Evaluation of Gallium-68 PSMA PET/CT for post-prostatectomy biochemical recurrence in comparison to CT abdomen/pelvis and bone scan
We aim to evaluate the use of Gallium-68 PSMA PET/CT, compared to conventional CT abdomen/pelvis and bone scan, for detection of local or distant metastasis following biochemical failure/recurrence in post-prostatectomy patients.
We conducted a chart review of our institutional prospective database to identify patients with post-prostatectomy biochemical failure/recurrence who underwent 68Ga-PSMA PET/CT (PSMA), CT abdomen and pelvis (CTAP) and whole body SPECT bone scan (BS). The results of the 3 imaging modalities were analysed for their ability to detect local recurrence and distant metastases. Concordance was assessed and Cohen’s Kappa statistic was applied.
A total of 384 patients were identified with a median PSA of 0.465ng/ml (IQR 0.19- 2.00ng/ml). When PSMA was compared to CTAP and BS for detection of local or distant metastases there was concordance for 266 patients (119 negative and 150 positive for local or distant metastasis). PSMA and CTAP concordance was 70%. A total of 94 patients had local or distant metastasis detected on PSMA only, while 21 patients had disease detected on CTAP and BS but not on PSMA. In terms of distant recurrences, the sum of positive PSMA scan was 204 as opposed to 119 for conventional imaging. The concordance rate in this setting was 70%. PSMA scan detected 100 cases of positive finding when CTPA failed to detect any lesions. In comparison, CTAP only detected 15 cases when PSMA scan was negative. In terms of local recurrence detection, PSMA scan had more positive results for 80 patients compared to 72 patients in CTAP scan. The concordance rate was 92.1% in this setting
The use of PSMA has a higher detection rate of predicted local or distant metastasis compared to CTAP and BS in the post-operative staging of biochemical recurrences after radical prostatectomy. Further studies are needed to evaluate the true sensitivity and specificity of PSMA in identification of local and distant metastatic disease in the post-prostatectomy setting.