Although there are some stories circulating about individuals who have been cured of cancer by eating a particular diet (such as the raw food diet) or a particular food or set of supplements, there is no scientific evidence to support the effectiveness of treatment of cancer with food or a combination of food and supplements alone.

Medical treatment is essential to eliminate tumors and reduce recurrence

If you have been diagnosed with breast cancer, it is essential that you complete treatment at a respected cancer facility. For most patients, the most important part of this treatment is surgery to remove the tumor or tumors. If the pathology report indicates that the surgery did not result in clean margins (i.e., a cancer-free area around the tumor removed), it should probably be redone to get clean margins. Think of the tumor as a cancer factory — it must be removed to shut it down.
In addition to surgery, you will probably receive some combination of radiotherapy, chemotherapy and/or endocrine treatment such as an aromatase inhibitor. These treatments are designed to clean up any remaining micrometastases. These procedures and drugs tend to be invasive and toxic, which gives you an idea of how powerful the arsenal must be to put breast cancer into remission. It's important to remember that these treatments actually work in the majority of cases.

Diet is more effective for breast cancer prevention than cure

While eating a well-designed breast cancer diet can potentially help you avoid breast cancer or a relapse once you are in remission, doing so will not eliminate a well-established tumor. Think of eating cancer-preventative food similarly to how you might take steps to prevent having your house catch fire if you are in a fire-prone area. You might establish a brush-free perimeter around your house, replace a wood-shingle roof with a tile roof, keep fire extinguishers on hand and make sure the water pressure is good in your neighborhood. However, should your house truly catch fire despite your efforts, your garden hose and fire extinguishers will not be enough - you need the fire department, with their heavy equipment and huge fire hoses. Similarly, if you have been diagnosed with breast cancer, you need the best that modern medicine has available to fight it.
This is not to say that you should not use complementary medicine during your fight with cancer, but this alone will not be as effective as traditional western medicine in putting cancer in remission and should not be used instead of it. The sad fact is that according to one study, breast cancer patients who use alternative medicine exclusively have shorter survival times overall than patients who undergo traditional U.S. medical treatment.