predictive factors of radiation-induced lung toxicity in lung cancer patients: a retrospective study

background: radiation-induced lung toxicity is an important dose-limiting toxicity in lung cancer radiotherapy, for which there are no generally accepted predictive factors. this study seeks to identify risk factors associated with the development of severe radiation-induced lung toxicity using clinical and dosimetric parameters. methods: we reviewed the medical records of 54 patients with histologically proven stage iii non-small cell lung cancer treated with three dimensional-conformal radiotherapy at alexandria main university hospital between january 2008 and december 2011. the original treatment plans for those patients were restored and imported to a treatment planning system. lung dose–volume histograms and various dosimetric parameters were calculated. univariate and multivariate logistic regression analyses were performed. results: the following grades of radiation-induced lung toxicity were observed in patients - grade 0: 17 (31.5%), grade 1: 5 (9.3%), grade 2: 13 (24.1%), grade 3: 15 (27.8%), and grade 5: 4 (7.4%). a total of 19 (35.2%) patients developed grade ≥3 and were considered to have an event. univariate analysis showed that age, presence of chronic obstructive pulmonary disease and location of the primary tumor had significant associations with severe radiation-induced lung toxicity. other dosimetric variables such as tumor side, histology, forced expiratory volume in 1 s, smoking, and gender showed no significant correlations with severe radiation-induced lung toxicity. multivariate analysis showed that the presence of chronic obstructive pulmonary disease (p=0.001) and location of the primary tumor (p=0.010) were the only predictive factors for severe radiation-induced lung toxicity. conclusion: this study demonstrates that patients with chronic obstructive pulmonary disease and lower lung lobe tumors have a high risk of severe radiation- induced lung toxicity when treated with combined chemoradiotherapy. these easily obtained clinical factors should be considered when calculating the risk for radiation- induced lung toxicity.