Utility of SUVmax on Primary Staging 68Ga-PSMA PET/CT in Determining Metastatic Status of Prostate Cancer

Abstract

Introduction

68Ga prostate-specific membrane antigen (PSMA) has been shown to have prognostic value in detecting PSMA expressing metastasis from prostate cancer, but inevitably, there are cases in which suspected metastases demonstrate equivocal uptake. This study aims to assess whether there is a direct relationship between SUVmax of the primary prostate lesion and the presence of nodal and distant metastasis.

Methods

Retrospective review of 265 primary staging 68Ga-PSMA PET/CT studies performed at a single centre on a single PET/CT was performed for the SUVmax of the primary lesion, and the presence of PSMA-avid nodal/distant metastases.

Results

Analysis shows that a single unit increase in SUVmax of the primary prostatic lesion corresponds with a 1.6% increased odds of nodal metastases, 1.7% increased odds of distant metastases and a 2% increased odds of having either. A single unit increase in the log of the SUVmax corresponds with odds ratios of 2.061, 2.038 and 2.294 respectively.

Conclusion

There is a weak but statistically significant correlation between the SUVmax of the primary prostate lesion and the presence of metastases on primary staging 68Ga-PSMA PET/CT for biopsy-proven prostate cancer. However, because the relationship is so weak and the significant overlap in SUVmax in local versus advanced disease, using SUVmax as the sole predictor of advanced disease is unreliable.