Q & A

On Cancer: Diagnostic Radiologist Carol Lee Gives More Insights into Breast Density and Breast Cancer Risk

By Jim Stallard, MA, Writer/Editor  |  Wednesday, August 20, 2014
Dense breast tissue can sometimes make cancer detection by mammogram more challenging. Dense breast tissue can sometimes make cancer detection by mammogram more challenging.

Last year, OnCancer featured a Q&A about breast density and breast cancer risk with Memorial Sloan Kettering diagnostic radiologist Carol Lee that drew a large number of questions and comments from readers. Recently, we checked in with Dr. Lee again to discuss breast density in more detail and gain additional insights into the topic.

Does dense breast tissue merely make it more difficult to detect cancer, or does dense tissue actually increase breast cancer risk?

The 10 percent of women with extremely dense breasts have four to six times increased risk [of breast cancer] compared with women who have completely fatty breasts [the least dense]. However, most women fall between these extremes, and it is impossible to determine a woman’s level of risk based solely on a mammogram.

It is very important to understand that women with non-dense breasts also can develop breast cancer.

Could some of the increased breast cancer risk be caused by the need for a higher radiation dose during screening mammograms in order to penetrate dense tissue? Or could the higher risk be due to the fact that dense breasts simply have more breast tissue that can be exposed to radiation?

It is unlikely that the difference in radiation dose, if any, contributes to risk associated with dense tissue. Everything else being equal, the amount of extra radiation required during mammography of dense breasts is extremely small. In addition, the amount of radiation needed depends not just on breast density but also breast size. So it is possible that a woman with large, non-dense breasts could actually receive more radiation than a woman with small, dense breasts.

Are there any tests that are better than mammography for women with dense breasts?

Mammography is the only screening test that has been proven to decrease deaths from breast cancer. However, mammography is not perfect and some cancers will not be seen on mammograms. For women with dense breasts, ultrasound is often used in addition to mammography for further evaluation. Ultrasound, however, picks up many things that turn out not to be cancer but that may require further testing, including biopsy.

Sometimes magnetic resonance imaging [MRI] can detect a cancer in dense breasts that was not seen by mammograms or ultrasounds. However, MRIs also have drawbacks. They require the injection of intravenous contrast dye; like ultrasound they may give a false-positive reading, resulting in the need for additional testing or biopsy that turns out to be benign; and they are very expensive and not always covered by insurance. In general, MRIs are used in women at very high risk of breast cancer such as those with a known genetic mutation associated with the development of breast cancer. Every patient is different, and decisions about which type of screening test is advisable should be made after discussion with a doctor.

Does the increase in breast density that naturally occurs while a woman is breastfeeding interfere with the ability to identify abnormalities in the breast?

The accuracy of screening tests such as mammogram, ultrasound, and MRI is reduced during breastfeeding because changes in the breast during this period make cancers harder to detect. For routine screening, it is generally preferable to wait a few months after breastfeeding has stopped before having a mammogram or MRI.

Do African-American women tend to have denser breasts than women of other races, and could this contribute to delayed diagnosis and increased mortality among black women with breast cancer?

Overall, African-American women do not have higher breast density than women of other races, so this does not seem to be a factor in the higher mortality rates among this population of women. Other factors, such as decreased access to care and more aggressive tumor types, are more likely to be causing the discrepancy.

Does breast density change from one year to the next? Does it generally stay the same after menopause and throughout one’s lifetime? What might cause breast density to change?

It is common for breast density to decrease gradually with age. However, many women maintain the same breast density throughout their lives, and it is not possible to predict how one person’s breast density may or may not change. Many things can affect breast density, such as taking or stopping hormone replacement medicines or gaining or losing weight, but this is quite variable.

What should women do if they are told after a mammogram that they have dense breasts?

As I recommended in the previous discussion, women with dense breasts should talk to their doctors about their individual risk for breast cancer and together decide whether additional screening makes sense.

Comments

Are 3D mammograms better at detecting breast cancer?

Carolyn, thank you for your comment. We consulted with Dr. Lee, who responds, "The experience with tomosynthesis (the actual name of the so-called 3D mammograms) is still early. Some studies have shown a better cancer detection rate but others have not compared it with the regular digital mammogram. All of the studies so far do show a decrease in false-positive readings with tomosynthesis."

I believe that tomosynthesis is used as a screening tool at MSK (for those not previously diagnosed), but not usually for diagnostic mammos, at least at this point in time. I was just curious as to the reasoning for that.

Laurie, thank you for your comment. We consulted with Dr. Lee, who responds:

"It is correct that tomo is used primarily for screening here at Memorial Sloan Kettering, though it is occasionally used in the diagnostic setting. Studies of tomosynthesis to date have mainly focused on its use as a screening tool. There is very little published information so far on its use for diagnosis. As our experience with tomosynthesis grows in this country, the most appropriate use should become clearer."

Thank you for your response. Of course, if someone had a previous diagnosis and then comes for yearly or bi-annual follow-up, then wouldn't the contralateral (non-diagnosed) breast be considered as appropriate for "screening" rather than diagnostic. The distinction is a bit confusing (regardless of whether tomo is used or not). So, maybe what I'm asking is what is the difference between "diagnostic" and "screening" when not in the acute diagnostic phase of evaluation, but rather in a follow-up setting? I hope this makes sense.

Laurie, we asked Dr. Lee for clarification and she responds: "A screening mammogram is one in which there is no specific question to be answered in an asymptomatic woman. For women who have been treated for breast cancer with lumpectomy and radiation, subsequent mammograms will be done as diagnostic examinations for several years even if they are having no problems just to be extra careful but the differentiation between screening and diagnostic is not always clear cut."

I was treated successfully for breast cancer 8 years ago; now my younger sister has breast cancer, too. Because I was told by my doctor, and because every annual mammo report has stated that I have dense breasts, I requested a sonogram this year. My doctor would not order a sonogram. Then, after this request's denial and after my mammogram last month, my report, for the very first time, reported a change in my breast density assessment: from "dense" and 51-75% every year thruout the past 8 years; to this year's "mild" or 25-50%. While this may be possible, it also appears conveniently coincidental; should I be concerned?

Pat, unfortunately we are unable to answer specific medical questions on our blog. If you would like to make an appointment with a Memorial Sloan Kettering physician, please call our Physician Referral Service at 800-525-2225 or go to http://www.mskcc.org/cancer-care/appointment. For questions about breast cancer density, you also can call the National Cancer Institute’s Cancer Information Service at 800-4CANCER (800-422-6237). To learn more about the CIS, including Live Chat help and how to send them an email message, go to http://www.cancer.gov/aboutnci/cis/page3.

Please comment on the pros and cons of thermography.

We sent your comment to Dr. Lee, who responded, "Thermography has not been demonstrated in any study to be of value as a screening tool. In 2011, the FDA issued a warning that thermography should NOT be used in place of mammography. You can see the FDA statement by visiting the website www.fda.gov and searching for thermography." Thank you for your comment.

Do elderly women 80 and over with dense breasts need to have mamography
exams (3-D) every year if they have never had breast cancer?

Wanda, thank you for your comment. In the United States, there is no set age after which screening is no longer recommended, though in Europe and other countries around the world screening mammography is generally not done after age 70 or 75, In the US, the recommendation is for screening to continue as long as a woman is in good health.

Is there any way to reduce breast density through diet, medication or homeopathic options?

Marilyn, thank you for your comment. This link provides some information addressing your question:

http://www.dslrf.org/breastcancer/content.asp?ATID=60&L2=2&L3=8&L4=0&P

For additional questions about breast density, you also can call the National Cancer Institute’s Cancer Information Service at 800-4CANCER (800-422-6237). To learn more about the CIS, including Live Chat help and how to send them an email message, go to http://www.cancer.gov/aboutnci/cis/page3.

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