The study was conducted by S.J. Nechuta of Vanderbilt University School of Medicine in Nashville, TN and colleagues.
The researchers wrote in their study report that soy isoflavones possess antiestrogenic and anticancer properties but also estrogen-like properties, which make it difficult to tell whether soy foods like tofu and soy milk help breast cancer survivors.
The study was intended to evaluate the association between postdiagnosis soy food consumption and outcomes of breast cancer in U.S. and Chinese women registered in the After Breast Cancer Pooling Project.
Enrolled in the study were 9,514 breast cancer survivors with diagnosed invasive breast cancer between 1991 and 2006 from two US cohorts and one Chinese cohort. Soy isoflavone intake was estimated based on data collected through validated food-frequency questionnaires.
During a mean follow-up of 7.4 years, a total of 1,171 deaths were identified with 881 from breast cancer and 1348 from recurrences.
Soy isoflavone consumption was found inversely associated with recurrence among both US and Chinese patients, regardless of whether data were analyzed separately by country or combined.
An analysis of combined data showed eating10 or more mg of soy isoflavones per day was associated with a 13 percent reduced risk of all-cause, 17 percent reduced risk of death from breast cancer, both reductions were statistically insignificant, and a statistically significant 25 percent reduced risk of recurrence.
The researchers concluded "In this large study of combined data on US and Chinese women, postdiagnosis soy food consumption of ≥10 mg isoflavones/d was associated with a nonsignificant reduced risk of breast cancer-specific mortality and a statistically significant reduced risk of recurrence."
Breast cancer is expected to be diagnosed in more than 220,000 American women in 2012 and the disease will kill about 40,000 in the same year in the U.S.
Breast cancer in many cases is preventable. Medical radiation used in diagnostics and cancer treatment, hormone therapies are two major risks for the disease. Taking vitamin D supplement is another way to drastically reduce the risk of developing the disease.
