the most essential genes acting upstream of NHEJ (Deschavanne & Fertil,1996). As a result, only little is known about the chromatin scaffoldof the syndromes of real clinical interest whose total incidence mayreach 5–15% individuals. The most common radiotherapy-inducedreactions are not necessarily associated with massive defect inDSB repair but with mild deficiencies ranging about 1–10% ofunrepaired DSB after 2 Gy gamma-rays (Foray et al., 2012). Theseremarks suggest therefore that efforts of chromatin and repairresearch should focus on syndromes of clinical interest despite theirlack of spectacular radiosensitivity. Lastly, a complete radiotherapytreatment is generally made of successive sessions of radiotherapy(e.g. 2 Gy every open day with about 40 Gy for breast cancer and70 Gy for prostate cancer treatment). The questions raised by thedynamics of the chromatin organization during the repetition ofdoses should also be the subject of interesting research.