Purpose
Identification of the dominant intraprostatic lesion(s) (DILs) can faciltiate diagnosis and treatment by targeting biologically significant intra-prostatic foci. [18F]DCFPyL is better than [18F]FCH in detecting and localizing DIL because of higher tumour contrast. However, the optimal imaging time for [18F]DCFPyL is in hours. The goal of this study was to investigate whether the different imaging performance of [18F]FCH and [18F]DCFPyL can be explained by their kinetic behaviour in PCa and to evaluate whether DIL can be accurately detected and localized using a short duration dynamic PET.
Methods
19 and 23 PCa patients were evaluated with dynamic [18F]DCFPyL and [18F]FCH PET, respectively. The dynamic imaging protocol with each tracer had a total imaging time of 22 min and consisted of multiple frames with acquisition times from 10–180 s. Tumour and benign tissue regions identified by sextant biopsy were compared using standardized uptake value (SUV) and tracer kinetic parameters from kinetic analysis of time-activity curves.
Results
For [18F]DCFPyL, logistic regression identified Ki and k4 as the optimal model to discriminate tumour from benign tissue (84.2% sensitivity and 94.7% specificity) while only SUV was predictive for [18F]FCH (82.6% sensitivity and 87.0% specificity) The higher k3 (binding) of [18F]FCH than [18F]DCFPyL explains why [18F]FCH SUV can differentiate tumour from benign tissue within minutes of injection. Superior [18F]DCFPyL tumour contrast was due to the higher k4/k3 (more rapid washout) in benign tissue compared to tumour tissue.
Conclusions
DIL was detected with good sensitivity and specificity using 22-min dynamic [18F]DCFPyL PET and avoids the need for delayed imaging timepoints. The dissimilar in-vivo kinetic behaviour of [18F]DCFPyL and [18F]FCH could explain their different SUV images.
Trial Registration:
ClinicalTrials.gov, NCT04009174. Registered July 5, 2019 – retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04009174?term=NCT04009174&draw=2&rank=1