Showing papers on "Radiation-induced lung injury published in 1995"

A perpetual cascade of cytokines postirradiation leads to pulmonary fibrosis

Abstract: PURPOSE Radiation-induced pulmonary reactions have classically been viewed as distinct phases--acute pneumonitis and, later, fibrosis--occurring at different times after irradiation and attributed to different target cell populations. We prefer to view these events as a continuum, with no clear distinction between the temporal sequence of the different pulmonary reactions; the progression is the result of an early activation of an inflammatory reaction, leading to the expression and maintenance of a cytokine cascade. In the current study, we have examined the temporal and spatial expression of cytokine and extracellular matrix messenger ribonucleic acid (mRNA) abundance in fibrosis-sensitive mice after thoracic irradiation. METHODS AND MATERIALS Radiation fibrosis-prone (C57BL/6) mice received thoracic irradiation of 5 and 12.5 Gy. At Day 1, and 1, 2, 8, 16, and 24 weeks after treatment, animals were killed and lung tissue processed for light microscopy and isolation of RNA. Expression of cytokine and extracellular matrix mRNA abundance was evaluated by slot-blot analysis and cellular localization by in situ hybridization and immunochemistry. RESULTS One of the cytokines responsible for the inflammatory phase (IL-1 alpha) is elevated at 2 weeks, returns to normal baseline values, then increases at 8 weeks, remaining elevated until 26 weeks when lung fibrosis appears. Transforming growth factor-beta (TGF beta), a proliferative cytokine, is elevated at 2 weeks, persists until 8 weeks, and then returns to baseline values. In parallel with the cytokine cascade, the fibrogenic markers for CI/CIII/IV (collagen genes) correlate by showing a similar early and then later elevation of activity. For instance, the collagen gene expression of CI/CIII is a biphasic response with an initial increase at 1-2 weeks that remits at 8 weeks, remains inactive from 8 to 16 weeks, and then becomes elevated at 6 months when collagen deposition is recognized histopathologically. CONCLUSION These studies clearly demonstrate the early and persistent elevation of cytokine production following pulmonary irradiation. The temporal relationship between the elevation of specific cytokines and the histological and biochemical evidence of fibrosis serves to illustrate the continuum of response, which, we believe, underlies pulmonary radiation reactions and supports the concept of a perpetual cascade of cytokines produced immediately after irradiation, prompting collagen genes to turn on, and persisting until the expression of late effects becomes apparent pathologically and clinically.

Radiographic changes following radiotherapy in the patients with lung cancer. Is the irradiated area of the mediastinum in the simulation film a significant factor

Abstract: BACKGROUND Radiation induced lung injury is an ominous adverse reaction in the management of thoracic disease by radiation therapy. Although the importance of the area of irradiated lung is well known, the irradiated area of mediastinum is little to be considered in the routine treatment. PURPOSE To evaluate the significance of the irradiated area of the mediastinum in the simulation film for radiation induced lung injury. PATIENTS AND METHODS A total of 208 patients with primary lung cancer treated with radiation therapy were analyzed for incidence of radiation induced lung injury. Lung injury was defined as the appearance of an abnormal shadow on the chest radiograph. CT images were used to differentiate recurrence or other conditions. Age, sex, irradiation dose, irradiated lung area, T and N factors of the tumor, irradiated mediastinum area, performance status of patients, location of irradiated fields and use of chemotherapy were analyzed with Cox's multivariate regression model. RESULTS The cumulative rate of radiation induced lung injury at 12 months was 85%. Significant factor of radiation induced lung injury was irradiated area of the mediastinum (p = 0.03). Irradiated area of the lung (p = 0.18, n.s.), total tumor dose (p = 0.1, n.s.), use of chemotherapy (p = 0.08, n.s.) and location of irradiated field (p = 0.08, n.s.) may also have an effect on radiation induced lung injury. CONCLUSION The irradiated area of the mediastinum is one of the significant factors in radiation induced lung injury.