ESTRO 37 Abstract book

S53

ESTRO 37

1 University Medical Center Groningen, Radiation Oncology, Groningen, The Netherlands

Purpose or Objective Several factors are known to influence survival and toxicity in patients treated with tri-modality therapy for esophageal cancer (EC). As survival improves there is a rising concern about treatment-related toxicity due to cardiac radiation dose. However, evidence remains scarce and most literature is based on retrospective patient cohorts. We evaluated the role of cardiac dose by assessing its relation with overall survival (OS) and cardiac toxicity in a prospective patient cohort. Material and Methods We selected all 137 patients treated with neo-adjuvant chemoradiation (neoCRT) included in our prospective data registration program (PDRP) for patients treated with curative intent for EC at our department until March, 2017. The prescribed dose to the PTV was 41.4 Gy delivered in 23 fractions with a hybrid IMRT or VMAT technique. Chemotherapy administered was carboplatin and paclitaxel. Treatment outcome and toxicity were scored at 3 months and yearly thereafter. The heart and its substructures (LA, RA, LV, RV) were contoured using an automatic delineation tool based on the atlas by Feng et al. The lungs were considered as one organ. To analyze the influence of radiation dose on OS and toxicity, we performed a preselection based on univariable analyses (p<0.2) and multi-collinearity (R- square <0.8) and included these variables in a multivariable Cox regression analysis. Results Of the 137 patients, 3 patients were excluded because of early withdrawal from neoCRT due to intercurrent causes. At time of analysis, 86 (64%) patients were alive and the median follow up was 12 months (range, 2 to 35 months). Cardiac toxicity was detected in 32 (24%) patients. The most frequently detected toxicity was atrial fibrillation (23 patients), for which medical intervention was indicated in 18/23 (78%) patients. Several clinical characteristics and DVH parameters were significantly associated with OS and cardiac toxicity at univariable analysis and were assessed for multi- collinearity. At multivariable Cox regression analysis (forward selection), relative weight loss, cardiac event history, PTV volume and RT technique (IMRT vs VMAT) were significant prognostic factors for OS. For cardiac toxicity, age, cardiac event history and the volume of the RV receiving 5 Gy (RV_V5) remained significant (p<0.05) in multivariable analysis. Results of multivariable analysis are summarized in table 1.

Conclusion Our data suggest that the volume of the lung receiving doses higher than 30 Gy is an important dosimetric parameter in the development of postoperative pulmonary complications in EC patients treated with preCRT followed by surgery. Moreover, the volume of the lung receiving doses from 5 to 10 Gy is predictive for postoperative cardiac complications, whereas no correlation was seen between heart dose and cardiac complications. This emphasizes that lung-heart interactions are important in dose-modelling. In that respect, further research should focus on optimizing the delivery of the radiation treatment to decrease the volume of the lung receiving both low and high radiation doses. Multivariable analysis, taking into account clinical and treatment-related factors, is currently ongoing. PV-0101 Impact of cardiac dose on survival and toxicity after neo-adjuvant treatment for esophageal cancer. E. Oldehinkel 1 , M.J. Van der Heiden 1 , J.C. Beukema 1 , M. Dieters 1 , A.C.M. Van den Bergh 1 , P. Van Luijk 1 , J.A. Langendijk 1 , C.T. Muijs 1

Conclusion This prospective cohort study demonstrated PTV volume and RT technique (in favour of IMRT) to be prognostic factors for OS. Moreover, cardiac radiation dose was a significant factor for the development of cardiac toxicity after neo-CRT and esophagectomy for EC. These results suggest that the RT dose distribution plays an important role in the outcome of EC patients. Our PDRP allows for an accurate assessment of cardiac toxicity and evaluation