A recent study published in the Journal of the American Medical Association (JAMA) shows evidence that a diet containing several daily servings of soy may have special benefits for breast cancer patients and survivors. Researchers concluded that a diet with moderate soy intake can be associated with a 29% decrease in mortality, and a 32% decrease in the risk of recurrence among those diagnosed with breast cancer.
This is the largest population-based study ever to examine soy intake and breast cancer outcomes. Scientists followed the diet and health status of more than 5,000 breast cancer patients over the course of several years, with ongoing research still underway.
The new research has been acknowledged as a significant soy science development by JAMA and experts from the National Cancer Institute and the Cancer Research Center. The findings offer encouraging confirmation that minimally processed foods made from whole soybeans are a safe choice for women with a history of breast cancer; a position long supported by the American Cancer Society.
Even more important are the findings suggesting that soy consumption may actually provide specific health benefits relevant to breast cancer patients. In the words of one specialist commenting on the study: "Clinicians can advise their patients with breast cancer that soyfoods are safe to eat, and that these foods may offer some protective benefit for long-term health."
This exciting study adds strong positive data to a large body of research examining the value of soy in the diet of breast cancer patients. We at Silk are encouraged by the study, and look forward to additional research that may help advance science in this area. Breast cancer patients or those known to be at high risk for the disease should always work closely with a doctor to determine the healthiest dietary choices.
Consumption of Soy Food Among Women With Breast Cancer Associated With Decreased Risk of Death, Cancer Recurrence
INFORMATION CONTAINED IN THESE NEWS RELEASES IS PROTECTED BY COPYRIGHT. JOURNAL ATTRIBUTION IS REQUIRED.
EMBARGOED FOR RELEASE: 3 P.M. (CT) TUESDAY, DECEMBER 8, 2009
Media Advisory: To contact Xiao Ou Shu, M.D., Ph.D., call Craig Boerner at 615-322-4747 or email craig.boerner@Vanderbilt.Edu. To contact editorial co-author Rachel Ballard-Barbash, M.D., M.P.H., call the NCI Press Office at 301-496-6641 or email ncipressofficers@mail.nih.gov.
Consumption of Soy Food Among Women With Breast Cancer Associated With Decreased Risk of Death, Cancer Recurrence
CHICAGO - Although there is a concern regarding the safety of soy food consumption among breast cancer survivors, researchers have found that women in China who had breast cancer and a higher intake of soy food had an associated lower risk of death and breast cancer recurrence, according to a study in the December 9 issue of JAMA.
"Soy foods are rich in isoflavones, a major group of phytoestrogens that have been hypothesized to reduce the risk of breast cancer. However, the estrogen-like effect of isoflavones and the potential interaction between isoflavones and tamoxifen have led to concern about soy food consumption among breast cancer patients," the authors write.
Xiao Ou Shu, M.D., Ph.D., of Vanderbilt University Medical Center, Nashville, Tenn., and colleagues examined the association between soy isoflavone intake with breast cancer recurrence and survival. The researchers analyzed data from the Shanghai Breast Cancer Survival Study, a large, population-based study of 5,042 female breast cancer survivors in China. Women ages 20 to 75 years with diagnoses of breast cancer between March 2002 and April 2006 were recruited and followed up through June 2009. Information on cancer diagnosis and treatment, lifestyle exposures after cancer diagnosis, and disease progression was collected at approximately 6 months after cancer diagnosis and was reassessed at three follow-up interviews conducted at 18, 36, and 60 months after diagnosis. A Shanghai Vital Statistics Registry database was used to obtain survival information for participants who were lost to follow-up.
After a median (midpoint) follow-up of 3.9 years, 444 total deaths and 534 recurrences or breast cancer-related deaths were documented among the group of 5,033 surgically-treated breast cancer patients. Soy food intake, as measured by either soy protein or soy isoflavone intake, was inversely associated with mortality and recurrence. Patients in the group with the highest intake of soy protein had a 29 percent lower risk of death during the study period, and a 32 percent lower risk of breast cancer recurrence compared to patients with the lowest intake of soy protein. The adjusted 4-year mortality rates were 10.3 percent and 7.4 percent and the 4-year recurrence rates were 11.2 percent and 8.0 percent, respectively, for women with the lowest and highest groups of soy protein intake.
"The inverse association was evident among women with either estrogen receptor-positive or -negative breast cancer and was present in both users and nonusers of tamoxifen," the researchers write.
"In summary, in this population-based prospective study, we found that soy food intake is safe and was associated with lower mortality and recurrence among breast cancer patients. The association of soy food intake with mortality and recurrence appears to follow a linear dose-response pattern until soy food intake reached 11 grams/day of soy protein; no additional benefits on mortality and recurrence were observed with higher intakes of soy food. This study suggests that moderate soy food intake is safe and potentially beneficial for women with breast cancer."
(JAMA. 2009;302[22]:2437-2443. Available pre-embargo to the media at www.jamamedia.org)
Editor's Note: Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.
Editorial: Challenges in Design and Interpretation of Observational Research on Health Behaviors and Cancer Survival
Rachel Ballard-Barbash, M.D., M.P.H., of the National Cancer Institute, Bethesda, Md., and Marian L. Neuhouser, Ph.D., of the Fred Hutchinson Cancer Research Center, Seattle, write in an accompanying editorial that while this study provides important information, there are several concerns, including differences in the quality, type and quantity of soy food intake between China and the U.S. (47 mg/d vs. 1 to 6 mg/d, respectively, average isoflavone intake). Also, they point out the relatively short median follow-up time of the study (4 years); that there likely are differences in screening rates in China compared with the U.S.; and a number of factors may make it difficult to compare stage- and treatment-specific results in China with outcomes in the U.S.
"Even though the findings by Shu et al suggest that consumption of soy foods among breast cancer patients is probably safe, studies in larger cohorts are required to understand the effects of these foods among diverse clinical subgroups of breast cancer patients and survivors. In the meantime, clinicians can advise their patients with breast cancer that soy foods are safe to eat and that these foods may offer some protective benefit for long-term health. Moreover, the potential benefits are confined to soy foods, and inferences should not be made about the risks or benefits of soy-containing dietary supplements. Patients with breast cancer can be assured that enjoying a soy latte or indulging in pad thai with tofu causes no harm and, when consumed in plentiful amounts, may reduce risk of disease recurrence."
(JAMA. 2009;302[22]:2483-2484. Available pre-embargo to the media at www.jamamedia.org)
Editor's Note: Please see the article for additional information, including financial disclosures, funding and support, etc.
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