Radiation Recall Pneumonitis: A Rare Syndrome That Should Be Recognized

SIMPLE SUMMARY: A combination of radiotherapy and systemic antineoplastic agents is a common treatment strategy for lung cancer. However, Radiation recall pneumonitis (RRP) is a rare disease which has been mainly detected in the previously irradiated lung of patients with cancer after the application of triggering agents, including, but not limited to, antineoplastic agents. Physicians should be aware of this rare reaction, as the occurrence of RRP could impact the outcome of anti-cancer treatment. Given that current studies on RRP are primarily case reports and retrospectively reviewed data, the aim of our article was to review the current understanding and evidence on RRP and define the characteristics of RRP. ABSTRACT: Radiation recall pneumonitis (RRP) is a rare but severe condition which has been mainly detected in the previously irradiated lung of patients with cancer after administering inciting agents, most commonly antineoplastic regimens including chemotherapy, targeted therapy, or immunotherapy. More recently, coronavirus disease vaccines were found to induce RRP. In addition to typical radiation pneumonitis (RP) or drug-induced interstitial lung disease, the management of RRP requires withholding inciting agents and steroid therapy. Thus, the occurrence of RRP could significantly impact cancer treatment, given that inciting agents are withheld temporarily and even discontinued permanently. In the present review, we discuss the current understanding and evidence on RRP and provide additional insights into this rare but severe disease.