LAUSR

5013Background: The AVPC are a subset of prostate cancers that share the clinical, therapy response and molecular profiles of the small cell prostate carcinomas, a histological variant of the disease that responds poorly to androgen receptor directed therapies. The AVPC are characterized by a molecular signature of combined tumor suppressor defects (≥ 2 alterations in Tp53, RB1 and/or PTEN by immunohistochemistry or genomic analyses). We conducted a randomized phase II study of cabazitaxel (CAB) plus or minus carboplatin (CARB) in men with CRPC and asked whether the AVPC-MS predicted for platinum benefit. Methods: 160 men with metastatic CRPC were randomized 1:1 to receive IV CAB (25 mg/m2) or CAB/CARB (25 mg/m2; AUC4) Q21 days with growth factor support until disease progression, unacceptable toxicity or for up to 10 cycles. Imaging occurred every 2 cycles. The primary endpoint was progression free survival (PFS). 73 tumor samples obtained within 1 year of registration from 65 of the 160 patients (pts) w...