Can We Smoke Out Cancer?July 30, 2022
On signing the National Cancer Act of 1971, which embodied his plan for a War on Cancer, President Nixon called for “a national commitment for the conquest of cancer.” In 2016, then-Vice President Biden inaugurated a Cancer Moonshot to accelerate progress against cancer. On February 2 this year, the White House announced that now-President Biden was reigniting the Cancer Moonshot “to reduce the death rate from cancer by at least 50% over the next 25 years, and…end cancer as we know it today.” The initiatives of both Presidents focused on research and development of new treatments but also included cancer prevention and screening and improved patient care.
Neither Nixon in 1971 nor Biden in 2016 mentioned reducing cigarette smoking, the leading cause of cancer death in both men and women. The February 2 Moonshot statement did, however, acknowledge progress against smoking. (Long the leading cause of male cancer mortality, lung cancer surpassed breast cancer as the leading cause of cancer death in women in 1987. Even decades later, two-thirds of women still believed breast cancer was the leading cause.)
More recently, on June 21, the Biden administration announced plans for what would likely be the most effective measure ever to reduce smoking: requiring the reduction of nicotine in combusted tobacco products to non-addictive levels. This could also be the most effective single measure to reduce future cancer mortality.
If seriously pursued, this controversial regulation will ignite a firestorm of opposition from the tobacco industry, tobacco product retailers, philosophical opponents, and of course many smokers. That opposition means that implementation will not occur for years, if ever. (Interestingly, a significant if uncertain fraction of current smokers supports reducing nicotine to non-addicting levels.)
How significantly might a very-low nicotine regulation impact cancer mortality? We can get a feel for the answer by looking back, asking how the War on Cancer has progressed to date, and how the decades-old battle against smoking has affected that progress.
While progress against cancer affects rates of cancer diagnosis, incidence, and 5-year survival, I will focus exclusively on arguably the most important metric: the cancer death rate. Smoking causes a myriad of cancers, including cancers of the mouth, throat, bladder, kidney, liver, stomach, pancreas, colon and rectum, and cervix. However, I will examine only lung cancer, the single largest source of smoking-produced cancer mortality and the most important cancer “marker” of smoking. The other cancer sites have several causes (some unknown), while 80-90% of lung cancers are linked to cigarette smoking and second-hand exposure to cigarette smoke.
Adult smoking prevalence has declined substantially since Nixon declared his War on Cancer, from 37% in 1971 to 12.5% in 2020. Both laws and norms impede smoking today, with smoking prohibited in many workplaces and public places, and cigarettes increasingly expensive due to increases in manufacturers’ wholesale prices and government excise taxes. In addition to reducing smoking prevalence, these factors have significantly reduced the percentage of current smokers who smoke every day, and the number of cigarettes daily smokers consume. The decreases in the percentage of smokers and the numbers of cigarettes they smoke have produced a sharp decline in a measure that combines both smoking prevalence and daily cigarette consumption: annual adult per capita cigarette consumption (APCCC). Defined as total cigarettes consumed nationwide each year divided by the number of adults ages 18 and older, APCCC rose dramatically from the beginning of the 20th century, when manufactured cigarettes first gained popularity, to 1963, the year before the first Surgeon General’s report on smoking and health. Smoking fell thereafter, equally dramatically (see figure 1). The stark rise and fall of smoking motivated Harvard historian Allan Brandt to label the 1900s The Cigarette Century.
As the development of lung cancer follows the onset of smoking decades later, lung cancer was essentially unknown in the early 20th century. Similarly, there is a lag between a decrease in smoking prevalence and the subsequent decrease in lung cancer. Thus, while adult smoking prevalence began falling in 1964, lung cancer mortality peaked in 1993, nearly 3 decades later.
How has the turn-around in smoking affected the overall cancer mortality rate? And how is that rate doing independent of decreases in smoking? Figure 2 below shows a very encouraging picture of the age-adjusted all-site cancer mortality rate.
Cancer mortality overall rose through the 1980s. For both sexes combined, the cancer mortality rate peaked in 1991. The rate for women also peaked that year. For men, the rate peaked a year earlier. From their peak rates to 2019, the all-site cancer death rate dropped 32.1% for both sexes combined: 28.2% for women and 38.2% for men. By any measure, this is a terrific accomplishment.
Figure 3 shows changes in the lung cancer mortality rate during the same period. The rate rose through 1990 for men, the same year that all-site cancer mortality peaked for men. For women, by contrast, the lung cancer rate increased through 2002. The 12-year gap between the sexes’ peak rates — and women’s lower peak rate — reflect women’s having started smoking later than men, never reaching men’s higher smoking prevalence rates, and starting to quit later as well. Male smoking prevalence peaked in the 1950s, with more than half of all men smoking, and remained fairly steady through the early 1960s. Female smoking prevalence increased until the 1964 Surgeon General’s report, which interrupted that upward trend. Smoking prevalence reached just over a third for women. The lung cancer mortality rate for men and women combined peaked in 1993. By 2019, the lung cancer mortality rate for both sexes had dropped by 43.5%. For women, the rate fell 32.5%. For men, the rate plummeted by 55.7%.
Examining the decrease in all-site cancer mortality except for lung cancer, beginning in 1991 when the all-site rate peaked, the drop was 27% for both sexes combined, or 19.7% for women and 29.8% for men.
What are the take-home messages? First, with all-site age-adjusted cancer mortality increasing through 1991, President Nixon, who died in 1994, barely lived to see his War on Cancer turn the corner. But turn the corner it did, with cancer mortality having dropped through 2019 by a third. Importantly, the increase and decrease in cancer mortality moved pretty much in tandem with the increase and decrease in lung cancer mortality, especially male lung cancer. The drop in smoking — and hence in lung cancer — has contributed mightily to the impressive decline in overall cancer mortality. Most strikingly, the decrease in the male lung cancer death rate accounts for almost half (47%) of the decrease in the male all-site cancer death rate. Of course, not all lung cancer deaths are caused by smoking — as many as 20% are not — but offsetting that consideration is the fact that decreases in smoking account for decreases in cancers of multiple other sites as well.
A second important message: Independent of progress against smoking, we have made substantial progress against cancer mortality, reflecting other forms of prevention, better screening and early diagnosis, and better treatment.
The third message: President Biden’s ambitious cancer mortality goal is possible. Reducing the cancer death rate by half over the next 25 years will require greater success than the decrease of the past 25 years. It will depend on continuing improvements in early diagnosis and treatment of cancer. And it may depend on the ability of President Biden’s administration (and likely that of his successor) to withstand enormous political and legal pressure in attempting to implement a very-low nicotine regulation. If the stars align, we might just be able to shoot the moon.
Kenneth E. Warner, PhD, is the Avedis Donabedian Distinguished University Professor emeritus and dean emeritus at the University of Michigan School of Public Health.