43 Retrospective analyses on toxicity in esophageal cancer patients treated with 3D-conformal radiotherapy (3D-CRT). In 205 out of 216 patients, radiotherapy was combined with chemotherapy which mostly consisted of 5-FU infusions combined with cisplatin. In case of renal dysfunction or poor performance status a combination of 5-FU with nedaplatin (8) or docetaxel (14) was administered. Only few patients received neo-adjuvant (9) and/or adjuvant (7) chemotherapy as well. All patients were subjected to a follow up program consisting of follow up visits every 3-6 months for the first 2 years and every 6 months thereafter. Each visit included a physical test, blood test, oesophageal endoscopy and CT scan of the neck, chest and abdomen. Hospital charts of all patients were reviewed for the occurrence of complications and tumour status. Late toxicities were assessed in accordance with the Common Terminology Criteria for Adverse Events version 4.0. The dose distributions were recovered from the treatment planning system. Dosevolume parameters including doses to whole heart, substructures of the heart and lungs in 5% bins and mean doses were imported in the database. The clinical endpoints were newly diagnosed cardiac and pulmonary events and overall survival. Dose-volume histogram (DVH) parameters, treatment and patientrelated parameters as mentioned in Table 1 and 2 were included as potential risk factors. Cardiac events were analysed as a composed endpoint for all cardiac events as listed in table 3, but also separately as their aetiologies may be different. Tumourrelated parameters, like stage, N-status and elective irradiation, were not taken into account in the logistic regression analyses because of their correlation with DVH parameters. However, for OS these known prognostic factors for OS were included in the multivariable Cox regression analysis. To analyse possible associations of clinical and treatment-related factors with cardiac and lung toxicity, univariable logistic regression analysis was performed, using a cut-off level of p-value <0.2. The selected parameters were tested for multicollinearity using an R-square threshold > 0.8. Clinical factors were excluded in case of a high number of missing data and in case the number of equivalent cases in one group was smaller than 10% (Table 2). The remaining clinical and dosimetric parameters were included in a multivariable forward stepwise logistic regression analysis based on largest significant loglikelihood differences, which was performed in SPSS. Variables were added to the final model when the model significantly improved (p<0.05) based on the likelihood 4
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