MRIs for Breast Cancer Screening—Who Needs Them?

Many experts believe that mammograms save lives. Since the widespread introduction of mammography to screen for breast cancer in the mid-1980s, the number of women ages 50 and older getting mammograms has more than doubled. Pair that figure with a drop in breast cancer deaths by almost 2% each year since 1992.

But some healthcare professionals argue that mammograms are not enough for some women at high risk for breast cancer. New studies suggest that MRIs (magnetic resonance imaging) may improve the early detection of cancer in women at high risk.

Current Screening Guidelines for Women at High Risk

You are considered at high risk for breast cancer if you answer yes to any of these questions.

• Have you had breast cancer before?

• Have you tested positive for genetic changes that increase the risk for breast cancer--BRCA1 or BRCA2 mutations?

• Has your mother, sister, daughter, or 2 or more close relatives, such as cousins, had breast cancer? Your risk is even higher if they were diagnosed before age 50.

• Do you have a breast condition, such as atypical hyperplasia or lobular carcinoma in situ?

• Have you had 2 or more breast biopsies for benign breast disease?

If you’re a woman at high risk for breast cancer, you should ask your doctor if you should have more frequent screenings, with a variety of tests, starting at a younger age. For women at high risk, some experts recommend monthly breast self-exams starting between ages 18 to 21, clinical breast exams 1 to 2 times a year, and yearly mammography starting between ages 25 and 35.

Currently, doctors sometimes use MRIs in high-risk women. But their role in breast cancer screening and who may benefit most from them are not yet known.

How MRIs Work

Instead of the X-rays used in mammography, an MRI uses magnets and radiowaves connected to a computer to make many detailed pictures of the breast. A woman receives an injection of a contrast dye, called gadolinium-DTPA, to better display the breast tissue and possible tumors.

Recent studies suggest that MRIs may detect more cancers in high-risk women than current screening methods. Researchers have found that MRIs given to women with a high risk of hereditary breast cancer detected tumors that mammography or clinical breast exams had missed. And one also showed that it was more sensitive than ultrasound.

One reason MRIs may find these tumors is because high-risk women tend to be younger and have denser breasts. This means that the breast has less fat and more fiberlike connective tissue, which can block X-rays during a mammogram. An MRI is not affected by dense, fibrous breast tissue.

Are MRIs Recommended?

Even if MRIs may detect more cancers and perhaps at an earlier stage, Dan Kopans, MD, director of breast imaging at Massachusetts General Hospital in Boston , says the next question is “Does finding that cancer earlier benefit the individual?” He notes the numerous large trials with American women that have found that mammography screening lowers the number of deaths from breast cancer.

“But does MRI screening help these high-risk women live longer? That still needs to be shown. I’m a strong supporter of MRI screening, but I don’t think it’s ready to recommend to women until we can prove it’s going to make a difference in their lives,” he adds.

Barbara Croft, PhD, program director of the Biomedical Imaging Program at the National Cancer Institute, reports, “MRIs and other new screening tests are appealing because mammography does not see everything. Also, with high-risk young women, anything we can do to decrease the amount of radiation from X-rays they get over the years is felt to be a positive thing.”

Could these women one day be advised to have an annual mammogram along with an MRI, ultrasound, or other tests to better their chance of finding tumors? Croft believes it is possible but far too soon to recommend it. “Every time you add another screening test, there’s more expense. We have to think very carefully and figure out a sensible plan for how we would use these costly instruments and identify the specific population who needs them,” Croft says.

It’s also important to weigh the pros and cons of MRIs for defined groups of high-risk women. Here are some of their drawbacks.

• MRIs may have a high rate of false positives. A false positive means it looks like cancer but is not. MRIs cannot always discern between lumps that are cancer and not cancer. The result is a need for further testing to determine if the suspicious lump is actually cancer. Those tests may include another MRI, other tests, or biopsies.

• MRIs are costly. They require special breast MRI equipment and a radiologist trained in breast imaging to interpret the images. Possible follow-up tests or biopsies add to the costs.

• Women may have an allergic reaction to the contrast dye. The dye gadolinium-DTPA is injected before an MRI. Very rarely, this may cause an allergic reaction, but even the thought of receiving an injection can increase anxiety in some patients.

• The MRI machine makes some people uncomfortable. The narrow tunnel-like opening of the MRI “machine that a patient is placed in during the exam may cause anxiety and discomfort, especially in those who are claustrophobic.

Kopans adds, “It’s a complicated issue. You want to do more good than harm. If there’s no shown benefit, then everything you do is basically harm. Using MRI without evidence of benefit will only add anxiety or trauma to the patient and increase their risk of complications from follow-up procedures.”

Studies funded by the National Cancer Institute on MRI screening for high-risk women are now underway. Visit their clinical trials website, http://www.cancer.gov.