Do scans or biopsies (tissue samples) have a role in diagnosing prostate cancer?

Role of Scans and Biopsies in Prostate Cancer Diagnosis

Prostate cancer diagnosis requires tissue biopsy—imaging scans alone cannot definitively diagnose cancer, though multiparametric MRI plays an increasingly important complementary role in guiding biopsy decisions and targeting suspicious lesions. 1

Biopsy Remains the Diagnostic Gold Standard

• Tissue diagnosis through biopsy is mandatory for confirming prostate cancer—neither MRI nor any other imaging modality can replace histopathologic confirmation 1
• TRUS-guided systematic biopsy (obtaining 8-12 cores from the peripheral zone) remains the standard diagnostic test and is rated as "usually appropriate" (rating 9/9) by the American College of Radiology for biopsy-naïve men with suspected prostate cancer 1, 2
• The diagnosis is typically triggered by elevated PSA levels or abnormal digital rectal examination, but confirmation requires tissue sampling 1

The Evolving Role of MRI Scans

MRI Cannot Replace Biopsy But Enhances Detection

• The NCCN strongly emphasizes that MRI alone should not be used to decide whether to perform biopsy, and a negative MRI is not an indication to forego biopsy in men with indications for first-time biopsy 1
• All men with indications for biopsy should receive standard 12-core TRUS-guided biopsy regardless of MRI results 1
• Using MRI to exclude men from biopsies may lead to as many as 12% of significant cancers being missed 1

MRI as a Complementary Tool

• Multiparametric MRI (with or without contrast) is rated 7/9 ("usually appropriate") by the ACR when performed before TRUS-guided biopsy in biopsy-naïve patients, allowing targeted sampling of suspicious lesions 1
• MRI-targeted biopsy significantly increases detection of clinically significant cancers while decreasing detection of clinically insignificant cancers compared to systematic biopsy alone 1
• In one prospective study of 223 biopsy-naïve men, adding MRI-guided targeted biopsies to standard TRUS biopsies identified clinically significant disease in an additional 13% of the population 1

Clinical Algorithm for Scan vs Biopsy Use

For Biopsy-Naïve Men (First-Time Diagnosis)

1. Perform standard 12-core TRUS-guided systematic biopsy as the primary diagnostic procedure 1, 2
2. Consider pre-biopsy multiparametric MRI to identify targets for additional MRI-targeted cores (complementary to, not replacing, systematic biopsy) 1
3. If MRI shows suspicious lesions (PI-RADS 3-5), perform both systematic biopsy AND targeted biopsy of the lesions 1
4. Never skip systematic biopsy based on negative MRI findings—proceed with standard 12-core biopsy regardless 1

For Men with Prior Negative Biopsies

• MRI becomes more valuable in the repeat biopsy setting—both multiparametric MRI and MRI-targeted biopsy are rated 8/9 ("usually appropriate") by the ACR for men with prior negative TRUS-guided biopsies 1
• MRI may help identify regions of cancer missed on previous biopsies and should be considered in selected cases 1, 2
• In men with previous negative biopsies, MRI-targeted approaches detected cancer in 51% of cases, with significantly more cancer found in targeted cores than systematic biopsies (30% vs 8.2%) 1

Important Caveats and Pitfalls

Limitations of Imaging

• Conventional grayscale TRUS cannot reliably localize tumors—only 11-35% of tumors are sonographically visible, and only 17-57% of hypoechoic lesions are malignant 1
• TRUS is used primarily to localize the prostate gland itself, not the cancer within it 1
• CT and bone scintigraphy are used for staging metastatic disease (nodal or bone), not for initial diagnosis 1

Biopsy Limitations

• Standard TRUS-guided systematic biopsy has a false-negative rate of 15-46% because needle positioning relative to tumor location is essentially random 1
• Tumor undergrading occurs in up to 38% of cases when biopsy results are compared with final pathology after radical prostatectomy 1
• Recognize that prostate biopsies are imperfect—they sometimes miss cancer even when present 2

Quality Requirements for MRI

• The NCCN emphasizes the need for high-quality MRI and radiologic expertise for optimal reading of scans 1
• Most published data on MRI-targeted biopsies come from only a few specialized centers with limited numbers of expert clinicians and radiologists 1

Recent Evidence on MRI Screening

• A 2024 population-based trial with 3.9 years of follow-up showed that omitting biopsy in patients with negative MRI results eliminated more than half of diagnoses of clinically insignificant prostate cancer 3
• However, the relative risk of detecting clinically significant cancer with MRI-targeted biopsy alone was 0.84 compared to systematic biopsy, indicating some significant cancers are still missed 3
• The risk of having incurable cancer diagnosed as interval cancer when using MRI-targeted approaches was very low but not zero 3