Ask an Expert: MRI screening for breast cancer

Q: Are MRI’s better than mammograms for detecting breast cancer? Should I be asking my doctor for an MRI with my annual exam?

Answer from the expert staff of breast cancer research at the Robert W. Franz Cancer Research Center at Providence Portland Medical Center:

Magnetic resonance imaging (MRI) offers a significant breast cancer screening advantage for some women, but not for most. MRI is a more sensitive screening tool than mammography, and picks up more breast growths than mammography. This increased sensitivity is especially beneficial to young women at high risk of breast cancer, including those with BRCA gene mutations or with a strong family history of the disease. Mammograms do not identify cancerous growths as effectively among young women, who typically have dense breast tissue, as in older women whose breasts are not as dense.

MRI offers the advantage of detecting abnormalities in even very dense breasts. The downside to MRI is that it detects all kind of growths, including those that prove not to be cancerous, but that can’t be definitively diagnosed until the patient has undergone further screening and, often, surgical biopsy.

For women at high risk of breast cancer, MRI screening may offer adequate benefit to make these potential, additional tests and procedures worthwhile. Two studies presented at the spring 2003 American Society of Clinical Oncology (ASCO) conference indicated that MRI may be significantly more effective than mammography in identifying invasive breast tumors.

The Dutch MRI screening study presented at ASCO compared the value of breast cancer screening approaches over the course of three years in 1,848 women at increased risk of breast cancer. Of the invasive breast tumors found, clinical breast examinations detected 20 percent, mammography detected 26 percent, and MRI detected 83 percent.

A second study presented at ASCO by researchers at the University of Bonn in Germany followed 462 women with an inherited high risk of breast cancer. These women were screened for five years with clinical breast exams, mammography, high-resolution breast ultrasound and MRI. Of 51 breast cancers identified, clinical breast exams detected 25 percent, mammography detected 43 percent, ultrasound detected 47 percent, and MRI detected 96 percent.

MRI screening for breast cancer is not recommended for everyone. There is no evidence that it offers results superior to mammography in older women with an average risk of breast cancer. Mammography also is preferred for these women because it’s not associated with the same risk as MRI of locating benign growths that prompt unnecessary biopsy.

MRI appears to offer significant benefit for women with a high risk of breast cancer, especially those under age 40. However, it’s critical to be screened by a radiologist with experience interpreting breast MRIs to determine which abnormalities require biopsy. 

Women who are known to have BRCA-1 or BRCA-2 mutations should talk with their doctor about annual screening with both MRI and mammography. Mammography continues to offer benefit to all women because of its superiority in identifying microcalcifications associated with breast cancer.

September 2003