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INTRODUCTION

Your 60-year-old female patient with metastatic non-small cell lung cancer never smoked.

She has been healthy all her life, and her social, family, and professional history is noncontributory.

She asks you why she has lung cancer.

Learning Objectives

  1. What are the risk factors for lung cancer?

  2. What is the second most common cause of lung cancer?

  3. How frequently does asbestos cause lung cancer?

  4. What professional exposures are risk factors?

RISK FACTORS

Tobacco

Tobacco smoking accounts for 80%-90% of all lung cancer incidence, with a reported 20- to 30-fold increased risk in smokers compared to non-smokers. This is by far the most thoroughly established causal relationship in medical literature. There is a lag period of approximately 20 years between the exposure and disease occurrence.1

The widespread use of tobacco in the form of cigarette smoking started after the invention of the cigarette-rolling machine in the late 19th century. In the mid-20th century, 2 large epidemiological studies established a definite etiologic role of tobacco smoking in lung cancer.2,3 This led to the US surgeon general issuing a public safety warning in 1964 regarding the potential harmful effects of tobacco smoking and then reemphasizing its stance in 2004.4 A combined effort has led to a significant decline in tobacco smoking: from 42.4% of the adult population in 1965 to 14.0% of all adults in 2017 (15.8% of men, 12.2% of women smokers).5

Since the 1950s, the cigarette has significantly evolved, with a shift to its filtered use. There has also been a decrease in the tar and nicotine contents as per machine-measured yields. Unfortunately, these changes have not resulted in a decrease in lung cancer risk or mortality, as evident by the results of the Cancer Prevention Studies (CPSs). In CPS-1 follow-up period 1960-1972, lung cancer mortality risk was compared based on tar yield of the products. The mortality in the low- and medium-yield group was 20% lower than that in the high-yield group. In CPS-2 follow-up period 1980-1986, with the composition of cigarettes changing, it was expected that there would be a decrease in mortality. To the contrary, the mortality was higher in CPS-2 (Figure 3-1).

Figure 3-1.

Age-specific death rates from lung cancer among current cigarette smokers and lifelong never-smokers. (Reproduced with permission from Alberg AJ, Samet JM. Epidemiology of lung cancer. Chest. 2003;123(1)(suppl):21s-49s; Adapted from Burns DM, Garfinkel L, Samet JM, eds. Changes in Cigarette Related Disease Risks and Their Implications for Prevention and Control. Bethesda, MD: US Government Printing Office; 1997: 317.)

It has been suggested that the change in smoking habits or more smoking as low-yield products were thought to be “safer” may have dampened any benefits of the low-yield cigarettes. Overall, there ...

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