- Question from LindaA: Are you saying that those of us who have breast cancer probably developed it in our teenage years?
- Answers —Sue Heffelfinger, M.D., Ph.D.: Some current thinking on the process of breast cancer formation is that some of the initial genetic events (a process we call “initiation”) probably occur in this very young age range. Breast cancer takes years and decades to develop from the first genetic damage until there's something you can feel or see on a mammogram.
There's a great deal of debate. If a woman gets breast cancer in her 90s, how long did it take to progress? If you're in your 40s, it's a much shorter time frame, but you can't prove that either one began in childhood or teen years. We just don't know.
All breast cancers are different from one woman to the next, so the genetic pathway will also be different. Many of these very early genetic events and exposures to carcinogens we think can occur very, very early, potentially even in utero, in sensitive stem cells in the mammary glands.
- Jennifer Griggs, M.D., M.P.H.: This long period for development of cancers makes the risk of developing them hard to study. For example, we're asking women in their 60s where they lived when they were teenagers. This may be one reason the answers are slow in coming.
- Devra Davis, Ph.D., M.P.H.: That's a very good point. It may be that breast cancer that occurs prior to menopause may be a fundamentally different type of disease compared with breast cancer that occurs after menopause. There may be very different factors for each.
There are some things, however, that appear to protect against breast cancer no matter what age they occur at. For example, vigorous exercise is protective against breast cancer. It's especially protective for young women who have been active for much of their lives, but there's also a benefit for older women who may not have started exercising until they're older.
- Jennifer Griggs, M.D., M.P.H.: Can you define “vigorous”?
- Devra Davis, Ph.D., M.P.H.: Leslie Bernstein, who's done much of this work, was herself a world class swimmer and “vigorous” refers to more than an hour a day of elevated cardio workout. The question of whether more moderate exercise is a benefit is still open, although as you know there are many good reasons why women should exercise regularly.
One of the theories why exercise does work to reduce the risk of breast cancer comes from the work of Brad Lowe and others. They have shown that women who exercise regularly and vigorously have lower amounts of circulating levels of free estradiols, and the lower amounts of free estradiols appear to be associated with a lower risk of breast cancer.
Alcohol has been shown to increase the amount of circulating estradiols, and so does hormone replacement therapy. So women who are on HRT and who drink regularly have an even greater risk of breast cancer, perhaps because both alcohol and HRT increase the amount of circulating estradiols.
- Jennifer Griggs, M.D., M.P.H.: Could you comment on the role of folate for women who are interested in reducing their breast cancer risk and who enjoy a glass of wine at dinner? I have been recommending that patients increase their intake of folate in vegetables and even consider supplementing their diets with folate if they want to continue to enjoy a glass of wine a day.
- Devra Davis, Ph.D., M.P.H.: I think that's an excellent suggestion. Also, there are probably some other benefits of alcohol, but clearly breast cancer is problematic.
- Sue Heffelfinger, M.D., Ph.D.: There's a limit to the amount of data correlating alcohol intake with family history. The data suggests it is an increased risk factor if you already have a family history.
- Jennifer Griggs, M.D., M.P.H.: I just want to stress at this point in the conversation that most women with breast cancer have no obvious risk factors for breast cancer and that, even if one of the things we've talked about applies to you or your sister or your friend, what we're talking about probably has more to do with populations or groups of women rather than applying to an individual woman. So if you were indulging back in your high school and college days and wonder if your breast cancer is a result of your own indiscretions, we want to relieve you of that concern.
- Devra Davis, Ph.D., M.P.H.: The sad truth is that only less than 1 in 10 cases of breast cancer occurs in a women who has inherited a defect in her genes that she received from her parents. So this means that 9 out of every 10, and more like 19 out of every 20 were born with healthy genes; they didn't inherit the disease. So something has happened in the course of their lifetimes to give them breast cancer and we know that most cancer comes about because our genes stop doing their job of keeping cells under control.
On Wednesday, August 17, 2005, our Ask-the-Expert Online Conference was called Environmental Issues and Breast Cancer. Devra Lee Davis, Ph.D., M.P.H., Sue Heffelfinger, M.D., Ph.D., and moderator Jennifer Griggs, M.D., M.P.H. answered your questions about which environmental hazards may increase your risk for breast cancer and how you can reduce them in the home and workplace.
The materials presented in these conferences do not necessarily reflect the views of breastcancer.org. A qualified healthcare professional should be consulted before using any therapeutic product or regimen discussed. All readers should verify all information and data before employing any therapies described here.
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Devra Lee-Davis, Ph.D., M.P.H. directs the Environmental Oncology Center at the University of Pittsburgh Cancer Institute.
Sue Heffelfinger, M.D., Ph.D. is director of an NIH Center for Breast Cancer and the Environment at the University of Cincinnati and also associate professor in the department of pathology and laboratory medicine.
Jennifer Griggs, M.D., M.P.H. is a medical oncologist specializing in the treatment of breast cancer, with a a special interest in cancer survivorship, patient-physician communication, and quality of care for women with breast cancer.
