Optimal cut‐off value for identifying objective response in patients with nasopharyngeal carcinoma after induction chemotherapy

Abstract Background We aimed to establish the most suitable threshold for objective response (OR) in the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 in patients with nasopharyngeal carcinoma (NPC). Methods According to RECIST 1.1, we retrospectively evaluated MR images of NPC lesions in patients before and after induction chemotherapy (IC). Restricted cubic spline and maximally selected rank statistics were used to determine the cut‐off value. Survival rates and differences between groups were compared with Kaplan–Meier curves and log‐rank tests. Results Of 1126 patients, 365 cases who received IC treatment were suitable for RECIST 1.1 evaluation. The 20% cut‐off value maximized between‐group differences according to maximally selected rank statistics. No difference in distant metastasis‐free survival between OR and non‐response groups was shown using the primary threshold of OR (30%), while it differed when 20% was employed. Conclusions With an optimal cut‐off value of 20%, RECIST may assist clinicians to accurately evaluate disease response in NPC patients.