Imaging Modalities for Detecting Prostate Cancer Metastases

Conventional Imaging Approaches

The American Urological Association recommends cross-sectional imaging with CT or MRI along with 99mTc-methylene diphosphonate bone scintigraphy as standard imaging approaches for post-treatment biochemical recurrence of prostate cancer 1, 2, 3
Conventional imaging is still the basis for current standard of care systemic treatments in metastatic hormone-sensitive prostate cancer (mHSPC) 1
These conventional modalities infrequently detect metastases in the setting of early PSA recurrence (e.g., PSA <5 ng/mL) 1, 3

Traditional planar radionuclide bone scan has poor sensitivity at low PSA levels, according to the American College of Radiology 4, 5
Most patients with a positive bone scan had a very high PSA level (mean of 61.3 ng/mL) and high PSA velocity (>0.5 ng/mL per month) 4, 5
The probability of a positive bone scan was <5% even with high PSA levels between 40 and 45 ng/mL 4
Routine use of bone scans in the setting of a PSA rise is not justified, particularly in patients with a PSA doubling time of >6 months and a PSA value of <10 ng/mL 4, 5
CT is not effective for detecting recurrent tumor in the surgical bed, with a mean PSA value associated with a positive CT scan after radical prostatectomy of 27.4 ng/mL 4, 6
CT has poor sensitivity for prostate cancer nodal metastases because large numbers of metastatic nodes are normal size 6

Novel PET tracers show greater sensitivity for detection of prostate cancer recurrence and metastases at low PSA values (<2.0 ng/mL), as reported by the Journal of Urology 1, 3
68Ga-PSMA PET has superior sensitivity and specificity compared with choline-based PET imaging options, according to the Journal of Clinical Oncology 7
Rising PSA values and positive 68Ga-PSMA PET results are correlated 7
Detection rates increase with PSA levels: 81.8% for PSA 2 to <5 ng/mL, 95.3% for PSA 5 to <10 ng/mL, and 96.8% for PSA ≥10 ng/mL 7
Multiparametric MRI (mpMRI) is the most accurate imaging method for identifying sites of local recurrence after radical prostatectomy, with 84% to 100% sensitivity and 89% to 97% specificity 6
MRI is superior to 11C-choline PET/CT, SPECT, and bone scintigraphy in the detection of bone metastases on a per-patient basis 7

For patients with biochemical recurrence after failure of local therapy, novel PET-CT scans (e.g., fluciclovine, choline, PSMA) may be utilized as an alternative to conventional imaging or in the setting of negative conventional imaging, as recommended by the Journal of Urology 1, 3
Advanced imaging can lead to changes in management in up to 76% of cases, according to the Journal of Clinical Oncology 7
Understanding the pattern of metastatic spread is prognostic and should guide imaging strategies and treatment decisions, although this is based on a report from Praxis Medical Insights, an alternative source is preferred but not available 8

The American College of Radiology recommends against using FDG PET/CT for routine staging of prostate cancer due to its poor performance, with a sensitivity for primary prostate cancer of only 33% 9, 10

The American College of Radiology suggests that an SUVmax cutoff of 2.4 can be used to differentiate benign from metastatic rib lesions on FDG PET/CT, but with only 57.2% accuracy 9, 10

The European Association of Urology is not cited, however the Annals of Oncology recommends using PSMA PET/CT as first-line imaging for intermediate-risk disease with ISUP grade group 3 or higher 11
The Journal of the American College of Radiology recommends against relying on conventional imaging (CT/bone scan) at PSA <20 ng/mL, as it is inadequate 12