Radiation pneumonitis: a possible lymphocyte-mediated hypersensitivity reaction

Area of Science:

• Pulmonary Medicine
• Radiation Oncology
• Immunology

Background:

• Thoracic irradiation is a common treatment for various cancers.
• The effects of unilateral thoracic irradiation on lung tissue beyond the direct radiation field are not fully understood.
• Lymphocytic alveolitis is an inflammatory condition of the lung's air sacs.

Purpose of the Study:

• To investigate whether unilateral thoracic irradiation induces lymphoid alveolitis in both the irradiated and unirradiated lung fields.
• To assess the impact of radiotherapy on lung inflammation and function.

Main Methods:

• Prospective study of women undergoing postoperative radiotherapy for breast cancer.
• Evaluation included bronchoalveolar lavage, gallium lung scanning, and respiratory function tests before and after treatment.
• Comparison between asymptomatic patients and those with clinical radiation pneumonitis.

Main Results:

• Unilateral thoracic irradiation led to a significant increase in lavage lymphocytes in both lung fields.
• Patients with clinical pneumonitis showed a more pronounced increase in lymphocytes and gallium uptake.
• Respiratory function tests revealed a progressive reduction in vital capacity and diffusing capacity, particularly in patients with pneumonitis.

Conclusions:

• A lymphocytic alveolitis develops in both lung fields following unilateral thoracic irradiation.
• The inflammatory response is more pronounced in patients who develop clinical pneumonitis.
• These findings suggest that radiotherapy can induce a generalized, lymphocyte-mediated hypersensitivity reaction in the lungs.