IL6 and cancer: In this connection, two clinical studies suggested an association between circulating proinflammatory cytokines and cognitive impairment in cancer patients, and they indicated that only the level of interleukin (IL)-6, among proinflammatory cytokines, including IL-1 and tumor necrosis factor-α, had a negative correlation with either cognitive function 24 or cognitive functioning QOL 25, while other proinflammatory cytokine levels had no correlation with it 24,25.