Changes in plasma transforming growth factor beta during radiotherapy and the risk of symptomatic radiation-induced pneumonitis

Purpose : To determine whether changes in the plasma Transforming Growth Factor β1 (TGFβ1) concentration during radiotherapy could identify patients at risk for developing symptomatic radiation pneumonitis. Methods and Materials : Thirty-six patients who received radiation therapy with curative intent for lung cancer ( n = 31), Hodgkin's disease ( n = 4), or thymoma ( n = 1) were evaluated prospectively. All patients had serial plasma TGFβ1 measurements obtained before, during, and after treatment. Plasma TGFβ1 was quantified using an enzyme-linked immunosorbent assay. Pneumonitis were defined clinically. Plasma TGFβ1 levels were considered to have normalized if the following occurred: the last on-treatment TGFβ1 level was both 7.5 ng/ml at baseline n = 22). Failure of plasma TGFβ1 to normalize by the end of treatment, as defined above, much more accurately identified patients at risk for symptomatic pneumonitis if their baseline TGFβ1 was >7.5 ng/ml than if it was 7.5 ng/ml.