Munich, Germany (UroToday.com) Dr. Stefano Fanti gave an overview on the role of PET/CT in prostate cancer. There are several PET/CT markers that are available including 18F-FDG, 18F-Fluoride, 11C-Choline, 18F-Choline, 18F-FDHT, 18F-FACBC, 68GA-PSMA, and 68GA-BOM. NCCN guidelines have incorporated 11C-Choline PET for diagnosis of biochemical failure after prostatectomy. Sodium Fluoride PET has alos been incorporated for diagnosis of bone metastasis. However, PET/CT is very expensive, and despite incorporation in guidelines, there is currently no systemic approval for reimbursement by insurances in the United States.
FDG PET has poor sensitivity in prostate cancer because there is limited uptake and because FDG has urinary secretion obscuring the disease within the pelvis. 18-F-Fluoride PET/CT has better sensitivity and specificity than bone scan for diagnosis of bone metastasis (100% vs 66.7% and 94.7% vs 84.2% respectively). However, while bone scan can only give information on bone disease, PET/CT gives information for both local, bone, and distant metastasis.
Of all the PET tracers, 11C-Choline PET/CT has been most widely studied in the recurrent setting of prostate cancer. Detection rates by 11C-Choline PET/CT are stronger than CT alone. However, sensitivity is dependent on PSA. Sensitivity of choline drops down with decreasing PSA to 36% in PSA< 1 ng/ml where screening is more clinically important.
Newer markers are being evaluated to see if they can overcome some of these limitations. Newer markers include hormonal receptors (18F-Dihydrotestosterone), PSMA tracers, and aminoacids (18F-FACBC). Recent studies with PSMA tracer suggest that it may have high sensitivities even at lower PSA<1ng/ml.
Dr. Fanti then highlights that the role of PET/CT may not just be in diagnosing recurrent prostate cancer but allow for therapy monitoring or planning. Patients may be monitored by PET/CT as they undergo chemotherapy. Dr. Fanti gives one case where a patient showed a significant response with docetaxel where several distant metastases disappeared with the exception of one location in the spine. Subsequently, this area was radiated and PSA decreased even further.
In summary, PET/CT is a promising modality to diagnose or stage prostate cancer in one imaging modality. It can show nodal metastasis, loco-regional metastasis, distant metastasis, and bone metastasis. However, the modality is limited by its financial expense currently. Current role for PET/CT is on a selective per-patient basis where a possibility of finding a metastatic disease may alter or change management.
Presented By: S. Fanti, Bologna (IT)
Reported By: Mohammed Haseebuddin, MD, at the 31st Annual EAU Congress - March 12 - 15, 2016 – Munich, Germany Fox Chase Cancer Center