it would be incorrect for the same reasons as the others.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that **PSA** levels can be influenced by various factors, including benign prostatic hyperplasia and certain medications, but in the context of post-treatment monitoring for prostate cancer, an increasing **PSA** level is highly suggestive of recurrence.
**Correct Answer:** D. Prostate Specific Antigen (PSA)