Local Ablative Radiotherapy: A Means To Revert Low Volume Castration-Resistant Prostate Cancer Into A Hormone-Sensitive Status?

188Background: (Stereotactic) Ablative radiotherapy (aRT) in patients with oligometastatic prostate cancer is safe, achieves high local control rates and its clinical benefit is currently being addressed in clinical trials. However, the selection of patients benefitting most from aRT remains unclear. Moreover, the highly specific and sensitive multimodality functional imaging modality, 68Ga-PSMA-PET-CT/-MR, is widely available. Therefore, we retrospectively evaluated the efficacy of PSMA-PET guided local aRT in low volume oligometastatic castration resistant prostate cancer (CRPC) patients. Methods: Fifteen patients with metachronous oligometastatic CRPC as diagnosed on PSMA-PET were treated with local aRT. Nine patients were treated with a conventionally fractionated regime (25 x 2 Gy) and six with stereotactic hypofractionated RT (3 x 10 Gy), while in all androgen deprivation was continued. The time to PSA-progression, i.e. PSA-nadir + 2 ng/ml (PSA+2) was estimated with the Kaplan-Meier method and compa...