This is a single center phase 1 trail to observe safety and efficacy of metronomic Capecitabine plus Camrelizumab as second-line regimen to treat head and neck cancer or esophageal squamous cancer patients.

This study is one of the cohorts of a multi-cohort trial called Combination of Metronomic Capecitabine with Camrelizumab for treatment of refractory solid tumor (McCrest) trial.

Head and neck cancer / Esophageal squamous cancer patients who have disease progression after first standard regimen will be treated by metronomic Capecitabine plus Camrelizumab. Metronomic Capecitabine will be given as fixed dose (500mg bid) orally. Camrelizumab will be given two-weekly (200mg once) intravenously. This regimen will be administered until progression of disease, intolerable toxicity or withdraw of consent.

Inclusion Criteria:

1. Male/female patients aged≥18 years.
2. Histologically confirmed Head and neck cancer or Esophageal squamous cancer, without uncontrolled pleural effusion or ascites.
3. Patients with advanced or metastatic disease who have disease progression after first standard regimen, with measurable or unmeasurable lesions.
4. MSS or pMMR.
5. ECOG performance status 0 to 2, expected lifetime≥3 months.
6. Adequate organ function: Absolute neutrophil count (ANC) ≥1.5x109/L, White blood count ≥3.5x109/L, Platelets ≥75x109/L, Hemoglobin (Hb) ≥70g/L, ALT/AST ≤2.5x ULN (for patient with liver metastasis ALT/AST ≤5x ULN), Serum bilirubin ≤1.5x ULN, Serum creatinine ≤1.5x ULN.
7. HBV infected patients (inactive/asymptomatic carrier, chronic or active) with HBV DNA<500IU/ml (or 2500 copies/ml).
8. Pregnancy test of female patients with fertile activity should be negative within 7 days before enrollment. Patients should keep contraception during treatment.
9. Willingness and ability to comply with the protocol for the duration of the study including scheduled visits, examinations, investigations and treatment plans with informed consent form.

Exclusion Criteria:

1. Pregnancy or children bearing potential.
2. brain or meningeal metastasis.
3. With second primary malignant diseases.
4. With uncontrolled auto-immune diseases, interstitial pneumonia, ulcerative colitis, or patients who should receive long-term glucocorticoid treatment (>10mg/d prednisone).
5. With uncontrollable complications
6. Inadequate organ function
7. Conditions which impact on pill taking (dysphagia, chronic diarrhea, bowel obstruction).
8. known hypersensitivity reaction to any of the study drugs or components.
9. Other unsuitable conditions determined by investigators.