Comparison of PSMA-based 18F-DCFPyL PET/CT and pelvic multiparametric MRI for lesion detection in the pelvis in patients with prostate cancer.

Purpose: To directly compare the performance of pelvic mpMRI versus recently approved and increasingly used PSMA-based ¹⁸F-DCFPyL PET/CT in intermediate-high risk and biochemical recurrent prostate cancer patient cohort while exploring their potential differing applications in specific clinical scenarios.

Methods: A retrospective analysis was performed on patients who had ¹⁸F-DCFPyL PET/CT and pelvic mpMRI done from September 2021 to January 2022 at a single institution. The inclusion criteria were paired exams within a 3-month interval. Exclusion criteria were intervening treatment between exams, a change in PSA by more than 50% and absolute difference more than 1 ng/mL, or concurrent history of other malignancy. Abnormal lesions on these 2 imaging exams were reviewed with the identification of concordant and discordant imaging findings. The findings were verified by pathology or other imaging techniques within minimal 5-month clinical follow-up.

Results: A total of 57 patients with 57 paired exams were included. The rate of concordant exams was 43/57 or 75.4%. Lesion-based analyses of sensitivity, specificity, PPV and NPV for mpMRI and ¹⁸F-DCFPyL PET/CT in the prostate bed were 96%, 94%, 98%, 89% and 96%, 100%, 100%, 90% respectively. For pelvic lymph node metastases, the sensitivity, specificity, PPV and NPV for mpMRI and ¹⁸F-DCFPyL PET/CT were 52%, 100%, 100%, 55% and 100%, 100%, 100%, 100% respectively. For bone metastases, the sensitivity, specificity, PPV and NPV for mpMRI and ¹⁸F-DCFPyL PET/CT were 86%, 73%, 50%, 94% and 100%, 98%, 95%, 100% respectively. Exact McNemar's test for paired data suggested that in diagnostic performance between ¹⁸F-DCFPyL PET/CT and mpMRI was not statistically significant in prostate bed (p-value = 1.00), but significantly in pelvic lymph nodes (p-value < 0.0001) and bone lesions (p-value = 0.0026).

Conclusion: Our study demonstrated that PSMA-based ¹⁸F-DCFPyL PET/CT and pelvic mpMRI have a good concordance rate in the detection of primary or recurrence prostate disease and can have complementary roles in the clinical assessment of the prostate bed lesions. However, there are key differences in their performance, with the notably superior performance of PSMA-based ¹⁸F-DCFPyL PET/CT in the detection of small metastatic nodal disease and bone metastases.