PSMA vs. FDHT PET/CT for restaging recurrent prostate cancer

Rationale: Recurrent prostate cancer occurs often and is preceded by a rise in PSA (prostate specific antigen). If the rise is more than 2 ng/mL above nadir, this is defined as a biochemical Recurrence (BCR). BCR precedes clinical evident recurrence by years. Restaging with imaging methods is necessary to determine the localisation of recurrence and the adequate treatment. Current restaging is performed with 11 C-choline PET/CT, but has a moderate sensitivity rate and is least accurate in low PSA ranges, while that is exactly the range in which salvage treatment was shown to be most effective. Studies on PSMA PET/CT the past few years are promising but often of retrospective nature and with heterogeneous patient populations. In our academic centre there are currently two trials running with 18 F-FDHT PET/CT. Results are promising, but more research is needed to determine exact value of both PET/CT scans.



Objective: to compare the value (i.e. detection rate) of 68 Ga-PMSA PET/CT with 18 F-FDHT PET/CT and evaluate the accuracy of both tracers.


Study design: A pilot prospective comparative imaging study. Only one point of measurement, where three scans will take place.


Study population: 20 men with biochemical recurrent prostate cancer after radiotherapy who are candidates for local salvage treatment.



Main study parameters/endpoints:

Primary:

- visual assessment of number of lesions en conclusion of re-staging (localized disease, systemic disease or a combination of the two) according to 68 Ga-PMSA PET/CT and 18 F-FDHT PET/CT on patient-by-patient basis.

- Semi-quantitative lesion by lesion comparison of tracers by measuring and evaluating the maximum and mean standardized uptake value (SUVmax , SUVmean)

Secondary:

Lesion-based analysis by comparing the detected lesions in different sites of recurrence/metastases with lesions detected by mMRI and information from follow-up (PSA response to salvage therapy, confirmative biopsy or lymph node dissection and other imaging studies (X-ray, bone scans)). To assess overall accuracy, sensitivity, specificity, PPV and NPV per imaging modality

Studies on PSMA PET/CT the past few years are promising but often of retrospective nature and with heterogeneous patient populations. In our academic centre there are currently two trials running with 18 F-FDHT PET/CT. Results are promising, but more research is needed to determine exact value of both PET/CT scans.

1 timepoint, with 2 scans close to each other

68Ga-PSMA PET/CT and a 18F-FDHT PET/CT