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 ۵۴ patients with histologically proven stage III non-small cell lung cancer treated with three dimensional-conformal radiotherapy at Alexandria Main University Hospital between January ۲۰۰۸ and December ۲۰۱۱. 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 ۰: ۱۷ (۳۱.۵%), grade ۱: ۵ (۹.۳%), grade ۲: ۱۳ (۲۴.۱%), grade ۳: ۱۵ (۲۷.۸%), and grade ۵: ۴ (۷.۴%). A total of ۱۹ (۳۵.۲%) patients developed grade ≥۳ 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 ۱ 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=۰.۰۰۱) and location of the primary tumor (P=۰.۰۱۰) 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.