"Radiation recall pneumonitis is a rare reaction occurring in previously irradiated areas of pulmonary tissue after the application of triggering agents (e.g. chemotherapeutic agents, immunomodulators). It is not thought to be due to the direct effect of radiation. Classically, this has been described with taxanes, anthracyclines, gemcitabine, erlotinib, nivolumab, and trastuzumab 3-5."