Our purpose in this study was to determine the influence of radiotherapy, especially brachytherapy, on the activity of natural killer cells (NK). We examined changes in NK activity before and after radiotherapy in 27 patients who underwent radiotherapy with or without brachytherapy, comprising of 16 cases of cervical cancer (three recurrences), 5 of prostate cancer, 4 of esophageal cancer and 2 of tongue cancer. Fourteen intracavitary procedures (for 13 cervical cancers and 1 esophageal cancer) and 10 interstitial brachytherapy (for 3 cases of recurrent cervical cancer, 5 of prostate cancer and 2 of tongue cancer) were performed with Ir-192 microSelectron HDR and Selectron Cs-137. External radiotherapy consisted of 10 MV X-ray administration for 13 cases of cervical cancer and 4 of esophageal cancer. The number of white blood cell was reduced by radiotherapy from 5065±2002 count/ml to 4281±1392 count/ml (p=0.02), that of lymphocytes from 1518±817 to 762±409 /ml (p<0.0001), and that of CD 16+ cells from 274±197 to 140±96 (p=0.03). No significant change was observed in the number of CD 56+ cells (274±166 to 211±153 /ml). Overall NK activity was reduced by radiotherapy from 37±19% to 30±19% (p=0.001). External radiotherapy with or without brachytherapy reduced NK activity from 33±18% to 23±16% (p=0.004). However interstitial brachytherapy produced little change in NK activity from 42±18 to 39±19%). Radiotherapy reduced the number of white blood cell, lymphocyte and CD 16+ cells. Although external radiotherapy suppressed NK activity, only brachytherapy showed little influence on NK activity alteration.

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