Ando et al listed risk factors for interstitial fibrosis occurring in a patient with non-small cell lung cancer (NSCLC) treated with gefitinib. These can help to identify a patient who should be monitored for this complication. The authors are from Kyoto University, Kinki University, Shizuoka Cancer Center, Osaki City General Hospital, Tokai University and the Aichi Cancer Center in Japan.