Detection of local recurrent disease at biochemical failure after prostatectomy by multiparametric MRI versus PSMA...

Whether the performance in detecting local recurrent lesions is similar between multiparametric MRI (mpMRI) and PSMA PET/CT at biochemical failure after radical prostatectomy is controversial and the present study was done to elucidate this point within a prospective phase II on extreme hypofractionation for prostate cancer.

Patients referred for salvage radiotherapy after surgery for pT2-3pN0-x prostate cancer at a single Institution were considered. PSA at biochemical failure had to be higher than 0.2 ng/ml but lower than 2 ng/ml. Patients underwent both mpMRI of the pelvis and PSMA PET/CT. The detection of a discrete lesion within the prostatic fossa was considered the endpoint of the present study. The proportion of patients with positive findings in the two paired groups was compared with the McNemar test, while agreement with Cohen's k test.

107 consecutive patients were accrued from September 2022 to September 2024. The mean PSA value at restaging was 0.53 ng/ml. Overall, 68 patients (63.5 %, 95 %CI: 54.1-72.1 %) were found to harbor at least one lesion in the prostatic fossa; 24 (35.3 %), 4 (5.9 %) and 40 (58.8 %) were detected only by mpMRI, only by PSMA PET/CT and by both tests, respectively. The percentage of discordant pairs was higher than expected (28/68, 41.2 %) and significantly different (p < 0.001). The Cohen's agreement between the two imaging modalities was 0.49, p < 0.001.

mpMRI and PSMA PET/CT show inadequate agreement with the former detecting a significantly higher number of local lesions than the latter with both prognostic and therapeutic implications.