Chemotherapy Significantly Increases the Risk of Radiation Pneumonitis in Radiation Therapy of Advanced Lung Cancer

Introduction: The reported rate of developing radiation pneumonitis (RP) in patients receiving definitive radiation therapy (RT) for lung cancer is 5% to 36%. However, this incidence is probably underreported because of the nonspecific symptoms of RP that may be erroneously attributed to another cardiovascular or respiratory disorder. The objective of this study was to evaluate the incidence of RP in lung cancer patients receiving RT or chemoradiation therapy. Methods: Of the 110 patients that were reviewed, 86 were chosen for a retrospective analysis. A diagnosis of RP was made based on clinical assessment in the first 6 to 12 months after RT. Radiation pneumonitis was graded as per Radiation Therapy Oncology Group grading criteria. Results: The incidence of developing grade 2 or higher RP was significantly associated with addition of chemotherapy. The incidence of RP in patients receiving chemotherapy was 62.7% (42/67) versus 15.8% (3/19) in patients receiving no chemotherapy (P < 0.001). However, there was no significant effect of the type or sequence of chemotherapy on the incidence of RP. The risk of developing RP is 5 times greater in patients receiving chemotherapy when compared with those not receiving this treatment (hazard ratio: 5.0; 95% confidence interval 1.5, 16.1). In addition, patients in age group 61 to 70 years had a significantly increased risk of developing RP compared with patients of age 60 or younger (hazard ratio: 3.0; 95% confidence interval: 1.4, 6.5). Histology and radiation dose were not significant factors in development of RP. Conclusion: The incidence of RP in patients receiving external-beam RT is significantly increased with addition of chemotherapy and 61 to 70 year age group.