Radiation pneumonitis is damage to the lung tissue that develops under the influence of high doses of ionizing radiation. It is manifested by shortness of breath, dry or productive cough, pleural pains, accompanied by an increase in body temperature. The diagnosis is made on the basis of anamnestic data and clinical symptoms, confirmed by the results of spirometry, X-ray examination, computed tomography and MRI of the chest organs. Treatment of pneumonitis is carried out with the help of pharmacotherapy with corticosteroid hormones, antibiotics, anticoagulants; oxygen therapy, physiotherapy.
ICD 10
J70.0 Acute pulmonary manifestations caused by radiation
Meaning
Radiation pneumonitis (radiation pulmonitis, radiation pneumonia) refers to local radiation lesions of the pulmonary parenchyma. Ionizing radiation damages a section of the alveolar tissue, hence the other name – radial alveolitis. Pronounced clinical manifestations occur in 15-60% of those receiving radiotherapy for lung and breast cancer. In 3-4% of cases, radiation pneumonitis becomes extremely severe and ends fatally. In some patients, it proceeds latently, characteristic changes are detected only by special research methods.
Causes of radiation pneumonitis
The trigger mechanism is the excess of a tolerant dose of radioactive exposure to lung tissue. With radiation therapy of oncological diseases of the thoracic cavity, breast cancer, the radiation dose is on average 70-80 Gy. The area of the lung with a maximum tolerance of 35-40 Gy falls into the focus of irradiation, as a result of which radiation lesions develop. The frequency of occurrence, the course of the pathological process directly depend on the value of the total focal dose. The following factors are of great importance:
The age of the patient. According to research in the field of oncology and pulmonology, patients over 70 years of age suffer from complications of radiotherapy 1.5 times more often than 40-60-year-olds. In children, the tolerance of respiratory organs to radiation exposure is 2.5 times lower than in adults.
Localization of the hearth. A direct dependence of the frequency of radiation-induced pulmonitis on the location of the focus on which the effect is performed has been established. The closer the focus of irradiation is to the mediastinum, the less often and later problems are detected. The peripheral areas of the lungs suffer more.
Complex and combined treatment. The combination of radiotherapy with surgical treatment and (or) chemotherapy increases the number of cases of radiation pneumonitis, provokes its early development, aggravates the course. Antitumor drugs can independently negatively affect the respiratory system, cause pneumopathy.
Pathogenesis
Ionizing radiation damages the cells of the alveolar endothelium. The surfactant production is disrupted, the alveoli subside. At the same time, the inner shell of the capillaries is affected, which leads to thrombosis, partial blockage and increased vascular permeability. Gas exchange suffers. Changes in the type of exudative alveolitis occur in the first days. Within 1-3 months, the damaged endothelium is partially restored, a number of vessels are recanalized. Fibroblasts are activated, dead cells are replaced by connective tissue.
Macroscopically, full-blooded areas of the pulmonary parenchyma of dense elastic consistency, fibrinous effusion in the pleural cavity are determined. Microscopic examination reveals thickening of the alveolar membrane, damage to the capillary network with signs of thrombosis, stasis and fullness. Fibrosis zones are formed in the area of the interalveolar septa.
Classification
Acute radiation pneumonitis is an early radiation damage to the respiratory organs. Occurs against the background of radiation or during the first three months after it. Stable changes detected at a later date are regarded as pneumofibrosis. American oncologists have developed a classification of the disease depending on the severity:
- I degree. Pain in the chest is absent or minimal. Cough is rare. Shortness of breath appears with significant physical exertion. A decrease in the vital capacity of the lungs (VEL) by 10-25% of the proper value is determined. There are indirect radiological signs of the disease.
- II degree. The patient is concerned about periodic tolerable thoracalgia, coughing attacks. When walking, there is a lack of air. The LEL is in the range of 50-75% of the normal value. Focal shadows are visible on the X-ray.
- III degree. The pain becomes intense, the cough is constant. Shortness of breath occurs at the slightest load. The LEL is 25-50% of the norm. The size of the infiltration in the image corresponds to the irradiated area.
- IV degree. Persistent pain syndrome, incessant cough require the appointment of narcotic analgesics. Breathing is difficult at rest. There is a significant (by more than 75%) decrease in LEL. Radiography reveals unilateral subtotal or total shading. The patient needs respiratory support.
Symptoms of radiation pneumonitis
The disease begins acutely. The leading symptom is a cough. Its intensity varies from rare coughing to constant painful attacks. Light mucous sputum can be separated, which, when a secondary infection is attached, becomes purulent yellow-green. Sometimes there is hemoptysis. Shortness of breath is caused by exertion, in severe cases it bothers when talking, at rest. Chest pain may be absent or appear sporadically; in the presence of fibrinous pleurisy, it becomes constant and intense. The temperature reaction ranges from persistent subfebrility to hyperthermia.
The classical clinical picture is sometimes preceded by a general radiation reaction. The patient becomes excessively irritable, complains of weakness, headache, dizziness, insomnia. Myocardiodystrophy develops, there are interruptions in cardiac activity. Disorders of the digestive tract are manifested by nausea, vomiting, diarrhea. Appetite sharply decreases, there is a perversion of taste, excessive saliva separation.
Complications
A small volume of radiation pneumonitis is often recognized untimely. It is found at the stage of pneumofibrosis with bronchiectasis, pleurodiaphragmatic adhesions, mediastinal displacement. Due to the massive sclerotic process, irreversible respiratory disorders occur. A chronic pulmonary heart is formed, the quality of life deteriorates significantly. With extensive changes, severe acute respiratory failure develops, requiring transfer to artificial ventilation of the lungs. A fatal outcome may occur.
Diagnostics
A clear connection of respiratory disorders with radiotherapy allows the pulmonologist to suspect radiation pneumonitis. When collecting anamnesis, the doses, number and duration of radiation sessions, combination with chemotherapy or surgery are specified. Particular attention is paid to the localization and size of the hearth. The presence of a general reaction should be taken into account. The main diagnostic measures include:
- Physical examination. The zones of dulling of percussion sound on the affected side are determined. Intermittent medium- and small-bubbly wheezes, pleural friction noise are heard auscultatively.
- Laboratory tests. Such manifestations of the radiation reaction as hematopoiesis inhibition, immune disorders are detected by laboratory methods. In a clinical blood test, there is a decrease in the level of leukocytes, platelets, and eosinophilia.
- Radiography and CT of the lungs. The X-ray shows an increase and deformation of the pulmonary pattern, foci of infiltration in the projection of the irradiation zone, pleural effusion. Unilateral lesion is a pathognomonic sign of the disease. CT allows you to identify earlier and more accurately determine the boundaries of the damage.
Additionally, a study of the gas composition of the blood and the function of external respiration is performed. In unclear cases, MRI is used to clarify the diagnosis. Radiation pneumonitis should be differentiated from metastatic infection, bacterial pneumonia, as well as tuberculosis and mycoses, which can be triggered by secondary immunodeficiency.
Treatment for radiation pneumonitis
When radiation pneumonia is confirmed, conservative therapy is prescribed. Pharmacological agents, physiotherapeutic methods, physical therapy are used. The main measures are aimed at reducing mortality, restoring respiratory functions of the body, minimizing the consequences. To achieve a therapeutic effect , the following groups of drugs are used comprehensively:
- Systemic corticosteroids. They are prescribed for the purpose of stimulating the production of surfactant. Reduce the inflammatory reaction of the lung, smooth out the symptoms. A positive response comes quickly, usually on 2-4 days. If the patient’s condition has not improved during this period of time, further use of corticoid hormones does not make sense.
- Anticoagulants. Prevent the formation of blood clots in the capillaries of the small circle of blood circulation. Reduce the risk of developing a deadly complication – pulmonary embolism.
- Antibiotics. They are used to treat bacterial complications in conditions of reduced immunity. They are prescribed taking into account the sensitivity of the sputum microflora to antibacterial agents. In the absence of data, preference is given to drugs with a wide spectrum of action.
Additionally, expectorants, angioprotectors, ascorbic acid are used. In acute respiratory failure, narcotic antitussive drugs and oxygen support are indicated. From physiotherapeutic methods, inhalations with dimexide, alternating magnetic fields are recommended. Massage and breathing exercises are widely used in the recovery period.
Prevention and prognosis
To prevent adverse reactions during radiation therapy, the patient is recommended a balanced calorie diet, walking in the fresh air. It is necessary to monitor blood counts, the general condition of the patient. If thrombopenia, leukopenia, hemoptysis appear, radiation therapy should be discontinued. A rational individual approach, the use of methods of shaped irradiation fields can significantly reduce the frequency of radiation-induced complications. In case of radical radiotherapy of lung cancer, simultaneous transfusion of irradiated autoflood and the use of enterosorbents are recommended for preventive purposes.
The prognosis is largely determined by the course of the underlying disease, the area of lung damage. Adequately treated small pulmonitis often undergo reverse development. The formation of fibrosis lasts from 6 months to 2 years, after which the changes are stable, and the disorders become irreversible. Rehabilitation measures can affect the process of fibrosis. Acute respiratory distress syndrome in some cases ends in death.
Literature
- Radiation pneumonitis and pulmonary fibrosis after the CT-planned radiotherapy of bronchial carcinoma. Müller G, Kiricuta IC, Stiess J, Bohndorf W. Strahlenther Onkol. 1994 Jul;170(7):400-7. link
- Radiation-induced lung injury: current evidence. Arroyo-Hernández M, Maldonado F, Lozano-Ruiz F, Muñoz-Montaño W, Nuñez-Baez M, Arrieta O.
BMC Pulm Med. 2021 Jan 6;21(1):9. link - Evaluation of dose-response models and parameters predicting radiation induced pneumonitis using clinical data from breast cancer radiotherapy. Tsougos I, Mavroidis P, Rajala J, Theodorou K, Järvenpää R, Pitkänen MA, Holli K, Ojala AT, Lind BK, Hyödynmaa S, Kappas C. Phys Med Biol. 2005 Aug 7;50(15):3535-54. link
- NTCP modelling and pulmonary function tests evaluation for the prediction of radiation induced pneumonitis in non-small-cell lung cancer radiotherapy. Tsougos I, Nilsson P, Theodorou K, Kjellén E, Ewers SB, Jarlman O, Lind BK, Kappas C, Mavroidis P. Phys Med Biol. 2007 Feb 21;52(4):1055-73. link
- Radiation and the lung: a reevaluation of the mechanisms mediating pulmonary injury. Morgan GW, Breit SN. Int J Radiat Oncol Biol Phys. 1995 Jan 15;31(2):361-9. link