Prolonged depression of cellular immunity in cured laryngopharyngeal cancer patients treated with radiation therapy

Immune competence was evaluated in cured patients who had been treated by irradiation for carcinoma of the laryngopharynx, and compared with that of similar patients treated by surgery alone, and normal controls. Cellular immunity was determined by quantitation of in vitro phytohemagglutinin (PHA)-induced lymphocyte reactivity and peripheral blood thymus-dependent lymphocyte (T cell) levels. Humoral immunity was assessed by measurement of serum immunoglobulin levels and by the effect of serum on in vitro normal lymphocyte reactivity to PHA. In 21 patients who were studied for 4-23 years (mean 8.4) after surgical treatment alone for laryngopharyngeal carcinoma, neither cellular nor humoral immunity differed from that of 44 controls. In contrast, 14 patients who had been irradiated and subsequently cured for 4-15 years (mean 9.0) prior to evaluation displayed significantly impaired cellular immune competence when compared to normals and patients treated by surgery alone. Since previous determinations of the effects of radiation therapy have been in patients who received irratiation to the thymic region or large area of bone marrow, this study indicates that radiation therapy for cancer administered via portals that encompass a minimal area of the immune system may be associated with prolonged impairment of cellular immunity.