Metastatic prostate cancer to Pagetoid bone - value of (Ga68)PSMA scan
Presentation
Gleeson 4 + 4 = 8 prostate cancer on biopsy. MRI and nuclear medicine scans for staging.
Patient Data
Tc99m MDP bone scan
Whole body bone scan shows isolated diffuse increase in isotope accumulation in the left hemipelvis.
Ga68 PSMA PET/CT
PSMA scan shows abnormal isotope activity (green) in the right prostate and focally in the left ilium in the region of more diffuse MDP bone scan abnormality. No other site of accumulation ie no regional lymph nodes or other bone lesions.
CT for biopsy
Findings typical of Paget disease in the left hemipelvis include bone expansion, sclerosis and coarsening of trabecular pattern. The patient was positioned in a prone position and biopsy of the left ilium undertaken at the site of PSMA scan abnormality.
MRI for local staging
Focal reduction in T2 signal in the right mid-prostate peripheral zone with restricted diffusion confirmed on the ADC image. Note bulging of the capsule on the right but no extra-prostatic extension. These findings are at the site of abnormal PSMA accumulation and G8 malignancy on biopsy.
Case Discussion
Paget disease of bone is said to be at increased risk of metastatic malignancy. In many cases, these metastases are disguised on conventional nuclear bone scan due to the increased bone turnover associated with Paget disease. PSMA (prostate-specific membrane antigen) scanning relies not on bone turnover (osteoclasts and osteoblasts) for positivity but attaches to tumor cells thus it can be used for detection in areas of non-malignant bone turnover.
In this case and others with high Gleeson grade prostate cancer (i.e. higher risk of spread), it is important to exclude metastases prior to prostatectomy as the surgery alone will not be curative. PSMA PET/CT using the positron-emitting isotope Ga 68 is really influencing the management of patients with high Gleeson grade prostate cancer as is MRI influencing primary detection of cancer and local staging prior to surgery.
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