Re-irradiation in the thorax - An analysis of efficacy and safety based on accumulated EQD2 doses

Abstract Introduction Thoracic re-irradiation remains a challenge regarding the balance of local efficacy and acceptable toxicities. In this retrospective analysis we analyzed dosimetrical and clinical data of patients treated with thoracic re-irradiation based on accumulated EQD2Gy doses. Methods and Material We retrospectively analyzed the data of 42 consecutive single-institutional patients treated with repeated courses of thoracic radiotherapy from 12/2011 to 01/2017. Accumulated EQD2 dose distributions were calculated and dose parameters for organs at risk and target volumes were analysed. Results The median prescription dose was 42.2 Gy (10–70.6 Gy) for all RT courses. The median Dmean of both lungs was 10.1 Gy3 (range: 1.9 Gy3–17.9 Gy3) with a maximum D0.1cc of 253.86 Gy3. The median D0.1cc of the esophagus was 62.2 Gy3 with a maximum of 103.78 Gy3. The maximum D0.1cc for the bronchial tree was 187.33 Gy3 (median 74.35 Gy3) and for the Aorta 216.1 Gy3 (median 70.9 Gy3). Median OS after first re-irradiation was 19 months (range 1–45 months). 12-month local control after a course of re-irradiation was 52.6%. 80% of patients suffered from a G1–G2 toxicity, most frequently coughing. One patient suffered from a G5 complication probably unrelated to re-irradiation. Conclusion Even though several organs at risk received maximum accumulated doses of >100 Gy3, thoracic reirradiation resulted in an acceptable toxicity profile. Local tumor control and overall survival remained encouraging even after multiple courses of thoracic radiotherapy.