LAUSR

e587Background: SABR is increasingly used for the treatment of men with oligometastatic prostate cancer, including patients (pts) presenting with oligoprogression. The latter is a clinical situation where a limited number of metastatic tumor sites progress (usually defined as ≤ 3-5), while all other metastases are controlled by a given systemic therapy. The frequency of oligoprogression potentially amenable to SABR is unknown. Methods: Thus, in a retrospective chart analysis we studied the progression pattern of 35 men with chemotherapy-naive mCRPC undergoing AA therapy, and of 20 men undergoing AA therapy after docetaxel chemotherapy. Applying RECIST1.1 and/or PCWG2 criteria, pts were considered SABR candidates if they radiologically progressed in ≤ 5 distinct metastatic locations, while all other metastases were stable or responding. Results: In chemotherapy-naive men, pre-AA metastatic lesions were located in bone (94%), lymph nodes (49%), lungs (17%) and liver (3%), whereas progression during AA thera...