Day 035 - 12 Oct 94 - Page 57


     
     1        disease, greatly increase the risk but because of their
     2        rarity these account for a very small proportion of cases.
     3          The rare familial polyposis syndromes are associated
     4        with  high risk, but also contribute only slightly to the
     5        overall incidence of colon  cancer.  The presence of
     6        adenomatous colon polyps, which can be considered as
     7        precursor lesions, is associated with an elevated risk of
     8        colon cancer.  Because the polyps can be examined directly
     9        by endoscopy, they provide a way of  studying the
    10        progression to colon cancer that does not exist for breast
    11        cancer."  So far so good or not?
    12        A.  Sure, yes, that is fine.
    13
    14   Q.   "Diet and cancers" -- sorry, do you want to add something?
    15        A.  His characterisation of polyps and so forth is fine.
    16        When he talks about "few specific risk factors for colon
    17        cancer have been established", his first sentence, that is
    18        a judgment call he is making, seemed to minimise the risk
    19        factors for colon cancer.
    20
    21   Q.   He expands on this later on?
    22        A.  Very good.
    23
    24   Q.   As you will see.  It is quite a long article.  We will
    25        have to read quite a lot of it:  "Diet and cancers of the
    26        breast and colon - dietary fat and breast cancer.  For the
    27        last decade, the dominant aetiological hypothesis for
    28        breast cancer has been that high fat intake, and animal
    29        fat in particular, is the primary cause of the large
    30        differences in rates between countries.  This notion is
    31        based largely on two lines of evidence: striking
    32        international correlations (approximately 0.8) between per
    33        capita consumption of fat and breast cancer rates, and
    34        animal experiments in which diets high in fat increase the
    35        occurrence of mammary tumours.   Subsequent  evidence has
    36        not, overall, supported this hypothesis."  As to 1989,
    37        Dr. Barnard, what comment about that statement?
    38        A.  Well, this is a common sort of thing that Walter
    39        Willett would say.
    40
    41   Q.   Very well.  "It is tempting", says Walter Willett, "to
    42        draw causal inferences from the international
    43        correlations, but these studies provide only weak evidence
    44        because the actual cases might involve many other factors
    45        related to economic development.  Factors such as physical
    46        activity, reproductive variables, body composition at
    47        different times in life and energy balance, are
    48        particularly difficult to measure and control in
    49        correlational analyses.  A recent survey of cancer rates
    50        in 65 rural counties in China with similar low levels of 
    51        economic development" -- this, I can tell you, is a study 
    52        I think it is called the China Health Study by Professor 
    53        Campbell, whom I am sure you are familiar with?
    54        A.  Yes.
    55
    56   Q.   I have also to tell you that Professor Campbell has said
    57        that Dr. Willett has misrepresented the effect of his
    58        findings in this article?
    59        A.  The thought did cross my mind as you were reading.
    60

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