Although the current study focuses on RB1 mutation analysis, previous work has shown that cfDNA can also reveal tumor‐derived somatic copy number alterations including changes in MYCN. 42, 43, 44Incorporating mutational and copy number analysis can potentially expand the scope of patient population and the sensitivity of detecting tumor‐derived cfDNA at diagnosis and in the relapse setting. The gene discussed is RB1; the disease is neoplasm.