Soluble interleukin 2 receptor in lung cancer. An indirect marker of tumor activity?

Circulating levels of the soluble interleukin 2 receptor (sIL-2R) could provide an in vivo measure of the immunologic response to human tumors. We performed a total of 326 sIL-2R serum assays in 126 patients with lung cancer (67 at diagnosis, 59 during and after treatment), 112 patients with pulmonary benign diseases, and 63 voluntary healthy subjects. Patients with lung cancer had a median value of sIL-2R of 791 U/ml, which was superior to that of both controls (398 U/ml, p less than 0.001) and patients with noninflammatory benign diseases (583 U/ml, p less than 0.02). However, infectious pulmonary disorders, such as tuberculosis and pneumonia, were associated with the highest values of the substance (median, 1150 U/ml; p less than 0.001). At the diagnosis of lung cancer, sIL-2R correlated neither with the stage of disease nor with the cell type. On the contrary, posttreatment levels of the receptor were significantly related to disease status (RO = .41, p less than 0.002), particularly in the subgroup of nonsurgical patients (RO = .48, p less than 0.001). Patients with abnormal sIL-2R levels had a nearly significant reduction in survival as compared with patients with normal values (p less than 0.1). Measurements of sIL-2R could be useful in monitoring patients under treatment for bronchogenic carcinoma, as well as in prognostication. In this setting, sIL-2R might open a new class of biologic markers, providing information that is complementary to those of the more classic tumor-derived markers.