NATURAL IMMUNITY IN BREAST-CANCER PATIENTS DURING NEOADJUVANT CHEMOTHERAPY AND AFTER SURGERY

Breast cancer is the most common cancer in women. Surgery, and more re cently neoadjuvant chemotherapy, are being utilized as the initial tre atment for breast cancer; however little is known about their effects on the natural immune system. The natural immune system (natural kille r [NK] cells) is thought to be important in immune surveillance, inclu ding protection from metastasis during the intravascular tumour seedin g that occurs during surgery. To investigate the effects of surgery on the natural immune system, we studied the pre-operative and post-oper ative peripheral blood lymphocytes (PBL) of 10 patients with stage I o r II breast cancer: there was a 71.6+/-25.3% post-operative reduction in NK cell function (P<0.005, Student's paired t-test). To investigate the effects of neoadjuvant chemotherapy and surgery, we examined PBL from five patients with stage III breast cancer: NK cell function drop ped 95.7+/-1.9% after neoadjuvant chemotherapy, and there was a furthe r 51.0+/-23.4% decrease after surgery (P<0.05, Student's paired t-test ). Neither group of patients had decreased numbers of NK cells, change s in the percentage of T helper or suppressor cells, or alterations in the production of cytotoxic factor by NK cells. These findings sugges t that the impairment in NK cell function reflects a defect in the abi lity of NK cells to recognize and/or bind to tumour target cells. We c onclude that the initial treatment of breast cancer patients, whether it involves surgery alone or with neoadjuvant chemotherapy, profoundly impairs their natural immune system and could increase the risk of me tastasis. Further studies are needed to delineate the mechanism of thi s derangement in natural immunity and possibly alter its course.