Radiation pneumonitis

Introduction to radiation pneumonitis Radiation pneumonitis is an inflammatory reaction caused by damage to normal lung tissue in the radiation field after radiotherapy in lung cancer, breast cancer, esophageal cancer, malignant lymphoma or other malignant tumors of the chest. Mild asymptomatic, inflammation can dissipate on its own; severe lungs undergo extensive fibrosis, leading to respiratory damage, resulting in respiratory failure. basic knowledge The proportion of illness: 0.003% Susceptible people: no special people Mode of infection: non-infectious Complications: bronchial pneumonia emphysema

Cause of radiation pneumonitis

(1) Causes of the disease

The incidence of radiation pneumonitis, the severity of lung injury is closely related to the radiation area, the amount of radiation, the rate of radiation and the method of radiation. Generally, the radiation dose threshold is safe at 25 Gy for 5 weeks, and the radiation dose is 6 In the week, 20Gy rarely produces radiation pneumonitis. In the same time, the dose exceeds 40Gy, the incidence of radiation pneumonitis reaches 100%, and the radiation dose exceeds 60Gy, which can cause severe lung injury. The larger the radiation, the higher the incidence, the lung injury. The more serious, the lung tissue damage caused by large-area irradiation treatment at the same large dose is far more serious than the local lung irradiation. The faster the irradiation speed, the more likely the lung injury is caused. Other influencing factors such as the sensitivity of the individual to radiation, the lungs The original diseases such as pneumonia, chronic bronchitis, emphysema, interstitial lung disease, etc. or the second radioactive exposure are all likely to promote the occurrence of radiation pneumonitis, radiotherapy for thyroid cancer and throat tumors, including frequent CT examinations. Can cause lung damage, produce radiation pneumonitis, poor tolerance of radiotherapy for the elderly and children, drugs used in chemotherapy (such as BLM) induced pulmonary toxicity may increase radiation-induced lung damage.

(two) pathogenesis

The pathological changes of radiation pneumonitis can be divided into acute radiation inflammatory changes and chronic fibrotic lesions. Acute inflammatory changes occur mostly 1 to 2 months after radiation therapy, and can also occur 6 months after the end of radiation therapy. Vascular, arteriole congestion, dilatation and embolism, increased vascular permeability, swelling of alveolar cells, increased type II alveolar cells and alveolar macrophages, lymphatic vessel expansion and formation of clear membranes in the alveoli, lymphocytic infiltration in the alveolar wall, acute Self-dissipation, connective tissue hyperplasia and fibrosis, lung tissue changes in the chronic phase are extensive alveolar fibrosis, alveolar septal thickening, alveolar atrophy, thickening of the vascular wall, hyaline degeneration and sclerosis, stenosis or obstruction of the lumen Reduced gas exchange function and increased pulmonary artery pressure, if secondary lung infection can promote radiation pulmonary fibrosis, is also an important cause of death.

Radioactive pneumonia prevention

The key to the prevention and treatment of radiation pneumonitis lies in the following three points: Prevention and Prevention:

(1) Strict control of radiation dose: It is generally safe to use a conventional dose of 2500 rad in 5 weeks.

(2) Control the radiation field, the larger the radiation field, the higher the incidence rate.

(3) Select an appropriate irradiation rate, preferably 800-1000 rad per week. Once the disease is found, treatment should be started as soon as possible to block the progression of the disease. If extensive pulmonary fibrosis has occurred, the prognosis is poor.

Radioactive pneumonia complications Complications, bronchopneumonia, emphysema

Complicated with bronchial pneumonia, emphysema and right heart failure. Bacterial pneumococcal pneumonia (ie pneumococci), Staphylococcus aureus, hemolytic streptococcus, Klebsiella pneumoniae, Haemophilus influenzae, Pseudomonas aeruginosa, Escherichia coli, Pseudomonas aeruginosa, etc. . Viral pneumonia such as coronavirus, adenovirus, influenza virus, cytomegalovirus, herpes simplex virus infection, etc.

Symptoms of radiation pneumonitis Common symptoms Pulmonary fibrosis Dry cough Low heat High fever Chest pain

Mild asymptomatic, irritating cough can occur immediately after radiation therapy, most of the symptoms appear after 2 to 3 months of radiation therapy, and some patients have irritating dry cough after half a year of radiation therapy, exacerbated after activity, accompanied by shortness of breath, palpitations And chest pain, no fever or low fever, occasionally high fever, body temperature up to 40 ° C, radiation damage caused by rib fractures, local pain, radiation esophagitis can produce dysphagia, with pulmonary fibrosis gradually dyspnea, prone to respiratory infections Increase the symptoms and cause cyanosis.

Physical examination revealed that the skin on the chest was atrophied and hardened. Most of the lungs had no positive signs. When the fibrosis was extensive in the lungs, it was sitting and breathing. The breath sounds were generally weakened, and crepitant rales or crackles could be heard. Secondary bacterial infection can occur dry, wet sputum, occasional pleural friction sound, accompanied by pulmonary heart disease can occur jugular vein filling, liver and tenderness, systemic edema and other right heart failure.

Due to radiation pneumonitis and pulmonary fibrosis, lung compliance decreased, lung capacity, total lung volume, residual air volume, forced expiratory volume in the first second, showed restrictive ventilation disorder, decreased ventilation/blood flow ratio, and gas diffusion disorder, resulting in Hypoxemia, pulmonary function tests can detect the disease early, often earlier than chest radiographs.

Radioactive pneumonia

Laboratory tests may have mild leukopenia, erythrocyte sedimentation rate, and arterial oxygen partial pressure lower than normal.

Most of the X-ray findings appear after 1 to 3 months of cessation of radiation therapy. The lungs have abnormal manifestations. The acute phase appears in the lung field and is flaky or fused into large pieces. The dense blurred shadows show a frosted glass-like appearance. The reticular shadow is faintly visible, similar to bronchial pneumonia or pulmonary edema. Pulmonary fibrosis occurs in the chronic phase, which is a reticular, strip-like or mass-like contraction shadow, mainly distributed on the hilar or mediastinum and other radiation lung fields. Due to lung fiber contraction, trachea, heart shift to the disease side, ipsilateral aponeurosis, normal lung tissue produces compensatory emphysema, pulmonary hypertension occurs, the right lower lung artery transverse diameter thickening, pulmonary artery segment Prominence or right heart hypertrophy, often accompanied by pleural effusion sign, occasionally spontaneous pneumothorax.

Pulmonary function changes: pulmonary radiation pneumonitis and fibrosis cause restrictive ventilatory dysfunction, decreased lung compliance, decreased ventilation/blood flow ratio, and reduced diffuse function, resulting in hypoxia, sometimes no abnormalities in chest radiographs, and pulmonary function tests The change has been shown.

Diagnostic identification of radiation pneumonitis

diagnosis

According to the history of radiation therapy, dry cough, progressive shortness of breath and chest X-ray with inflammation or fibrotic changes can make a diagnosis.

Differential diagnosis

Acute radiation pneumonitis should be differentiated from the following diseases. The main point is to combine the etiology, medical history, clinical manifestations, and multiple examinations.

1. Non-radioactive pneumonia: including pneumonia mycoplasma pneumonia, pneumococcal pneumonia, staphylococcal pneumonia, Klebsiella pneumoniae and some anticancer drugs such as bleomycin and other drug-induced interstitial pneumonia.

2, tuberculosis.

3, lung tumors: including primary bronchogenic carcinoma and lung metastatic tumors.

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