Evidence-Based Oncology

50th Anniversary Report: Even More Known About Smoking, Cancer Connections

Published Online: March 20, 2014
Mary K. Caffrey
If you thought the link between cigarette smoking and cancer was old news, you would be wrong.

To be sure, it’s been 50 years since the announcement from US Surgeon General Luther L. Terry, MD, that smoking causes lung cancer in men and probably in women.1 Terry’s action unleashed the public health crusade against cigarettes; since 1964, adult smoking rates have fallen from 43% to 18%.2

But a report issued on the milestone of Terry’s bold step, in a White House ceremony held on January 17, 2014,3 pores through the most recent data and makes several new findings about smoking and cancer, including:

• Female smokers face a greater risk of lung cancer than ever.4

• Cigarettes are linked to multiple other cancers; scientists can say with certainty that smoking causes colorectal cancer. While the report stops short of saying that smoking causes breast cancer, it states, “The evidence is sufficient to identify mechanisms by which cigarette smoking may cause breast cancer3 (see Figure 1).

• Falling rates of squamous cell cancer of the lung, accompanied by the relative rise of adenocarcinoma of the lung among smokers, are most certainly due to changes in the design of cigarettes themselves.3,5 The consequences have been deadly, and US cigarettes may be the deadliest of all.3,6

An important lesson of the anniversary report, officially titled, The Health Consequences of Smoking: 50 Years of Progress, is aimed at oncologists and payers, rather than smokers: According to Timothy McAfee, MD, director of the Office of Smoking and Health, the amazing advances in cancer therapy, which have created drugs with $100,000 pricetags, are not as important to survival as getting a smoker with cancer to quit.

“Does it make sense to spend this kind of money, $100,000 for a drug to add a few months to someone’s life, and ignore somebody’s tobacco status during treatment?” McAfee asked in an interview with Evidence-Based Oncology. All the evidence, he said, indicates that quitting smoking will do as much good for the cancer patient as “the best available chemotherapy,” and yet there are cases where a cancer patient undergoes the rigors of treatment while his or her smoking goes unaddressed.

“In 2014, after this report, it isn’t fair to individuals for smoking status to be ignored,” McAfee said. “There are historical and cultural reasons why that was the case. But that doesn’t make sense anymore.”

McAfee’s call to arms has implications not only for healthcare providers, but also for the US taxpayer. Demographic data contained in the report3 and available from the Centers for Disease Control and Prevention (CDC)2,7 show that while smoking has declined significant-ly since 1964, progress against tobacco is leveling off. Those who still smoke or who start smoking are more likely to be poor and have limited education2,7; this means without a renewed commitment to end smoking, the expanding ranks of Medicaid clients under the Affordable Care Act (ACA) will include a larger share of smokers than the population as a whole.

The Rise of Adenocarcinoma of the Lung

When Terry unveiled the first Surgeon General’s Report in 1964, “lung cancer in men” typically meant squamous cell carcinoma of the lung. Men smoked more than women, and thus, accounted for more cases of lung cancer.3 In the wake of the 1964 announcement, the tobacco industry’s attempts to create “safer” cigarettes, coupled with efforts to market directly to women in an era of change, led to shifts in both the type of lung cancer diagnosed and in the makeup of who suffered, changes that are only now fully understood.4

A study of smokers by the American Cancer Society (ACS) from 1959-1965 had been an important source for the advisory panel that created the 1964 report.3 Behaviors exhibited by those smokers informed scientists who created models to predict the number of future lung cancer deaths. They also informed tobacco company researchers, who created machines to measure supposedly lower levels of “tar” and “nicotine” on filtered and ventilated cigarettes that were put on the market in the decade after 1964.

This new Surgeon General’s report chronicles how scientists missed the mark for years in predicting lung cancer deaths, until they began to account for the changes in smoking behavior that were a direct result of modifications to cigarettes, supposedly to make them “safer.” Re-engineered cigarettes did not provide the same “hit” of nicotine, so smokers responded by puffing longer or holding smoke in their mouths, actions that fundamentally altered the nature of the way their bodies reacted to the 69 different carcinogens identified in cigarette smoke.3-5

Over time, health consequences of a different cigarette became clear. The United States and other countries saw falling rates of squamous cell cancer of the lung, which may first affect the bronchial areas and cause a patient to cough up blood. Among smokers, the United States in particular saw rising rates of adenocarcinoma of the lung, which develops in the far reaches of the lung tissue and may not cause symptoms symptoms beyond a cough until the cancer is in later stages. While overall death rates for men from lung cancer peaked in 1990 and for women in 2003, likely due to reduced prevalence of smoking, the climb of adenocarcinoma of the lung continues among those who do smoke, and rising incidence has been steeper for women3,8 (see Figure 2). Differences in the composition and manufacturing practices of US cigarettes, compared with those in Canada and Australia, are believed to account for larger increases in adenocarcinoma incidence here than in those nations.3,6

Key work in this area includes a 2011 study led by David M. Burns, MD,5 which first factored the change in cigarette design in modeling to account for changing rates of adenocarcinoma; and the 2013 study in the New England Journal of Medicine led by Michael J. Thun, MD,4 which tracked smoking-related mortality over a 50-year period. Thun and his coauthors concluded that the relative risk (RR) of lung cancer for women smokers, compared to women who have never smoked, are higher than ever: RR was 2.73 in the original ACS study, 12.65 in a follow-up study begun in 1982, and was 25.66 in a cohort ending in 2010. Women smokers today face higher lung cancer risks than men relative to their non-smoking counterparts; for men, RR of lung cancer in the 2010 cohort was 24.97.4

A panel of experts convened recently by The American Journal of Managed Care to discuss non-small cell lung cancer said the increased understanding about adenocarcinoma of the lung has changed treatment over the past decade, putting more onus on the pathologist to properly evaluate tumor types.10 It has also caused the US Preventive Service Task Force to recommend lung

cancer screening among smokers and former smokers who meet certain criteria (see related story, page SP160). McAfee said that while lung cancer screening is important and will save lives, the CDC is working hard to craft an education message that does not lead smokers to believe that screening is a substitute for quitting; in fact, the CDC hopes that being screened will provide an opening for a conversation with a smoker about how to stop. “We are working very closely with our cancer prevention control office on this specific issue,” McAfee said. “How do we turn this into a positive, educational opportunity?”

Smoking’s Links to Other Cancers

While smoking is most associated with lung cancer, successive Surgeon General’s Reports (SGRs) have assembled evidence of its ties to other cancers. Reports are careful to never overstep what is known at the time; thus, when anyreport says for the first time there is a “causal relationship,” it is an important step, as no SGR has ever had to reverse a previous finding, according to Terry F. Pechacek, PhD, associate director for science at the Office of Safety and Health (OSH), and a veteran of crafting multiple reports.

So, the finding for the first time that “the evidence is sufficient to infer a causal relationship between smoking and colorectal adenomatous polyps and colorectal cancer,”3 is a critical statement, especially since colorectal cancer is now the second-leading cause of cancer deaths in the United States, according to CDC statistics.9

The report also examined possible connections to liver, prostate, and breast cancers and found:

• The evidence is sufficient to infer a causal relationship between smoking and hepatocellular carcinoma.

• The evidence is suggestive of no causal relationship between smoking and the risk of incident prostate cancer; however, there is evidence suggestive of a higher risk of death from prostate cancer among smokers than nonsmokers.

• In men who have prostate cancer, the evidence suggests a higher risk of advanced-stage disease and less well-differentiated cancer in smokers than nonsmokers.

• Besides the evidence of mechanism by which smoking may cause breast cancer, the report says there is “suggestive but not sufficient” evidence to infer a causal relationship between smoking and breast cancer.

The same characterization was made of evidence linking secondhand tobacco smoke and breast cancer.

Smoking Hinders Cancer Care, Survivorship

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