We aim, in this study, to examine whether reduction of FLT PET derived SUV before and after carbon ion radiotherapy can predict the treatment response and survivals for patients with locoregionally recurrent nasopharyngeal carcinoma.

This is a single-arm phase II clinical trial evaluating the prognostic value of FLT PET/CT for patients with locoregionally recurrent nasopharyngeal carcinoma. All patients will receive FLT PET/CT scans before and after carbon ion radiotherapy (CIRT). The sensitivity and specificity of reduction of FLT uptake reduction in terms of predicting the treatment outcome evaluated by MRI at 3 months after completion of CIRT according to RECIST 1.1. Its predictive value of OS, LPFS, RPFS and DMFS will be examined as well.

Inclusion Criteria:

• Pathologically confirmed as primary nasopharyngeal carcinoma;
• With recurrence at nasopharynx and/or recurrent retropharyngeal lymph node, recurrence was diagnosed by imaging or pathology studies;
• Already received one course of definitive radiation therapy, at least 6 months ago;
• Able to receive contrast MRI scan and PET/CT scan;
• ECOG: 0-2;
• Anticipated survival time >= 12 months;
• With sufficient major organ functions;
• Willing to sign informed consent.

Exclusion Criteria:

• Metal implants that might significantly influence the radiation dose distribution;
• Dose constrains for organs-at-risk are beyond acceptable limit;
• With comorbidities/conditions that might influence the effectiveness of carbon-ion therapy;
• Pregnant or within lactation period;
• Drug/alcohol addiction;
• With mental disorder that might impede the completion of therapy.

Consecutive LR-NPC patients treated at SPHIC will be recruited.