AUA 2022: 18F-DCFPyL PSMA PET Imaging Improves Detection of Nodal Metastases in Comparison to Conventional Imaging in Patients with Locally Advanced or Oligometastatic Prostate Cancer

(UroToday.com) In a moderated poster presentation at the 2022 American Urologic Association Annual Meeting held in New Orleans and virtually, Dr. Esdaille discussed the role of 18F-DCFPyL (DCFPyL) PSMA-based PET imaging to detect nodal disease in men with locally advanced and/or oligometastatic prostate cancer. While there is an increasingly large role for next generation imaging including PSMA-PET/CT, Dr. Esdaille highlighted that NCCN guidelines recommend conventional imaging with CT, bone scan +/- MRI to identify extraprostatic disease in patients with high risk prostate cancer.

The authors designed UW17009 as an IRB-approved open-label, single-arm trial among 30 patients with newly diagnosed advanced prostate cancer. All patients in the trial received ADT and docetaxel for three cycles (3 months) followed by radical prostatectomy (RP) and pelvic lymph node dissection (PLND). This presentation examined exploratory interventions including PSMA PET/CT and MRI imaging as a method for determining treatment response and heterogeneity in primary prostate cancer and metastatic lesions performed before and after chemohormonal therapy. In the course of the study protocol, patients received DCFPyL PET/CT and PET/MR imaging as well as conventional imaging, including CTs and Bone Scans. Patients received a mean dose of 7.86 mCi DCFPyL. Whole-body PET/CT images (General Electric [GE] Discovery 710 PET/CT) were acquired beginning approximately 60 minutes after radiotracer injection followed by dedicated pelvic PET/MR and whole-body PET/MR (GE Signa PET/MR). PET imaging findings were compared to conventional dedicated CT imaging and were correlated with final pathologic examination of each pelvic nodal dissection packet.

 

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Among 30 patients in the overall study, 26 patients underwent conventional and exploratory imaging with subsequent neoadjuvant treatment followed by RP and PLND. At the time of diagnosis, the mean PSA was 32.1 ng/dl and 88.5% of patients had Gleason 9 disease.

Using standard conventional imaging, nodal disease was identified in 6/26 patients. Pelvic lymph node uptake was identified in 12/26 patients using DCFPyL-based PSMA PET. On final pathology, 10 patients (38.4%) had pathologic evidence of nodal disease.

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Initial correlation of the pathologic specimens with pre-treatment PSMA PET imaging revealed pelvic nodal metastatic PCa in 10/12 (83%) patients who had nodal disease on pre-operative DCFPyL-based PSMA PET. On a per-lymph node packet basis (6 per patient), there were 156 evaluable regions, including 65 among those patients with positive nodes. PSMA detected 14 packets that were positive for prostate cancer and 102 packets that were negative on imaging and final pathology. Notably, pathological evidence of cancer was missed by DCFPyL-based PSMA PET in 5 packets. The mean tumor size in the missed nodes was 2.3 mm (range 1-4 mm).

In the detection of nodal disease, the calculated sensitivity of DCFPyL-based PSMA PET was 73.7% (95% CI [48.8, 90.8), 85.7 % specificity (95% CI [78.1, 91.4]), and 95.3 % negative predictive value (95% CI [90.5, 97.7]).

Thus, the authors conclude that, in this high cohort of patients treated with neoadjuvant therapy, DCFPyL PSMA-based PET imaging identified nodal positive disease at twice the rate of conventional imaging, and when evaluating on a per-packet basis, there was high negative predictive value.


Presented by: Ashanda Esdaille, MD, University of Wisconsin


Written by: Christopher J.D. Wallis, University of Toronto, Twitter: @WallisCJD during the 2022 American Urological Association (AUA) Annual Meeting, New Orleans, LA, Fri, May 13 – Mon, May 16, 2022.

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