Tumor volume instead of recurrent T category predicts clinical outcome of patients with locally recurrent nasopharyngeal carcinoma salvaged by carbon ion radiation therapy

•We assessed the value of tumor volume as a predictive tool to guide individualized carbon ion radiation therapy (CIRT).•We first put out the possibility that tumor volume instead of recurrent T category could predict the OS and LPFS of patients with locally recurrent nasopharyngeal carcinoma salvaged by CIRT.•We proposed that tumor volume should be considered in the risk stratification and CIRT-based treatment for patients with LR-NPC. Although carbon ion radiation therapy (CIRT) substantially improves the overall survival (OS) of patients with LR-NPC, approximately 40% of the patients may develop local recurrence. The purpose of study is to assess the value of tumor volume (TV) as a predictive tool to guide individualized CIRT. Consecutive patients with LR-NPC treated using CIRT at Shanghai Proton and Heavy Ion Center between April 2015 and May 2019 were included. TV before CIRT was delineated and calculated. The generalized additive Cox model was used to examine the relationship between TV and OS and local progression-free survival (LPFS). A cutoff value of tumor volume was identified to best discriminate patients with different 2-year OS rates, using receiver operating characteristic (ROC) analysis. A total of 157 patients were enrolled. The median tumor volume was 22.49 (2.52–90.13) ml. In the univariable analyses, tumor volume was significantly associated with OS (p 25 ml, respectively. Tumor volume could predict the OS and LPFS of patients. We propose that tumor volume should be considered in the risk stratification and CIRT-based treatment for patients with LR-NPC.