Clinical results of proton beam therapy for elderly patients with non-small cell lung cancer. - Ono, Takashi; Nakamura, Tatsuya; Yamaguchi, Hisashi; Azami, Yusuke; Takayama, Kanako; Suzuki, Motohisa; Wada, Hitoshi; Kikuchi, Yasuhiro; Murakami, Masao; Nemoto, Kenji (Radiation Oncology, 2018)