H2AX and Familial prostate cancer: Recently, we found that a less efficient repair of DNA double-strand breaks (DSBs) in ex vivo irradiated lymphocytes, as quantified by the γ-H2AX foci decay ratio (FDR), is an independent risk factor for the development of CTCAE grade ≥ 2 late toxicity in prostate cancer patients treated with EBRT [10].