Detection and localization of carcinoma within the prostate using high resolution transrectal gamma imaging (TRGI) of monoclonal antibody directed at prostate specific membrane antigen (PSMA)—Proof of concept and initial imaging results

Purpose

Molecular imaging methods may identify primary prostate cancer foci and potentially guide biopsy and optimal management approaches. In this exploratory study, safety and first human imaging experience of a novel solid state endocavity transrectal gamma-imaging (TRGI) device was evaluated.

Methods

Twelve patients received 5 ± 0.5 mCi In-111 capromab pendetide (ProstaScint^®) intravenously and the prostate of each was imaged 4 days later transrectally using an endoluminal cadmium zinc telluride (CZT)-based compact gamma camera (ProxiScan™, Hybridyne Imaging Technologies, Inc.). Immediate and 5–7-day post imaging safety assessments were performed. In those patients with a prostate cancer diagnosis (N = 10), single photon emission computed tomography (SPECT-CT) and magnetic resonance imaging (MRI) of the pelvis were also acquired. Images were reviewed and sites of suspected cancer were localized by prostate quadrant by consensus of two nuclear medicine physicians. Pathology from TRUS biopsy, or surgical pathology following prostatectomy (N = 3) when available, served as the gold standard.

Results

There were no serious adverse events associated with TRGI. No focal signal was detected in patients without a diagnosis of prostate cancer (N = 2). Of 40 quadrants evaluated in the cancer cohort (N = 10), 22 contained malignancy. In 8 of these 10 patients, the most focal site of uptake on TRGI corresponded to a prostatic quadrant with biopsy-proven malignancy. In 6 cancer-containing quadrants, TRGI was positive where SPECT-CT was negative; MRI showed a detectable abnormality in only 1 of these 6 quadrants. Qualitative image review of the planar TRGI images for prostate cancer localization was severely limited in some cases by scatter artifact within the vicinity of the prostate gland arising from physiologic urine and blood pool activity from nearby structures.

Conclusions

TRGI is a safe imaging method that can potentially detect radiopharmaceutical uptake of primary prostate cancer and facilitate prostatic quadrant – localization of cancer. Further investigation of this technology is warranted.