A pilot study examining circulating interleukin-6 and transforming growth factor-β levels during pelvic radiation therapy

OBJECTIVES: To determine if circulating levels of the inflammatory cytokines interleukin-6 (IL-6) and transforming growth factor-β (TGF-β levels) are elevated during pelvic radiotherapy (RT). METHODS: Patients receiving pelvic RT with a minimum dose of 45 Gy were eligible for this prospective observational study. Patients were assessed before RT, during week 3 of RT, and during the last week of RT. Assessment included determination of gastrointestinal toxicity and laboratory evaluation for serum IL-6 and plasma TGF-β using quantitative 2-site enzyme immunoassays. Dose to the rectum, colon, and small bowel were analyzed using dose-volume histograms. A 2-sided 0.05-level Kruskal Wallis one-way analysis of variance test was used to test the equality of the means of IL-6 and TGF-β levels at the different time points. RESULTS: Twenty patients were enrolled, of whom 18 were eligible. The mean (95% confidence interval) serum IL-6 levels at baseline, 3 weeks, and during the last week of RT were 5.1 (1.9-8.3) pg/mL, 4.1 (2.6-5.7) pg/mL, and 7.5 (4.9-10.1) pg/mL, respectively (P-value > 0.05). The mean (95% confidence interval) plasma TGF-β levels at baseline, 3 weeks, and during the last week of RT were 8.7 (5.0-12.3) ng/mL, 5.5 (3.8-7.2) ng/mL, and 7.0 (4.5-9.5) ng/mL, respectively (P-value> 0.05). There was no correlation between cytokine levels and clinically evident RT enteritis or volume of bowel receiving RT. CONCLUSIONS: We did not observe significant changes in circulating levels of TGF-β and IL-6 during pelvic RT.