SFTPD and Interstitial pneumonitis: Yamashita et al. [16] reported that the incidence of severe RP (Grade 4 or higher) was significantly correlated with a shadow of interstitial pneumonitis on pretreatment CT, which they defined as a mandatory observation beneath the pleura and honeycomb lung, as well as higher pretreatment values of serum KL-6 (Krebs von den Lungen-6) and SP-D (surfactant protein-D), the upper limits of which were defined as 500 U/mm3 and 110 ng/mm3, respectively.