Accuracy of Ga-PSMA-11 PET/CT and multiparametric MRI for the detection of local tumor and lymph node metastases in early biochemical recurrence of prostate cancer.

Anatomical and functional imaging plays a decisive role for detection and staging, of prostate cancer both primarily and post-treatment. While multiparametric MRI offers anatomic imaging with excellent soft tissue contrast, hybrid imaging based on positron emission tomography in combination with computed tomography (PET/CT) contributes functional imaging capacities. Since Ga-PSMA-11 was expected to be more efficient than the prior Choline-based PET radiotracers, it was the aim of the study to evaluate the diagnostic performance of the Ga-PSMA-11 PET/CT and multiparametric MRI in patients with recurrent prostate cancer and low PSA levels. 32 out of a cohort of 128 prostate cancer patients with biochemical relapse were referred for Ga-PSMA-11 PET/CT, MRI and bone scintigraphy. According to the histopathologically or clinically defined reference standard all results were classified as true positive, false positive, true negative or false negative. Local recurrence was present in 11/32 patients, lymph node metastases - in 13/32 patients and, bone metastases - in 6/32 patients. Against the standard of reference, sensitivity, specificity and accuracy for local recurrence of PET/CT were 63.6 %; 73.7%; 77.8%, respectively. MRI reached 90.9%; 94.7%; 92.3%, respectively. For local lymph node metastases PET/CT - 83.3%; 80.0% and 90.6%, respectively. MRI - 41.7%; 94.4%; 72.0%, respectively. For evaluation of bone metastases in PET/CT - 83.3%; 92.0%; 71.0%, respectively. Bone scintigraphy - 50.0%; 84.0%; 77.4%, respectively. In conclusion, mpMRI offered the better diagnostic accuracy in the detection of local recurrence and while PSMA PET/CT was superior in the detection of distant and lymph node metastases.