Philip Morris
Cigarette Smoking and Cancer: A Scientific Perspective
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Related Documents:- 2501442800-2806 Report of the Surgeon General's Advisory Committee on the Health Consequences of Using Smokeless Tobacco
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- Author (Organization)
- TI, Tobacco Inst
- Litigation
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- MISS, MISSING PAGES
- Date Loaded
- 05 Jun 1998
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- wyh22e00
Document Images
will surpass $100 million. Only with such continued research
can the pieces of the cancer "puzzle" be put together.
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References for Overview
l. Straus, D., "Somatic Mutation, Cellular Differentia-
tion, and Cancer Causation," J Natl Cancer Inst 67(2):
233-241, August, 1981.
2. Enstrom, J., "Rising Lung Cancer Mortality Among Non-
smokers," J Natl Cancer Inst 62(4): 755-760, April,
1979. -
3. Feinstein, A., Comments in "Discussion" of presentation
by P. Burch, "Smoking and Lung Cancer: The Problem of
Inferring Cause (With Discussion)," J R Stat Soc A 141
(Part 4) : 437-477, 1978.
4. Appel, J., "The Numbers Game," Address, Newsmakers
Luncheon, Overseas Press Club, New York City, New York,
June 23, 1965.
5. Anonymous, "Is Ca Epidemiology More Than Merely Gazing
Into Entrails?," Internal Med News: 2, February 15,
1981.
6. Devesa, S. and D. Silverman, "Cancer Incidence and
Mortality Trends in the United States: 1935-74," J_
Natl Cancer Inst 60(3): 545-571, March, 1978.
7. Siemiatycki, J., et al., "Discovering Carcinogens in
the Occupational Environment: A Novel Epidemiologic
Approach," J Natl Cancer Inst 66(2): 217-225,
February, 178I: -
8. Sterling, T., "Does Smoking Kill Workers or Working
Kill Smokers? or The Mutual Relationship Between
Smoking, Occupation, and Respiratory Disease," Int J
Health Serv 8(3): 437-452, 1978.
9. Medical Services Study Group of the Royal College of
Physicians of London, "Death Certification and
Epidemiological Research," Brit Med J: 1063-1065,
October 14, 1978.
10. Lamont-Havers, R., Statement, U.S. Congress, House,
Subcommittee of the Committee on Appropriations,
Departments of Labor and Health, Education and Welfare
Appropriations for 1976, Hearing, 94th Cong., lst
Sess., April 9, 1975 (Washington: Government Printing
Office, 1975), pp. 6-7.
10
Cancer of the Lung
Foremost among the charges against cigarette smoking is
the assertion that it causes bronchial carcinoma, or lung
cancer. Few have not heard that allegation. An American
Cancer Society president even declared some time ago that
"without smoking we would not have lung cancer."1
That assertion belies the facts. Lung cancer appears
in nonsmokers as well as smokers. Moreover, there is an
indication that lung cancer seems to be increasingly occurring
in nonsmokers -- especially in males.2
In an April 1979 report on this phenomenon, a Cali-
fornia epidemiologist who believes that smoking does cause
lung cancer conceded that factors besides cigarette smoking
must have had a significant effect on the
tality rate.2
lung cancer mor-
Certainly, a higher proportion of the cases in lung
cancer stu dies are smokers. But such findings cannot estab-
lish cause. They can only raise questions -- ones that remain
unanswered in the dilemma of smoking and cancer.
Animal Experiments
A major question about lung cancer is why experiments
in which.animals supposedly mimic human smoking repeatedly
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have failed to produce the type of lung cancer for which
smoking is most often blamed.
The Surgeon General's report of 1968 admitted this
deficiency. Using a variety of animals, large-scale inhala-
tion studies have, it said, "essentially failed in producing
squamous cell cancer of the lung."3
Today, the situation remains basically unchanged4 --
despite much-publicized efforts to promote findings reported
from a beagle inhalation experiment5 as laboratory proof
that cigarettes cause lung cancer. Indeed, one of the in-
vestigators in that experiment announced in the press that he
and his colleagues had "closed the circle in linking cigarette
smoking and lung cancer."6 Shortly afterward, the methodol-
ogy and findings of the dog stu dy were questioned by other
scientists, inclu ding members of a special National Academy of
Sciences panel.7-10 Further doubt was cast on the project
with subsequent reports that the dogs might have been diseased
before the experiment began.ll-12
Other animal experiments have been cited as proof that
smoking causes lung cancer. These entailed daubing shaved
animal skin with tobacco smoke condensate (tar), which is the
particulate matter collected in smoking machines by passing
smoke through a cold trap at extremely low temperatures.
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That experiments like this cannot be equated with the
human smoking experience should be obvious, even to the lay-
man, for at least three reasons:
Rabbit ears and the backs of mice are not
the same as human lung tissue.
Inhalation differs markedly from "paint-
ing "
The chemical properties of the so-called
tar in such experiments may be quite dif-
ferent from the smoke inhaled by smokers.
Then, too, tar quantities used in many of the experi-
ments were completely unrealistic. The amount has been de-
scribed as the equivalent of an individual smoking 100,000
cigarettes a day.13 One researcher went so far as to say
such experimental evidence was "claptrap."14 Even the 1979
Surgeon General's report rather gru dgingly conceded that "con-
siderable criticism" has been directed at these studies.15
Statistical Studies
Many of the reported findings used as "evidence" that
cigarette smoking causes lung cancer come from epidemiologic
studies.
There are two primary experimental methods used in
these stu dies. A retrospective study selects a group of lung
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cancer patients, and a group without lung cancer, then back-
tracks in time to determine smoking histories. A prospective
study identifies a specific population group, supposedly free
of disease, records their smoking habits and then observes the
disease patterns that arise. Both kinds of studies arrange
the raw data into various categories and run statistical tests
to determine if one group (smokers) differs from another (non-
smokers) in specific disease experience.
Such statistical studies can provide a great deal of
information, but, it is important to remember, as one eminent
statistician has said, that "cancer is a biologic, not a
statistical, problem."16 Basicall
y, statistics gathered in
these ways can prove nothing. They can indicate the likeli-
hood that any observed patterns are not due to chance. But
even "statistically significant" results may have no biologi-
cal relevance.
These epidemiological studies, moreover, can always be
affected by inherited tendencies to develop certain diseases,
the undiscovered effects of occupational or other environ-
mental exposures and many other behavioral and biological
unknowns.
That is why this concession from the Surgeon General's
1979 report15 is important:
14
Most large scale stu dies on smoking and
health have tended to investigate the role of
smoking independently of other behavioral
variables, such as alcohol consumption and
other life style factors, occupational and
environmental hazards an d certain psychologi-
cal factors. These variables are known to be
related to health status. Emphasis added]
Thus, such statistical studies, no matter how large or
covering how many years, "do not permit statements about
causality. They can only point to differences between the
observed groups."l7
Irregularities have been pointed out18-20 in the
major epidemiological studies2l-26 that have been used to
condemn cigarettes. Their precise meaning may be unclear, bu t
they show, obviously, that the case against cigarettes is not
as simple as some would suggest.
A recent comment on the subject27 would appear appro-
priate:
Those epidemiological studies that purport to
show a causal connection between cigarette
smoking and various cancers, but particularly
lung cancer, fail when examined critically to
establish the causalclaim. Emphasis added]
Mortality Rates vs. Consumption Levels
One large dilemma for the cigarette causalists
is the
inconsistency of cigarette consumption patterns with lung
15
cancer rates around the world. Among the developed nations,
the U.S. and Canada have among the highest per capita ciga-
rette consumption figures in the world. But they rank 8th and
15th, respectively, in lung cancer mortality for males. Con-
versely, while the United Kingdom, Finland and the Netherlands
have lower per capita consumption than the U.S. and Canada,
they have substantially higher lung cancer death rates.
These examples are based on cigarette consumption and
bronchopulmonary cancer rates in the middle 70's, the latest
available for comparison internationally.28-29 Even allow-
ing for a lag period, the trends in cigarette consumption
going back to the 1930's are inconsistent with national mor-
tality rates.
Increased Mortality -- Real or Apparent?
Recently, there have been cries of "epidemic" in those
nations where sharp rises in lung cancer have been reported.
Anti-smokers point to these reported increases and the simul-
taneous rise in the prevalence of smoking as "proof" that
smoking causes cancer of the lung. Such a simple explanation
is no doubt appealing to them, but is it right?
The biggest problem in the unquestioning acceptance of
this simplism is the kind of data
on which the cries of
large-scale "epidemics" are based. Most of it is derived from
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death certificates, a less than perfect source, to say the
least. (For a discussion, see the chapter on mortality data.)
Another development -- improved medical technology --
also presents problems for this argument. In the early part
of this century, doctors had limited capabilities for diagnos-
ing lung cancer in living patients. Not until after 1930 did
the main clinical tools -- X ray, bronchoscopy and sputum
cytology -- become available to diagnosticians.30 The "epi-
demic," then, may reflect medical progress.
But medical progress can become a two-edged sword:
Clinicians can overuse their new tools. A Swedish medical
team hinted as much in a report in 1975. The scientists, who
believe that smoking is related to lung cancer, discussed the
clinical and pathologic aspects of more than 700 primary lung
cancer cases autopsied in a university teaching hospital over
11 years. They said it is clear that until recently lung
cancer was frequently not diagnosed. They added that the
increased interest in cancer in general and in bronchial car-
cinoma in particular had le d to a more frequent recognition of
it during the patient's life and, in some cases, even when it
wasn't present.31 In other words, they said:
It is obvious that the frequency figures
based on clinical methods are too low in
earlier series, whereas in recent years the
figures may be too high because of over-
17
diagnosis. This m~ give a false impression
of the real increase. Emphas si added)
Changing Patterns
Even if one assumes for the moment that part of the
"epidemic" is real, the trends in lung cancer death rates
still cannot be explained satisfactorily by smoking patterns.
For example, statisticians have suggested that the rate
of increase in lung cancer mortality may be declining. Others
have been quick to suggest that changes in cigarettes and
smoking habits have caused the decline. In 1975, a British
thoracic surgeon asked whether such changes could explain the
shifting lung cancer patterns. He said that this explanation
seemed "likely" until one realized that the lung cancer
changes actually began 50 years ago, long before the altera-
tions in the smoking habit. He conclu ded that the observed
patterns merely represented the "natural history" of the
disease.32
Lung Cancer in Women
Reports of rapidly increasing lung cancer death rates
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for women have sparked the claim that increased smoking in o
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