5795 - Efficacy of Enzalutamide in Hormone-sensitive Metastatic Prostate Cancer: Clinical Utility of 18F-Choline PET and Whole Body MRI.

Background

AR-inhibition with Enzalutamide may be an attractive alternative for 1L treatment of men with hormone-sensitive prostate cancer compared to androgen deprivation therapy (ADT). There is an unmet need for robust, reproducible imaging technology allowing accurate quantification and qualification of bone plus soft tissue metastases and assessment of early tumour responses to novel agents. PET/CT or WB MRI imaging offer advantage over traditional bone and CT scans.

Methods

Sixty patients with metastatic hormone-sensitive PC were included in this prospective cohort study. Patients received Enzalutamide 160 mg once daily until progression of disease. Imaging tests were performed at baseline and bone scintigraphy and CT repeated at 3 month intervals, 18F-choline PET/CT at 2 weeks, 2, 6, 9 and 12 months and WB-MRI at 6 and 12 months. Enumeration of circulating tumor cells and quality of life assessments were secondary outcomes.

Results

Sixty patients with a median age of 72 yrs (range 57 − 85) and a median PSA of 62.8 μg/L (range 3-622) were enrolled. This study is ongoing; all of the first 50 patients experienced a ≥ 50% PSA decline and 49 a ≥ 90% PSA decline. Choline-PET imaging and WB MRI were more frequently able to detect metastases and measure favorable responses than bone scan or CT thorax and abdomen. Investigator and central review of all imaging results are ongoing. Treatment was well tolerated.

Conclusions

18F-choline PET/CT and WB-MRI were superior in detection of bone and lymph node metastases and 18F-choline PET/CT was useful for early response detection already at 2 weeks. Based on results both 18F-choline-PET and WB MRI imaging have great clinical utility in aiding clinicians treating men with hormone-sensitive metastatic prostate cancer.

Clinical trial identification

NCT02815033.

Editorial acknowledgement

Legal entity responsible for the study

European Uro-Oncology Group (EUOG).

Funding

Astellas Pharma.

Disclosure

All authors have declared no conflicts of interest.