A cough is a natural reflex that expels air from the lungs, clearing irritants from the throat and airways. This reflex serves as a protective mechanism, helping the body remove foreign particles, fluids, or microbes. While occasional coughing is normal, a persistent cough can signal an underlying medical issue. For individuals with cancer, coughing can be a particularly distressing and common symptom, indicating various factors related to their disease or its treatment. Understanding the diverse causes of coughing in cancer patients is important for effective management and improving their overall comfort.
How Cancer Directly Causes Coughing
Cancer itself can directly trigger a cough through several mechanisms, particularly when the disease affects the lungs or nearby structures. Primary lung tumors, for instance, can irritate the airways or obstruct them, leading to a persistent cough. This irritation stems from the stimulation of cough receptors, which are abundant in the airways.
When cancer spreads from other parts of the body to the lungs, a process known as metastasis, it can also induce a cough. These metastatic tumors can cause inflammation or directly interfere with lung function, manifesting as a new or worsening cough. Approximately 65% of individuals with advanced lung cancer experience a chronic cough by the time of diagnosis. Tumors located in the mediastinum, the central chest area, can also cause coughing by pressing on the airways or nerves, triggering the cough reflex.
Coughing as a Side Effect of Cancer Treatments
Various cancer therapies can lead to a cough as a side effect, often due to their impact on lung tissue. Chemotherapy, for example, can induce a cough, which may be dry or associated with lung inflammation. Certain chemotherapy drugs can cause lung injury, leading to symptoms like cough and shortness of breath.
Radiation therapy directed at the chest is another common cause of cough in cancer patients, frequently resulting in radiation pneumonitis. This inflammatory lung condition arises from damage to lung tissue caused by radiation, typically appearing 4 to 12 weeks after treatment completion. Radiation pneumonitis often presents as a dry cough, along with shortness of breath and chest discomfort. Targeted therapies and immunotherapies can also cause inflammatory lung reactions, known as pneumonitis. These drug-induced pneumonitis cases can manifest as a cough.
Other Medical Conditions Contributing to Cough in Cancer Patients
Beyond the direct effects of cancer or its treatments, other medical conditions commonly affect cancer patients and can contribute to a cough. Infections are a frequent cause, as cancer patients often have weakened immune systems. Respiratory infections such as pneumonia, bronchitis, or viral infections are common in this group, leading to cough, fever, and breathing difficulties.
Fluid accumulation around the lungs (pleural effusion) can also cause a cough in cancer patients. This occurs when excess fluid builds up between the layers covering the lungs, leading to pressure and irritation that triggers coughing and breathlessness. Pulmonary embolism, a condition where blood clots travel to the lungs, is another potential cause of cough. Cancer patients have an increased risk of developing blood clots, and a pulmonary embolism can cause sudden shortness of breath, chest pain, and sometimes a cough.
Gastroesophageal reflux disease (GERD) can irritate the airways and lead to a chronic cough. Heart conditions, such as congestive heart failure, can also cause a cough in cancer patients. Heart failure can lead to fluid buildup in the lungs (pulmonary edema), which the body attempts to clear by coughing, often producing a wet cough with foamy or pink-tinged mucus.