Imaging for Prostate Cancer: Diagnosis and Staging
Initial Diagnostic Imaging
Multi-parametric MRI (mpMRI) should be performed before prostate biopsy in all men with suspected prostate cancer based on elevated PSA or abnormal digital rectal examination. 1
Pre-Biopsy mpMRI Protocol
mpMRI is recommended before initial biopsy to identify high-value targets, improve detection of clinically significant cancer (Gleason ≥3+4), and reduce overdiagnosis of insignificant disease. 1, 2
The diagnostic accuracy of mpMRI shows sensitivity of 94-95% and specificity of 30-37% for detecting clinically significant prostate cancer (Gleason score ≥7). 3
A negative mpMRI does not eliminate the need for biopsy in men with clinical indications for first-time biopsy, as approximately 12% of significant cancers may be missed. 2
When mpMRI identifies suspicious lesions, perform both MRI-targeted biopsy AND systematic TRUS-guided 12-core biopsy—do not rely on targeted biopsy alone. 2
Important Timing Consideration
- Perform mpMRI before any biopsy, or wait 6-8 weeks after biopsy, as post-biopsy hemorrhage significantly degrades MRI quality and interpretation. 2
Risk-Stratified Staging Imaging
The imaging approach for staging depends entirely on disease risk category after diagnosis:
Low-Risk Disease (T1/2, Gleason 6, PSA <10)
- No additional imaging beyond local mpMRI is required for staging, as the probability of nodal or distant metastasis is extremely low. 1, 4
Intermediate-Risk Disease
For unfavorable intermediate-risk disease:
- Perform CT or MRI of abdomen/pelvis PLUS bone scan for metastatic screening. 1
- Consider PSMA PET/CT if available, though evidence is still evolving for this risk category. 4
High-Risk Disease (T3/4, PSA ≥20, or Gleason ≥8)
PSMA PET/CT is the preferred imaging modality for all high-risk patients if available. 4
PSMA PET/CT demonstrates 27% greater accuracy than conventional imaging, with sensitivity of 85% (vs. 38% for conventional imaging) and specificity of 98% (vs. 91% for conventional imaging) for detecting nodal metastases. 4
PSMA PET/CT leads to management changes in 28% of high-risk patients compared to 15% with conventional imaging. 4
PSMA PET/CT exposes patients to less radiation (8.4 mSv vs. 19.2 mSv) and results in fewer equivocal findings (7% vs. 23%) compared to conventional imaging. 4
If PSMA PET/CT is unavailable:
- Perform bone scan PLUS either pelvic mpMRI or CT scan of abdomen/pelvis for all high-risk patients. 4, 5
- Add CT chest for very high-risk features. 2
Local Staging with MRI
MRI provides T-staging and can inform surgical planning regarding nerve-sparing approaches and areas requiring wide excision for potential extracapsular extension. 1
MRI demonstrates high specificity (91-98%) but moderate sensitivity (57-58%) for detecting extracapsular extension and seminal vesicle invasion. 2, 3
Lesion size on mpMRI correlates with the presence of Gleason score ≥7 cancers (p = 0.005). 3
Critical Pitfalls to Avoid
Do not deny radical local treatment solely because metastatic lesions are identified on novel imaging techniques (PSMA PET/CT) when conventional imaging shows localized disease. 1
MRI quality and interpretation vary significantly between centers and radiologists, affecting diagnostic performance—ensure studies are performed at centers with dedicated prostate MRI expertise. 2
Do not skip systematic biopsy even when MRI-targeted biopsy is performed, as combined approaches detect more clinically significant cancers than either approach alone. 2
Patients not suitable for curative treatment due to poor general health or life expectancy <10 years do not require staging investigations. 1