Impact of $^{68}$Ga-PSMA-11 PET staging on clinical decision-making in patients with intermediate or high-risk prostate cancer

Abstract

BACKGROUND
Accurate staging is of major importance to determine the optimal treatment modality for patients with prostate cancer. Positron emission tomography (PET) with prostate-specific membrane antigen (PSMA) is a promising technique that outperformed conventional imaging in the detection of nodal and distant metastases in previous studies. However, it is still unclear whether the superior sensitivity and specificity also translate into improved patient management. The aim of this study was to assess the performance of $^{68}$Ga-PSMA-11 PET for staging of intermediate and high-risk prostate cancer and its potential impact on disease management.

METHODS
In this retrospective analysis, 116 patients who underwent $^{68}$Ga-PSMA-11 PET/CT or MRI scans for staging of their intermediate or high-risk prostate cancer between April 2016 and May 2018 were included. The potential impact of $^{68}$Ga-PSMA-11 PET staging on patient management was assessed within a simulated multidisciplinary tumour board where hypothetical treatment decisions based on clinical information and conventional imaging alone was determined. This treatment decision was compared with the treatment recommendation based on clinical information and $^{68}$Ga-PSMA-11 PET imaging.

RESULTS
The primary tumour was positive on $^{68}$Ga-PSMA-11 PET in 113 patients (97%). Nodal metastases were detected in 28 patients (24%) and bone metastases in 14 patients (12%). Compared with clinical staging and conventional imaging, $^{68}$Ga-PSMA-11 PET resulted in new information in 42 of 116 patients (36%). In 32 of 116 patients (27%), this information would most likely have changed the management into a different therapy modality (15 patients, 13%) or adjusted treatment details (e.g. modification of radiotherapy field or lymph node dissection template; 17 patients, 14%).

CONCLUSION
Information from $^{68}$Ga-PSMA-11 PET staging has the potential to change the management in more than a fourth of the patients who underwent PET staging for their intermediate to high-risk prostate cancer. Whether these more personalized $^{68}$Ga-PSMA-11 PET-based treatment decisions will improve patient outcome needs further investigation.