INCREASED MUTAGEN SENSITIVITY IN PATIENTS WITH HEAD AND NECK-CANCER IS LESS PRONOUNCED IN PATIENTS WITH NASOPHARYNGEAL CARCINOMA

Background: Mutagen sensitivity tested with bleomycin sulfate can dete rmine a susceptible phenotype, which is relevant only in organs and ti ssues that have direct contact with the external environment. Patients with head and neck cancers have more mutagen sensitivity than control subjects without cancer, and the hypersensitive phenotype has a risk for the development of a second primary cancer. Head and neck cancers, however, represent a heterogeneous group of neoplasm. The biological behavior of nasopharyngeal carcinoma (NPC) and other head and neck can cers differs. Objective: To evaluate the difference in mutagen sensiti vity among patients without cancer, patients with NPC, patients with o ral or oropharyngeal cancer (ORC), and patients with laryngeal or hypo pharyngeal cancer (LHC). Design: Peripheral blood was cultured at 37 d egrees C, using 5% carbon dioxide, for 72 hours. After 67 hours of inc ubation, bleomycin in a concentration of 30 IU/L was added to induce c hromatid breaks. The number of chromatid breaks per cell was scored in 50 metaphases of cultured lymphocytes and compared in the 4 groups. S ubjects: Patients with histologically proven squamous cell carcinoma o f the mucosa of the upper digestive tract, which included 3 groups: pa tients with NPC, patients with ORC, and those with LHC. Control subjec ts were hospital inpatients with no tumor history. There were 35 patie nts in each group. Results: The mean (+/-SD) number of breaks per cell in the control group and in the groups with NPC, ORC, and LHC were 0. 80 (+/-0.32), 1.03 (+/-0.45), 1.30 (+/-0.44), and 1.35 (+/-0.46), resp ectively. All the cancer groups had significantly higher mean breaks p er cell and a higher prevalence of hypersensitivity than the control g roup. Patients with NPC had a significantly lower mean number of break s per cell than the group with ORC or that with LHC. Conclusions: Pati ents with NPC had less mutagen sensitivity than those with ORC or LHC. Our results support the clinical and epidemiological findings of a di fference between NPC and other head and neck cancers. Environmental fa ctors might play a less pronounced role in the carcinogenesis of NPC.