The single most important risk factor for the development of lung cancer is smoking. For smokers, the risk for lung cancer is on average tenfold higher than in lifetime nonsmokers (defined as a person who has smoked <100 cigarettes in his or her lifetime). The risk increases with the quantity of cigarettes, duration of smoking, and starting age.
Smoking cessation results in a decrease in precancerous lesions and a reduction in the risk of developing lung cancer. Former smokers continue to have an elevated risk for lung cancer for years after quitting. Asbestos exposure may exert a synergistic effect of cigarette smoking on the lung cancer risk.
A significant number of patients cured of their smoking-related lung cancer may develop a second malignancy. In the Lung Cancer Study Group trial of 907 patients with stage T1, N0 resected tumors, the rate was 1.8% per year for nonpulmonary second cancers and 1.6% per year for new lung cancers. Other studies have reported even higher risks of second tumors in long-term survivors, including rates of 10% for second lung cancers and 20% for all second cancers.
Because of the persistent risk of developing second lung cancers in former smokers, various chemoprevention strategies have been evaluated in randomized control trials. None of the phase III trials with the agents beta carotene, retinol, 13-cis-retinoic acid, [alpha]-tocopherol, N-acetylcysteine, or acetylsalicylic acid has demonstrated beneficial, reproducible results.[7,8,9,10,11][Level of evidence: 1iiA] Chemoprevention of second primary cancers of the upper aerodigestive tract is undergoing clinical evaluation in patients with early-stage lung cancer.
Refer to the PDQ summaries on Lung Cancer Prevention and Smoking in Cancer Care for more information.
In patients considered at high risk for developing lung cancer, the only screening modality for early detection that has been shown to alter mortality is low-dose helical CT scanning. Studies of lung cancer screening with chest radiography and sputum cytology have failed to demonstrate that screening lowers lung cancer mortality rates.
(Refer to the Screening by low-dose helical computed tomography subsection in the PDQ summary on Lung Cancer Screening for more information.)
Lung cancer may present with symptoms or be found incidentally on chest imaging. Symptoms and signs may result from the location of the primary local invasion or compression of adjacent thoracic structures, distant metastases, or paraneoplastic phenomena. The most common symptoms at presentation are worsening cough or chest pain. Other presenting symptoms include the following:
- Weight loss.
Symptoms may result from local invasion or compression of adjacent thoracic structures such as compression involving the esophagus causing dysphagia, compression involving the laryngeal nerves causing hoarseness, or compression involving the superior vena cava causing facial edema and distension of the superficial veins of the head and neck. Symptoms from distant metastases may also be present and include neurological defect or personality change from brain metastases or pain from bone metastases. Infrequently, patients may present with symptoms and signs of paraneoplastic diseases such as hypertrophic osteoarthropathy with digital clubbing or hypercalcemia from parathyroid hormone-related protein. Physical examination may identify enlarged supraclavicular lymphadenopathy, pleural effusion or lobar collapse, unresolved pneumonia, or signs of associated disease such as chronic obstructive pulmonary disease or pulmonary fibrosis.