Preexistence of CT findings with usual interstitial pneumonia (UIP) pattern correlates to radiation pneumonitis (RP) in non-small cell lung cancer (NSCLC) patients receiving chemoradiotherapy (CRT).

Abstract

e20063 Background: RP is a major toxicity commonly observed in NSCLC patients who receive CRT; RP prediction is a critical issue. Although preexisting interstitial pneumonia (IP) is considered as one of the risk factors of RP, the correlation between interstitial lung shadows (ILSs) in the pretreatment CT scan and RP is not well examined. Methods: We reviewed patients with stage III NSCLC who received CRT at our hospital from January 2011 until December 2014. The pretreatment CT scans were retrospectively evaluated, and preexisting ILSs were classified according to the ATS/ERS/JRS/ALAT statement for idiopathic pulmonary fibrosis (IPF) as follows: UIP pattern, possible UIP pattern, and others (not UIP pattern). The incidence, severity, and features of RP were compared between ILS patterns. Results: In total, 105 patients with stage III NSCLC had received CRT. ILSs in pretreatment CT scans were identified in 16 (15.2%) of 105 patients. Of all the identified patterns, one (0.9%) was UIP pattern, six (5.7%) were possible UIP pattern, and nine (8.6%) were not UIP pattern. Grade 3 or higher RP was observed in 2 of 7 (28.6%) patients with UIP pattern or possible UIP pattern and 1 of 9 (11.1%) patients with not UIP pattern ( P = 0.55). RP that extended outside the irradiation field like an acute exacerbation of IP was observed in 4 of 7 (57.1%) patients with UIP pattern or possible UIP pattern and 1 of 9 (11.1%) patients with not UIP pattern ( P = 0.106). Conclusions: Preexistence of ILSs classified as UIP pattern or possible UIP pattern should be considered as a risk factor for severe or extensive RP after CRT.