Inclusion Criteria:

- Primary squamous cell carcinoma of head and neck, after tumor excision and neck
dissection, pathology has confirmed three or more of the following adverse prognostic
factors, including:

1. Marginale surgery but a safe distance from the residual tumor ≦ 4mm.

2. The tumor is located in the hard palate or the retromolar region.

3. Poorly differentiated cell type.

4. Tumor invasion to the nerve.

5. Tumor invasion to lymphatic vessels.

6. Tumor invasion to the small blood vessels.

7. Tumor invasion to the bone.

8. Tumor invasion to the skin.

9. Depth of tumor invasion ≧ 10mm.

10. Occurred in single lymph node metastasis.

Exclusion Criteria:

- No or presence of adverse prognostic factor but less than 2.

- Presence of either one conditions listed here: positive resection margin, resection
margin negative but less than 1 mm, pathologic N2 or N2, or presence of nodal
metastasis with extracapsular spreading.

- ECOG performance status > 2.

- Previous cancer history (except basal cell or squamous cell skin cancer) or other
synchronous malignant disease.

- Women during pregnancy.