A Study of Toripalimab as Consolidation Therapy After Postoperative Chemoradiotherapy in HNSCC

Inclusion Criteria: * Postoperative with adverse prognostic factors in patients with locally advanced head and neck squamous cell carcinoma. * Have received postoperative adjuvant radiotherapy (chemo) therapy, and the end of the treatment is not more than 2 months. * Greater than or equal to 18 and less than 70 years of age at time of study entry. * ECOG performance status of 0 or 1. * Measurable disease as per RECIST 1.1. * Screening labs must meet the following criteria and must be obtained within 14 days prior to registration: 1. Adequate hepatic and renal function as demonstrated by 1. Serum creatinine \< 1.5 X ULN or CrCl \> 40mL/min (if using the Cockcroft-Gault formula below): * Males: Creatinine CL (mL/min) = (Weight (kg) x (140 - Age))/(72 x serum creatinine (mg/dL)） * Females: Creatinine CL (mL/min) = (Weight (kg) x (140 - Age))/(72 x serum creatinine (mg/dL))x 0.85 2. AST/ALT ≤ 3 x ULN 3. Total Bilirubin ≤ 1.5 x ULN (except subjects with Gilbert Syndrome, who can have total bilirubin \< 3.0 mg/dL) 2. Adequate bone marrow function as demonstrated by: 1. Absolute Neutrophil Count \>1,500/µL 2. Platelets \> 100 X 103/µL 3. Hemoglobin \> 9.0 g/dL * Women of reproductive potential should have a negative serum or urine pregnancy test (minimum sensitivity 25 IU/L or equivalent units of human chorionic gonadotropin \[HCG\]) within 7 days of study enrollment. * Women of reproductive potential must use highly effective contraception methods to avoid pregnancy for 3 months after the last dose of study drugs; "women of reproductive potential" is defined as any female who has experienced menarche and who has not undergone surgical sterilization (hysterectomy or bilateral oophorectomy) or who is not postmenopausal; menopause is defined clinically as 12 months of amenorrhea in a woman over 45 in the absence of other biological or physiological causes; in addition, women under the age of 55 must have a documented serum follicle stimulating hormone (FSH) level less than 40 mIU/mL. * Men of reproductive potential who are sexually active with women of reproductive potential must use any contraceptive method with a failure rate of less than 1% per year; men who are receiving the study medications will be instructed to adhere to contraception for 3 months after the last dose of study drugs; men who are azoospermic do not require contraception. * Ability to understand and willingness to sign an IRB approved written informed consent document (or that of legally authorized representative, if applicable). * Subject is willing and able to comply with the protocol for the duration of the study including undergoing treatment and scheduled visits and examinations including follow up. Exclusion Criteria: * Is currently participating in or has participated in a study of an investigational agent within 4 weeks of the first dose of treatment or has not recovered (i.e., ≤ Grade 1 or at baseline) from adverse events due to agents administered more than 4 weeks earlier. * Has had another known invasive malignancy within the previous 5 years （With the exception of basal cell carcinoma of the skin, carcinoma in situ of the cervix, and papillary carcinoma of the thyroid, which has been cured）. * If subject received major surgery for any other reason, they must have recovered adequately from the toxicity and/or complications from the intervention prior to starting therapy. * Active, known or suspected autoimmune disease. * Has evidence of interstitial lung disease or active, non-infectious pneumonitis. * Has an active infection requiring systemic therapy. * Has received prior therapy with an anti-PD-1 antibody . * A history of allergic reaction attributed to compounds of similar chemical or biologic composition to the treatment or other agents used in the study. * Has known psychiatric or substance abuse disorders that would interfere with cooperation with the requirements of the trial. * Is pregnant or breastfeeding, or expecting to conceive or father children within the projected duration of the trial, starting with the pre-screening or screening visit through 23 weeks after the last dose of trial treatment. * Has a known history of Human Immunodeficiency Virus (HIV) infection (HIV 1/2 antibodies). * Has known active Hepatitis B or C. * Known history of active TB ( bacillus tuberculosis ).