Læknablaðið - 01.12.1978, Page 65

LÆKNABLAÐIÐ
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one hundred years developed slowly and
was mostly concerned with the exotic
cancers of the non-european world, often
of custom and usage, such as the Kang and
Kangri cancers, the dhoti and other cancers
of India, but amongst these oddities over
100 years ago the frequency of plantar
melanomas in darkly pigmented peoples
had been observed, though almost nothing
was known of their internal cancers.18
Then an era ensued dominated by natio-
nal and international cancer mortality
statistics which markedly illuminated so
many aspects of cancer but which tended
to obscure others as it tended to conceal
the importance of specific cancer types.
It also showed remarkably similar cancer
site and type patterns in all the countries
producing such figures, not surprising, in
that all were technically advanced in-
dustrial countries. In Japan the pattern,
however, was different suggesting perhaps
the influence of race.8
All through this period, attention had
been paid to the mysteries of that disease
first described by Thomas Hodgkin in 1839
to which his name was attached. Some de-
gree of specificity had been attained in
diagnosis by 18781- but its mysteries per-
plex us still, its diagnosis is difficult and
is made by recognising a cell, not specific
to the disease, the Reed-Sternberg cell, and
which is not the cell described by either
Reed or Sternberg38 against a background
of lymphocytic cells and histiocytes, which
are modified lymphocytes. No other cancer
is diagnosed histologically in this queer
way and the true nature of this disease is
as obscure as ever. Long considered an in-
fective condition, and classified internatio-
nally as such, all attempts by laboratory
methods, still continuing today, have utter-
ly failed to oncover an infective causative
agent. Mainly today it is considered a
cancer but the causative factors elude us
and still, though a relatively uncommon
disease, it has attracted attention quite dis-
proportionately to its incidence.2-111 20 How
then are we to grapple with this problem
other than perhaps by laboratory techni-
ques that have so far provided no answers
save negative ones?
In 1944 Sir Ernest Kennaway23 drew
attention to the established infrequency of
primary liver cancer in the American negro
in contrast to the reported high frequency
of this disease in West Africa, the ancestral
home of the US negro. If this was a true
discrepancy, as Charles Berman1 in S.
Africa was trying to show, and indeed, was
demonstrating, that the differences were
entirely in the different frequency of
primary hepatocellular cancer, then this
indicated the overwhelming importance of
environmental factors in this carcinoma.
If in this, why not in other cancers. This
occurred when the link between cigarette
smoking and lung cancer, rising so rapidly
in incidence11 was reported, again a rise
linked to certain specific histologic types
of lung cancer. These reports emphasised
three things: (1) the importance of accu-
rate specific diagnosis of particular cancers
under study; (2) the importance of en-
vironmental factors in certain specific
internal cancers, and; (3) that national
cancer figures were of little use in seeking
the environmental causes of cancers.
It was also becoming likely that if
environmental factors were responsible for
certain cancers of remarkably high inci-
dence in certain societies, then it was
possible that they were responsible for
much human cancer and that the rise in
cancer incidence with age in developed
societies might not be connected with
aging per se but be due to more prolonged
exposure to environmental carcinogens.
The late Dr. George Oettle put this in
words33 when he pointed out that based on
experience in Africa 84% of human cancer,
at least, was environmentally determined
and hence theoretically preventable. In
Africa too, age and cancer were found to
dissociate. Doll12 considers that the best
comparisons are made by comparing cancer
incidence rates in persons aged 35—65,
thus avoiding the imbalances produced in
populations with a large population of
children or of the aged. Looking at the
widest discrepancies in Doll’s tables,10 as
optimist and pessimist view a half filled
glass, those concerned with carcinogenesis
and pollution look to the high figures, but