How Common is Lung Cancer?
Lung cancer is the most common type of cancer globally and the third most common cancer in the United States. The American Cancer Society estimates there will be about 238,000 new cases of lung cancer in 2023 alone. Most people diagnosed with lung cancer are at least 65 years old, with a minority of diagnoses happening in people younger than 45. Lung cancer is the leading cause of cancer deaths in the U.S., and it is estimated it will claim the lives of about 127,000 people in 2023. More people die from lung cancer than colon, breast, and prostate cancer combined.
The most common risk factor for lung cancer is smoking. Cigarette smoking is a contributor to about 80-90% of all lung cancer deaths. Tobacco smoke contains over 7,000 chemicals, of which at least 70 are known to cause cancer. Smokers are 15-30 times more likely to be diagnosed with lung cancer compared to non-smokers and secondhand smoke increases the risk as well. Fortunately, studies have shown that quitting smoking may reduce a person’s risk compared to someone who continually smokes. Other risk factors may include exposure to radon, radiation therapy, asbestos, diesel exhaust, and heavy metals such as arsenic and chromium, among others. A family history of lung cancer may also be a risk factor.
Different medical societies and organizations recommend screening for people who are high risk for lung cancer. The U.S. Preventive Services Task Force (USPSTF) recommends annual screening for lung cancer using low-dose computed tomography in adults age 50-80 years who have a history of smoking at least 20 packs per year within the last 15 years. These recommendations are in alignment with the National Comprehensive Cancer Network and the American Cancer Society.
Types of Lung Cancer
There are three main types of lung cancer. Non-Small Cell Lung Cancer (NSCLC) is the most common form of lung cancer, representing about 85% of all cases. This cancer type begins in the cells that are a part of the lining of the lungs. Small Cell Lung Cancer (SCLC) accounts for about 15-20% of lung cancer diagnoses. SCLC begins in the neuroendocrine cells which surround the bronchi of the lungs and may spread to other organ systems, which makes treatment challenging. Greater than half of all patients diagnosed with SCLC have advanced disease. Lung Carcinoid Tumors are the least common type of lung cancer, which also starts in neuroendocrine cells, but can be found in other organs besides the lungs.
Genetic Risk Factors for Lung Cancer
While rare, there are some variants in a few hereditary cancer genes that can increase the risk for lung cancer that can be passed on to offspring. BRCA2, CDKN2A, EGFR, FAM11B, and TP53 are a few such genes. These typically are inherited in an autosomal dominant manner, meaning only one variant in one of these genes may increase the risk for lung cancer. There is testing available for these and other lung cancer susceptibility genes. Usually, testing is performed on a patient’s blood, but other sample types have been validated, such as saliva or dried blood spots. Hereditary genetic testing for lung cancer (and other types of cancer) can have three possible results:
- Negative – no pathogenic variants identified.
- Positive – a known pathogenic variant is identified. Healthcare providers may make management decisions based on the positive result.
- Variant of Uncertain Significance (VUS) – these are genetic changes where there is not conclusive evidence for an increased risk for lung cancer. Unfortunately, a VUS may cause stress and anxiety for the patient and family since it is an uncertain result. VUS results should not change medical management. These results may be reclassified in the future as we learn more through medical research and published studies.
There is also tumor genetic testing for lung cancer, especially NSCLC. Variants in some genes are specific to the cancer tumor and are not passed to offspring, these are also known as somatic genetic variants. Variants in somatic genes such as ALK, EGFR, FGFR1, HER2, KRAS, MET, and ROS1, may impact a patient’s treatment. Therefore, cancer centers are starting to test for these and other genes more routinely. There are also clinical trials available for certain somatic genetic variants.
August 1st is World Lung Cancer Day and was first observed in 2012. The purpose of World Lung Cancer Day is to raise awareness of lung cancer and the need for increased funding for research, treatment, and patient support. Multiple groups observe and celebrate this day to have a positive impact including the Lung Cancer Foundation of America, American Lung Association, Lung Cancer Research Foundation, and other organizations. Together, the combined efforts of healthcare providers, researchers, patients, and advocates can reduce the prevalence and improve the treatments for lung cancer on a global scale.
References
Biernacka A, Tsongalis PD, Peterson JD, de Abreu FB, Black CC, Gutmann EJ, Liu X, Tafe LJ, Amos CI, Tsongalis GJ. The potential utility of re-mining results of somatic mutation testing: KRAS status in lung adenocarcinoma. Cancer Genet. 2016 May;209(5):195-8. PMID: 27068338.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5506544/
Eccles BK, Copson E, Maishman T, Abraham JE, Eccles DM. Understanding of BRCA VUS genetic results by breast cancer specialists. BMC Cancer. 2015 Nov 25;15:936. PMID: 26608569.
https://pubmed.ncbi.nlm.nih.gov/26608569/
Li MM, Datto M, Duncavage EJ, Kulkarni S, Lindeman NI, Roy S, Tsimberidou AM, Vnencak-Jones CL, Wolff DJ, Younes A, Nikiforova MN. Standards and Guidelines for the Interpretation and Reporting of Sequence Variants in Cancer: A Joint Consensus Recommendation of the Association for Molecular Pathology, American Society of Clinical Oncology, and College of American Pathologists. J Mol Diagn. 2017 Jan;19(1):4-23. PMID: 27993330.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5707196/
Nooreldeen R, Bach H. Current and Future Development in Lung Cancer Diagnosis. Int J Mol Sci. 2021 Aug 12;22(16):8661. PMID: 34445366.
https://pubmed.ncbi.nlm.nih.gov/34445366/
Schabath MB, Cote ML. Cancer Progress and Priorities: Lung Cancer. Cancer Epidemiol Biomarkers Prev. 2019 Oct;28(10):1563-1579. PMID: 31575553.
https://pubmed.ncbi.nlm.nih.gov/31575553/
Wood DE, Kazerooni EA, Aberle D, Berman A, Brown LM, Eapen GA, Ettinger DS, Ferguson JS, Hou L, Kadaria D, Klippenstein D, Kumar R, Lackner RP, Leard LE, Lennes IT, Leung ANC, Mazzone P, Merritt RE, Midthun DE, Onaitis M, Pipavath S, Pratt C, Puri V, Raz D, Reddy C, Reid ME, Sandler KL, Sands J, Schabath MB, Studts JL, Tanoue L, Tong BC, Travis WD, Wei B, Westover K, Yang SC, McCullough B, Hughes M. NCCN Guidelines® Insights: Lung Cancer Screening, Version 1.2022. J Natl Compr Canc Netw. 2022 Jul;20(7):754-764. PMID: 35830884.
https://pubmed.ncbi.nlm.nih.gov/35830884/
American Cancer Society
https://www.cancer.org/cancer/types/lung-cancer/about/key-statistics.html
American Lung Association
Blueprint Genetics
https://blueprintgenetics.com/tests/panels/hereditary-cancer/hereditary-lung-cancer-panel/
Centers for Disease Control and Prevention
https://www.cdc.gov/cancer/lung/statistics/index.htm
https://www.cdc.gov/cancer/lung/basic_info/risk_factors.htm
National Institutes of Health: National Library of Medicine, Clinical Trials
https://www.clinicaltrials.gov/search?cond=Cancer&term=Somatic%20Mutation
U.S. Preventive Services Task Force