According to "Harrison's Principles of Internal Medicine," lung cancer causes more deaths than any other type of cancer in the United States. The mortality rate five years after diagnosis is close to 90 percent. According to the Centers of Disease Control and Prevention, close to 200,000 people were diagnosed with lung cancer in 2006. Symptoms arise from local growth, from metastases and from hormones produced by the tumors.
Symptoms Caused by Local Growth
The first symptoms of lung cancer are often shortness of breath, wheezing or bloody sputum. The tumor can block the esophagus, causing difficulty swallowing. Growth into the heart can cause heart failure. Compression of nerves can lead to various symptoms, depending on the nerve affected. Symptoms can include hoarseness, drooping of the eyelid on one side, shoulder pain and paralysis of the diaphragm. Superior Vena Cava syndrome, caused by blockage of one of the two main veins that return blood to the heart, leads to severe shortness of breath, swelling of the face, upper body and arms. Tumors can lead to accumulation of fluid in the chest and destruction of ribs.
Metastatic Disease
Lung cancer can metastasize to the brain, causing headaches, vomiting and neurological problems that depend on the location of the tumors. Metastases to the bones lead to pain and fractures. If the bone marrow is invaded, blood cell production is reduced. Liver metastases cause hepatic dysfunction, pain and loss of appetite. Metastases to the spinal cord can cause spinal cord compression, with paralysis and loss of sensation.
Paraneoplastic Syndromes
Paraneoplastic syndromes refer to effects of the tumor on the entire body that are not caused by direct presence of the tumor, but rather by secretion of various substances or by the body's reaction to the tumor. Fever, weight loss and loss of appetite are common, though according to "Harrison's Principles of Internal Medicine," their cause is unknown. Lung tumors can secrete parathyroid hormone, which causes an elevation of blood calcium and osteoporosis. Secretion of antidiuretic hormone by lung tumors causes low blood sodium, which can lead to confusion, seizures and coma. Production of adrenocorticotrophic hormone, or ACTH, can cause low blood potassium, which can cause fatal arrhythmias.
References
- Centers for Disease Control and Prevention: Lung Cancer
- National Cancer Institute: Cancer Topics
- "Harrison's Principles of Internal Medicine, 17th Edition"; Antoni Fauci (ed.); 2008
