INDICATORS OF FREE-RADICAL ACTIVITY IN PATIENTS DEVELOPING RADIATION PNEUMONITIS

Purpose: Radiation pneumonitis is thought to occur as the result of ex cess free radical generation following radiotherapy. Various in vitro studies have shown that large doses of irradiation can cause membrane lipid peroxidation and the oxidation of protein sulphuryl groups. We, therefore, studied two circulating markers of lipid peroxidation and a n indicator of ''catalytic iron'' (potentially available iron to catal yze the generation of free radicals) in patients undergoing radiothera py. Methods and Materials: The 9,11 diene conjugate of 9,12 linoleic a cid, expressed as their molar ratio (percentage molar ratio (MR)) and thiobarbituric acid reactive acid-substances (TEARS), as well as level s of circulating desferrioxamine-chelatable iron assay, were assayed. Serial blood samples were taken over a 3-month period in 25 patients w ith inoperable nonsmall cell lung cancer. Results: Ten patients develo ped radiation pneumonitis. The patients who developed pneumonitis show ed a tendency for the serum percentage molar ratio to increase after a week. The change in the percentage molar ratio between Time 0 and 1 w eek of radiotherapy was significantly higher in the group that subsequ ently developed pneumonitis compared to the group that did not (p = 0. 002). The initial serum TEARS levels in patients were not significantl y elevated compared to controls and there was no difference in the ser um TEARS levels in the pneumonitis and nonpneumonitis groups throughou t the study period. After 1 week of radiotherapy the group that subseq uently developed pneumonitis had a significantly higher level of desfe rrioxamine-chelatable iron (DFx-iron) compared with the nonpneumonitis group (p = 0.05). Conclusion: These data suggest that both the percen tage MR and DFx-iron appear to reflect an increased susceptibility to develop radiation pneumonitis and after 1 week of radiotherapy they in dicate patients who are likely to subsequently develop pneumonitis. He nce, these indicators could indicate the group of patients that could benefit from intervention therapies with antioxidants.