In the phase II TOPARP-A clinical trial, patients with metastatic 
castrate-resistant prostate cancer who were treated with the PARP inhibitor 
olaparib lived nearly three times longer without their cancer worsening if their 
tumors had mutations in at least one of 12 DNA repair genes. However, physicians 
say that a larger trial is needed to confirm olaparib's effectiveness against 
the disease before they start routinely sequencing tumors and prescribing the 
drug.