Accuracy and sensitivity of 18F-PSMA PET/CT versus 11c-choline PET/CT in the evaluation of prostate cancer patients with suspected recurrence

Introduction: Prostate specific membrane antigen (PSMA) PET/CT has been more sensitive and accurate than conventional imaging. The aim of this study was to evaluate whether 18F-PSMA-1007 PET/CT was more accurate than 11c- choline PET/CT in the investigation of prostate cancer patients with suspected recurrence, who had either underwent radical prostatectomy or radical radiotherapy. In addition, the level of PSA levels by which the nodal and distal metastasis were detected by 11c-choline PET/CT versus 18F-PSMA PET/CT was evaluated.<u1:p></u1:p>

This is in accordance with the guidance produced from “Evidence-based indications for the use of PET/CT in the UK 2016”, which suggested that a PSMA tracer was superior to choline.<u1:p></u1:p>

Methods: Retrospectively 18F-PSMA PET/CT studies were reviewed from the year 2021 in patients post therapy for recurrence/metastasis. <u1:p></u1:p>

100 patients were evaluated. The results were obtained on our CRIS (radiology information system) and ICE (order communication system).<u1:p></u1:p>

The results of the 18F-PSMA PET/CT studies were correlated with any previous choline PET/CT, and this was further correlated to the levels of PSA the patients had. The results of this were collated on to a database and further analysed. <u1:p></u1:p>

The primary outcome was to evaluate the accuracy of 18F-PSMA PET/CT vs 11c-Choline PET/CT for evaluating local recurrence, soft tissue and skeletal metastasis<u1:p></u1:p>

Results: 28 patients had both 11c-choline PET/CT and18F- PSMA PET/CT. In 22/28 (78%) of patients, the 18F-PSMA PET was superior to 11c-choline PET/CT, and this included both local recurrence, soft tissue and bone metastasis.

In 12/28 (42%) patients 18F-PSMA PET/CT was superior in finding bone metastasis.

In 11/28 (39%) patients 18F-PSMA PET/CT was superior in finding soft metastasis.<u1:p></u1:p>

In 9/28 (32%) patients PSMA was superior for detecting local recurrence. Examples of local recurrence includes prostate bed and bladder base. <u1:p></u1:p>

18F-PSMA PET/CT was able to pick up metastasis in PSA levels as low as 0.3 and choline PET/CT was higher at PSA levels of 0.7<u1:p></u1:p>

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Conclusions: 18F-PSMA-1007 PET/CT is superior to 11c-choline PET/CT in evaluating soft tissue and distance metastasis.<u1:p></u1:p>

It provides superior accuracy and is able to detect metastasis at lower PSA levels. Therefore it can be utilised effectively when evaluating patients at very low PSA levels to detect recurrence/metastasis. <u1:p></u1:p>

The level of detection at low PSA levels implies a much more sensitive study. This potentially impacts on patient management as to whether they have stereotactic ablative radiotherapy (SABR) for pelvic only disease or systemic chemotherapy for extensive metastatic disease.