⁶⁸Ga-PSMA-11 PET/MRI in patients with newly diagnosed intermediate or high-risk prostate adenocarcinoma: PET findings correlate with outcomes after definitive treatment

Abstract

Prostate-specific membrane antigen (PSMA) PET offers superior accuracy to other imaging modalities in initial staging of prostate cancer and is more likely to affect management. We examined the prognostic value of ⁶⁸Ga-PSMA-11 uptake in primary lesion and presence of metastatic disease on PET in newly diagnosed prostate cancer patients prior to initial therapy. Methods: In a prospective study from April 2016 to December 2020, ⁶⁸Ga-PSMA-11 PET/MRI was done in men with new diagnosis of intermediate or high-grade prostate cancer who were candidates for prostatectomy. Patients were followed up after initial therapy for up to 5 years. We examined the Kendall correlation between PET (intense uptake in primary lesion and presence of metastatic disease) and clinical and pathologic findings (grade group, extraprostatic extension, nodal involvement) relevant for risk stratification, and examined the relationship between PET findings and outcome using Kaplan–Meier analysis. Results: Seventy-three men, 64.0±6.3 years of age were imaged. Seventy-two had focal uptake in prostate and in 20 (27%), PSMA-avid metastatic disease was identified. Uptake correlated with grade group and prostate-specific antigen (PSA). Presence of PSMA metastasis correlated with grade group and pathologic nodal stage. PSMA PET had higher per-patients positivity than nodal dissection in patients with only 5-15 nodes removed (8/41 vs. 3/41) but lower positivity if more than 15 nodes were removed (13/21 vs. 10/21). High uptake in primary (SUV_max>12.5, P = .008) and presence of PSMA metastasis (P = .013) were associated with biochemical failure, and corresponding hazard ratios for recurrence within 2-years (4.93 and 3.95, respectively) were similar or higher than other clinicopathologic prognostic factors. Conclusions: ⁶⁸Ga-PSMA-11 PET can risk stratify patients with intermediate or high-grade prostate cancer prior to prostatectomy based on degree of uptake in prostate and presence of metastatic disease.