Updates on Radiation-induced Lymphopenia

Book excerpt: Radiation-induced lymphopenia (RIL) is a long-known and frequent toxicity of radiotherapy and is the direct consequence of cell death of lymphocytes crossing the radiation field during treatment. In recent years, interest and evidence have been growing for the negative influence of RIL on treatment outcomes and survival of patients with solid tumors. Especially since the rise of immunotherapy, which is largely reliant on vital lymphocytes. Insight into clinical and dosimetric risk factors can help identify patients with an increased risk of RIL and possible management. Methods to mitigate RIL aim to reduce unintentional exposure of the circulating blood pool and secondary lymphoid organs to radiotherapy, with the ultimate goal of improving survival.