Mammograms vs. MRIs for Breast Cancer Screening

Breast cancer is a disease that is all-too prevalent in our society. It is a disease the kills thousands every year, and numerous cases are diagnosed every day.

Early detection of breast cancer is key to helping treat the disease; the longer that it is present, the greater the risk that it will be incurable. To that end, it is of the utmost importance that women regularly get screened for the possibility of breast cancer. That brings forth a debate, however; should mammograms or Magnetic Resonance Imaging be used to weigh a womans risk?

Increased Risk from X-rays

New studies have shown that a woman’s risk for developing breast cancer may be increased due to mammograms. X-rays are used in a mammogram, and radiation that is used in the process may be responsible for the gene mutations BRCA1 and BRCA2.

Ionizing radiation is the type of radiation present in x-rays, and it can also be found in nuclear fallout.

While the risk of developing the gene mutation from these small doses of radiation is small, it still poses a problem that needs to be addressed. These mutations, while relatively rare, greatly increase a womans risk for developing breast cancer.

The mutations can be inherited, and for that reason, women that have the mutations run a significant chance of passing the mutation onto their children.

Genetic Factors

Between 5 to 10 percent of all breast cancer cases that are diagnosed are due to an inheritance of the gene abnormality. For these reasons, Magnetic Resonance Imaging is now being considered when it comes to helping diagnose the disease.

The MRI process is not perfect; as a matter of fact, it can be very hard to read for doctors, and many false-positive diagnoses have been performed due to a lack of sufficient information from the MRI. These false positives often result in unnecessary biopsies, which can cause much mental and physical trauma on the part of the patient.

So, whats the solution? Doctors are still unsure. While mammograms may cause problems in a small portion of the population, there is the risk of unnecessary biopsies due to MRIs.

Recommended Guidelines

While there is no scientific consensus when it comes to which screening process a woman should have, there are some simple suggestions laid out by experts in the field.

– Women that are known to be carriers of the BRCA1 and BRCA2 mutations should do their best to avoid x-rays of the chest. Getting mammograms before age 35 may not be the best idea for this small part of the population, and Magnetic Resonance Imaging may be a better solution for diagnosis.

– Women that do not have the BRCA1 or BRCA2 mutations are often encouraged to undergo the regular mammogram process. While the risk of developing the mutation may be present, mammograms are more efficient at properly diagnosing the possibility of breast cancer.

Be sure to study both options thoroughly before deciding what is right for your body.

MRI Detects more breast cancers in high-risk women

Magnetic resonance imaging (MRI) enables radiologists to accurately identify tumors missed by mammography and ultrasound, according to a multicenter study comparing the three screening methods in women at high-risk for breast cancer.

The findings of the study appear in the August issue of the journal Radiology.

“Women at high risk for breast cancer can benefit from undergoing screening MRI” said the study lead author, Constance Dobbins Lehman, M.D., Ph.D., professor of radiology at the University of Washington School of Medicine and director of breast imaging at the Seattle Cancer Care Alliance. “Of all the breast imaging tools we have currently available, MRI is clearly the best at detecting cancer.”

According to the National Cancer Institute, genetic predisposition accounts for five to 10 percent of all breast cancers. Women who are genetically at high risk for breast cancer need to begin screening at a younger age, because they often develop cancer earlier than women at average risk. However, women below age 50 are more likely to have dense breast tissue, which can limit the effectiveness of mammography as a screening tool. The American Cancer Society recommends that women with a high risk of developing breast cancer should be screened with MRI in addition to their yearly mammogram beginning at age 30.

“It is frightening to be told that you are at very high risk for developing breast cancer,” Dr. Lehman said. “Its important that these women understand that there is something they can do to increase their chances of early detection in the event that they do develop breast cancer.”

For this study, researchers at six facilities studied 171 asymptomatic women over age 25 (average age 46) with at least a 20 percent lifetime risk of developing breast cancer to compare screening performance of MRI and mammography in high-risk patients. Each of the women underwent MRI, mammography and ultrasound.

Sixteen biopsies were performed, and six cancers were detected for an overall cancer yield of 3.5 percent. All six of the cancers were detected with MRI, while two cancers were detected with mammography and only one cancer was detected with ultrasound.

The four cancers found in women with dense breast tissue were only detected with MRI. Biopsy rates were 8.2 percent for MRI and 2.3 percent for mammography and ultrasound. The positive predictive value (PPV) of biopsies performed as a result of MRI findings was 43 percent.

Based on these findings, the researchers estimate that, compared to mammography and ultrasound, screening with MRI will allow detection of 23 more cancers per 1,000 high-risk women screened.

While MRI has been shown to be an effective screening tool for women genetically predisposed to developing breast cancer, there is no evidence to support MRI screening in average-risk women.

“Although MRI is a very powerful tool for detecting cancer, it is not perfect,” Dr. Lehman cautioned. “There are benign areas of breast tissue that can look suspicious but do not represent breast cancer and yet may lead to a biopsy.”

photo by liz west/flickr