This is a phase 3 randomized clinical trial to determine the efficacy of maintenance chemotherapy for the treatment of metastatic chemotherapy and how it should be delivered. Participants will be randomized to 3 arms. Arm 1 (control group), participants will receive only conventional chemotherapy; arm 2 (experimental group), participants will receive up to 6 cycles of maintenance chemotherapy after conventional chemotherapy; arm 3 (experimental group), after conventional chemotherapy, participants will receive maintenance chemotherapy until disease progression or intolerable toxicities. Participants in all 3 arms will receive similar conventional chemotherapy. Four to eight cycles of conventional chemotherapy with platinum-based regimen is preferred. Maintenance chemotherapy should use one of the regimens: S1 (40mg, twice a day for 14 days, every 3 weeks), capecitabine (1000mg/m^2, twice a day for 14 days, every 3 weeks) or Tegafur-uracil (100mg/m^2, q8h, for 14 days, every 3 weeks). The response of treatment will be evaluated according to RECIST criteria. Adverse events will be documented according to CTCAE v4.03.
The purpose of this study is to examine the efficacy of maintenance chemotherapy for the treatment of metastatic nasopharyngeal carcinoma. Participants will be randomized to 3 arms. Arm 1, control group, participants will receive only 4-8 cycles of conventional chemotherapy; arm 2, participants will receive 6 cycles of maintenance chemotherapy after conventional chemotherapy; arm 3, experiment arm, after conventional chemotherapy, participants will receive maintenance chemotherapy until disease progression or intolerable toxicities.