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 determine a susceptible phenotype, which is relevant only in organs and tissues 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 cancers differs.

OBJECTIVE

To evaluate the difference in mutagen sensitivity among patients without cancer, patients with NPC, patients with oral or oropharyngeal cancer (ORC), and patients with laryngeal or hypopharyngeal cancer (LHC).

DESIGN

Peripheral blood was cultured at 37 degrees C, using 5% carbon dioxide, for 72 hours. After 67 hours of incubation, bleomycin in a concentration of 30 IU/L was added to induce chromatid breaks. The number of chromatid breaks per cell was scored in 50 metaphases of cultured lymphocytes and compared in the 4 groups.

SUBJECTS

Patients with histologically proven squamous cell carcinoma of the mucosa of the upper digestive tract, which included 3 groups: patients with NPC, patients with ORC, and those with LHC. Control subjects were hospital inpatients with no tumor history. There were 35 patients 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), respectively. All the cancer groups had significantly higher mean breaks per cell and a higher prevalence of hypersensitivity than the control group. Patients with NPC had a significantly lower mean number of breaks per cell than the group with ORC or that with LHC.

CONCLUSIONS

Patients with NPC had less mutagen sensitivity than those with ORC or LHC. Our results support the clinical and epidemiological findings of a difference between NPC and other head and neck cancers. Environmental factors might play a less pronounced role in the carcinogenesis of NPC.