Hormone And Breastfeeding Impacts On Breast Cancer
October 19, 2012

Investigating The Impact Of Hormones And Breastfeeding On Breast Cancer

Connie K. Ho for redOrbit.com — Your Universe Online

While phrases like “I love Big Bird” and “binders full of woman” are tidbits that people remember about the past two presidential candidate debates, another facet of the debates is the clothing that the spouses of the presidential candidates wear. In this past week´s debate, both Michelle Obama and Ann Romney chose to wear the striking color of pink. The color reflects October as breast cancer awareness month. While awareness of the illness is all around, researchers are hard at work on studying various traits of the disease. Specifically, three studies that were recently presented at the Annual American Association for Cancer Research (AACR) International Conference on Frontiers in Cancer Prevention Research. The studies dealt with the theme of hormones and its impact on subtypes of breast cancer.

A new study from Columbia University´s Mailman School of Public Health revealed that breastfeeding helped lower the risk for estrogen receptor-negative and progesterone receptor-negative (ER/PR) breast cancer.

In the project, researchers looked at the relationship between reproductive risk factors and discovered that there was a heightened risk for ER/PR negative breast cancer in women who did not participate in breastfeeding. Some of the factors the scientists looked at included oral contraceptives and the amount of children delivered by one individual.

"Women who had children but did not breast-feed had about 1.5 times the risk for ER/PR-negative breast cancer," explained the study´s first author Meghan Work, a doctoral student in the Department of Epidemiology, in a prepared statement. "If women breast-fed their children, there was no increased risk for ER/PR-negative cancer. This is particularly important as breast-feeding is a modifiable factor that can be promoted and supported through health policy.”

The team of investigators looked at data from three different sites of the Breast Cancer Family Registry, which gave them access to information on women who had breast cancer and who did not have breast cancer in Australia, Canada, and the United States. 4,011 women who had breast cancer and 2,997 controls based on population were included in the study. Based on the findings, the researchers believe that oral contraceptive use is not related to ER/PR-negative cancer risk, except for versions of oral conception options prior to 1975.

"These earlier formulations contained higher doses of estrogen and progestin than more recent versions," noted Work in the statement.

The scientists believe that the results of the study are similar to the findings from past studies that have supported that premise that breastfeeding has certain advantages in terms of reducing the risk of breast cancer.

"The consistency of the association with breast-feeding and estrogen receptor negative tumors across a number of studies is particularly noteworthy as there have been few modifiable risk factors identified for this tumor subtype," remarked the study´s senior author Mary Beth Terry, an associate professor of Epidemiology, in the statement.

Along with the publication of the Columbia study at the AACR, another study on breast cancer was revealed at the conference. This study analyzed heightened levels of hormones to demonstrate how hormones could lead to increased risk for hormone receptor-negative (HR-negative) breast cancer. In particular, increased amounts of estradiol and progesterone, two forms of pregnancy hormones, is believed to lead to higher risk for breast cancer diagnosis in females that are 50 years of age.

The study focused on the impact of hormonal exposure during the early stage of pregnancy, which could possibly lead to maternal breast cancer.

"Pregnancy influences maternal risk for breast cancer, but the association is complex and the biological mechanisms underlying the associations are unknown," noted Dr. Annekatrin Lukanova, an associate professor at the German Cancer Research Center, in a prepared statement. "Understanding the mechanisms underlying the protective effect of childbearing on cancer risk can form the basis for primary prevention of breast cancer."

Utilizing the Northern Sweden Maternity Cohort, the scientists conducted a study of 417 controls and 223 women who provided blood samples taken from their first trimester of pregnancy; these females were later diagnosed with breast cancer. The team of investigators studied the participants in relation to two groups of hormones. Estradiol, estrogen, and progesterone were included in the first group as these were hormones that could elevate during the pregnancy period. The other group included testosterone and insulin growth factor-1, as these were hormones that had similar concentrations before pregnancy and during the pregnancy.

In the study, the hormones were only measured in the first trimester of pregnancy. Based on the findings, the researchers found that approximately three quarters of breast cancer cases were determined to be hormone receptor (HR) - positive. They believe that there was a correlation between higher levels of estradiol and progesterone along with a higher risk for HR-negative cancer for women diagnosed before the age of 50.

"We found that circulating concentrations of IGF-1 and testosterone are directly associated with risk for HR-positive breast cancer, in line with studies in nonpregnant women," continued Lukanova in the statement.

The scientists believe that further studies are needed to better understand the relationship of pregnancy hormones along with the risk for maternal breast cancer.

Besides the study from the German Cancer Center, another study revealed at the AACR dealt with blood hormone level. A collaborative effort from Brigham and Women´s Hospital along with Harvard Medical School, the researchers examined how blood hormone tests could possibly diagnose a female patient´s chance of developing postmenopausal breast cancer within a 20-year period. The findings were based off of data from the Nurses´ Health Study.

"We found that a single hormone level was associated with breast cancer risk for at least 16 to 20 years among postmenopausal women not using postmenopausal hormones," explained Dr. Xuehong Zhang, an epidemiologist at Brigham and Women's Hospital, in a prepared statement. "We, and others, are now evaluating if the addition of hormone levels to current risk prediction models can substantially improve our ability to identify high-risk women who would benefit from enhanced screening or chemoprevention. If so, the current data suggest that hormone levels would not need to be measured in the clinic more than once every 10, or possibly 20, years."

The researchers studied a group of 796 patients who had postmenopausal cancer, but who had not undergone hormone therapy. Blood hormone tests were given to the patients once between 1989 and 1990 and a second time between 2000 and 2002. Each patient was then paired with two controls that did not develop breast cancer. The team of investigators looked to see if higher hormone levels were related to HR-receptor positive breast cancers.

Due to the results of the study, the scientists concluded that females with the highest 25 percent in estradiol, dehydroepiandrosterone sulfate (DHEAS), and testosterone had a 50 to 107 percent higher chance of being diagnosed with breast cancer than women who had the lowest 25 percent in those particular hormones. Overall, elevated hormone levels, minus DHEAS, were found to heighten the risk for HR-positive breast cancer. In particular, increased levels of estradiol elevated a female´s risk for HR-positive cancer. Breast cancer thought to be recurrent or fatal was also linked to increased levels of hormones.

"The relationship was comparable or possibly stronger for recurrent and fatal breast cancer than it was for overall breast cancer risk, although these results were based on relatively small numbers of participants," remarked Zhang, who also serves as an instructor in medicine at Harvard Medical School, in the statement.

Even though many of the blood hormones had a negative effect, the researchers found that sex hormone-binding globulin (SHBG) had the opposite result and defended the body against breast cancer. They believe that SHBG reversed the cancer-causing effects from particular hormones. Compared to women who had the lowest 25 percent for SHBG levels, those who had the highest 25 percent of SHBG levels showed a 30 percent lower risk for breast cancer.

Zhang states that more research needs to be done on the study to identify the connection between breast cancer subtypes and higher hormone levels.

Even with these advanced studies on breast cancer, the disease is still a major concern for a significant proportion of the population in the U.S. The U.S. Centers for Disease Control and Prevention (CDC) reported that, in 2008, 210,203 females were diagnosed with breast cancer. In particular, breast cancer normally forms in the tissues of the breast, the ducts, and the lobules of both males and females.

According to the Mayo Clinic, breast cancer is the most frequently diagnosed cancer following skin cancer. Those who suffer from the disease have had symptoms like bloody discharge from the nipple, noticeable differences in the size or shape of the breast, redness over the breast, as well as peeling or flaking of the breast skin or nipple. Diagnosis of breast cancer takes the form of breast exams, mammograms, breast ultrasounds, biopsies of the breast, as well as magnetic resonance imaging (MRI) of the breast. To limit the development of breast cancer, the organization recommends that individuals limit alcohol consumption, engage in exercise daily, as well as become familiar with one´s breasts for early detection of the illness.