Long-term changes in natural killer activity after external pelvic radiotherapy

Peripheral lymphocytes from 24 Stage I endometrial cancer patients treated 3–5 years earlier were tested for their natural killer (NK) cell activity against K562 cell line targets and for surface markers. The patients were free of recurrence at the time of investigation. They belonged to a clinical trial where group A (control) received surgery only and group B also received 4000 rad external pelvic field irradiation post surgery. Lymphocyte suspensions from group B patients showed, on a per cell basis, a higher NK activity and a higher percentage of cells bearing receptors for the Fc part of immunoglobuline G than did group A lymphocytes. Expressed per volume unit of blood, however, these differences were insignificant. A depletion of T lymphocytes from the peripheral circulation was seen 3–5 years after radiotherapy. On a per cell basis, however, the T cell functional capacity, as estimated from the mitogenic (PHA) response, seemed unaffected.