Re-irradiation in the thorax – An analysis of efficacy and safety based on accumulated EQD2 doses. (November 2020) - Schröder, C.
Highlights: Cumulative dose distributions were calculated using non-rigid registration. Thoracic re-irradiation has a good local efficacy and overall survival. Treatment related toxicity was low within the reported dose range. Interval between rt-courses was predictive for overall survival. 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 D0.1 cc of 253.86 Gy3 . The median D0.1 cc of the esophagus was 62.2 Gy3 with a maximum of 103.78 Gy3 . The maximum D0.1 cc 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.