For a high‑risk prostate cancer patient (Gleason score ≥ 8, PSA > 20 ng/mL, or clinical stage ≥ T3), is a full‑body CT scan routinely required for staging?

Full-Body CT Scan in High-Risk Prostate Cancer

For high-risk prostate cancer patients, obtain CT of the chest, abdomen, and pelvis plus bone scan as the standard staging approach; if PSMA PET/CT is available, use it instead as it provides superior accuracy with less radiation exposure. 1

Risk-Based Staging Algorithm

Defining High-Risk Disease

High-risk prostate cancer is defined by any of the following criteria 1:

• PSA ≥ 20 ng/mL
• Gleason Grade Group 4-5 (Gleason score ≥ 8)
• Clinical stage ≥ T3

Standard Imaging for High-Risk Disease

Conventional imaging consists of 1:

• CT chest, abdomen, and pelvis (full-body CT coverage)
• Bone scan for skeletal metastases

This combination is the established standard recommended by both ESMO and AUA/ASTRO guidelines when PSMA PET/CT is unavailable 1.

Preferred Imaging: PSMA PET/CT

If available, PSMA PET/CT should replace conventional imaging because it demonstrates 1, 2:

• 27% greater accuracy than CT plus bone scan (92% vs 65%)
• Sensitivity of 85% for nodal metastases vs 38% for conventional imaging
• Specificity of 98% vs 91% for conventional imaging
• Changes management in 28% of patients vs 15% with conventional imaging
• Lower radiation exposure: 8.4 mSv vs 19.2 mSv for conventional imaging
• Fewer equivocal findings: 7% vs 23% with conventional imaging

What NOT to Image

Do not obtain staging scans in 1, 3:

• Low-risk disease (PSA <10 ng/mL AND Gleason Grade Group 1 AND clinical stage T1-T2a) - metastasis probability is extremely low
• Favorable intermediate-risk disease - routine staging not indicated unless specific clinical concerns exist
• Patients unsuitable for curative treatment due to poor general health or limited life expectancy

The evidence is clear: in one study of 236 low and intermediate-risk patients who underwent staging CT and bone scans, zero metastases were detected, representing approximately $191,000 in wasted healthcare expenditure 3.

Role of MRI

Pelvic multiparametric MRI should be obtained in high-risk patients for 1:

• Local T-staging to assess extraprostatic extension
• Surgical planning regarding nerve-sparing and extent of resection
• Alternative to CT for abdominopelvic imaging if PSMA PET/CT unavailable

MRI is preferred over CT for local staging but has similar accuracy for nodal assessment 1.

Critical Clinical Pitfalls

Common Errors to Avoid

Over-imaging low-risk patients 3, 4:

• Studies show 70-86% of low-risk patients inappropriately receive staging scans
• In patients with Gleason score 2-7, PSA ≤15 ng/mL, and clinical stage ≤T2b, the yield of positive CT scans is essentially zero

Under-imaging high-risk patients 5:

• Underuse of appropriate staging in high-risk disease remains substantial
• Missing metastatic disease leads to inappropriate treatment selection

Denying curative treatment based solely on novel imaging findings 1:

• If conventional imaging shows localized disease, do not withhold radical local treatment solely because PSMA PET/CT identifies additional lesions
• The clinical benefit of detecting these additional lesions remains uncertain

Specific Thresholds

Bone scan is generally unnecessary when 1, 4:

• PSA <20 ng/mL in the absence of bone pain or high-grade disease
• However, consider bone scan even with PSA <10 ng/mL if Gleason ≥8 or clinical stage ≥T3

CT abdomen/pelvis has minimal yield when 4:

• Gleason score 2-7 AND PSA ≤15 ng/mL AND clinical stage ≤T2b
• All 244 patients meeting these criteria in one study had negative CT scans

Practical Implementation

For a patient presenting with high-risk features (e.g., PSA 25 ng/mL, Gleason 4+4=8, clinical T2c) 1, 6:

1. First choice: Order PSMA PET/CT if available at your institution
2. If PSMA PET/CT unavailable: Order CT chest/abdomen/pelvis PLUS bone scan
3. Add pelvic mpMRI if not already performed and patient is candidate for surgery or radiation
4. Do not order additional skeletal imaging (like F-18 Fluoride PET) beyond bone scan or PSMA PET/CT 7

The radiation exposure difference is clinically meaningful: conventional imaging delivers more than double the radiation dose of PSMA PET/CT (19.2 vs 8.4 mSv) 2.