Indole-3-carbinol (I3C), a natural plant chemical found in cruciferous vegetables of the Brassica genus, such as broccoli, cauliflower, brussel sprouts, radishes, and cabbage, is a promising anti-breast cancer compound.  Indole-3-carbinol influences a range of cellular processes, including lowering toxic estrogen. I3C has been shown to regulate the expression of numerous genes.  Combinations of I3C and the anti-estrogen drug tamoxifen work together to inhibit the growth of the estrogen-dependent breast cancer more effectively than either agent alone.
To boost intake of I3C, eat more cruciferous vegetables of the Brassica genus, such as broccoli, cauliflower, brussel sprouts, radishes, and cabbage or take as a supplement; 300 mg per day for breast cancer prevention.

A recent study suggests that women who’ve been treated for breast cancer who are in satisfying romantic relationships may have a lower risk of health problems after treatment. This is mainly because breast cancer survivors in satisfying romantic relationships felt less stressed and in turn had lower inflammation throughout cancer treatment and after.  But this doesn’t mean you’re compromising your health if you’re not in a relationship. Having a romantic partner isn’t for everyone. Single people can be happy and healthy, too, especially if they have a good social network of family, friends, clubs, hobbyists, or a religious organization.

The human microbiome is composed of trillions of microorganisms (bacteria, viruses, fungi) living inside and outside the human body.
The risk of breast cancer and recurrence could be associated with the composition and function of the breast/gut microbiome.
Research shows that there are different bacteria in the breast tissue of healthy women vs those with breast cancer and that the breast microbiome in women with cancer is different from that of women with benign disease, indicating that certain bacteria may be associated with breast cancer development and different responses to treatment.  Diet, drugs, toxins, lack of sleep, inactivity, and stress can negatively change the human gut microbiome which can alter blood estrogen levels, estrogen metabolism, chronic inflammation, the local breast immune microenvironment and its influence on breast cancer recurrence and metastasis. http://ow.ly/2WwJ50BftoE http://ow.ly/OPbN50BftoC
You can increase your good gut bacteria and improve your gut and breast microbiome with:
A plant-based diet
No refined sugar, processed and fast foods
Diverse foods
Fermented foods
High Fiber - 20-30 grams/day
Fasting
Exercise
Stress reduction
Sleep - 7-9 hrs/night
Quality probiotics

Interesting new research showing the important link between gut microbiome and cancer treatment outcomes. Good gut health with an abundance of diverse good bacteria is essential to good health and cancer prevention as well.  You can improve your gut microbiome by eating a high-fiber diet, including fruits and vegetables high in fructo-oligosaccharides such as bananas, dried fruit, onions, leeks, garlic, asparagus and artichokes, as well as grains with resistant starches such as barley or uncooked potato starch, for example. Read the new research findings here: http://ow.ly/ooY150B9cdh

For breast cancer prevention, it's important to eliminate or limit processed, packaged, sugary, fast foods, which:
Decrease appetite suppressing hormones
Increase hunger
Cause weight gain
Increase cellular inflammation
Kill good gut bacteria
Weaken the immune system
"A processed food is a food item that has had a series of mechanical or chemical operations performed on it to change or preserve it. Processed foods are those that typically come in a box or bag and contain more than one item on the list of ingredients."
Here are some unprocessed snack ideas:
Raw or roasted seasoned veggies
Fresh fruit
Dates
Nut butters - all natural
Pitaya and Acai bowls & smoothies
Roasted chickpeas
Zucchini chips
https://www.purplecarrot.com/.../zucchini-chips-with...
Nice cream with frozen bananas
https://www.purplecarrot.com/plant.../vanilla-nice-cream
Cherry Chia Pudding
https://www.purplecarrot.com/plant.../cherry-chia-pudding
No Bake Peanut Butter Cookies
https://www.purplecarrot.com/.../no-bakes-peanut-butter...
Purple Carrot

BPA is a chemical that acts like estrogen in the body. Estrogens have been linked to the increased risk of developing breast cancer.  BPA is found in many plastic products, food and formula can linings, dental sealants, and on the shiny side of paper cashier receipts (to stabilize the ink).  Recently, researchers at Duke University Hospital were among the first to discover that BPA helps the survival of inflammatory breast cancer cells. http://ow.ly/k1j150B48sg.  France has banned BPA in food packaging and California lists BPA as being toxic to the female reproductive tract.
Changing to BPA free plastic may not be better. BPA free chemicals BPF, BPS, bisphenol F, bisphenol AP, bisphenol AF, bisphenol Z, bisphenol B are not safe alternatives to BPA.  Learn how to Limit your exposure to BPA at http://static.ewg.org/pdf/ewg_bpa_guide.pdf.