Trial Evaluating Maintenance Chemotherapy for Metastatic Nasopharyngeal Carcinoma

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.

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.

Eligibility Criteria:
Inclusion Criteria:

* Age ≥ 18 and ≤ 70 years
* Histologically confirmed nasopharyngeal carcinoma, WHO (World Health Organization) classification II/III
* With distant metastasis
* With measurable lesions that can be detected by imaging studies
* Achieving PR (partial response) after 4 cycles of conventional chemotherapy
* Life expectancy ≥ 6 months
* ECOG (Eastern Cooperative Oncology Group): 0-1, no significant active concurrent medical illnesses
* Adequate laboratory values within 30 dyas of enrollment to study defined as follows: N \> 2000/mm\^3; PLT (platelet count) \> 100,000/mm\^3; total bilirubin \< 1.5mg/dl; AST (aspartate aminotransferase)/ALT (alanine aminotransferase) \< 1.5 ULN (upper limit of normal); SCr (serum creatinine) \< 1.5mg/dl; CCR (creatinine clearance rate) \> 60ml/min
* 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:

* Received previous treatment for metastatic disease
* Pregnant or lactating women
* A diagnosis of malignancy other than CIS (carcinoma in situ) of the cervix, BCC (basal cell carcinoma) and SCC (squamous cell carcinoma) of the skin within the past 5 years
* Refusal of the patient to participate into the study