The present invention provides methods of treatment of cancer patients having deficiency in at least one non-BRCA1/2 gene involved in the homologous recombination repair (HRR) pathway with a poly(ADP-ribose) polymerase (PARP) inhibitor such as niraparib. In particular, cancer patients having a deficiency in at least one gene selected from the group consisting of BRCA1, BRCA2, ATM, ATR, BAP1, BARD1, BLM, BRIP1, MRE11A, NBN, PALB2, RAD51, RAD51B, RAD51C, RAD51D, RAD52, RAD54L, XRCC2, TP53, or RB1 can benefit from treatment with niraparib.本發明提供用聚(ADP-核糖)聚合酶(PARP)抑制劑，諸如尼拉帕尼，治療在涉及同源重組修復(HRR)路徑之至少一個非BRCA1/2基因中具有缺陷的癌症患者的方法。特定言之，在選自由以下組成之群之至少一個基因中具有缺陷之癌症患者可自用尼拉帕尼之治療獲益：BRCA1、BRCA2、ATM、ATR、BAP1、BARD1、BLM、BRIP1、MRE11A、NBN、PALB2、RAD51、RAD51B、RAD51C、RAD51D、RAD52、RAD54L、XRCC2、TP53或RB1。
