Eating soy foods on a regular basis-especially during adolescence-might lower the risk of breast cancer, according to preventive medicine researchers at the Keck School of Medicine of USC and colleagues.
Asian-American women who consumed soy foods on a weekly basis during their teen years and adulthood had about half the risk of developing breast cancer compared to similar women who ate little soy during the same time periods, according to a study in the September issue of Carcinogenesis.
Risk also was somewhat lowered for women who ate soy regularly during the teen years but consumed little during adulthood. However, preliminary data suggest little added benefit for women who ate little soy during adolescence but a high amount of soy during adulthood.
"There has been a lot of talk and controversy about the Asian diet and connections between soy food intake and breast cancer. We wanted to look at soy very carefully, to better understand if soy by itself is protective or if the level of soy consumption is just a marker for acculturation," says Anna H. Wu, Ph.D. professor of preventive medicine at the Keck School of Medicine.
Wu and colleagues conducted a case-control study of breast cancer among Chinese, Japanese and Filipino women in Los Angeles County, specifically looking at the importance of soy. From 1995 to 1998, they interviewed 501 Asian-American breast cancer patients and compared them to 594 healthy Asian-American women.
The researchers asked about eating habits, including how many times each week during adolescence they ate tofu. They also asked about the frequency and amounts of whole soy foods, such as tofu, soymilk, miso and fresh soybeans, usually eaten during adulthood.
Intake was highest among Chinese (26.8 milligrams of isoflavones a day), intermediate among Japanese (18.4 mg of isoflavones a day) and lowest among Filipinas (9.3 mg of isoflavones a day). Migrants ate a little more soy than American-born women did. Most of the Chinese and Filipino women in this study-more than 90 percent-were born in Asia, compared to less than 30 percent of the Japanese women.
When women were grouped by how often they ate soy during adolescence and adult life, researchers found that women who were high consumers during both time periods had a 47 percent reduction in risk. Those who ate little soy during adult life but were regular soy consumers during adolescence showed a 23 percent reduction in risk Women who were low consumers during adolescence and high consumers during adulthood showed little reduction in risk. However, the number of such women was small, and researchers note that larger studies must be conducted to confirm this result.
So how does soy work? Scientists are not sure, but they have some ideas.
Animal studies indicate that early life exposure to genistein-the main isoflavone in soybeans-seems to help protect against chemically induced breast tumors. Getting genistein early in life may help the mammary glands develop in a favorable way.
Eating soy might also lead to lower levels of estrogen circulating within the body, some theorize. And some studies show that genistein seems to inhibit some enzymes that are important in metabolizing estrogen.
Regardless of the protective mechanism, Wu notes that if the mounting soy research shows promise, many may ask, "How much soy is enough?" There may be a point at which eating more soy does not further reduce risk, she says. Researchers are still seeking to understand the relationship between soy food dose and risk reduction, though in this study the greatest risk reduction was seen among women with the highest level of consumption: 12.68 mg or more of isoflavones per 1000 kilocalories during adulthood and eating soy foods four or more times a week during adolescence.
Isoflavone levels in soy foods vary considerably, but a serving of store-bought tofu-a quarter of a box-contains about 10 mg of isoflavones, Wu says.
Wu notes that a much larger study is needed to sort out the benefits of adult soy food intake and what levels of soy intake are most helpful. Her study looked only at traditional soy foods, not at genistein or other isoflavones that may be contained in pills and supplements.
July 5, 2002 - Breakthrough in hormonal breast cancer therapy
Highlights from the ground-breaking study into the management of early breast cancer – the ATAC 'Arimidex', Tamoxifen Alone or in Combination) study – were presented today at the 18th UICC Cancer Congress in Oslo.
These data mark a breakthrough in hormonal breast cancer therapy as they clearly demonstrate that anastrozole is significantly more effective than the current 'gold standard' treatment tamoxifen in terms of
The ATAC results show that anastrozole, an aromatase inhibitor (AI), is more effective in reducing the risk of cancer recurring in the same breast, the opposite breast, or elsewhere in the body when compared to tamoxifen. This is the first time an AI has been proved to be superior to tamoxifen in early breast cancer.
Anastrozole was also associated with a number of important tolerability advantages over tamoxifen – a key consideration in early breast cancer where women who are otherwise 'healthy' routinely take hormonal treatment for up to 5 years after initial tumour-removing surgery. Perhaps the most important of these, as presented in Oslo today, is the benefit of anastrozole in reducing the risk of developing abnormalities of the lining of the womb (endometrium) when compared to tamoxifen. Data presented from a sub-study of 279 trial patients*) demonstrated that anastrozole halved the risk of endometrial abnormalities compared to tamoxifen.
Speaking today at the UICC Congress, Dr Sean Duffy, from the Division of Obstetrics and Gynaecology at St James University Hospital in Leeds, UK, and lead ATAC sub-protocol investigator said; "This is an extremely important finding. Even though the risk of developing endometrial cancer when taking tamoxifen is small, and the benefits of this therapy far outweigh the risk, it has been a well known concern for doctors and their patients for some time. However, the ATAC study now demonstrates that anastrozole reduces the risk of endometrial cancer as well as the incidence of vaginal bleeding, compared to tamoxifen. This suggests that women treated with anastrozole are less likely to suffer the anxiety of having to undergo invasive procedures in hospital to rule out endometrial cancer as the cause of the bleeding."
Other tolerability advantages in favour of anastrozole reported at the UICC meeting today, include a significant reduction in the incidence of hot flushes and thromboembolic events such as deep vein thrombosis when compared to tamoxifen. Although the overall incidence of fractures was lower in the tamoxifen group, the incidence of hip fractures, which are associated with the highest mortality, was lower in the group treated with anastrozole (11 vs. 13 cases, respectively). Tamoxifen is known to have protective effects on bone in postmenopausal women and this may account for the difference in fracture rates between treatments to some extent.
ATAC is the largest cancer treatment trial ever conducted, involving over 9,300 post-menopausal women world-wide.
Asian-American Women
June 10, 2002 - Breast cancer rising among Asian-American women - Study shows Japanese-American women are hardest-hit
Asian-American women have traditionally had a lower risk of breast cancer than others, but epidemiologists at the Keck School of Medicine of USC and USC/Norris Comprehensive Cancer Center have found that their breast cancer rates have been rising.
Cases of breast cancer among Japanese-American women, in particular, have been increasing rapidly, according to research published in the June 10 issue of the International Journal of Cancer.
The study is based on cancer cases reported in the mid-to-late 1990s to the Los Angeles Cancer Surveillance Program (CSP). The registry records cancers throughout Los Angeles County, the most populous and probably most ethnically diverse county in the nation. Breast cancer rates in Los Angeles are similar to rates nationwide.
Researchers found that the breast cancer incidence rates for Japanese and Filipino women were about double those for Chinese and Korean women, and rates rose during the 1993-1997 period for all except Chinese women.
"Although Asian-American women in the past have had low breast cancer rates, that appears to no longer be the case," says Dennis Deapen, professor of preventive medicine and director of the Los Angeles County CSP. "And if trends from the 1990?s have continued, rates among Japanese-American women in Los Angeles County may have surpassed those of non-Hispanic white women, who have historically had the highest rates of breast cancer."
The study indicated the following about breast cancer:
Among Asian women 50 years or older, diagnosed cases increased about 6.3 percent a year during the five-year period. Among non-Hispanic white women 50 years or older, diagnosed cases increased about 1.5 percent a year during the same time period.
In 1997, Asian-American women experienced 78 cases per 100,000 women. Non-Hispanic whites had about 129 per 100,000, African-Americans had about 98 per 100,000 and Hispanics had about 64 per 100,000.
Breaking down Asian-Americans by national origin shows disparities. In 1997, Japanese women experienced 114 cases per 100,000 women. Flipinas had about 98 per 100,000, Chinese women had about 51 per 100,000 and Korean women had about 45 per 100,000. "Breast cancer incidence for Japanese-American women in Los Angeles County is the highest reported anywhere in the world," Deapen notes. In Japan itself, studies have shown that breast cancer incidence also has increased dramatically, more than doubling from 1960 to the late 1980s. The Japanese lifestyle has become increasingly Westernized, study authors note, influencing factors known to increase risk for breast cancer: having fewer children, engaging in less physical activity and experiencing increasing obesity. Japanese are also eating more fats and fewer soy products.
Research has shown that when Asian women migrate to the United States, breast cancer risk increases in subsequent generations. Among the four Asian groups analyzed in this study, Japanese were the first population to migrate to Los Angeles County in substantial numbers, followed by Filipinos. Chinese and Koreans tend to be more recent and less acculturated immigrant populations.
Deapen and colleagues note that the trends point out the need for increasing awareness of breast cancer as a significant health hazard among Asian-American women, especially those of Japanese descent. Although Asian-American women have traditionally had lower-than-average breast cancer risk, physicians need to know that is no longer true?and breast cancer screening among such women is just as important as it is in other groups.
Adds Deapen: "The rapid increase in cancer rates also suggests that outside factors?such as diet and exercise?are prominent in risk, and these factors can potentially be altered."
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