Table 4 Side effects after re-irradiation and the correlation to the overlapping volume. Abbreviations: V100 – the volume at re-irradiation with a cumulative dose of ≥100 Gy (EQD2). Toxicity was graded according to Radiation Oncology Group (RTOG) and the European Organization for Research and Treatment of Cancer (EORTC) Radiation Morbidity Schema