Circulating IL-6 as a predictor of radiation pneumonitis

Purpose: We report results from a clinical research protocol investigating circulating pro-inflammatory cytokines (interleukin-6 [IL-6] and tumor necr osis factor alpha [TNF alpha]) in relation to radiation pulmonary injury. Methods and Materials: In a protocol for cytokine measurement, 25 patients had clinical follow-up longer than 12 months, and 24 had serial cytokine da ta, Serial plasma specimens before, during, and after thoracic radiotherapy were analyzed for IL-6 and TNF alpha using enzyme-linked immunosorbent ass ay (ELISA), Radiation pulmonary injury was defined using National Cancer In stitute Common Toxicity Criteria. Results: Of the 24 patients, 6 had Grade 1 pneumonitis, and 13 had Grade 2 pneumonitis, There was no Grade 3/4 pneumonitis. Median time of radiation p neumonitis was between 8 and 12 weeks post-therapy. IL-6 levels before, dur ing. and after thoracic radiation therapy were significantly higher in thos e who developed pneumonitis, In contrast, we did not detect a significant c orrelation between plasma TNF alpha and radiation pneumonitis. Conclusions: High pretreatment plasma levels of IL-6 predisposed patients t o the risk of radiation pneumonitis. Pretreatment IL-6 level may serve as a predictor for radiation pneumonitis. Serial plasma IL-6 was consistently h igher for the pneumonitis group. The role of IL-6 in the cytokine cascades that promote radiation pulmonary injury deserves further investigation. (C) 2001 Elsevier Science Inc.