Concept proposal for a six-tier integrated dual tracer PET-CT (68Ga-PSMA and FDG) image scoring system ('Pro-PET' score) and examining its potential implications in metastatic castration-resistant prostate carcinoma theranostics and prognosis.

OBJECTIVES

To develop and examine a scoring system in metastatic castration-resistant prostate carcinoma (mCRPC) that integrates findings of both 68Ga-prostate-specific membrane antigen (PSMA) and flurodeoxyglucose (FDG) PET-CT imaging in a single combined parameter and referred to as the 'Pro-PET' score.

METHODS

A six-tier integrated dual tracer PET-CT (68Ga-PSMA and FDG) Image Scoring System ('Pro-PET' score) was conceptualized, based on the findings of both 68Ga-PSMA-11 and FDG PET-CT in patients of mCRPC. This proposed integrated scoring was examined in a retrospective analytical study assessing mCRPC patients (n = 47) referred for 177Lu-PSMA-617 peptide receptor radioligand therapy (PRLT) and had both FDG and 68Ga-PSMA PET-CT undertaken within 15 days of each other without any interim treatment intervention. The 'Pro-PET' score grades and subgrades were assigned and compared with clinical data, such as histopathology, Gleason score, serum prostate-specific antigen (PSA), treatment response (symptomatic, biochemical, metabolic and anatomical) and survival [overall survival (OS) and progression-free survival (PFS)].

RESULTS

The Pro-PET score significantly correlated with symptomatic (P = 0.05), biochemical (P = 0.05), metabolic (P = 0.001) and anatomical (P = 0.012) responses, PFS (P = 0.03) and OS (P = 0.027). On multivariate analysis, histopathology, Gleason score and PSA as individual parameters were not significantly associated with OS and PFS, whereas the Pro-PET score was found to have a significant association (P = 0.001 for PFS and 0.011 for OS).

CONCLUSION

The 'Pro-PET' scoring system integrating dual tracer PET-CT imaging findings in a single parameter appeared as a potentially promising prognostic marker that has the potential to enhance the objectivity and scientific basis of prostate carcinoma theranostics and prognostication.