Cancer

Key Points

* Average annual number of deaths, 2000—2004.

Figure 50-1 Deaths attributable each year to smoking. (From CDC Office, on Smoking and Health. http://www.cdc.gov/tobacco/data_statistics/tables/index.htmj

• A dose-response relationship exists between the number of cigarettes smoked and the risk of cancer. Those smoking more than one pack a day have 20 times the risk of nonsmokers.

• Smoking formerly labeled "low-tar" and "low-nicotine" cigarettes provides no benefit over smoking regular cigarettes.

• Less than half of all smoking deaths are from cancer; the rest are from heart disease, chronic lung disease, and stroke.

• Tobacco use increases the risk of cancer in most organs.

About 30% of all cancer deaths are attributable to cigarette smoking, with the evidence increasingly stronger. Box

50-1 lists diseases, including many cancers, for which the

Box 50-1 Evidence-Based Relationship between Smoking and Disease

The evidence is sufficient to infer a causal relationship between smoking and:

Cancer of the bladder, cervix, esophagus, kidney, larynx, lung, oral cavity, pharynx, pancreas, stomach

Acute myeloid leukemia

Abdominal aortic aneurysm

Subclinical atherosclerosis

Stroke (cerebrovascular accident)

Coronary heart disease

Chronic obstructive pulmonary disease (COPD) Acute respiratory infections, including pneumonia Reduced lung function in infants

Impaired lung growth during childhood and adolescence Respiratory symptoms in children and adolescents, including cough, phlegm, wheezing, and dyspnea

Asthma-related symptoms (e.g., wheezing) in childhood and adolescence

Premature onset of age-related decline in lung function

All respiratory symptoms among adults, including coughing, phlegm, wheezing, and dyspnea

Poor asthma control

Sudden infant death syndrome (SIDS)

Reduced fertility in women

Fetal growth restriction and low birth weight

Premature rupture of membranes, placenta previa, and placental abruption

Preterm delivery and shortened gestation Cataracts

Increased absenteeism from work

Adverse surgical outcomes related to wound healing and respiratory complications

Hip fractures

Low bone density in postmenopausal women Peptic ulcer disease

The evidence is suggestive of a causal relationship between smoking and:

Colorectal cancer Liver cancer

Increased prostate cancer mortality

Acute respiratory infections in persons with COPD

Increased lower respiratory tract illnesses during infancy

Impaired lung function in childhood and adulthood (with maternal smoking)

Poorer prognosis for children and adolescents with asthma Increased nonspecific bronchial hyperresponsiveness Ectopic pregnancy Spontaneous abortion Cleft palate

Low bone density in older men Dental caries Erectile dysfunction Macular degeneration Graves' disease

From US Surgeon General. The Health Consequences of Smoking: a Report of the Surgeon General, 2004. Rockville, Md, US Department of Health and Human Services, Public Health Service, Office of the Surgeon General, 2004.

Figure 50-2 Mechanisms that contribute to tobacco-caused cancer. (From American Chemical Society, for Stephen S. Hecht. Progress and Challenges in Selected Areas of Tobacco Carcinogenesis.)

evidence is sufficient to infer a causal relationship, as well as those for which the evidence is sufficient only to suggest a causal relationship. Reviewing tobacco's role in carcinogenesis, Hecht (2008) discusses several mechanisms that contribute to cancer, including metabolic changes in DNA and formation of DNA-carcinogen adducts, leading to mutation; inhibition of genes such as p53, a tumor suppressor; and mutations in the K-RAS oncogene (Fig. 50-2).

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