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Breast cancer detection: MRI vs. mammogram?

Dr. Judith Reichman advises on the two methods of diagnosis.

Q: I'm 45 years old and my mom had breast cancer in her late 60s. I've heard that an MRI is better than a mammogram for detecting breast cancer. Should I get one?

A: It has taken us 30 years to get women to accept and get their yearly mammograms. I suspect that in less than 30 years MRI will become the imaging method of choice for early detection of breast cancer, but presently it’s not quite ready for primetime. MRI is currently a very special tool that is indeed extremely sensitive in detecting early cancer, but unfortunately it is “too” sensitive and also picks up many breast changes that are not cancer, leading to a high incidence of negative biopsies. In other words, the false positive rate is high and may be unacceptable for low risk women.

Yes, MRI can detect cancers that may be missed in a routine mammogram. A study published in a March issue of the New England Journal of Medicine followed 969 women who had a recent diagnosis of breast cancer in one breast. MRI was able to detect breast cancer in the second (contra lateral) breast of some of these women even when mammogram had been read as normal. Specifically, 121 of these women had a suspicious (positive) MRI, even though their mammogram showed no abnormalities. (This is equal to 12.5 percent of the women). All of these MRI positive women had biopsies, and 30 were found to be positive for cancer.

Had these 30 women not had an MRI, the cancer in their other breast would have been missed and their surgery and treatment might have been inadequate. But we have to remember that even in these very high-risk women (who already had cancer) the majority (91 of them) had false positives. The false positive rate in a normal group of women may be even higher. The good news is that the women in the study who had a negative MRI were followed for another year and continued to have no cancer occurrence or reoccurrence in their second breast. This means that MRI had a negative predictive value (if nothing is found, nothing is there) of 99 percent.

Right now the American Cancer Society (ACS) and most breast imaging researchers feel that the "responsible use of MRIs for the evaluation of the breast should be focused on patients with a high probability of breast cancer." This is felt to include women who have a 20 percent or higher lifetime risk of breast cancer. Women in this high-risk category include those with a strong family history of breast and/or ovarian cancer or those who are likely or known carriers of the BRCA1 or BRCA2 mutation (a breast and ovarian cancer gene mutation). Annual breast screening by means of an MRI is also recommended for women who have undergone radiotherapy to the chest for Hodgkin's disease.

The ACS, however, doesn't feel that there's sufficient evidence to recommend for or against MRI screening in women who have a higher-than-average risk of breast cancer. This includes women who have lobular carcinoma in situ or atypical lobular hyperplasia, those with atypical ductal hyperplasia, women with very dense breasts, and those who have already had breast cancer. The jury is still out on whether an MRI would be beneficial in these situations.

Let's not forget the role of mammograms, though, despite the fact that they're not perfect. The ACS does recommend that women at average risk for breast cancer get an annual mammogram starting at age 40 and that women at high risk begin mammograms ten years earlier than the age in which their relative was diagnosed or if BRCA testing is positive as young as age 25. The ACS also suggests shorter screening intervals and/ or the addition of screening methods like ultrasound or MRI.

I suspect that this latest study may change the ACS’s and many physicians' guidelines for breast cancer work up once the disease has been diagnosed in one breast. In the future these other indications that I mentioned (such as atypical lobular hyperplasia, lobular carcinoma in situ etc.) may also be more routinely used and accepted by doctors, insurance companies, and patients as a basis for MRI screening. We hope that eventually MRI will also show fewer false positives and result in less "unnecessary" biopsies.

Keep in mind that MRI is also very expensive. Unless you fall within the current ACS recommendations most insurance companies won’t cover this imaging technique. Moreover, it's not available at half of the radiological imaging practices. The ACS strongly recommends that a breast MRI not be performed in an imaging center where there's no capability of performing a biopsy if a positive result is found.

In answer to your question (finally, after all that background), you don't “need to” get a MRI as you don't "qualify" for one. You are not in a category considered high risk (your mom was post-menopausal when she got breast cancer and I’m assuming you don't have any other family history of breast and/or ovarian cancer). But please be sure to get your annual mammogram. If your breasts are dense request that it be digital (this has been show to be more accurate in young women or women with dense breasts) and some radiologists would also suggest that you get a breast ultrasound.

Dr. Reichman’s bottom line: MRI offers tremendous reassurance if it's negative, but if it's positive it may indicate changes that are not due to cancer. MRI imaging is at the forefront of a new era of breast cancer diagnosis, but currently should be reserved for those women who are at high risk for breast cancer.

Dr. Judith Reichman, the TODAY show's medical contributor on women's health, has practiced obstetrics and gynecology for more than 20 years. You will find many answers to your questions in her latest book, "Slow Your Clock Down: The Complete Guide to a Healthy, Younger You," which is now available in paperback. It is published by William Morrow, a division of .

PLEASE NOTE: The information in this column should not be construed as providing specific medical advice, but rather to offer readers information to better understand their lives and health. It is not intended to provide an alternative to professional treatment or to replace the services of a physician.