Patient Characteristics

Demographic data abstracted from the patient medical file included age, sex, marital status, occupation, region, and whether the patient resided in an urban or rural setting. Other patient characteristics abstracted were comorbidities (HIV/AIDS, diabetes mellitus, hypertension, and cardiovascular disease) and performance status (Eastern Cooperative Oncology Group).

Tumors were classified by primary anatomic and histology according to ICD-O-3 for head and neck cancer. Grade of tumor was recorded for squamous cell carcinoma (well differentiated, moderately differentiated, and poorly differentiated). No information was available on human papillomavirus, Epstein-Barr Virus (EBV), p16 status, or further subcategorization of the squamous cell carcinoma (ie, keratinizing, nonkeratinizing, and basaloid). TNM staging classification (American Joint Committee on Cancer, seventh edition) was abstracted from the chart as recorded by the treating physician. Stage I and II tumors were classified as early stage, and stage III-IVB were classified as locoregionally advanced. Stage IVC had evidence of distant metastatic disease. Routine evaluation to make staging determinations typically consisted of laboratory data such as complete blood count and chemistries and imaging which included chest x-ray, ultrasound, and CT scan. Immunohistochemistry was not available to aid histologic diagnosis. Magnetic resonance imaging scan was available but not routinely used for staging except in selected cases.