The Relationship between Cancer and Smoking

The 1982 United States Surgeon General's report stated that "Cigarette smoking is the major single cause of cancer mortality in the United States." (1) This statement is as true today as it was then. Tobacco smoke contains over 4,000 chemical compounds. More than 60 of these are known or suspected to cause cancer. For example, about 90,000 men die of lung cancer each year in the U.S. About 78,700 lung cancer deaths among men are caused by smoking. This means that the smoking causes about 90% of lung cancer deaths among men (2). Statistics also shows that 80% of all lung cancer deaths in women are caused by smoking (2).
Lung cancer is not the only type of cancer that is linked with smoking. Cigarette smoking accounts for at least 30% of all cancer deaths. It is linked with an increased risk of the following cancers: lung, larynx (voice box), oral cavity (mouth, tongue, and lips), pharynx (throat), esophagus (tube connecting the throat to the stomach), stomach, pancreas, cervix, kidney, bladder, acute myeloid leukemia (3).
The effect of smoking on each type of cancer is different. For example, smoking greatly increases the risk of getting and of dying from cancers of the lungs and larynx (voice box). It has a smaller effect on cancer of the cervix.
Lung cancer is the leading cause of cancer death in both men and women, and is one of the hardest cancers to treat. It claims more than 150,000 lives each year (3). Smoking is responsible for almost 9 out of 10 lung cancer deaths. It increases the risk of getting lung cancer by the factors of 23 and 12 in men and women respectively (2). Lung cancer kills more people than cancers of the breast, prostate, colon and pancreas combined. There are tens of millions of current, former and secondhand smokers in the United States, all of whom are at high risk for lung cancer (3).
Former smoker or ex-smoker means someone who has smoked more than 100 cigarettes over his or her lifetime but does not now smoke every day or some days (2). Even decades after quit¬ting, the risk of lung cancer in former smokers is increased by the factors of 9 and 5 in men and women respectively (2). It has been shown that the risk of lung cancer in ex-smokers never returns to the rate seen in persons who have never smoked.
Even if a person never smoked he or she might have been exposed to secondhand smoke. It is a mixture of 2 forms of smoke that come from burning tobacco: sidestream smoke (smoke that comes from the end of a lighted cigarette, pipe, or cigar) and mainstream smoke (smoke that is exhaled by a smoker) (4).
Secondhand smoke is classified as a "known human carcinogen" (cancer-causing agent) by the U.S. Environmental Protection Agency (EPA), the U.S. National Toxicology Program, and the International Agency for Research on Cancer (IARC), a branch of the World Health Organization (5).
Scientific evidence indicates that there is no safe amount of secondhand smoke. Breathing even a little secondhand smoke is harmful to your health. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), the preeminent U.S. standard-setting body on ventilation issues, has concluded that ventilation technology cannot be relied on to completely control health risks from secondhand smoke exposure (5).
Non-smokers who breathe in secondhand smoke take in nicotine and other toxic chemicals just like smokers do. Secondhand smoke causes lung cancer in adults who don’t smoke. In the United States alone, each year it is responsible for about 3,400 lung cancer deaths in non-smoking adults (5). Breathing in secondhand smoke increases your chances of getting lung cancer by 20 percent to 30 percent. Moreover, concentrations of many cancer-causing and toxic chemicals are potentially higher in secondhand smoke than in the smoke inhaled by smokers.
Although no current screening guidelines for the lung cancer are established, the American Cancer Society recommends that people who are at increased risk for lung cancer, such as smokers, former smokers, or secondhand smokers, be aware of their lung cancer risk. They should talk to their doctors about their chances of getting lung cancer and the lung cancer screening (3).
Currently, when lung cancer is detected, the disease has already spread outside the lung in more than half of all cases. Most people with early lung cancer do not have any symptoms, so only a small number of lung cancers are found at an early stage. When lung cancer is found early, it is often because of tests that were being done for something else. Screening is the use of tests or exams to find a disease like cancer in people who don't have any symptoms. Because lung cancer often spreads beyond the lungs before it causes symptoms, a good screening test to find lung cancer early could save many lives (3). This means part of your health care should focus on related screening and preventive measures to help you stay as healthy as possible.
Several testing options could be available for pro-active people who are at increased risk for lung cancer:

Chest x-ray is the first test your doctor will do to look for any spots on the lungs. It is a plain x-ray of your chest. Studies have shown that this kind of screening does not find many lung cancers early enough to improve a person's chance for a cure (3, 6).
CT scan (computed tomography): A CT (or CAT) scan is a special kind of x-ray. Instead of taking just one picture, the CT scanner takes many pictures as it moves around you. A computer then combines these pictures into a picture of a slice of your body. Spiral CT can pick up tumors well under 1 centimeter in size, while chest x-rays detect tumors about one to two centimeters (0.4 to 0.8 inches) in size (3, 6).
MRI scan (magnetic resonance imaging): Like CT scans, MRI scans give detailed pictures of soft tissues in the body. But MRI scans use radio waves and strong magnets instead of x-rays. MRI scans take longer than x-rays -- often up to an hour. MRI scans are useful in finding lung cancer that has spread to the brain or spinal cord (6).
PET scan (positron emission tomography): PET scans use a form of sugar that contains a radioactive atom. Cancer cells in the body absorb large amounts of the sugar. A special camera can then spot the radioactivity. This test can show whether the cancer has spread to the lymph nodes. PET scans are also useful when the doctor thinks the cancer has spread, but doesn't know where (6).
Tests of tissues and cells, such as lung biopsy or sputum cytology, can be used to follow up on imaging tests to be sure that something seen on an imaging test is really lung cancer. These tests are also used to decide the exact type of lung cancer and how far it may have spread (3, 6).
Screening blood tests are offered from the private sector to meet the needs of pro-active people who are at increased risk for lung cancer. It is up to the individual to be aware of their lung cancer risk by determining whether she/he belongs to one or more risk groups such as smokers, former smokers, or secondhand smokers and talk to his/her doctor to determine if screening tests should be implemented. If the health care provider does not cover screening tests which are preferred by the patient, other options are available from the private sector to address these needs at the patient’s own cost.
This article is brought to you by GenWay Biotech Inc. GenWay offers a cancer assessment aimed to detect 20 different types of cancer in the early stages under the brand name You Test You™.
References:
1. U.S. Department of Health and Human Services. The Health Consequences of Smoking – Cancer: A Report of the Surgeon General. Atlanta, GA: U.S, 1982
2. American Cancer Society (ACS), Smoking and Cancer Mortality Table: http://www.cancer.org/docroot/PED/content/PED_10_2X_Smoking_and_Cancer_Mortality_Table.asp
3. American Cancer Society (ACS), Detailed Guide: Lung Cancer.
4. U.S. Department of Health and Human Services. The Health Consequences of Smoking: A Report of the Surgeon General. Atlanta, GA, 2004.
5. U.S. Department of Health and Human Services. The Health Consequences of Involuntary Exposure to Tobacco Smoke: A Report of the Surgeon General. Atlanta, GA, 2007
6. American Cancer Society (ACS), Detailed Guide: Lung Cancer - How Is Lung Cancer Diagnosed?