Fractionated dose radiolabeled antiprostate specific membrane antigen (PSMA) radioimmunotherapy (177Lu-J591) with or without docetaxel for metastatic castration-resistant prostate cancer (mCRPC).

194 Background: A phase II trial single-dose 177Lu-J591 was published. Dose fractionation offers theoretic advantages and 2 phase I dose-escalation studies of 177Lu-J591 have been performed to test the hypothesis that higher cumulative radiation doses can be administered with an acceptable toxicity profile. Methods: Pts with mCRPC and normal neutrophil and platelet counts were enrolled in 2 sequential phase I dose-escalation studies: (1) 177Lu-J591 administered as a single-agent 2 doses 2-weeks apart to determine the maximum tolerated dose (MTD) with expansion cohorts at the recommend phase II doses (RP2D) and (2) fractionated dose 177Lu-J591 in combination with docetaxel 75 mg/m2q3 weeks to determine the MTD. Results: 44 men with median age 75.4 (range 55.1-95.2) were enrolled in the single-agent fractionated dose escalation 177Lu-J591 trial and 15 men with median age 69.1 (49.3-80.8) were enrolled in 177Lu-J591 + docetaxel trial. The RP2D’s of fractionated 177Lu-J591 were 40 mCi/m2 x2 or 45 mCi/m2 x2 wi...