Radiotherapy for thoracic tumors: association between subclinical interstitial lung disease and fatal radiation pneumonitis

Background We evaluated the association between subclinical interstitial lung disease (ILD) and fatal radiation pneumonitis (RP) in patients with thoracic tumors treated with thoracic radiotherapy (RT). Methods Sixty-two consecutive patients with thoracic tumors treated with thoracic RT were retrospectively analyzed. According to our protocols, patients with subclinical ILD (untreated and asymptomatic) were considered to be indicated for thoracic RT, while patients with clinical ILD (post-or during treatment) were not considered candidates for thoracic RT. The presence, extent and distribution of subclinical ILD on CT findings at pre-thoracic RT were reviewed and scored by two chest radiologists. The relationships between RP and clinical factors, including subclinical ILD, were investigated. Results Subclinical ILD was recognized in 11 (18 %) of the 62 patients. Grade 2-5 RP was recognized in eight (13 %) of the 62 patients, with Grade 5 in three patients and Grade 2 in five patients. Grade 2-5 RP was observed in four (36 %) of the 11 patients with subclinical ILD. Subclinical ILD was found to be a significant factor influencing the development of Grade 2-5 RP (p = 0.0274). Subclinical ILD tended to be significant for the occurrence of Grade 5 RP (p = 0.0785). Regarding the CT score, more extensive ILD (bilateral fibrosis in multiple lobes) was recognized in two of the three patients with Grade 5 RP. Conclusions In this study, fatal RP tended to be more common in the patients with subclinical ILD. In particular, the presence of extensive fibrosis on CT may be a contraindication for thoracic RT.