 The purpose of this study is to determine the maximal tolerated dose MTD of re-irradiation using carbon ion radiotherapy CIRT 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 maximal tolerated dose MTD in terms of acute and subactue toxicity observed during and 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. 