Serum Level of Interleukin 6 as a Prognosis Factor in Metastatic Renal Cell Carcinoma

Interleukin (IL) 6 was measured in the serum of 138 patients with metastatic renal carcinoma before the initiation of IL-2 treatment. IL-6 was detectable in 66 patients with renal cancer (48%) and in only 8 of 70 normal adults (11%). Serum C reactive protein (CRP) and IL-6 levels are correlated, suggesting that IL-6 is involved in CRP increase in these patients. The interval between diagnosis of the primary tumor and metastasis was shorter in patients with a detectable serum IL-6 and/or serum CRP level >50 mg/liter. Serum IL-6 and CRP levels were higher in subgroups of patients previously defined as having a poor life expectancy according to the Eastern Cooperative Oncology Group criteria. Pretreatment concentrations of IL-6 and CRP were higher in patients who experienced progressive disease after IL-2 treatment. Patients with detectable IL-6 had a shorter survival from the beginning of IL-2 treatment than patients without circulating IL-6 (median, 8 versus 16 months). Similarly, the median survival from the beginning of IL-2 therapy of patients with CRP levels >50 mg/liter was 6 months, compared to 16 months in those with CRP levels below this threshold. None of the 21 patients with serum IL-6 concentrations >300 pg/ml achieved response to any of the three IL-2 regimens. This subgroup has a median survival of 5 months after IL-2 treatment and consisted of 15% of the patients in our series. These results indicate that serum IL-6 and CRP levels are adverse prognosis factors in patients with metastatic renal cell carcinoma. Serum IL-6 level could help in the selection or stratification of the patients in future IL-2 trials.