Application of the Immunohistochemical Method as a Predictive Assay in Radiotherapy of Squamous Cell Carcinoma of Oropharynx and Hypopharynx

We analyzed various subsets of lymphocytes infiltrated into cancer tissues from 15 patients (10 cases of oropharyngeal cancer and 5 of hypopharyngeal cancer) before treatment and after irradiation with approximately 10 Gy (1,000 rad) and 30 Gy by the method of biotin-avidin-horseradish peroxidase using mouse monoclonal antibodies. The infiltration was graded + + + (marked) to – (none). In 3 cases, tumor-infiltrating lymphocytes were remarkably increased at the delivery of a small dose of irradiation (approx. 10 Gy): 2 of them showed remarkable radiosensitivity, and the lymphocyte subpopulation of the cancer tissue was mainly composed of Leu-3a + 3b-positive and Leu-8-negative lymphocytes (helper inducer T lymphocytes or delayed-type hypersensitivity cells). On the other hand, the third one proved to be rather radioresistant, and the lymphocyte subpopulation was mainly composed of Leu-14-positive lymphocytes (B lymphocytes). These findings indicate that the analysis of the lymphocyte subpopulation infiltrating into cancer tissues at the delivery of small doses of irradiation is applicable as a predictive assay in radiotherapy of squamous cell carcinoma of the oropharynx and hypopharynx.