Prospective Validation of Gallium-68 Prostate Specific Membrane Antigen-Positron Emission Tomography/Computerized Tomography for Primary Staging of Prostate Cancer

Abstract

Purpose: Prospective validation of ⁶⁸Ga prostate specific membrane antigen positron emission tomography/computerized tomography is lacking in initial staging of prostate cancer. In this study we evaluated the diagnostic accuracy of ⁶⁸Ga prostate specific membrane antigen positron emission tomography/computerized tomography for detecting lymph node metastasis in patients with intermediate-high risk prostate cancer.

Materials and methods: Patients with newly diagnosed prostate cancer and negative bone scan findings at greater than 10% MSKCC (Memorial Sloan Kettering Cancer Center) risk for lymph node metastasis were prospectively included in study from October 2017 to October 2018. In candidates for extended pelvic lymph node dissection ⁶⁸Ga prostate specific membrane antigen positron emission tomography/computerized tomography was performed prior to planned surgery. Scan results were evaluated in a second tumor board meeting to assess a potential change of management. Sensitivity, specificity, and positive and negative predictive value for detecting lymph node metastasis were calculated per patient and per resection template using histopathology as the reference. A positron emission tomography based change of management was also reported.

Results: A total of 103 patients were eligible for analysis and 97 extended pelvic lymph node dissections were performed. In 41 patients (42.3%) there was a total of 85 lymph node metastases. Positron emission tomography was positive in 17 patients, resulting in 41.5% patient based sensitivity (95% CI 26.7-57.8) for detecting lymph node metastasis. The patient based specificity rate was 90.9% (95% CI 79.3-96.6), and positive and negative predictive values were 77.3% (95% CI 54.2-91.3) and 67.6% (95% CI 55.6-77.7), respectively. A positron emission tomography based change of treatment was observed in 13 patients (12.6%).

Conclusions: In patients with newly diagnosed prostate cancer at greater than 10% MSKCC risk for lymph node involvement ⁶⁸Ga prostate specific membrane antigen positron emission tomography/computerized tomography detected lymph node metastasis with high specificity and moderate sensitivity. This led to a treatment change in 12.6% of patients.

Keywords: lymph nodes; neoplasm metastasis; neoplasm staging; positron emission tomography computed tomography; prostatic neoplasms.