TGFB1 and Atrophy: Atrophy is also associated with an early acute radiation response, but as atrophy is not associated with any of the QTG analysed, including XRCC1 (R399Q) or TGFβ1 (C-509T), the identity of the variant gene(s) that predispose patients to atrophy as a distinct radiation injury phenotype is unknown.