With surgical removal at the front line of defense against prostate cancer, oncologists are considering prostate-specific molecular imaging at the point of initial biopsy and preoperative planning to root out the full extent of disease, researchers showed at the 2016 Annual Meeting of the Society of Nuclear Medicine and Molecular Imaging (SNMMI).¹

Positron-emission tomography (PET) and computed tomography (CT) are often used in conjunction to image both the physiologic function and structure of recurrent prostate cancer. In recent years, scientists have been developing a PET imaging agent that targets a protein called prostate-specific membrane antigen (PSMA). This protein is overexpressed on the surface of prostate cancer cells and can be detected even after the disease has become metastatic.

The results of our study indicate that Ga-68 PSMA PET/CT accurately identifies affected regions of the prostate and might [be] a promising tool for noninvasive tumor characterization and biopsy guidance.

— Wolfgang P. Fendler, MD

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Closer Look at PSMA

Researchers are able to detect prostate cancer by combining a small amount of radioactive gallium-68 and the molecular compound PSMA-HBED-CC (collectively known as Ga-68 PSMA), which is then injected into patients prior to PET/CT scanning. Once administered, the agent binds to cells expressing PSMA and emits a signal detected by the scanner.

Scan images of the tumor data show active tumors clearly where they are most virulent. Although PSMA PET/CT is not yet the standard of image guidance for biopsies and surgical resection, the findings of this study show that this molecular imaging technique stands to improve tumor staging from the start.

“PSMA shows significant overexpression on prostatic cancer cells, and Ga-68 PSMA PET/CT demonstrates a high rate of detection in patients with recurrent, metastatic prostate cancer. However, much less research has been conducted for the accuracy of PSMA imaging at the start of the disease,” said Wolfgang P. Fendler, MD, of the Department of Nuclear Medicine at Ludwig Maximilian University of Munich. “The results of our study indicate that Ga-68 PSMA PET/CT accurately identifies affected regions of the prostate and might [be] a promising tool for noninvasive tumor characterization and biopsy guidance.”

Study Findings

Researchers evaluated patients with histopathology and maximum standard uptake values using Ga-68 PSMA PET/CT to determine the boundaries of prostate tumor burden in the days prior to surgical resection. Results showed that the 67% of segmented tissues that tested positive for cancer via histologic evaluation were positively identified by PET/CT via Ga-68 PSMA tumor uptake.

With further investigation and regulatory approval of this imaging technique, oncologists may use prostate-specific molecular imaging in the future to aid needle biopsy and primary staging for better care of patients with prostate cancer. ■

Disclosure: Dr. Fendler reported no potential conflicts of interest.

Reference

1. Fendler WP, Schmidt DF, Wenter V, et al: 68Ga-PSMA-HBED-CC PET/CT detects location and extent of primary prostate cancer. 2016 Society of Nuclear Medicine and Molecular Imaging Annual Meeting. Abstract 608.