Prostate-specific membrane antigen positron emission tomography in the management of recurrent prostate cancer

There is an unmet clinical need for early, accurate imaging of recurrent prostate cancer to improve patient outcomes. Staging, by conventional bone scintigraphy and CT have become outdated. 68Ga-PSMA PET/CT imaging in this setting has developed rapidly, with widespread International adoption in line with evidence-based guidelines in this group of patients.

A PubMed search of English language articles was performed using following keywords: PSMA, PET/CT, biochemical recurrence, prostate cancer. The search revealed 85 articles, of which 75 were original; 70 of these involved use of the most widely available type of PSMA tracer (HBED). The review also relied on the clinical experience of reporting over 1000 PSMA PET/CT studies at a major tertiary referral centre for uro-oncology, with the majority of cases having been performed in the biochemical recurrence setting from 2015 to 2018.

68Ga-PSMA PET is a game changer and superior to choline PET and other established tracers which have been used in prostate cancer evaluation. Detection of recurrence at the prostate bed remains challenging due to bladder and urethral tracer accumulation. The main strength of PSMA PET/CT is its ability to identify small (<8 mm) pathological lymph nodes, upstaging nodal status in up to two-thirds of cases. Additionally, PSMA PET/CT, detects bone and bone marrow metastases missed by conventional bone and CT imaging. Thus, PSMA PET/CT has major impact on patient management, with studies reporting overall changes in 39-76% of cases.

Controversy exists regarding patient access and NHS affordability of PSMA PET/CT imaging. Currently, no reimbursement is available under the NHS tariff system. The cost outlay for tertiary hospital linked PET centres ranges from £150-170 K. Large referral volumes, and technical advances in manufacturing process will make this tracer cost neutral and similar to the current funded, but less sensitive, choline PET. Current NICE guidelines for prostate cancer management do not include a recommendation on when PSMA PET/CT should be used and this is likely to remain the case in the next revision, due in 2019.

Although PSMA PET/CT imaging results in significant management change, there is a need for high quality economic evaluation and cost analysis for this modality. Lack of this data will result in poor adoption of this technique and thus limit patient access. Furthermore, it is hoped that future tracers will become even more sensitive and identify disease at earlier thresholds.

Well-designed clinical trials with consideration of the health economic benefit of using PSMA PET/CT will be essential to provide a basis for entry into guidelines such as NICE and to provide a rationale for reimbursement.