This is a randomized phase 2 trial with 2 groups (control group vs experimental group). Patients with locally recurrent nasopharyngeal carcinoma (LR-NPC) assigned to the control group will receive standardized carbon-ion radiotherapy (CIRT). For patients assigned to the experimental group, a predictive model will be used to predict the chance of developing mucosal necrosis after salvage carbon-ion radiotherapy, and individualized dose prescription will be given. The primary endpoint of the study is to compare the 2-year progression-free survival (PFS) between 2 groups.

This is a randomized phase 2 trial with 2 groups (control group vs experimental group). Patients with locally recurrent nasopharyngeal carcinoma (LR-NPC) assigned to the control group will receive standardized CIRT with a dose of 63 gray equivalent (GyE) in 21 fractions (fx). This regimen was obtained from our previous phase 1 (dose escalation) study. For patients assigned to the experimental group, a predictive model will be used to predict the chance of developing mucosal necrosis after salvage carbon-ion radiotherapy, and individualized dose prescription will be given. A dose of 60 GyE/20 fx, 63 GyE/21 fx and 66 GyE/22 fx will be given to patients with high, moderate and low risk of developing mucosal necrosis, respectively. The primary endpoint of the study is to compare the 2-year progression-free survival (PFS) between 2 groups. The secondary endpoints include 2-year overall survival (OS), local progression-free survival, regional progression-free survival, distant metastasis-free survival, toxicities and quality of life.

Inclusion Criteria:

• Aged between 17-70 years.
• Pathologically diagnosed as WHO type 2/3 nasopharyngeal carcinoma.
• Failed previous definitive radiotherapy at least 6 months ago.
• Only had 1 previous course of radiotherapy.
• Eastern Cooperative Oncology Group score: 0-1.
• Adequate laboratory values within 30 dyas of enrollment to study defined as follows: 1) neutrophil > 2000/mm^3; 2) platelet > 100,000/mm^3; 3) total bilirubin < 1.5mg/dl; 4) alanine aminotransferase/aspartate aminotransferase < 1.5 upper limit of normal; 5) SCr < 1.5mg/dl; creatinine clearance rate > 60ml/min.
• Willing to accept adequate contraception for women with childbearing potential.
• Willing to sign the written informed consent; Informed consent must be signed before the enrollment in the trial.

Exclusion Criteria:

• Presence of distant metastasis.
• Without measurable lesion.
• Previous history of malignant tumor (within 5 years) or simultaneous existence of multiple primary tumors.
• Accompanied with severe major organ dysfunction.
• Presence of mental disease that may influence the understanding of informed consent.

Individual participant data including baseline characteristics, treatment information and follow-up data on toxicity, survival and disease control will be shared.

Within 5 years after the publication of the study.

Data may be shared with radiation oncologists who are interested in examining the efficacy and toxicity of locally recurrent nasopharyngeal carcinoma patients treated with particle beam radiotherapy. Detailed study protocol should be emailed along with the request of the data. We may carefully review the study protocol, and data will only be shared with well-designed studies.