AUA 2019: The Role of 68Ga-PSMA PET-CT in Initial Staging of Treatment-Naïve High-Risk Prostate Cancer

Chicago, Illinois (UroToday.com) In patients diagnosed with high-risk prostate cancer, staging is typically performed prior to local therapy to rule out distant spread. Conventional prostate cancer staging, involving computed tomography of the chest, abdomen and pelvis and bone scan, is relatively insensitive in the detection of low volume nodal or bony metastases. 68Ga-PSMA PET/CT has gained an increasingly large role in the evaluation of patients with biochemical recurrence following initial localized prostate cancer treatment.  Dr. Pooli examined the utility of 68Ga-PSMA PET/CT as an initial staging modality among previously untreated patients with high-risk prostate cancer, compared to conventional imaging approaches.

The authors examined their prospective institutional dataset of patients undergoing PSMA PET/CT. They identified 112 patients in this dataset with high-risk prostate cancer. Among these, 29 patients lacked conventional imaging for comparison and 11 patients had previously undergone treatment. Thus, the cohort comprised 72 patients with treatment-naïve high-risk prostate cancer who had undergone both 68Ga-PSMA PET/CT and conventional staging investigations. The authors compared the performance of PSMA PET/CT and conventional imaging for the identification of pelvic lymphadenopathy, extra-pelvic lymphadenopathy, bone metastasis, and visceral metastasis.

The 72 included patients had a mean age of 65 years (range 44 to 82 years). Median PSA was 42 ng/mL (range 2.4 to 155 ng/mL) and the majority had GGG ≥2. PSMA results were discordant with conventional imaging in 15 of 72 patients (21%). Among these 15 patients, PSMA detected twelve new findings among nine patients who had apparently normal conventional imaging studies. In these patients, PSMA identified 8 positive pelvic lymph nodes, two positive extra-pelvic lymph nodes, and two bony metastases. Additionally, the authors report that PSMA ruled out suspected bony metastasis in 6 patients.

These results serve to highlight both the lack of sensitivity but also the lack of specificity of conventional staging imaging in prostate cancer. The authors, therefore, advocate that PSMA PET/CT may have utility in the initial staging of patients with high-risk prostate cancer. PSMA PET/CT may serve to both augment equivocal findings on conventional imaging or identify lesions missed on conventional imaging. Further work, with pathologic correlation, is necessary to better understand the positive and negative predictive abilities of PSMA PET/CT.

Presented by: Aydin Pooli, MD, Urologic Oncology Fellow/Clinical Instructor, Department of Urology, David Geffen School of Medicine at UCLA, Los Angeles, California 

Written by: Christopher J.D. Wallis, Urology Resident, University of Toronto, @WallisCJD at American Urological Association's 2019 Annual Meeting (AUA 2019), May 3 – 6, 2019 in Chicago, Illinois
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