Diet and Breast Cancer: Fine-tuning the Science
Saturday, March 29, 2008 Washington, D.C.
American Institute for Cancer Research
Food Screening methods and treatment options have improved significantly for breast cancer. Now, the science of breast cancer prevention is catching up as scientists are discovering that breast cancer is not a single disease, although studies have historically treated it as only one.
For example, pre-menopausal breast cancer has surprisingly little in common with post-menopausal breast cancer. Similarly, breast tumors that contain receptors for estrogen (ER-positive tumors) are different from tumors that don't have those receptors (ER-negative tumors). Accounting for these differences, and several others, is crucial to treatment - and likely for prevention as well.
Most headline-making results on diet and breast cancer you hear about today come from cohort studies (studies that track a large group over several years) that began a long time ago - before scientists understood the distinctions between types of breast cancer.
So a study that analyzes, for example, the link between a certain food and breast cancer, may simply be grouping all the women in the study who developed breast cancer together. But focusing on one kind of breast cancer or another means that these formerly large cohort studies (of perhaps 1,000 breast cancer cases) are really studies of a few hundred of the various types, which means less certainty overall. Distinguishing the pre- or post-menopausal, ER-negative or -positive breast cancers means the findings for one group won't get watered down by mixing them with all the other types of breast cancer.
We need large cohort studies that look specifically at each different type of breast cancer and ask subjects more detailed questions from the beginning. And we need to let the studies run long enough for each different category of breast cancer to show up in significant numbers.
This need doesn't invalidate all those studies on diet and breast cancer that you've been reading about for years. Their focus is simply becoming more refined so important connections between the complex human diet and different types of breast cancer may be found.
Today's scientists are collecting detailed information about things like diet during adolescence (because research indicates breast tissues are particularly sensitive to dietary influence during breast development), physical activity (type, intensity and duration) and a host of other factors. However, these studies are only the beginning, and it may take years for these studies to achieve the kind of statistical power necessary to draw conclusions.
In the meantime, the most important thing to keep in mind is this: don't regard any single study as definitive, no matter how large it is and how much statistical power it packs. As we continue to refine the study of breast cancer prevention, it will still be necessary to look for agreement among different studies and examine any new results in the context of findings that have come before. The AICR is continuously compiling high-quality data to help scientists and the public understand the big picture for cancer prevention.