Overview
Lung cancer
Lung cancer is a malignant tumor of the lung originating from the respiratory epithelium of the bronchi, bronchioles, and alveoli.
Epidemiology
- Lung cancer is the leading cause of cancer-related death in the United States.
- 90% of cases are fatal.
- 5-year survival in approximately 18% of cases (even with advances in treatment)
- Annual deaths:
- 160,000 in the United States
- 1.6 million worldwide
- 230,000 new cases are reported annually in the United States.
- Accounts for 13% of all cancer cases
- Incidence increases with age:
- Rare under the age of 50 years
- Incidence peaks at ages 75–79 years.
- 85%‒90% of lung cancer cases are attributed to smoking.
Risk factors
- Smoking (most common):
- Increased risk related to the number of cigarettes smoked, in pack-years (py) (py = number of cigarettes smoked daily x number of years smoked) / 20.
- Smoking at a lower intensity for a long time: more likely to develop lung cancer than smoking at a higher intensity for a shorter time
- The association with electronic cigarettes is not yet clear.
- Environmental exposures:
- 2nd-hand smoke
- Air pollution
- Asbestos
- Radon
- Chromium
- Nickel
- Arsenic
- Polycyclic aromatic hydrocarbons
- Radiation treatment
- Lung disease:
- Idiopathic pulmonary fibrosis
- Alpha-1 antitrypsin deficiency
- Chronic obstructive pulmonary disease (COPD)
- Human immunodeficiency virus (HIV) infection
- Family history
- Alcohol consumption
Risk factor reduction
Smoking cessation reduces the risk of lung cancer.
- Most important factor
- The greatest benefit is seen in those who quit by age 30.
- 39% lower risk 5 years after quitting (after a median history of 21 py)
- 41% of the lung cancers in former smokers occur 15 years after quitting.
- Dietary changes may be of benefit (not well established).
- Quitting smoking also lowers the risk for other diseases/conditions (such as other cancers, atherosclerosis, and chronic obstructive pulmonary disease).
Screening Rationale
Benefits of screening
- Goal is to detect early disease, which is:
- More amenable to treatment
- Associated with better prognosis
- Several studies also show a favorable association with smoking cessation.
Risks of screening
- High false-positive rate
- Most abnormalities detected are benign nodules.
- Leads to unnecessary biopsy or surgery
- Increased radiation exposure
- Overdiagnosis:
- Detection of cancers that would not have affected morbidity or mortality for the patient
- Leads to unnecessary aggressive management
- Mental distress
Screening Recommendation
- Annual low-dose computed tomography (LDCT)
- Patient selection based on organization recommendations:
- The United States Preventive Services Task Force (USPSTF) 2020 recommends lung cancer screening for (must meet all criteria):
- Adults aged 50‒80 years
- Those with a 20-py smoking history
- Current smoker or has quit within the past 15 years
- The American Cancer Society recommends screening for (must meet all criteria):
- Adults aged 55‒74 years
- 30-py smoking history
- Current smoker or quit within the past 15 years
- Other organizations have similar recommendations, although the age range varies.
- The United States Preventive Services Task Force (USPSTF) 2020 recommends lung cancer screening for (must meet all criteria):
- All patients in a screening program should receive smoking-cessation interventions.
- Screening can be discontinued if the patient:
- Has not smoked for 15 years
- Develops a health condition that will limit life expectancy
- Is unable or unwilling to have curative lung surgery
Strategies for Screening
Low-dose computed tomography
- Demonstrated reduction in mortality in the National Lung Screening Trial (NLST):
- 20% reduction in lung cancer mortality
- 6.7% reduction in all-cause mortality
- LDCT produces high-resolution images with less radiation.
- Abnormal findings should be followed up with diagnostic computed tomography (CT).
- Lung CT screening reporting and data system (Lung-RADS®)
- Standardized-result reporting system
- Designed to minimize the false-positive rate
| Category | Assessment | Follow-up |
|---|---|---|
| 0 | Incomplete | Awaiting prior CT images or images were technically inadequate |
| 1 | Negative (no lung nodules) | Continue normal annual screening. |
| 2 | Benign-appearing nodule(s) | Continue normal screening. |
| 3 | Probably benign nodule(s) | Repeat LDCT in 6 months. |
| 4 | Suspicious | Varies and includes short-term follow-up LDCT, diagnostic CT, positron emission tomography, biopsy, or surgery |
Low-dose CT screening image (left) and follow-up diagnostic CT image (right) for a patient diagnosed with adenocarcinoma
Image: “Low-dose CT scan screening for lung cancer: comparison of images and radiation doses between low-dose CT and follow-up standard diagnostic CT” by Ono K, Hiraoka T, Ono A, Komatsu E, Shigenaga T, Takaki H, Maeda T, Ogusu H, Yoshida S, Fukushima K, Kai M. License: CC BY 2.0
Low-dose CT screening (left) and follow-up diagnostic CT image (right) for a patient diagnosed with bronchoalveolar carcinoma
Image: “Low-dose CT scan screening for lung cancer: comparison of images and radiation doses between low-dose CT and follow-up standard diagnostic CT” by Ono K, Hiraoka T, Ono A, Komatsu E, Shigenaga T, Takaki H, Maeda T, Ogusu H, Yoshida S, Fukushima K, Kai M. License: CC BY 2.0
Chest radiograph
- Previously used in combination with sputum cytology
- Did not provide a mortality benefit
- No longer recommended
References
- Deffebach, M.E., and Humphrey, L. (2020). Screening for lung cancer. UpToDate. Retrieved December 15, 2020, from https://www.uptodate.com/contents/screening-for-lung-cancer
- Midthun, David E., MD (2020). Clinical manifestations of lung cancer. UpToDate. Retrieved December 15, 2020, from https://www.uptodate.com/contents/overview-of-the-risk-factors-pathology-and-clinical-manifestations-of-lung-cancer
- McKee, B.J. (2019). Lung-RADS standardized reporting for low-dose computed tomography for lung cancer screening. UpToDate. Retrieved December 15, 2020, from https://www.uptodate.com/contents/lung-rads-standardized-reporting-for-low-dose-computed-tomography-for-lung-cancer-screening
- Keith, R.L. (2020). Lung carcinoma. MSD Manual Professional Version. https://www.msdmanuals.com/professional/pulmonary-disorders/tumors-of-the-lungs/lung-carcinoma
- U.S. Preventive Services Task Force. (2020). Screening for lung cancer: U.S. Preventive Services Task Force draft recommendation statement. https://www.uspreventiveservicestaskforce.org/uspstf/draft-recommendation/lung-cancer-screening1
- Siddiqui, F., and Siddiqui, A.H. (2020). Lung cancer. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK482357/
- Tindle, H. A., Stevenson Duncan, M., Greevy, R. A., Vasan, R. S., Kundu, S., Massion, P. P., & Freiberg, M. S. (2018). Lifetime smoking history and risk of lung cancer: Results from the framingham heart study. JNCI: Journal of the National Cancer Institute, 110(11), 1201–1207. https://doi.org/10.1093/jnci/djy041
- Markaki, M., Tsamardinos, I., Langhammer, A. et al. (2018). A Validated Clinical Risk Prediction Model for Lung Cancer in Smokers of All Ages and Exposure Types: A HUNT Study. / EBioMedicine, 31(2018), 36–46. https://www.thelancet.com/action/showPdf?pii=S2352-3964%2818%2930114-2
- Pleasants, R.A, Rivera, M.P., Tilley, S.L., Bhatt, S.P. (2020). Both Duration and Pack-Years of Tobacco Smoking Should Be Used for Clinical Practice and Research. Annals of the American Thoracic Society, 17(7), 804–806. https://doi.org/10.1513/AnnalsATS.202002-133VP
- ELF. Lung cancer. Retrieved December 15, 2020, from https://www.europeanlung.org/en/projects-and-research/projects/smokehaz/lung-conditions/home/adults/lung-cancer/active-smoking/detailed-findings-and-data
- CDC. (2020). Smoking and Cancer. https://www.cdc.gov/tobacco/campaign/tips/diseases/cancer.html
- Kumar, V., Abbas, A. K., Aster, J.C., (Eds.) (2020). Effects of Tobacco. Robbins & Cotran Pathologic Basis of Disease. (10 ed. pp. 415–418).
