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Circulating IL-6 as a predictor of radiation pneumonitis
1Department of Radiation Oncology, James P. Wilmot Cancer Center, University of Rochester, 601 Elmwood Ave., Box 647, Rochester, NY 14642, USA. ychen@radonc.medinfo.rochester.edu
Purpose:
We report results from a clinical research protocol investigating circulating pro-inflammatory cytokines (interleukin-6 [IL-6] and tumor necrosis factor alpha [TNFalpha]) 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 data. Serial plasma specimens before, during, and after thoracic radiotherapy were analyzed for IL-6 and TNFalpha using enzyme-linked immunosorbent assay (ELISA). Radiation pulmonary injury was defined using National Cancer Institute 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 pneumonitis was between 8 and 12 weeks post-therapy. IL-6 levels before, during, and after thoracic radiation therapy were significantly higher in those who developed pneumonitis. In contrast, we did not detect a significant correlation between plasma TNFalpha and radiation pneumonitis.
Conclusions:
High pretreatment plasma levels of IL-6 predisposed patients to the risk of radiation pneumonitis. Pretreatment IL-6 level may serve as a predictor for radiation pneumonitis. Serial plasma IL-6 was consistently higher for the pneumonitis group. The role of IL-6 in the cytokine cascades that promote radiation pulmonary injury deserves further investigation.