Plasma transforming growth factor β₁ as a predictor of radiation pneumonitis

Purpose: To investigate prospectively the utility of plasma transforming growth factor β1 (TGFβ1) as a marker for the development of symptomatic radiation pneumonitis. Materials and Methods: Seventy-three patients with lung cancer treated with curative intent are reported herein. Plasma TGFβ1 samples were obtained before, weekly during, and at each follow-up after radiation therapy (RT). TGFβ1 was extracted using an acid/ethanol method. An enzyme-linked immunosorbent assay was used to quantify plasma TGFβ1 concentrations. The TGFβ1 level at the end of RT was considered 'normal', if it was both ≤ 7.5 ng/ml and less than the pretreatment value. All patients were followed for at least 6 months, unless symptomatic pneumonitis developed sooner. Pneumonitis was defined by National Cancer Institute (NCI) common toxicity criteria. Results: Fifteen of the 73 patients (21%) developed symptomatic pneumonitis and the remaining 58 (79%) did not. A normal plasma TGFβ1 by the end of RT, as defined above, was more common in patients who did not develop pneumonitis. A return of the plasma TGFβ1 to normal accurately identified patients who would not develop pneumonitis with both a sensitivity and positive predictive value of 90%. Conclusion: Plasma TGFβ1 levels appear to be a useful means to identify patients at low risk for the development of pneumonitis from thoracic RT. Thus, monitoring of plasma TGFβ1 levels may identify candidates for dose escalation studies in the treatment of lung cancer.