Prostate cancer imaging agent detects regional/distant metastases

¹⁸F-DCFPyL PET/CT imaging demonstrated excellent performance in identifying regional or distant metastases in men with prostate cancer in the prospective OSPREY study.

In an analysis that included data for 93 men who underwent image-guided biopsy for suspected locoregional recurrence of their cancer or distant metastasis, ¹⁸F-DCFPyL positron emission tomography/computed tomography imaging had an overall sensitivity of 96% and an overall positive predictive value (PPV) of 82%. The sensitivity and PPV remained excellent regardless of the site of metastasis, and the imaging agent was safe and well-tolerated, reported Michael J. Morris, MD, at the American Society of Clinical Oncology annual meeting in Chicago.

“Current imaging methods perform poorly in accurately detecting locoregional or metastatic prostate cancer. The OSPREY study is designed to provide evidence in support of credentialing the tracer for FDA approval of ¹⁸F-DCFPyL PET/CT imaging for prostate cancer in the United States,” said Dr. Morris, OSPREY scientific committee chair and clinical director of the Genitourinary Medical Oncology Service at Memorial Sloan Kettering Cancer Center, New York.

“The results from the cohort of men with suspected recurrent or metastatic disease indicate that a positive scan is highly likely to represent pathologically proven distant disease. The findings support the potential of ¹⁸F-DCFPyL as a PET imaging agent to favorably influence treatment planning.”

¹⁸F-DCFPyL is a small molecule radiopharmaceutical PET imaging agent targeting prostate-specific membrane antigen (PSMA), a dimerized type II transmembrane glycoprotein that is mainly expressed extracellularly in primary and metastatic prostate cancer tissue. The radiopharmaceutical binds selectively to PSMA with high affinity, and it is associated with relatively low radiation exposure to all organs (<50 mGy).

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The patients included in the OSPREY arm investigating ¹⁸F-DCFPyL PET/CT imaging for detecting local recurrence or metastases had evidence of disease outside the confines of prior treated site(s) or new or progressive metastatic disease demonstrated by CT/magnetic resonance imaging, ultrasound, or whole-body bone scan. They received a single intravenous injection of ¹⁸F-DCFPyL 9±1 mCl 1 to 2 hours prior to PET/CT imaging and then underwent image-guided biopsy of at least one amenable lesion.

The ¹⁸F-DCFPyL PET/CT imaging results were evaluated independently by three blinded, central readers, and the performance of the technique was analyzed using findings from pathology review of the biopsied tissue.

The 93 men included in the performance analysis had a median PSA of 11.3 ng/mL. Approximately three-fourths of the patients had undergone prostatectomy, almost two-thirds had received radiation, and two-thirds had received systemic therapy.

The sensitivity rates of ¹⁸F-DCFPyL PET/CT imaging for bone, lymph node, and visceral/soft tissue metastases were 97%, 97%, and 100%, respectively; the PPV values for the three sites of metastases were 82%, 81%, and 90%, respectively.

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The performance of the imaging technique was also analyzed with men stratified into six groups according to PSA (<0.2, 0.2 to <1, 1 to <2, 2 to <5, 5 to ≤20, and >20 ng/mL). Results showed that the ¹⁸F-DCFPyL PET/CT scan maintained good performance in detecting disease in men with low PSA.

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OSPREY included another cohort of patients who had high-risk prostate cancer at diagnosis. Previously reported outcomes evaluating the performance of ¹⁸F-DCFPyL PET/CT imaging for detecting pelvic lymph node metastases compared to surgical pathology showed that the technique had 40% sensitivity, 98% specificity, 87% PPV, and 83% negative predictive value.

The safety review, which included data for 385 men who received ¹⁸F-DCFPyL in OSPREY showed that 27 men (7%) experienced at least one treatment-related adverse event, the most frequent of which were dysgeusia (2.1%) and headache (2.1%). There were no serious adverse events judged related to ¹⁸F-DCFPyL injection.

Dr. Morris is an uncompensated consultant for Progenics, Astellas, Bayer, and Endocyte. He has received compensation as a consultant for Advanced Accelerator Applications, Blue Earth Diagnostics, Tokai, Tolmar, and Oric. For full disclosures, see bit.ly/ospreydisclosures.