Novel Technique May Improve Detection of Aggressive Prostate Cancer

Small study demonstrates the promise of PET-CT using a radiotracer that targets the prostate-specific membrane antigen.

PET imaging with a PSMA-targeting agent showed an ability to detect larger and higher-grade tumors.
PET imaging with a PSMA-targeting agent showed an ability to detect larger and higher-grade tumors.

A molecular imaging biomarker detects fast-growing prostate cancer (PCa) on positron-emission tomography-computed tomography (PET-CT) and differentiates it from benign lesions, a small study finds.

The study employed the radiotracer 18F-DCFBC targeting the prostate-specific membrane antigen (PSMA), which is associated with PCa aggressiveness. If PSMA-based radiotracers continue to prove reliable, combining PET-CT results with magnetic resonance imaging (MRI) can improve PCa detection.

“The most important application would be the potential to combine the PSMA-based PET molecular imaging information with the anatomic definition of MRI for improved tumor detection of patients with newly diagnosed prostate cancer,” lead investigator Steve Y. Cho, MD, of Johns Hopkins Medical Institutions in Baltimore, told Renal & Urology News. “The additional information from PSMA-based PET with MRI will allow confident selection of the most clinically significant prostate lesions for targeted biopsy guidance for a correct diagnosis compared with the current standard, transrectal ultrasound-guided biopsy.”

Additionally, the imaging tools may be especially helpful for evaluating patients on active surveillance or with suspected cancer but non-confirmatory biopsy results, he said.

The investigators evaluated the ability of PSMA-based PET-CT to characterize PCa in 13 patients by comparing results with MRI and prostatectomy pathology. They examined 12 segments of the prostate and the dominant lesion.

PSMA-based PET-CT detected high-grade (Gleason 8 and 9) and larger-sized (greater than 1.1 mLl) prostate tumors, according to results published online in The Journal of Nuclear Medicine. It was more limited in detecting smaller and lower grade tumors. MRI showed more overall sensitivity (MRI 0.39 and 0.92 vs. PET 0.17 and 0.46, per segment and dominant lesion, respectively), whereas PSMA-based PET-CT showed greater specificity for detecting PCa (PET, 0.96 vs. MRI, 0.89).

Importantly, the radiotracer had low uptake in areas of benign prostatic hyperplasia, showing an ability to differentiate PCa from benign lesions.

The overall detection rate was lower than with multiparametric MRI, the researchers noted. They suggested, however, that newer second generation PSMA-targeting agents display better signaling and hold promise for detecting lower grade and smaller tumors.

Source

  1. Rowe, SP; Gage, KL; Faraj, SF; et al. The Journal of Nuclear Medicine; doi: 10.2967/jnumed.115.154336.
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