A molecular imaging biomarker is able to detect fast-growing primary prostate cancer and distinguish it from benign prostate lesions, addressing an unmet clinical need.

The new research, published in The Journal of Nuclear Medicine (2015; doi:10.2967/jnumed.115.154336), is significant for patients with suspected prostate cancer that has not been confirmed by standard biopsy.

“We were able to demonstrate in our research that prostate-specific membrane antigen (PSMA) positron emission tomography (PET) imaging was more specific than magnetic resonance (MR) imaging for detection of clinically significant high-grade prostate cancer lesions, stated Steven P. Rowe, MD, PhD, resident at Johns Hopkins Medical Institutions in Baltimore, Maryland.

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“Importantly, PSMA PET was able to distinguish benign prostate lesions from primary prostate cancer, currently a difficult diagnostic imaging task. Additionally, this work demonstrated a direct correlation between PSMA PET radiotracer activity in prostate cancer and prostate adenocarcinoma aggressiveness (Gleason score).”

The study enrolled 13 patients with primary prostate cancer who were imaged with F-18 DCFBC PET prior to scheduled prostatectomy, with 12 of the patients also undergoing pelvic prostate MR imaging. F-18 DCFBC is a low molecular-weight radiotracer that targets PSMA.

Prostate 18F-DCFBC PET was correlated with MR imaging and histologic and immunohistochemical analysis on a prostate-segment (12 regions) and dominant-lesion basis. There were no incidental extraprostatic findings on PET suggestive of metastatic disease.

Results showed that MR imaging was more sensitive than 18F-DCFBC PET for detection of primary prostate cancer in a per-segment (sensitivities of 0.17 and 0.39 for PET and MR imaging, respectively) and per-dominant (sensitivities of 0.46 and 0.92 for PET and MR imaging, respectively) lesion analysis.

However, 18F-DCFBC PET was more specific than MR imaging by per-segment analysis (specificity of 0.96 and 0.89 for PET and MR imaging for nonstringent analysis and 1.00 versus 0.91 for stringent analysis, respectively) and highly specific for detection of high-grade lesions 1.1 milliliters or greater in size (Gleason 8 and 9).

The findings contribute to the importance of PSMA-based PET imaging for detection and characterization of the biology of the prostate cancer, stated senior corresponding author Steve Y. Cho, MD, associate professor at the University of Wisconsin School of Medicine and Public Health in Madison.

“There are a number of PSMA-based PET agents currently being introduced into prostate cancer imaging, many with improved signal to background uptake and sensitivity from this earlier first-generation PSMA 18F-DCFBC PET radiotracer, which should further improve the detection of prostate cancer,” said Cho.

“While it is difficult to predict which of the numerous prostate cancer molecular imaging agents being developed will ultimately become clinically adopted, this work, in aggregate with that of other groups, suggests there are important advantages to the PSMA ligands for prostate cancer molecular imaging.”

Aside from skin cancer, prostate cancer is the most prevalent form of cancer among men in the United States, according to 2014 statistics from the American Cancer Society. An estimated 233,000 new cases of prostate cancer and an estimated 29,480 prostate-cancer related deaths are expected this year.