Ph II Long Term/Low Dose Xeloda in Head and Neck Squamous Cell Carcinoma After Surgery, Radiation & or Chemo

DISEASE CHARACTERISTICS: * Histologically confirmed squamous cell carcinoma of the head and neck, including 1 of the following primary tumor sites: * Oral cavity * Oropharynx * Nasopharynx * Hypopharynx * Larynx * Unknown primary * Any disease stage allowed * No evidence of active disease * Must have undergone curative surgical resection, radiotherapy, and/or chemotherapy at least 1 month, but no more than 4 years ago PATIENT CHARACTERISTICS: Performance status * Karnofsky 70-100% Life expectancy * More than 3 months Hematopoietic * White blood count (WBC) ≥ 3,000/mm\^3 * Granulocyte count ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 Hepatic * Bilirubin ≤ 1.5 times upper limit of normal (ULN) * Aspartate Aminotransferase (AST) or Alanine Aminotransferase (ALT) ≤ 2.5 times ULN * Alkaline phosphatase ≤ 2.5 times ULN * Hepatitis B and/or C negative Renal * Creatinine clearance \> 50 mL/min Cardiovascular * No myocardial infarction within the past 12 months * No uncontrolled congestive heart failure * No unstable or uncontrolled angina Gastrointestinal * No lack of physical integrity of the upper gastrointestinal tract * Must be able to swallow tablet * No malabsorption syndrome Other * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * HIV negative * No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of the cervix, or stage I or II cancer for which the patient is currently in complete remission * No history of uncontrolled seizures, central nervous system (CNS) disorders, or psychiatric disability that would preclude study compliance or giving informed consent * No ongoing postoperative fistula * No prior unanticipated severe reaction to fluoropyrimidine therapy or known sensitivity to fluorouracil * No other serious uncontrolled medical or surgical condition that would preclude study participation PRIOR CONCURRENT THERAPY: Chemotherapy * See Disease Characteristics * Prior oral fluoropyrimidine therapy allowed provided it was given in the adjuvant setting and completed ≥ 12 months ago Radiotherapy * See Disease Characteristics Surgery * See Disease Characteristics * More than 4 weeks since prior major surgery and recovered * No prior organ allografts Other * More than 4 weeks since prior participation in any investigational drug study