MRIs for Younger Women at High Risk

MRI Offers Good Detection for Younger Women at High Risk

San Antonio Breast Cancer Symposium, December 2004, Abstract #P3

Warner E. Sunnybrook

Background and importance of the study: Women with a strong family history of breast cancer or a known breast cancer genetic abnormality (a mutation in the BRCA1 or BRCA2 gene) have a high risk of developing breast cancer.

Early detection is especially important for these women. Currently, doctors recommend diagnostic mammograms—and sometimes also ultrasound—for women at high risk, starting at age 30. But cancers are harder to see on the mammograms of younger women than on those of older women. This is because younger women have thicker breast tissue that may look as dense as cancer tissue on a mammogram.

Breast cancers also tend to grow faster in high-risk women. So a yearly mammogram might not be frequent enough to spot cancers that develop during the year.

MRI (magnetic resonance imaging) and ultrasound are very good at detecting breast cancers in women with dense breasts. The Canadian study reviewed here looked to see whether ultrasound and MRI in addition to yearly mammogram and breast examination improves breast cancer detection in high-risk women.

Study design: The study looked at a total of 437 women at high risk for breast cancer:

• 318 had a BRCA1 or BRCA2 abnormality, and
• 119 had a 25% or greater chance of developing breast cancer based on family history.

All of the women were in a screening program that included:

• yearly breast MRI, ultrasound, and mammogram, and
• twice-yearly clinical breast exam by a doctor.

The women's average age was 43. All had at least one round of screening, and some had up to five.

Study results: The screening program found 36 breast cancers in 35 women. Thirty of these women had an abnormal BRCA1 or BRCA2 gene. MRI detected more of the breast cancers than mammograms and ultrasounds:

• MRI detected 30 cancers (83%).
• Mammogram detected 11 cancers (31%).
• Ultrasound detected 14 cancers (39%).
• Clinical exams detected 3 cancers (8%).

MRI detected 13 cancers (36% of the total) that other methods did not. Three cancers (8%) were detected by mammogram and not MRI. All of the cancers detected were two centimeters or smaller.

Conclusions: The researchers found that when high-risk women were screened every year, MRI was better than mammograms and ultrasound at finding breast cancers.

Take-home message: This study confirms the results of other studies that found MRI scans were better than ultrasound and mammograms at finding cancers early in high-risk women. (Still, a few cancers were detected only by mammography, not MRI.)

MRIs have some drawbacks. They're not available everywhere, few centers have the necessary expertise to read the tests reliably, and they're expensive.

Most of the women in this study were pre-menopausal, and that's where MRI has the biggest advantage over mammography. MRI does a better job at finding cancer within the dense breast tissue often seen in younger women. In post-menopausal women, MRI also does a very good job of early detection, as does mammography.

If you're at high risk for breast cancer, talk to your doctor about a screening plan that would be best for YOU.