Redefining 18F DCFPyl PSMA-PET detected local recurrence from radical prostatectomy histopathology.

18F-DCFPyL PET localises tumour recurrence in patients with biochemical recurrence post-radical prostatectomy. Correlations exist between disease recurrence and poor histopathological parameters such as the presence of extra prostatic extension (EPE) and positive surgical margins. We aim to assess topographic concordance between these histopathological features and the location of the PSMA PET local recurrences, qualitatively and quantitatively.

Our cohort was selected from the 100 men who received a 18F-DCFPyL PET scan through IMPPORT trial, a prospective non-randomised study completed by GenesisCare Victoria. Eligibility included patients with a rising PSA (>0.2 ng/mL) post radical prostatectomy and PSMA PET detected local recurrence. Histopathological parameters collated included the location of tumour, EPE and positive margins. Criteria for the location and 'concordance' between histopathological features and local recurrences were predefined.

24 patients were eligible, median age was 71 years old, median PSA 0.37ng/ml and time between prostatectomy and PSMA PET was 2.6 years. 15 patients had recurrences within the vesicourethral anastomotic region and 9 within the lateral surgical margins. 100% concordance in the left to right plane between tumour location and local recurrence was found, with 79% of these lesions concordant three-dimensionally; across cranio-caudal, left-right and anterior-posterior planes. 10/16 (63%) patients' with EPE and 5/9 (55.5%) of patients' with positive margins had three-dimensional concordance between their pathology and their local recurrence. In quantitative assessment, 17 of the 24 patients, had local recurrences that correlated with the location of their original tumour in the cranio-caudal plane.

Local recurrence is highly concordant with the position of the tumour within the prostate. Predicting the location of local recurrence using the location of the EPE and positive margins is less helpful. Further investigation into this field, could impact surgical technique and salvage radiotherapy clinical target volume.

BJU international. 2023 May 22 [Epub ahead of print]

Sophie Tissot, Jessica Wynn, Vy Tran, Matthew Farag, Lih-Ming Wong, Michael Ng

Urology Department, St Vincent's Hospital Melbourne, Victoria, Australia., GenesisCare St Vincent's Hospital Melbourne, Victoria, Australia.