INTRODUCTION
The aim of the study was to compare 11C-Choline and 68Ga-PSMA in men undergoing SLND for nodal recurrent PCa.
MATERIALS AND METHODS
The study included 641 patients who experienced PSA rise and nodal recurrence after radical prostatectomy and underwent SLND. Lymph node recurrence was documented by PET/CT scan using either 11C-Choline (n=407; 63%) or 68Ga-PSMA ligand (n=234; 37%). The outcome was underestimation of tumour burden (difference between number of positive nodes on final pathology and number of positive spots at PET/CT). Multivariable analysis tested the association between PET/CT tracer (11C-Choline vs. 68Ga-PSMA) and underestimation of tumour burden.
RESULTS
Overall, the extent of underestimation of tumour burden was significantly higher in the 11C-Choline group compared to the 68Ga-PSMA (p<0.0001). This was confirmed on multivariable analysis (p=0.028). Repeating these analyses according to PSA, the underestimation of tumour burden was lower with 68Ga-PSMA only when the PSA was ≤1.5 ng/ml. Conversely, the underestimation of the two tracers became similar when PSA was >1.5 ng/ml. Furthermore, we evaluated the risk of underestimation by number of positive spots on PET/CT scan. The higher the number of positive spots the higher the underestimation of tumour burden regardless of the tracer used (p=0.2).
CONCLUSIONS
PET/CT scan significantly underestimates the burden of PCa recurrence, regardless of the tracer used. 68Ga-PSMA was associated with a lower rate of underestimation in patients with a PSA below 1.5 ng/ml and a limited nodal tumour load. In all other men, there was no benefit from 68Ga-PSMA over 11C-Choline in assessing the extent of nodal recurrence.