Patients with durable RECIST SD included those with HNSCC with ARID2 frameshift (99 weeks), HNSCC with no sequencing available (48 weeks), HNSCC with CCND1 amplification (49 weeks), and digital papillary adenocarcinoma with TP53 mutation (51 weeks). The gene discussed is ARID2; the disease is head and neck squamous cell carcinoma.