Despite advances in the treatment of many malignancies, the five-year survival rate for all patients with lung cancer still is only 13 percent.

Cigarette smoking is associated with approximately 85 to 90 percent of primary lung cancers. The risk is proportional to the number of cigarettes smoked daily, the duration of smoking, an earlier age of initiation of smoking, and tar content of the cigarette. Unfortunately, the risk of developing lung cancer subsequent to smoking cessation remains elevated even 16 years after the last cigarette. Although a causal role for secondhand smoke is more controversial, the aggregate data suggest there is a small but significant increase in lung cancer in nonsmokers exposed to passive smoke inhalation.

Environmental causes of lung cancer include asbestos, radon decay products, chromium, nickel, arsenic, chloromethyl ether, mustard gas, vinyl chloride, and polycyclic aromatic hydrocarbons. Of these, asbestos is the most common cause of environmental lung cancer in the United States (in addition to its role in the pathogenesis of pleural and peritoneal mesothelioma). Exposure occurs in occupations such as construction, plumbing, insulation and shipbuilding. Remodeling old homes also may result in significant asbestos exposure. Cigarette smoking enhances the risk of developing lung cancer from these environmental carcinogens in a synergistic fashion. A causal role for radon in the development of lung cancer was first described in underground uranium miners. Between 1950 and 1970, the association of high levels of radon and excess lung cancers in eastern Pennsylvania (the Reading Prong) ignited national concern over the potential public health hazards of residential radon. Radon accumulates in houses and buildings through cracks in the walls and foundation. The precise contribution of residential radon to the development of lung cancer is poorly defined because risk assessments are based on extrapolations from high-level occupational exposure. The Environmental Protection Agency recommends radon remediation for continuous residential levels of 4 pCi/L or more.

Prevention of lung cancer centers on the prevention of smoking initiation and, failing that, the success of smoking cessation. Smoking cessation immediately reduces overall mortality and lung cancer risk, although it never returns to the risk of developing lung cancer among nonsmokers.

Figure 1 - Age-adjusted cancer death rates, by site, for females in the United States, 1930-1992 (from Parker SL, et al. Cancer Statistics, 1996. CA 46:5-29. Reproduced with permission).

Figure 2 - Age-adjusted cancer death rates, by site, for males in the United States, 1930-1992 (from Parker SL, et al. Cancer Statistics, 1996. CA 46:5-29. Reproduced with permission).

Note: Due to changes in the ICD coding, numerator information has changed over time. Rates for cancer of the liver are particularly affected by these coding changes. Denominator information for the years 1930-1967 and 1991-1992 is based on intercensal population estimates, while denominator information for the years 1968-1990 is based on postcensal recalculation of estimates.

* Rates per 100,000 age-adjusted to the 1970 standard U.S. population.

+ Uterine cancer death rates for the cervix and corpus combined.

There are numerous strategies for smoking cessation, but combined modality approaches are the most successful. The initial role of the physician is to inquire about smoking habits and provide education regarding the benefits of smoking cessation. All patients should receive self-help materials such as the American Lung Association guide, Freedom From Smoking In 20 Days, or the American Cancer Society publication, Smart Move, A Stop Smoking Guide. Smoking cessation rates for these self-care strategies range from 5 to 18 percent.

Nicotine replacement may be provided on an individualized basis. Nicotine polacrilex, a nicotine-containing gum, was first marketed in the United States in 1982. Use of the gum provides the flexibility to titrate the delivery of nicotine to the severity of symptoms. The gum has limited utility for patients with dentures and for those who find the taste unpleasant, however. Transdermal nicotine delivery systems overcome these limitations. Success rates for nicotine patches range from 22 to 30 percent. Prescribing information for the various nicotine patches is shown in Table 1.

Referral to self-help group programs should be considered early, particularly for heavier smokers. The American Lung Association sponsors such programs (412-621-0400; 1-800-553-1990). The Allegheny Center for Lung and Thoracic Disease also has a well-established and successful smoking cessation program known as "Smoke No More." Information regarding the program can be obtained through the center's clinical coordinator at (412) 359-4192.

Lung cancer exacts a considerable toll on our society -- in human suffering, lost productivity and utilization of valuable health-care resources. Albert Einstein once said, "In the middle of difficulty lies opportunity," and it is so with lung cancer. Because most lung cancers are preventable, health professionals have considerable opportunity to reduce this toll by preventing smoking in our children and encouraging smoking cessation in our patients.

References

1. Doll R, Peto R. The causes of cancer: Quantitative estimates of avoidable risks of cancer in the United States today. J Natl Cancer Inst. 1981;66:1191-1308.
2. Parker SL, Tong T, Bolden S, Wingo PA. Cancer Statistics, 1996. CA 1996;46:5-27.
3. Samet JM. Radon and lung cancer. J Natl Cancer Inst. 81:745-757.
4. Schwartz JL. Methods for smoking cessation. Clin Chest Med. 1991;12:737-753.

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