The purpose of this study is to determine the maximal tolerated dose (MTD) of re-irradiation using carbon ion radiotherapy (CIRT) with the fraction size of 3 gray equivalent (GyE) in the treatment of locally recurrent nasopharyngeal cancer (NPC) and to evaluate the efficacy of such treatment at the MTD. Participants will be treated with CIRT with escalating dose regimens to evaluate the MTD in terms of acute and subacute toxicity observed within 4 months after the completion of CIRT. Once the MTD for locally recurrent NPC is determined, the MTD will be used as the recommended dose to patients fulfilling the inclusion criteria in the Phase II part of the trial.

The purpose of this study is to determine the maximal tolerated dose (MTD) of re-irradiation using carbon ion radiotherapy (CIRT) with the fraction size of 3 GyE in the treatment of locally recurrent nasopharyngeal cancer (NPC) and to evaluate the efficacy of such treatment at the MTD. Participants will be treated with CIRT with escalating dose starting from 54GyE (3GyE/daily fraction) to potentially 63GyE (3GyE/daily fraction) to evaluate the maximal tolerated dose (MTD) in terms of acute and subacute toxicity observed during and within 4 months after the completion of CIRT. The TITE-CRM method is used for the phase I dose escalating part of the trial and approximately 25 patients will be accrued. Once the MTD for locally recurrent NPC is determined, the MTD will be used as the recommended dose to patients fulfilling the inclusion criteria in the Phase II part of the trial. The Phase II part of the trial will be a single stage single arm study.

Inclusion Criteria:

• Completed a definitive course of intensity-modulated photon radiation therapy (IMXT) to a total dose of ≥ 66 Gy
• Recurrence diagnosed more than 12 months after the initial course of IMXT
• Age ≥ 18 and < 70 years of age
• Karnofsky Performance Score ≥70
• Willing to accept adequate contraception for women with childbearing potential
• Ability to understand character and individual consequences of the clinical trial
• Willing to sign the written informed consent; Informed consent must be signed before the enrollment in the trial

Exclusion Criteria:

• Presence of distant metastasis
• Technology used other than IMXT (including brachytherapy following IMXT) for the treatment of initial diagnosis of NPC
• Pregnant or lactating women
• Patients who have not yet recovered from acute toxicities of prior therapies
• A diagnosis of malignancy other than carcinoma in situ of the cervix, basal cell carcinoma and squamous cell carcinoma of the skin within the past 5 years