Natural cytotoxicity in patients undergoing radiation therapy

Natural cytotoxicity against K562 target cells was measured in 51 adults with solid epithelial malignant tumors who were untreated, in 42 patients who were studied within 6 weeks following completion of radiotherapy (4,000-7,000 rads), and in 27 normal subjects. In both the radiated and the nonirradiated groups, mean cytotoxicity for patients with localized cancers was not significantly different from that of the normal controls, whereas mean cytotoxicity for patients with advanced cancers was significantly lower than that for normal controls and patients with localized disease. Twelve percent of nonirradiated patients and 13% of radiated patients with localized tumors, but 46% of nonirradiated patients and 44% of irradiated patients with advanced cancers, failed to exhibit normal NK activity. Mean cytotoxicity for irradiated patients was not significantly different from that of untreated patients. PBL from most patients showed enhanced cytotoxicity after preincubation of PBL with interferon (IFN alpha). Mean cytotoxicities for nonirradiated and irradiated patients after IFN alpha pretreatment of PBL were not significantly different. In both patient groups, IFN alpha-boosted killing was significantly less in patients with advanced disease than in patients with local tumors or normals. These results indicated that radiotherapy has no significant effect on spontaneous or IFN alpha-boosted natural cytotoxicity.