To investigate whether changes in cytokine profiles correlate with radiation-induced acute genitourinary toxicity, the concentrations of IL-1β, IL-2, IL-6, IFN-γ and TGF-β1 were measured in serum of patients with prostate cancer undergoing radiotherapy before treatment initiation, after 5th, 15th and 25th radiotherapy fractions, at the end of radiotherapy after last fraction, and 1 month after the end of radiotherapy. The gene discussed is IL1B; the disease is prostate cancer.