To evaluate YTHDF1 expression in patients receiving RT, we measured YTHDF1 levels in PBMCs from patients with metastatic non–small cell lung cancer (NSCLC) enrolled in a clinical trial at our institution (COSINR study, NCT03223155); patients were treated with sequential or concurrent stereotactic body radiotherapy (SBRT) and immune checkpoint blockade therapy (31). The gene discussed is YTHDF1; the disease is lung cancer.