Tadalafil in Treating Patients Undergoing Surgery for Cancer of the Oral Cavity or Oropharynx

OBJECTIVES: * To analyze the phenotype and the function of the tumor-induced suppressive network associated with squamous cell carcinoma (SCC) of the head and neck in patients with SCC of the oral cavity or oropharynx treated with tadalafil followed by definitive surgical resection. * To analyze the immune response before and after treatment with tadalafil to determine whether or not tadalafil treatment modulates in these patients. * To compare two doses of tadalafil to determine whether there are measurable differences in immune response in these patients. * To analyze treatment-related side effects of tadalafil at each of the two doses tested in these patients. OUTLINE: Patients are randomized to 1 of 3 treatment arms. * Arm I: Patients receive oral tadalafil once daily on days 1-20 in the absence of unacceptable toxicity. * Arm II: Patients receive oral tadalafil (at a higher dose than in arm I) once daily on days 1-20 in the absence of unacceptable toxicity. * Arm III: Patients receive oral placebo once daily on days 1-20 in the absence of unacceptable toxicity. All patients undergo scheduled definitive surgical resection on day 23. Patients undergo blood sample collection at baseline, on day 20, and at 6 weeks after surgical resection for correlative laboratory studies. Patients also undergo tumor tissue sample collection at baseline and at the time of surgical resection. Samples are analyzed for immunological markers by Fluorescence-activated cell sorting (FACS) and Immunohistochemistry (IHC). After completion of study treatment, patients are followed periodically for at least 3 years.