Prospective validation of Ga 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 Ga prostate specific membrane antigen positron emission tomography/computerized tomography for detecting lymph node metastasis in patients with intermediate-high risk prostate cancer.

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 Ga 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.

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%).

In patients with newly diagnosed prostate cancer at greater than 10% MSKCC risk for lymph node involvement Ga 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.