Why Breast Cancer is Higher in Black Women

Copyright 2005, James Michael Howard, Fayetteville, Arkansas, U.S.A.

http://www.anthropogeny.com/Why%20Breast%20Cancer%20is%20Different%20in%20Black%
20Women.htm

In 1994 I first suggested that testosterone may be involved in causing
breast cancer (International Journal of Cancer 2005; 115: 497 and
Annals of Internal Medicine 2005; 142: 471-472).  For example, smoking
increases breast cancer risk (Cancer Causes Control. 2005
Oct;16(8):975-85) and smoking in premenopausal women increases
testosterone (Eur J Epidemiol. 2005;20(4):331-7).  Alcohol "is
associated with increased breast cancer risk" (Alcohol. 2005
Apr;35(3):213-25) and alcohol increases testosterone levels in
premenopausal women (J Clin Endocrinol Metab. 2001 May;86(5):1981-5).
"Abdominal fat has been shown to be an important risk factor for
…breast cancer." in premenopausal women (Genet Epidemiol. 2001
May;20(4):458-78) and higher free testosterone has been connected with
abdominal fat accumulation (Wien Klin Wochenschr. 2002 May
15;114(8-9):321-6).  Again, I suggest testosterone is involved in
breast cancer.  The mechanism involves the effect of reduced DHEA on
certain genes, as a consequence of reduced conversion of DHEAS to DHEA
caused by testosterone.  (Hormone replacement therapy (HRT) also
reduces DHEA and may be why HRT increases breast cancer.)  However, to
satisfy the intention of this treatise, I will deal only with
testosterone.

While controversial, that is, there is not absolute agreement, most
studies find higher levels of testosterone in African-American women
compared to European-Americans (black and white).  Testosterone was
recently reported to be higher in African-American women compared to
Caucasian women (Cancer Epidemiol Biomarkers Prev. 2005
Jun;14(6):1514-20).  I suggest this increased testosterone affects the
epidemiology of breast cancer within these two populations.  

"African American women have a lower overall incidence of breast
cancer but a higher overall mortality than do white women. African
American women with breast cancer present for medical care at an
earlier age, with more advanced stage disease, and with higher-risk
tumor biology. While the advanced stage at presentation and
higher-risk tumor biology appear to account for much of the excess
mortality in African American women, differences persist even after
controlling for these factors. This paper discusses the factors that
may contribute to differences in survival and differences in stage at
diagnosis between African American and white women." (Perspect Biol
Med. 2005 Winter;48(1 Suppl):S166-75)

As a biologist, I suggest some diseases produce differential
reproduction in some groups by reducing representation within current
populations.  Breast cancer may cause this phenomenon in black women.
If black women are more prone to breast cancer, it is possible that
vulnerable black women were adversely affected in the past before
comprehensive epidemiological studies could have found them.  That is,
there may have been a time when black women exhibited more breast
cancer incidence than white women.  This may have reduced the
percentage of vulnerable black women at that time.  However, when
those who are currently vulnerable develop breast cancer, the
increased testosterone may produce much earlier, more pronounced
cancers.  The quotation, above, does report earlier age and more
aggressive tumors in black women who develop breast cancer at this
time.  I suggest this supports my interpretation that the population
of black women of today may have been preceded by a population of
black women in the past who developed breast cancer early in their
lives and are reduced in the current population.  I suggest this may
be seen in the following quotation.

"RESULTS: Women from sub-Saharan Africa were found to have a low
incidence of breast cancer. This was partly explained by a largely
protective reproductive history, including late menarche, early
menopause, high parity with prolonged breastfeeding, irregular menses,
and fewer ovulatory cycles. The average age at diagnosis, however, was
approximately 10 years younger than breast cancer patients of western
nations, and disease stage distribution was shifted toward more
advanced disease, which resulted in higher mortality rates. These
features were found to be similar to data on breast cancer in
African-American women. Mutations in BRCA1 and BRCA2 have been
reported in African-American women, but the extent of the contribution
of BRCA1 and BRCA2 to breast cancer burden in Africa was uncertain.
Limited financial resources lead to suboptimal cancer data collection,
as well as delayed diagnosis and treatment of many African breast
cancer patients." (Cancer. 2005 Apr 15;103(8):1540-50)

It is my hypothesis that the "secular trend," the increase in size and
earlier puberty of children, is caused by an increase in the
percentage of individuals of higher testosterone within populations.
This is driven by increases in the percentage of women of higher
testosterone.  (Some say the trend is due to increased calories;
increased calories only increases reproduction of this percentage of
the population, not cause it.)  It is this increase in percentage of
women of higher testosterone that may be the cause of the increase in
breast cancer …if increased testosterone is part of the causative
mechanism.  If I am correct, at some time in the future epidemiology
will find a reduction of breast cancer in white women along with an
increase in earlier age at onset with more aggressive tumors.