Sequence variants of several genes such as ataxia-teleangiectasia mutated (ATM), breast cancer type 1 susceptibility protein (BRCA1), H2A histone family member X (H2AFX) and mediator of DNA damage checkpoint protein 1 (MDC1) were linked to increased radiosensitivity and could distinguish prostate cancer patients with high radiation toxicity from those with low toxicity [153,154]. Here, MDC1 is linked to prostate cancer.