To assess the efficacy of poly (ADP-ribose) polymerase (PARP) inhibition and the extent of DNA damage, patients will undergo serial tumor biopsies to measure DNA damage as quantified by levels of ᵞH2AX and RAD51 foci formation, as well as an assessment of PARP inhibitory activity. Tumor biopsies will also be used to assess the mechanisms of resistance to PARP inhibitor-based therapy.