Lately I have been reading about obesity and the possible link to increased risk of Breast Cancer. Following are some interesting and informative articles I found on the web from various sources:
The National Cancer Institute:
What is known about the relationship between obesity and breast cancer?
Many studies have shown that overweight and obesity are associated with a modest increase in risk of postmenopausal breast cancer. This higher risk is seen mainly in women who have never used menopausal hormone therapy (MHT) and for tumors that express both estrogen and progesterone receptors.
Overweight and obesity have, by contrast, been found to be associated with a reduced risk of premenopausal breast cancer in some studies.
The relationship between obesity and breast cancer may be affected by the stage of life in which a woman gains weight and becomes obese. Epidemiologists are actively working to address this question. Weight gain during adult life, most often from about age 18 to between the ages of 50 and 60, has been consistently associated with risk of breast cancer after menopause.
The increased risk of postmenopausal breast cancer is thought to be due to increased levels of estrogen in obese women. After menopause, when the ovaries stop producing hormones, fat tissue becomes the most important source of estrogen. Because obese women have more fat tissue, their estrogen levels are higher, potentially leading to more rapid growth of estrogen-responsive breast tumors.
The relationship between obesity and breast cancer risk may also vary by race and ethnicity. There is limited evidence that the risk associated with overweight and obesity may be less among African American and Hispanic women than among white women.
The Cancer Network:
A study demonstrated that women who were overweight or obese had a 5-year survival rate of 55.6%, compared with a rate of 79.9% in leaner women. The study also showed that obese women were more likely to have larger tumors, with higher rates of lymphatic invasion and nodal involvement.
WebMD:
Obese women may be more likely to develop breast cancer largely because their bodies produce more estrogen than thin women do.
New research suggests that the increase in breast cancer risk faced by obese postmenopausal women may largely be due to higher levels of estrogens circulating in their bodies. High levels of estrogen are known to stimulate certain types of breast cancer tumors to grow and develop.
The study, published in the Journal of the National Cancer Institute, shows that the average concentration of estrogens in obese women was between 50% and 219% higher than in thin women, and the risk of breast cancer increased by about 18% with each increase in body mass index (a measurement of weight and height used to indicate obesity).
Researchers say that previous studies have also shown that breast cancer risk among postmenopausal women increases with increasing BMI or obesity, but until now the reasons for the increase in health risk associated with obesity and breast cancer have not been clearly understood. “The association between obesity and breast cancer risk is important because obesity may be the principal contributing factor for a substantial number of cases of breast cancer and because the prevalence of obesity is high and increasing,” write researcher Timothy J. Key, DPhil, of the Endogenous Hormones and Breast Cancer Collaborative Group, and colleagues.
CBS News:
Study: Breast cancer more likely to recur, cause death in obese women
Obese and overweight women with breast cancer are significantly more likely to have the cancer return regardless of treatment, new research suggests.
The study, published online Aug. 27 in the American Cancer Society’s journal, Cancer, suggests that excess body fat may cause hormonal changes in the body that fuel cancer to spread and recur.
“We found that obesity at diagnosis of breast cancer is associated with about a 30 percent higher risk of recurrence and a nearly 50 percent higher risk of death despite optimal treatment,” study author Dr. Joseph Sparano, a professor of women’s health at the Albert Einstein College of Medicine in New York City, said in a press release.
For the study, researchers looked at data from three studies sponsored by the National Cancer Institute that involved nearly 7,000 women. All the women had stage 1 to 3 breast cancer but were otherwise healthy with normal heart, kidney, liver and bone marrow function.
By looking at the participants’ body mass indexes (BMI) – a ratio of height over body weight that scientists use to measure obesity – the scientists found that BMI increases significantly increases a women’s risk of her breast cancer coming back. These women also were more likely to die of breast cancer than their thinner counterparts in the study.
The effect remained despite optimal treatments including chemotherapy and hormonal therapy. Women who had hormone receptor-positive breast cancer, the most common type of breast cancer that’s found in two-thirds of all breast cancer cases worldwide were most likely to experience these negative outcomes if obese or overweight.
“To me the big news is that it is showing obesity is only related to one subtype [of breast cancer],” Dr. Bette Caan, a senior research scientist at the Kaiser Permanente Division of Research in Oakland, Calif. who was not involved in the study, said to HealthDay. “It’s the most common subtype.”
Sparano told TIME that overweight and obese people produce more estrogen, which may cause hormone receptor-positive cancers to grow. He also said insulin-resistance found in overweight people may contribute to this effect, or a combination of these factors along with general inflammation.
“Treatment strategies aimed at interfering with hormonal changes and inflammation caused by obesity may help reduce the risk of recurrence,” Sparano said in the press release.
Obesity is associated with increased risks for cancers of the esophagus, breast, the lining of the uterus, colon and rectum, kidney, pancreas, thyroid and gallbladder, according to the National Cancer Institute.
