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Race and Cancer Genetics: Lessons From BRCA1

Race and Cancer Genetics: Lessons From BRCA1

The study of cancer in specific populations can offer clues useful in
determining the extrinsic and intrinsic factors influencing cancer in all
populations. Extrinsic factors are sometimes called "environmental" in
the broadest sense of the word. They are modifiable or mutable. Intrinsic
factors are more inherent to the individual. They are almost always genetic and
are immutable or unchangeable. Targeting research on specific populations is and
should be a significant ethical issue.

Incidence and cancer outcomes vary among populations, no matter how the
populations are defined. The American medical literature commonly categorizes
populations by race or ethnicity. A few studies have even categorized
populations by socioeconomic status, area of geographic origin, or religion.
Since 1994, the National Institutes of Health (NIH) has mandated that virtually
all NIH-funded clinical research be conducted in such a way that
"differences amongst the races and ethnicities can be determined," and
it urges researchers to publish results by race, ethnicity, and gender.[1]

Population Categorization

It is unfortunate that we in medicine rarely think in rigorous fashion about
how we divide and describe populations and what these divisions might imply.
Very often, epidemiologic and clinical research using population categorizations
will demonstrate weak correlates with extrinsic influences on biology. When
conducted using racial and ethnic categorizations, the findings can easily be
mistaken as surrogates for, or evidence of intrinsic influences.

While it is true that the incidence and mortality of disease often vary by
race and ethnicity, neither is a biological categorization. Despite common
belief, race does not equate with genetic homogeneity; rather, it is a
sociopolitical construct. Racial data, as such, often correlate with many
sociopolitical factors that influence health. Ethnicity, while also
sociopolitical, is somewhat more scientific, as it can equate with culture and
other environmental influences on health status.

The burgeoning fields of genetic and molecular epidemiology make it
imperative that population categorization be better understood.
Single-nucleotide polymorphisms, other genetic polymorphisms, and mutations can
have varying prevalences or frequencies among populations, however they are
defined. These differences in risk best relate to familial inheritance.

Indeed, virtually every genetic difference or polymorphism that has been
correlated or associated with race should be considered familial and not racial.
A specific gene or series of genes can be conserved among families. Family as a
categorization clearly preserves genetic markers more efficiently than race or
ethnicity. A complicating factor is that race and ethnicity are also commonly
preserved by family.

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