 6. Post-operative Patients: Histology confirmed oral cavity, oropharynx, larynx and hypopharynx squamous cell carcinoma AJCC Staging of HNSCC: Stage III and IV squamous cell carcinoma treated with surgery as the primary modality requiring post-operative RT, but not receiving concurrent chemotherapy. Indications for post-operative RT include: unfavorable T3 and T4 primaries, compromised margins, nodal metastases, extracapsular nodal extension, perineural invasion and lymphovascular invasion. 