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A Midpoint Assessment of the American Cancer Society Challenge Goal to Decrease Cancer Incidence by 25% Between 1992 and 2015  

Cancer incidence during the time period from 1992 to 2004 has been decreasing, due mostly to a favorable trend among men and among those aged older than 65 years. However, there is considerable variation across cancer sites in both the magnitude and the direction of cancer incidence trends over this time period. Here we discuss the likely reasons for variations in incidence trends and speculate on the changes that can be expected between now and the year 2015. We first discuss trends by specific cancer sites and then by cross-cutting issues of tobacco, obesity, screening, and race/ethnicity. . . .

Lung Cancer. The lung is the second leading site for cancer incidence and the leading site for cancer death among both US men and women.1 Lung cancer incidence rates are approximately 1.7 times higher in men than in women. The downward trend of lung cancer incidence in men is exceeding the 25% reduction goal, but the trends among women are not (see Figure 1). The primary cause of lung cancer is tobacco use, so incidence trends are largely a reflection of tobacco-use trends over the preceding 20-year period.32,33 The prevalence of smoking declined from 52% to 33% among men and from 34% to 28% among women during the time period from 1965 to 1985. Between 1985 and 1995, there was about a 5% decrease in the prevalence of tobacco use among both men and women.34 Despite a persistently higher rate of lung cancer among African Americans than among Whites, a steeper decline has been observed for African Americans compared with Whites over this time period, likely due to historical changes in smoking. Declines in lung cancer incidence have also been observed due to reductions in occupational carcinogen exposures; however, the relative contribution to overall lung cancer rates of these exposures is small compared with tobacco use.32 Screening is not recommended for lung cancer in the general population, but low-dose computed tomography (CT), chest x-ray, sputum cytology, molecular sputum testing, or a combination of these tests are still under investigation and, therefore, may hold promise.24,35–40 Promising findings for screening with spiral CT scans have led to the implementation of large randomized clinical trials (RCTs) now underway that will be completed by 2010.37 Apart from possible effects of screening, the incidence rates for lung cancer will likely decline in the coming decade as a consequence of past tobacco trends. If CT screening begins to be used widely, then incidence rates will substantially increase as an artifact of the initiation of screening and the detection of prevalent cases, as was observed for prostate cancer in the early 1990s. Apart from this potential artifact of screening, the major factor that will determine lung cancer incidence in the coming decade is the past history of tobacco use. Incidence will, therefore, likely continue to decline among men and soon begin to decline among women. . . .

Tobacco. Tobacco usage has been demonstrated to be either the primary or contributing factor for numerous cancers, including lung, oral, bladder, pancreas, esophagus, stomach, and many others.66 Declines in incidence and mortality for tobacco-related cancers92 have been observed following declines in smoking prevalence, primarily due to smoking cessation, between 5 and 20 years previously. Recently, the trends in current smoking prevalence have been stable (Table 3), though smokers are smoking fewer cigarettes per day. Recent leveling of tobacco-use prevalence raises concern that the downward trends in tobacco-related cancers may eventually flatten as well. Clearly, tobacco remains the most modifiable factor for cancer prevention, thus US public policy to further discourage tobacco use is the most important continuing opportunity to decrease future cancer incidence.

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