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Pulmonary disease during cancer therapy
KEY POINTS
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Pulmonary complications in patients with cancer may involve any intrathoracic structures
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Differential diagnosis of parenchymal infiltrates in patients with cancer includes infection, inflammation, neoplastic involvement, and other miscellaneous diagnoses (e.g., pulmonary edema).
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Clinical presentation of drug-induced pneumonitis ranges from asymptomatic infiltrates to hypoxemic respiratory failure
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Drug-induced pneumonitis is a diagnosis of exclusion; its work-up includes laboratory and imaging studies with bronchoscopy reserved for cases when infectious, neoplastic, and miscellaneous (e.g., heart failure) causes cannot otherwise be excluded
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Treatment of drug-induced pneumonitis involves temporary or permanent discontinuation of the presumed offending agent and initiation of corticosteroids if there are significant symptoms or pulmonary functional impairment (e.g., reduced vital or diffusing capacity)
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Lung injury is an important dose-limiting factor in chest radiation therapy
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Radiation pneumonitis generally occurs one to six months following completion of therapy and may be asymptomatic or present with dyspnea, hypoxemia or, rarely, respiratory failure
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Radiographic findings typically progress from ground glass opacities to patchy consolidation to fibrosis and volume loss, and usually develop within the field of radiation
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Treatment of radiation pneumonitis with steroids is indicated in the presence of symptoms, hypoxemia, or significant pulmonary function abnormalities
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Organizing pneumonia is a rare complication of radiation therapy described predominantly after breast radiation. Radiographic opacities occur outside the radiation field and may be migratory. This process usually responds to steroids, but a prolonged taper may be required
Overview of pulmonary complications of cancer therapy and their evaluation
Pulmonary complications in patients who have cancer may involve any intrathoracic structures, including the airways, lung parenchyma, pulmonary vasculature, and pleura. They may be caused by a direct neoplastic involvement or result from the untoward effects of cancer therapy. Owing to the sheer breadth of the differential diagnosis, it is helpful to categorize pulmonary conditions afflicting these patients. For example, a quartet of infection , inflammation , malignancy, and miscellaneous causes provides a useful frame of reference.
Many patients present with symptoms such as dyspnea and cough (with or without hemoptysis), sometimes in conjunction with fever or hypoxemia. Physical examination may reveal tachypnea, crackles, or wheezes. Often, however, a respiratory disorder will come to light incidentally, as a result of routine body imaging revealing an abnormality, such as nodule(s), ground glass opacities, or consolidations. Whether demonstrating an incidental finding or obtained as part of a diagnostic evaluation, cross-sectional chest imaging plays a key role in developing a differential diagnosis. Pulmonary function testing can identify and stage the severity of an obstructive or restrictive ventilatory deficit as well as diffusion impairment and is particularly useful to monitor response to therapy. Cardiac evaluation with an electrocardiogram (ECG), transthoracic echocardiogram, and/or serum levels of (Pro-)brain natriuretic peptide is often required to identify or rule out a cardiac condition (e.g., congestive heart failure) as the cause of respiratory symptoms and imaging abnormalities. Noninvasive microbiologic investigation is an integral component of evaluation. Specific tests depend on the clinical suspicion and the level of immunodeficiency. They may include a respiratory viral polymerase chain reaction panel, sputum (induced if necessary), and blood culture for bacterial pathogens and serum procalcitonin, urinary streptococcal and legionella antigens, serum beta-D-glucan, aspergillus galactomannan, cytomegalovirus DNA, and others.
More invasive testing may become necessary if the above investigations do not result in a diagnosis. Thoracentesis is usually performed to elucidate the etiology of a pleural effusion that may be transudative (often from heart failure, renal failure, or fluid overload) or exudative (e.g., malignant, parapneumonic). Bronchoscopy with bronchoalveolar lavage and, when safe, transbronchial biopsies are useful primarily to identify pathogens or neoplastic lung disease. When malignancy, infection, and heart failure are excluded as the causes of abnormal chest imaging, drug (or radiation) induced lung injury is usually presumed. It is, in other words, a diagnosis of exclusion.
Pulmonary toxicity associated with antineoplastic agents
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