Radiation Injury of the Lung: Experimental Studies, Observations After Radiotherapy and Total Body Irradiation Prior to Bone Marrow Transplantation

Caffeic acid phenethyl ester decreases acute pneumonitis after irradiation in vitro and in vivo

Background

Lung cancer is relatively resistant to radiation treatment and radiation pneumonitis is a major obstacle to increasing the radiation dose. We previously showed that Caffeic acid phenethyl ester (CAPE) induces apoptosis and increases radiosensitivity in lung cancer. To determine whether CAPE, an antioxidant and an inhibitor of NF-kappa B, could be a useful adjuvant agent for lung cancer treatment, we examine the effects of CAPE on irradiated normal lung tissue in this study.

Methods

We compared the effects of CAPE on cytotoxicity and intracellular oxidative stress in normal lung fibroblast and a lung cancer cell line. For in vivo analysis, whole thorax radiation (single dose 10 Gy and 20 Gy) was delivered to BALB/c male mice with or without CAPE pretreatment. NF- kappaB activation and the expression levels of acute inflammatory cytokines were evaluated in mice after irradiation.

Results

The in vitro studies showed that CAPE cause no significant cytotoxicity in normal lung as compared to lung cancer cells. This is probably due to the differential effect on the expression of NF-kappa B between normal and malignant lung cells. The results from in vivo study showed that CAPE treatment decreased the expression of inflammatory cytokines including IL-1 alpha and beta, IL-6, TNF-alpha and TGF- beta, after irradiation. Moreover, histological and immunochemical data revealed that CAPE decreased radiation- induced interstitial pneumonitis and TGF-beta expression.

Conclusion

This study suggests that CAPE decreases the cascade of inflammatory responses induced by thoracic irradiation without causing toxicity in normal lung tissue. This provides a rationale for combining CAPE and thoracic radiotherapy for lung cancer treatment in further clinical studies.

Target cells in radiation pneumopathy

Radiation pneumopathy is the reaction of the organ lung to radiation effects in various target cells. It starts as an exudative inflammation, with the clinical picture of interstitial pneumonia 6-12 weeks after irradiation, and proceeds to a productive chronic inflammation lasting several months and terminating, as other chronic inflammations do, in scar formation, called lung fibrosis. Lung fibrosis is the common end point after lung damage from a wide range of damaging agents. The pathogenetic process leading to the signs and symptoms of radiation pneumopathy is an integrated response of the complex organization of lung tissue. Clinical and pathologic data in patients do not support the hypothesis that the early inflammatory phase of radiation "pneumonitis" and late "radiation fibrosis" are independent pathogenetic processes in the same way as acute radiodermatitis and subcutaneous fibrosis are separate pathologic entities. The target cell population that initiates the pathogenetic process in the lung is not known, and it has been suggested that no single identifiable target exists. The entire process is the result of complex functional alterations in endothelial cells, pneumocytes, macrophages, and other resident and transient cells. No evidence has been found for a role of stem cell sterilization, for impaired transit cell proliferation, or for hypoplasia, which is the hallmark of other acute inflammatory normal tissue damage (i.e., in the mucosa). The radiobiologic concepts developed in cellular radiobiology are not adequate for the quantitative analysis of radiation pneumopathy. A new analytical framework based on structurally defined intercellular interaction by signaling molecules and their activation needs to be developed. This would not be only an abstract radiobiologic paradigm but would be the key to the development of potential therapeutic interventions in irradiated patients.

A descriptive study of pulmonary complications after postoperative radiation therapy in node-positive stage II breast cancer

This study was conducted to assess the frequencies of symptomatic pulmonary complications following adjuvant postoperative radiotherapy using different treatment techniques in patients with Stage II node-positive breast cancer. During 1991-1993, 177 patients were referred to the Radiotherapy Department of Stockholm Söder Hospital; 144 after modified radical mastectomy and 33 after partial mastectomy. The records of these patients were studied retrospectively for clinically diagnosed radiotherapy-induced lung complications 1-7 months after treatment. Thirty-three of 138 patients (24%) irradiated after modified radical mastectomy developed pulmonary complications and 20 (14%) of these were diagnosed as severe, i.e. needing medical treatment with corticosteroids. No statistically significant difference could be found between the different electron energies used for treating the chest wall and the frequency of respiratory side-effects. Eighteen of 33 patients completed the prescribed treatment after partial mastectomy. Nine of these 18 patients (50%) developed pulmonary complications and 4 (22%) developed severe reactions. Fifteen patients received alternative treatments. With the techniques used after partial mastectomy the median central lung distance was 32 mm among the patients who experienced respiratory side-effects compared with 25 mm among the patients who were not affected (p = 0.03). This study identifies acute/subacute pulmonary side-effects as a clinically significant problem. Prospective follow-up with lung function tests, identification of risk factors, and individual lung dose volume histograms is warranted to assess the long-term implications.

[Pneumonitis after radiotherapy of bronchial carcinoma: incidence and influencing factors]

BACKGROUND

The most important side effect in radiotherapy of lung cancer is pneumonitis. The incidence of pneumonitis was evaluated in a retrospective study in the patient collective of the University of Heidelberg. Therapy related and therapy independent factors have been evaluated.

PATIENTS AND METHODS

In 348 of 392 cases with lung cancer who were treated by local irradiation between January 1989 and January 1992 the patient's records were evaluable for response and toxicity. All patients were treated by megavolt equipment with a conventional fractionation in most cases. Standard target volumes were irradiated including the lymphatic drainage. From a dose of above 30 Gy a technique sparing the spinal cord was chosen. Retrospectively pneumonitis was classified into 4 grades starting from slight symptoms to respiratory insufficiency requiring O2. Grade I and II were summarized to slight, grade III and IV to severe pneumonitis.

RESULTS

Regarding the treatment prior to irradiation patients with primary irradiation were affected in 26.5% (17% slight, 9.5% severe), with postoperative irradiation in 14% (9.3% slight, 4.7% severe), with radiochemotherapy of small cell lung cancer (SCLC) in 15.4% (12% slight, 3.4% severe) by this side effect. These differences were not significant (p = 0.32). The median onset of pneumonitis was 31 days after end of irradiation (severe 23 days, slight 44 days, p = 0.026). By a univariate analysis the total dose at the prescription point was the most important factor (30 to 50.5 Gy 11%, 52 to 59 Gy 15%, 60 to 74 Gy 26%, p = 0.007). High single doses (2.5 Gy) were only applied within a study of radiochemotherapy with a randomised sequential and alternating schedule. So that the increased rate of pneumonitis (42%) is not clearly separable from other influencing variables. A correlation between the applied techniques and the irradiated volume (measured by planimetric methods) was not demonstrable. Regarding the independent factors a high age, female sex and a low FeV1 were unfavourable. However, age and sex corrected FeV1 was not predictive.

CONCLUSIONS

The observed incidence is within the range of literature. By a clinical point of view the total dose is an obvious factor. Also single doses above 2 Gy have to be seen critically (a total dose of 50 Gy). The results confirm the fact that patients with a low FeV1 are not suitable to a high dose irradiation of the chest. In this connection old patients and women also should be seen as patients at risk.