A study published in the Cancer Epidemiology, Mile Markers, and Prevention journal analyzed the eating patterns of 1,800 Mexican women and concluded that participants who got more than half of their total calories from refined carbohydrates (white flour, sugar, chips, cookies, etc.) had a 220 percent higher risk of developing breast cancer, than subjects whose carbohydrate intake consisted mostly of whole grains.
Does this mean you should never have a refined carbohydrate again? No.
However, refined carbohydrates should make up the minority of your total carbohydrate intake. I encourage a 75/25 division, wherein 75% of your daily grains are whole.
If you want -- and are able -- to make 100% of your grains whole, go right ahead! However, I allow a 25% window for situations where these might not be available to us as well as for personal taste (as much as I love whole wheat pasta, I respect that it doesn't float some people's boats).
It's worth keeping in mind that refined carbohydrates should not be blamed exclusively for increasing one's cancer risk.
After all, it is usually these types of foods (cookies, cakes, muffins) that also contain high amounts of sugars, sodium, and saturated fats. Or, in the case of hamburgers buns, accompany foods with these same properties.