PCa agent detects 97% of lesions when paired with PET

The investigational modality was compared with surgical pathology in men undergoing radical prostatectomy.

In a small study of men with prostate cancer, researchers found a novel agent combined with positron emission tomography (PET) imaging detected 97% of cancerous lesions.

The new modality holds promise but will require validation in a larger cohort of patients in one or more separate institutions, one thought leader told Urology Times.

The modality, known as 64Cu-TP3805 PET imaging, consists of TP3805, which latches on to VPAC1 receptors, and Cu-64 (a radiation-emitting copper peptide), that is hooked onto TP3805, according to a press release about the study.

“VPAC1 is known to be upregulated in a variety of malignancies, including prostate cancer. The estimates are that there are about 1,000 times more VPAC receptors on prostate cancer than benign prostates,” said study author Edouard J. Trabulsi, MD, of the Prostate Diagnostic Center at the Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia.

The study’s senior investigator, Mathew Thakur, PhD, of Thomas Jefferson’s Sidney Kimmel Medical College, came up with a proprietary peptide analog that binds the VPAC receptor by coupling a radioisotope copper-64 (64Cu) and a fluorophore for fluorescent spectroscopy, TP3805. NuView Life Sciences, which co-funded the study with the National Institutes of Health, is the exclusive licensee for the technology. Dr. Thakur is a consultant to NuView Life Sciences.

The technology is being commercialized for use in breast cancer. In a study of 19 women with breast cancer, researchers reported that 64Cu-TP3805 is worthy of further investigation in patients requiring biopsy of suggestive imaging findings, to further evaluate its ability to distinguish malignant lesions from benign masses noninvasively.

The current study, the first such study on prostate cancer patients, included 25 men undergoing radical prostatectomy. The findings were published online in Urology (Oct. 28, 2015).

“Pre-op, we did a VPAC1 targeted 64Cu-TP3805 PET scan-it’s a PET/CT fusion scan. Then, we compared the images from the PET scan and their surgical pathology. We also did staining of the prostate pathology slides with VPAC, using both autoradiography and digital fluorescence with the fluorescent antibody. We compared the pathology slides and the VPAC,” Dr. Trabulsi said. “We found the correlation of the areas of the prostate that had prostate cancer was strikingly high-97%.”

Next: Test identified 105 of 107 cancerous lesions found in pathologic exams

The new test identified 105 of 107 cancerous lesions found in pathologic exams of the removed glands, as well as nine lesions that the pathologic exam did not find. Positive and negative lymph nodes were also correctly identified, as were cases of BPH and cysts, according to the press release.

Also see: Number of pre-op prostate biopsies not linked to outcomes

Dr. Trabulsi said he and colleagues at Jefferson are optimistic the approach will play important roles in several areas of the prostate cancer spectrum. They are contemplating a clinical trial to use it for clinical staging and one to study response to treatment in men who have had radiation for prostate cancer and a rising PSA.

“Lastly, [it could be used] for prostate cancer detection for men that have had prostate biopsies but the PSA is going up, to try to better target biopsies or, potentially, for men that have what we think is very low-risk, low-volume prostate cancer that are on active surveillance to get a better handle on whether they might have more aggressive disease,” he said.

The authors are already conducting a second protocol of men who have not been diagnosed with prostate cancer but are getting prostate biopsies and comparing VPAC PET imaging with MRI and biopsy to determine how accurate VPAC is at picking out areas that have prostate cancer.

The technology appears safe, according to Dr. Trabulsi. It doesn’t include any nephrotoxic contrast or dye, but there is radiation, just like with any PET scan, he said.

Computed tomography/PET imaging technology has changed tremendously in the recent past, and this new technology holds promise for identifying recurrent lesions after definitive treatment, said Urology Times Editorial Consultant J. Brantley Thrasher, MD, of the University of Kansas Medical Center, Kansas City.

“It could also help identify lesions at initial diagnosis, as these authors have shown,” Dr. Thrasher said. “However, I think a study like this one will need to be validated with a larger cohort of patients in an institution/institutions other than Jefferson.”