(UroToday.com) The TRITON2 study led to the approval of the PARP inhibitor rucaparib in patients with BRCA-mutated mCRPC that has progressed on prior androgen receptor signaling inhibition and one taxane chemotherapy. While response rates to rucaparib in different subgroups (germline vs. somatic, type of alteration) were similar, it is unknown how other co-occurring mutations, especially those that confer poor prognoses like TP53, PTEN, or RB1, impact the efficacy of rucaparib.