Background. Positron emission tomography (PET) with labeled fluorodeoxyglucose (FDG) demonstrates in creased tracer uptake in many neoplasms. This study was undertaken to define the patterns of FDG uptake in head and neck neoplasms before and after high dose irradiation. Methods. Twenty‐five patients were evaluated prospectively with PET and standard clinical and radiographic techniques before and after irradiation. Results. Twenty‐seven primary sites were confirmed pathologically in 23 patients and included the nasopharynx (four lesions), oropharynx (14 lesions), larynx (five lesions), oral cavity (two lesions), and paranasal sinuses (two lesions). Two patients had unknown primary sites. Twenty‐four of 27 primary sites correlated with areas of increased tracer uptake on PET scans. Five patients had increased uptake in cervical lymph nodes that were uninvolved by radiographic or clinical criteria. Position emission tomography seemed to be able to differentiate tumor activity from fluid‐filled sinuses in two patients with paranasal sinus tumors. In two patients with unknown primary sites, increased uptake in the base of tongue after PET suggested occult primary sites. Positron emission tomography scans obtained 1 month after high dose irradiation (RT) indicated decreased levels of FDG uptake in all patients' tumors. However, these scans did not accurately reflect the status of disease in these patients. Scans obtained 4 months after RT were believed to assess more accurately the presence of malignancy. Conclusions. Positron emission tomography is a new modality that may be useful in defining tumor activity in clinically negative areas. Appropriately timed posttreatment PET may be useful in predicting outcome after definitive RT and in distinguishing viable tumors from normal tissue changes after RT in patients with head and neck carcinomas.

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The inferior control rate for stage T2b lesions has implications for treatment. Our study supports the conclusions of reports in the literature showing that low fraction size negatively influences outcome in patients with early glottic cancer.

The proportion of T and B lymphocytes in the peripheral blood was determined in patients with either mammary cancer or with various pelvic malignancies. In cancer patients studied prior to irradiation the level of cells forming either E-rosettes or EAC'-rosettes was similar to that found among healthy controls. Radiation therapy resulted in a striking lymphopenia. The level of cells with T-cell markers was diminished to a greater extent than the level of cells with B-cell markers. T h e relative proportion of T-cells forming high affinity E-rosettes was not reduced following radiation, so that it can be concluded that radiation affects predominantly the subpopulation of T-cells which do not form high affinity E-rosettes. Irradiation of the pelvic area resulted in a more rapid reduction of the level of T lymphocytes than irradiation of the mediastinum, although the final relative proportions of the cells were similar in both groups of patients. The results of the present study suggest that the reduction of the level of T lymphocytes following irradiation results from its effect on the lymphocytes in the major blood vessels, and that radiation of the thymus is not a prerequisite for this phenomenon.