After
spending a week discussing cancer prevention, I became incredibly interested in
the role of lifestyle choice in cancer development. Though we discussed this briefly,
our everyday nutrition, exercise, and routine choices are proving to play an
integral role in our individual overall health, including decreasing our risk
for developing cancer. And as one of the leading subsets of cancer incidence
among women, breast carcinomas have become a highly researched and dissected
cancer; in the year 2010 alone about 1.5 million people worldwide were
diagnosed. Thus, more individuals have become concerned with lifestyle-oriented
health, looking specifically at the modifiable factors in breast cancer
prevention.
In this graph above, it seems quite clear
that breastfeeding significantly lowers a women’s risk of developing breast
cancer both pre and post menopause, but what accounts for this risk reduction?
Before delving into the data, there are second central theories regarding the
mechanism behind breastfeeding as a cancer preventative that warrant
explanation. First, hormone regulation in the body is proving to correlate with breast cancer development. In other words, lowering exposure of the breast
tissue to estrogen reduces disease risk. Breastfeeding in fact lowers and
maintains stable estrogen levels in the body for the duration of lactation.
Thus, the longer and more frequently a woman chooses to breastfeed, she is very
well balancing hormone levels in her body, limiting exposure of her breast
tissue to estrogen, and reducing her risk for developing breast cancer.
Secondly, buildup of DNA damage in breast
tissue cells can lead to uncontrolled cell proliferation, the mechanism behindbreast tumor growth. However, soon after a woman has breastfed, the body
essentially cleanses itself of many cells contained in the breast tissue, some
of which will certainly contain DNA damage. Ridding the body of potential
cancer causing cells by means of breastfeeding seems to be yet another
mechanism of risk reduction.
Browsing through the JSTOR library, I
came across a case-control study in Tunisia that looked specifically at the
relationship between breastfeeding history and breast cancer risk in 800 women.
The study originated in 2006 and was concluded in 2009, with 400 breast cancer
patients randomly selected into the “case group” and another 400 disease-free
women selected into the “control group.” During the three-year duration of the
study, each woman was given a standardized structured questionnaire to discern
information regarding individual health, family, and lactation history. In
addition, this study accounted for the variable of pre verses post menopausal,
in regards to each woman, looking at stratification and consistency generated
by menopausal status, lactation, and cancer development.
All 800 patients were randomly selected
through prior admittance in participating Tunisia hospitals. Participants had
all received treatment, either breast cancer related or not, prior to the start
of this study. All women included in the “case group” had been diagnosed with
breast cancer in one of the participating Tunisia hospitals, while the “control
group” drew from women given non-cancer related medical care, all the women
randomly selected were between 25 and 75 years of age. Following selection,
each woman was interviewed by an interviewer blind to the study hypothesis and
group allocation, and each questionnaire was standardized and specific, five
questions were asked with additional follow-up. The questions were as follows:
(1) Have you ever been pregnant, (2) How many pregnancies have you had, (3) At
what age did you first deliver successfully, (4) Did you breastfeed your
infant(s), and (5) If you responded yes to the previous question, how many
months did you breastfeed each infant? After these five questions were
answered, follow-up information was gathered regarding potential confounding
variables such as family cancer history and past medical history. Non-breastfeeding
women were defined as women without children and women that had breastfed in
total 1 month or less.
Logistic regression was used to ascertain
correlation and statistical significance between breast cancer risk and
breastfeeding; breastfeeding was broken down into four categories: mean
duration of breastfeeding per child, lifetime duration of breastfeeding, number
of children breastfed, and menopausal status. The overall results obtained demonstrated a clear “inverse association
between breastfeeding and breast cancer risk,” however further relativity
was obtained by comparing each of the four subsets with breast cancer risk.
A mean duration of breastfeeding per
child became the margin of risk reduction, women who had breastfed for at least
24 months per child displayed a strong risk reduction for developing disease.
The strength of this result was magnified when comparing lifetime duration of
breastfeeding and cancer risk. For women who reported a lifetime breastfeeding
duration of greater than 73 months, the risk of developing breast cancer was
significantly reduced. Next, when examining the correlation between number of
children and risk reduction, the study observed a consistent and significant
reduction in breast cancer risk in women with 2 or more children and that had
breastfed for at least 72 months. Though the data proved consistent regardless
of menopausal status, the most reliable data was observed among premenopausal
women, however no concrete conclusions were made regarding differences due to
menopausal state.
Though this study was relatively
straightforward and introduced important data, the method introduces two main
points of concern, first in regards to how the 800 patients were selected, and
second, in the inclusion of a potential confounding variable.
Like mentioned previously, all 800 study
participants were randomly selected from Tunisia hospitals participating in
this study. Each woman had been selected after receiving some form of care from
these study hospitals, the care was either breast cancer specific or non-cancer
medical care. However, the study itself mentions a noteworthy downside of such
a method, all participants in the study were region specific, meaning because
they were all randomly selected from the same location pool, the results
yielded are not representative of the entire Tunisia population. “The
generalizability of the results may be limited because of the hospital-based
study design.”
Furthermore, in analyzing the “case”
group, the study discovered a potential confounding variable: genetic
predisposition. Within the “case” group, “a positive family history of breast
cancer was associated with a significantly increased risk of breast cancer.” Of
course this makes sense genetically, however this potentially undermines the significance
of the actual study conclusion. Perhaps those participants genetically
predisposed for breast cancer have skewed the observed results associating breastfeeding
and breast cancer risk.
Regardless, enough foundational research
has demonstrated a clear inverse correlation between breastfeeding and breast
cancer risk, asserting the importance of breastfeeding. This study itself
touches on a very exciting and promising field of cancer prevention, and serves
as a call to action for individuals to maintain healthy and informed lifestyle
choices.
Awatef, Msolly, et al. "Breastfeeding reduces breast cancer risk: a case-control study in Tunisia."Canc er Causes and Control 21.3 (2010): 393-97. Print.
"Breast cancer prevention should begin early in life." Cancer News in Context. Siteman Cancer Center, n.d. Web. 18 May 2014. <http://www.cancernewsincontext.org/2013_10_01_archive.html>.
"Breastfeeding and Cancer." American Institute for Cancer Research. N.p., n.d. Web. 18 May 2014. <http://www.aicr.org/reduce-your-cancer-risk/tell-me-about/tellmeabout_breastfeeding. html?gclid=CIjNsr79tb4CFcU-Mgod1lwAlA>.
"Breast Cancer Prevention." National
Cancer Institute. N.p., n.d. Web. 18 May 2014<http://www. cancer.gov/cancertopics/pdq/prevention/breast/Patient/page3#Keypoint12>.
