**Question:** Best investigation for prostate cancer is -

A. Prostate Specific Antigen (PSA) test
B. Digital Rectal Examination (DRE)
C. Transrectal Ultrasound (TRUS)
D. Prostate Biopsy

**Correct Answer:** D. Prostate Biopsy

**Core Concept:**
Prostate cancer is a common malignancy in male patients, and early detection is crucial for effective treatment. The following investigations are used to diagnose prostate cancer:

**Why the Correct Answer is Right:**
Prostate biopsy is considered the gold standard for diagnosing prostate cancer because it directly examines prostate tissue for the presence of cancer cells. It allows pathologists to confirm the presence of malignancy, determine the Gleason score, and stage the cancer. The other options have their roles in the diagnostic process but prostate biopsy is essential for a definitive diagnosis.

**Why Each Wrong Option is Incorrect:**

A. Prostate-Specific Antigen (PSA) test: PSA is a blood marker that increases in prostate cancer and other prostate conditions. A high PSA value does not confirm cancer and requires further evaluation, typically with a prostate biopsy.

B. Digital Rectal Examination (DRE): DRE evaluates the prostate for abnormalities but cannot confirm cancer. It may suggest suspicious findings that require further investigation, such as a prostate biopsy.

C. Transrectal Ultrasound (TRUS): TRUS is an imaging modality that helps locate the prostate and guide biopsy procedures. It provides information about prostate size, shape, and potential abnormalities, but it does not confirm cancer.

**Clinical Pearl:**
Prostate biopsy is crucial for obtaining a definitive diagnosis of prostate cancer. A combination of PSA screening and DRE can help identify high-risk patients who should undergo prostate biopsy. However, a definitive diagnosis can only be made through a biopsy of prostate tissue.