In Reply McCaw et al raise important considerations on duration of response (DOR) reporting in clinical trials. Achievement of an objective radiographic response (ORR) as measured by reduction in size of a contrast-enhancing lesion is thought to represent a bona fide parameter of therapeutic benefit associated with cytotoxic agents or immunotherapy for patients with solid tumors, including glioblastoma.1 However, this argument is less clear with vascular endothelial growth factor–targeting agents because of potential false responses owing to their effect on contrast uptake.2 Therefore, further value is added if the response is maintained for a meaningful duration. Longer DOR has been consistently noted following anti–programmed cell death 1 (PD-1) therapy across tumor types, explained by generation of polyclonal and memory-adaptive tumor immunity.3 Therefore, DOR is an increasingly important end point, in addition to ORR, for evaluating the efficacy and long-term clinical benefit of immunotherapy. Given the above rationale, we presented a descriptive summary of DOR.4