In Yamashita et al.’s evaluation of SBRT in 117 ILD-LC patients, 9 cases of Grades 4–5 RP were noted and investigated; pretreatment blood KL-6 and SP-D levels, as well as the presence of an interstitial pneumonitis shadow, were found to be predictive of RP [25]. The gene discussed is SFTPD; the disease is interstitial lung disease.