Soy Vey! Is Soy Safe for Breast Cancer Survivors or Not?

Is soy safe for breast cancer survivors? Traditionally, caution was advised. Then, a big study in April suggested that survivors needn't worry about soy consumption. Now, a new study raises concerns again. Today we'll share the latest research on soy for breast cancer survivors.

Links to all of the studies, news stories and overviews discussed below may be found on the soy page of the LATESTBreastCancer.com website. If the link does not take you directly to the soy page, please click the "Treatments" tab, then search for "soy" in the search box in the top right corner.

A little biology

The issue for breast cancer survivors involves the isoflavones in soy. Isoflavones are phytoestrogens, or an estrogen-like compounds found in plants. They act like weak estrogens and are able to bind to estrogen receptors in cells. For women with estrogen receptor positive breast cancer, there is some concern about the estrogen-like behavior of isoflavones in soy.

April 2011 study: Dietary soy is safe after breast cancer

An April 5 presentation to the American Association for Cancer Research caused quite a media stir, with headlines in the Los Angeles Times ("Soy: Breast cancer survivors can eat soy foods without risk, study finds") and Consumer Reports Health ("No need to avoid soy after breast cancer").

The study analyzed soy consumption data from 18,000 breast cancer survivors in China and America followed for an average of more than 9 years. According to the study conclusion, "Soy food consumption was not associated with an increased risk of mortality or cancer recurrence among breast cancer survivors."

On the positive side, this data represented a large number of women over a long period of time. On the other hand, the study has not yet been published in a medical journal or subject to critical peer review. Also, the study conclusions relate to dietary soy not soy supplements.

August 2011 study: Soy supplements may affect aromatase inhibitor activity

An August 10 study from The Netherlands published in Toxicology examined the effects of the soy isoflavone genistein on estrogen dependent breast cancer cells. In the study, genistein induced tumor cell growth and increased aromatase expression and activity. The data suggested that soy-based supplements "might affect the efficacy of breast cancer treatment with aromatase inhibitors." The authors caution,

Considering the high number of breast cancer patients using soy supplements to treat menopausal symptoms, the increasing risk for adverse interactions with breast cancer treatment is of major concern and should be considered with care.

NAMS 2011 Isoflavones Report: More studies are needed

The North American Menopause Society (NAMS) issued a comprehensive report on soy isoflavones for menopausal symptoms (link to full report). It provides a thorough review of the biology of soy and the recent research on hot flashes, breast safety and bone health. With respect to use after a breast cancer diagnosis, the report notes,

Specific recommendations regarding soy or isoflavone
consumption by breast cancer survivors cannot be made at
this time; studies in human subjects indicate a null or
protective effect, whereas cell culture and rodent studies
indicate potential for risk. Further studies are needed. (p. 739)

Interestingly, the report discusses human studies from both China and the United States which support the safety of soy after breast cancer. (p. 740) Nevertheless, it does not recommend soy due to safety concerns in cells and animals.

NAMS is not alone in recommending caution when using soy after breast cancer. The National Institutes of Health National Center for Complementary and Alternative Medicine webpage on soy notes,

Soy's possible role in breast cancer risk is uncertain. Until more is known about soy's effect on estrogen levels, women who have or who are at increased risk of developing breast cancer or other hormone-sensitive conditions (such as ovarian or uterine cancer) should be particularly careful about using soy and should discuss it with their health care providers.

The American Cancer Society publishes a similar warning,

The isoflavones in soy have weak estrogen-like activity, and it is unclear how they might affect the growth of estrogen receptor-positive breast cancers. Some researchers suggest they may act as anti-estrogens and reduce cancer growth, while others suggest their estrogen-like activity could cause cancer to grow faster. Until this issue is resolved, many oncologists recommend that people taking tamoxifen or aromatase inhibitors and people with estrogen-sensitive breast tumors should avoid adding large amounts of soy, including soy supplements or isoflavones, to their diets.

At LATESTBreastCancer.com, we'll continue to follow and share the latest research on soy for breast cancer survivors. Any new developments will be added to the LATESTBreastCancer.com website and highlighted here. Please stay tuned.

Breast Cancer News (8/10): Exercise, Avastin and Soy

In today's breast cancer news update, we'll share the latest media headlines on exercise, Avastin and soy. As always, links to the news stories discussed below may be found on the treatment pages of the LATESTBreastCancer.com website.

The New York Times: "The Benefits of Exercise After Cancer"

Yesterday, The New York Times shared a recent report on the benefits of exercise during and after cancer treatment. In the report, "The importance of physical activity for people living with and beyond cancer:
A concise evidence review," Macmillan Cancer Support (UK) reviewed 60 studies on exercise during and after cancer treatment. Exercise was found to reduce the risk of breast-cancer mortality and recurrence. It also improved physical function, fatigue, well-being, body composition and bone health. For women with advanced breast cancer receiving chemotherapy, exercise affected quality of life and fatigue. The Macmillan Cancer Support webpage is full of additional information on physical activity for cancer patients and healthcare providers.

Bloomberg: "Roche Seeks ‘Middle Ground’ in U.S. Appeal of Avastin Breast Cancer Ruling"

The Avastin (bevacizumab) regulatory saga continues. According to a story in Bloomberg, Roche has appealed the recent FDA withdrawal of approval of Avastin for metastatic breast cancer with a "middle ground proposal." Roche asked the FDA to allow patients with advanced, aggressive cancer with few treatment options to use Avastin with Taxol (paclitaxel). The proposal includes an offer to provide doctors with a "risk-evaluation strategy" and additional information on Avastin effectiveness and risks. Roche also plans a 480 patient follow-up trial. Trial failure would trigger an "immediate voluntary withdrawal of Avastin for breast cancer." The trial is to include a test of a protein biomarker (VEGF-A) to identify patients who may benefit from Avastin.

The Los Angeles Times: "Study indicates soy won't fight bone loss after menopause"

After breast cancer treatment, some women turn to natural remedies, such as soy, for menopausal symptoms such as hot flashes and bone loss. According to a story in yesterday's Los Angeles Times, a recent study in the Archives of Internal Medicine has found that soy tablets do not reduce bone loss in post-menopausal women. Further, the women who took soy experienced more hot flashes and constipation. The women in the study were not breast cancer survivors, but the effects of soy on menopausal symptoms should still apply.

Please check back tomorrow for more breast cancer news and research updates from LATESTBreastCancer.com.

The Breast Cancer News Update: July 22

There's been a lot of buzz about a recent study which found that tall women have a higher risk of breast cancer. According to the story in the Los Angeles Times, breast cancer risk increased 17% with every 4 inches in height. While this may be interesting, it's not really useful. Height is not a modifiable risk. Today we'll look at recent studies on modifiable risk factors such as diet, exercise, and alcohol use. All of the studies below can be found on the complementary therapy and lifestyle pages of the LATESTBreastCancer.com website.

Diet and breast cancer risk: soy, omega-3s and vitamins

Breast cancer research does not always have a positive ending. This month, two studies found that soy and omega-3 fatty acids do not reduce the hormones associated with breast cancer risk. Another study found that while vitamin A may reduce risk, vitamins C and E do not appear to have an effect.

Dietary soy does not modify estrogen levels

A July 8 study in Cancer Epidemiology, Biomarkers & Prevention examined the effect of dietary soy on blood and nipple aspirate fluid estrogen levels to assess impact on breast cancer risk. The authors concluded that soy in the amounts typically consumed by Asians did not significantly modify blood or nipple fluid estrogen levels. They did observe a non-significant trend towards lower estrogen levels in nipple fluid during the high-soy diet, which "counters concerns about adverse effects of soy foods on breast cancer risk."

Omega-3 fatty acids do not reduce hormones associated with risk

A July 11 study in Nutrition and Cancer found, contrary to expectations, that omega-3 fatty acids did not reduce the hormones associated with breast cancer risk.

Retinol and vitamin A may reduce breast cancer risk

A July 15 review in Cancer Causes & Control analysed the research on retinol, vitamin A, vitamin C and vitamin E and breast cancer risk. The authors concluded that intake of retinol and vitamin A "could reduce breast cancer risk," but the association between vitamins C and E and risk "seem to be limited."

Lifetime exercise reduces precancerous benign breast disease

According to a July 12 study in Cancer Causes & Control, "exercise may be inversely associated with the risk of developing proliferative benign breast disease, one of the earliest steps in the development of breast cancer." The study followed over 40,000 women for four years. Women in the study reported on levels of physical activity during adolescence and adulthood. A significant inverse association was found between walking and the risk of benign breast disease.

Alcohol and breast cancer risk

This month there have been two stories on the use of alcohol and breast cancer risk.

First, a July 11 story in the Los Angeles Times reported that although government health agencies often publish recommended drinking limits, no amount of alcohol is safe in terms of breast cancer risk.

On July 19 and 20, BBC News and Cancer Research UK reported on a study which found that obesity has the greatest effect on the hormones associated with breast cancer risk, followed by alcohol use then smoking. Women who drank 2.5 units of alcohol a day had higher levels of all hormones. A large glass of wine is 3 units of alcohol.

Please check back Monday for highlights of the weekend breast cancer news. Until then, all the latest breast cancer news and research may be found on the treatment pages of the LATESTBreastCancer.com website.