['Acute dysphagia is a distressing dose-limiting toxicity after concurrent chemoradiation or high-dose radiotherapy for lung cancer. We therefore identified factors associated with the occurrence of acute dysphagia in lung cancer patients receiving radiotherapy alone or combined with chemotherapy.', 'Radiotherapy, chemotherapy and patient characteristics were analyzed using ordinal regression analysis as possible predictors for acute dysphagia (CTCAE 3.0) in 328 lung cancer patients treated with curative intent.', 'The most significant association was seen between the maximal grade of neutropenia during chemoradiation and dysphagia, with an odds ratio increasing from 1.49 [95% confidence interval (CI) 0.63-3.54, P = 0.362] for grade 1-2 neutropenia to 19.7 (95% CI 4.66-83.52, P < 0.001) for patients with grade 4 neutropenia. Twice-daily schedule, mean esophageal dose and administration of chemotherapy were significant predictive factors. By combining these factors, a high-performance predictive model was made. On an individual patient level, 64% of patients were correctly classified and only 1.2% of patients were misclassified by more than one grade.'] Is maximal neutropenia during chemotherapy and radiotherapy significantly associated with the development of acute radiation-induced dysphagia in lung cancer patients?