Radiation recall pneumonitis in the setting of immunotherapy and radiation: a focused review

Radiation recall pneumonitis (RRP) is an entity described as pneumonitis localized to a previously irradiated field after exposure to a systemic agent. It has previously been described in the literature in the context of chemotherapeutic agents as well as certain biologics. With immunotherapy taking a more prominent role in the treatment of several different malignancies and its own baseline risk of pneumonitis, it is important to explore the likelihood of RRP, specifically in those patients who have been previously treated with radiation therapy. The current literature regarding RRP with checkpoint inhibitors is reviewed in this article. Alongside this review, we report a case of RRP after pembrolizumab initiation in a patient in our practice. Lay abstract: When patients undergo radiation to the chest there is a risk of inflammation to the lung tissue called pneumonitis. This inflammation can also be a result of certain medications, including checkpoint inhibitors, which are used to treat cancers. There is a specific phenomenon, radiation recall pneumonitis, where patients who receive radiation to the chest followed by checkpoint inhibitors experience pneumonitis only in the lung fields that were exposed to previous radiation. This paper reviews the existing body of literature and describes a case of radiation recall pneumonitis seen in our practice.