In this study, we aimed to assess the in vitro radiobiological response of prostate cancer cell models to different radiation qualities (X-rays and 223Ra) in combination with inhibitors of key proteins of the DDR system, including an ATM inhibitor (AZD0156), an ATR inhibitor (AZD6738), and a PARP inhibitor (AZD2281). This evidence concerns the gene ATM and prostate carcinoma.