Currently, there is no research to show that soy has adverse effects with ductal carcinoma in situ (DCIS). Soy isoflavones (found in soybeans) are currently being researched to help women who are at a high risk of breast cancer. Although a single serving of soybeans per day should not be an issue, due to the varying arguments for and against soy, in terms of cancer, it is best to discuss the use of soy with your doctor.