Relationship of natural killer cytotoxicity to clinical and biochemical parameters of primary human breast cancer.

We have determined the natural killer (NK) activity of peripheral blood lymphocytes obtained from 121 women undergoing surgery for primary breast cancer. NK activity was measured using 51Cr-labeled K562 target cells and effector: target ratios of 100:1, 50:1 and 10:1. The patients' lymphocytes gave a wide range of values with a mean (+/- S.E.) cytotoxicity of 22.6% +/- 1.3, and a median of 20.9% at the 50:1 effector:target ratio. These results did not differ significantly from the mean and median NK levels obtained with the peripheral blood lymphocytes of normal blood donors (mean = 23.1% +/- 1.9, median = 18.8%). Mean NK activity determined at the first postsurgical examination (less than or equal to 6 months postoperative) was significantly lower than the mean NK activity at surgery. The most significant decreases were seen in patients undergoing chemotherapy prior to the first follow-up examination. Subsequent tests (greater than 6 mo, less than or equal to 12 mo) show a recovery of NK activity to preoperative levels. A negative correlation was seen between NK level and maximum tumor diameter. NK levels also varied with tumor histiotype. No association was seen between NK levels and either the number of involved lymph nodes, pathologic tumor grade, the presence of estrogen or progesterone receptor, or the age, menopausal status or smoking history of the patients. A positive correlation was seen, however, between NK levels and number of pregnancies and live births.