Association of Computed Tomography-detected Pulmonary Interstitial Changes with Severe Radiation Pneumonitis for Patients Treated with Thoracic Radiotherapy

We evaluated associations of interstitial changes with radiation pneumonitis (RP) for patients treated with thoracic radiotherapy. Between 2005 and 2009, patients who received thoracic radiotherapy of 40 Gy or more for lung cancer or thymic tumors and were followed-up for more than 6 months were eligible for this study. Possible risk factors for RP included the presence of interstitial changes on computed tomography before radiotherapy, and elevated C-reactive protein (CRP) and lactate dehydrogenase (LDH) levels; these were compared with the incidences of severe RP. A total of 106 patients were included. The incidences of RP were 4 (4%), 0 (0%), and 5 (5%) for grades 3, 4, and 5, respectively. For those with interstitial changes, the incidence of RP >= grade 3 was significantly increased from 3% (2/79) to 26% (7/27) (p<0.001). CRP and LDH levels were also associated with increased RP, as were pulmonary emphysema and performance status >= 2. Among 91 patients with RP >= grade 1, RP grade >= 3 occurred significantly earlier than grades 1 and 2. In conclusion, pulmonary interstitial changes, LDH and CRP levels, pulmonary emphysema, and performance status >= 2 were significantly associated with RP >= grade 3. RP grade >= 3 occurred significantly earlier than grades 1 and 2. The early appearance of interstitial changes requires careful management due to the possibility of severe RP.