The value of ⁶⁸Ga-PSMA enhanced PET-CT and MR-PET in patients with biochemical recurrent prostate cancer

Aim of study

In patients with prostate cancer increased levels of PSMA can be measured. Recently a new tracer, ⁶⁸Ga-PSMA, was developed as a specific marker for hybrid imaging (PET/CT, MR-PET). In this study we evaluated the accuracy of ⁶⁸Ga-PSMA in patients with rising PSA after radical prosatectomy, so called “biochemical recurrent prostate cancer” (BRPC).

Materials and methods

A total of 322 patients with BRPC underwent either a PET-CT or a MR-PET examination (Siemens Biograph mMR) after injection of about 150 mBq⁶⁸Ga-PSMA. Images were evaluated in cosensus by one experienced nuclear medicine physician and one radiologist. Pelvine lymphnode dissection was performed in most of the patients according to a predefined template with 8 fields. Lymphnode involvement was evaluated according to a 5 point scale with a patient- and a field-based analysis. These findings were stratified according to PSA-values.

Results

Four patients were excluded from the study for different reasons. Sensitivity for detection of recurrence was 95.7 % for PSA-values ≥ 2ng/ml, 81.4 % for PSA-values of 1-2 ng/ml, 76% for PSA-values 0.5-1 ng/ml, and 51% for PSA values ≤ 0.5 ng/ml. In comparison to the MR-images alone MR-PET was of superior diagnostic value.

Conclusions

MR-PET using ⁶⁸Ga-PSMA is a sensitive and highly accurate technique for the diagnosis of biochemical reccurence of prostate cancer after radical prostatectomy. It yields high diagnostic performance at relatively low PCA-values.