#1414

Diagnostic Accuracy of 68Ga-PSMA PET/CT to Identify Residual Prostate Cancer Following Focal Therapy with Irreversible Electroporation for Localised Prostate Cancer: A Prospective Study

D. Feng¹, I. Williams¹, L. Emmett², S. Agrawal¹, J. Thompson¹, P. Stricker¹

¹St. Vincent’s Private Hospital (St. Vincent’s Prostate Cancer Research Centre), Sydney, Australia
²St. Vincent’s Hospital, Sydney, Sydney, Australia

Introduction:

Currently the follow up of prostate cancer following primary focal therapy with irreversible electroporation involves serial PSA, and an MRI at 6 months, and repeat prostate biopsy at 12 months. Due to scarring post IRE, MRI can be difficult to interpret, particularly for radiologists in centres with low volumes of focal therapy. This study aims to establish the diagnostic accuracy of PSMA PET/CT in detecting residual/recurrent clinically significant PCa at 12 months post focal IRE, defined as ISUP grade group 2-5 (with >1mm of pattern 4 present).

Material and methods:

This is a prospective single site study. All male patients over the age of 18 undergoing primary focal IRE (Nanoknife®) for prostate cancer were sequentially recruited, and underwent a PSMA PET/CT 9-12 months post IRE (Nanoknife®) which will be double read by St Vincent’s Hospital Theranostic and Nuclear Medicine department in addition to current best practice; an MRI at 6-12 months post IRE procedure and a Transperineal systematic template biopsy at 12-18 months post IRE. The accuracy of the PSMA PET/CT was then calculated using the biopsy as the gold standard.

Results:

The calculated sample size was 154 patients. Due to slow recruitment and cost, an interim analysis was carried after 19 patients were recruited. At the 1 year biopsy, 7 patients had no recurrence of prostate cancer, 6 patients had clinically insignificant ISUP 1 disease, and 6 patients had clinically significant disease ISUP 2 or greater, with a calculated incidence of 31.5%. In our full series of primary IRE cases, the calculated incidence of clinically significant recurrence was 23.1%. When corrected, the sensitivity was 50% (95% CI 11.81% to 88.19%), the specificity was 38.46% (8=95% CI 13.86% to 68.42%), and the NPV was 71.92% (95% CI 47.14% to 88.03%).