Re-defining 18 F-DCFPyl prostate-specific membrane antigen positron emission tomography detected local recurrence from radical prostatectomy histopathology

To assess topographic concordance between the histopathological features of patients' radical prostatectomy (RP) specimens and the location of the prostate-specific membrane antigen positron emission tomography (PSMA PET) local recurrences, qualitatively and quantitatively. Our cohort was selected from the 100 men who received a F-DCFPyL PET scan in the IMPPORT trial (Australian New Zealand Clinical Trials Registry Number: ACTRN12618001530213), a prospective non-randomised study completed by GenesisCare Victoria. Eligibility included patients with a rising prostate-specific antigen (PSA) level (>0.2 ng/mL) after RP and PSMA PET detected local recurrence. Histopathological parameters collated included the location of tumour, extraprostatic extension (EPE), and positive margins. Criteria for the location and 'concordance' between histopathological features and local recurrences were pre-defined. A total of 24 patients were eligible; the median age was 71 years, the median PSA level was 0.37 ng/mL, and the time between RP and PSMA PET was 2.6 years. In all, 15 patients had recurrences within the vesicourethral anastomotic region and nine within the lateral surgical margins. There was 100% concordance in the left-right plane between tumour location and local recurrence, with 79% of these lesions concordant three-dimensionally; across craniocaudal, left-right, and anterior-posterior planes. In all, 10 of the 16 (63%) patients with EPE and five of the nine 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 craniocaudal 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.