MRI too expensive, less accurate detecting breast cancer

Most of us know at least one woman — if not a half dozen — who’s had breast cancer. Many of us have had a friend who has died of this all too common disease. It must be truly frightening for women who have breast cancer cases throughout their family tree, with a case or two of ovarian cancer thrown in as well. Often these women carry one of the “breast cancer genes,” BRCA1 or BRCA2. While they account for only 5 to 10 percent of breast cancer cases, they carry a lifetime risk of getting breast cancer of up to 80 percent.

The breast cancer that runs in families is not kind. Compared to the garden variety, these cancers tend to occur in younger women, are larger when they are discovered, and are often highly aggressive cancers.

We know that for the average Jane, annual mammography after age 50 really does save lives. Cancers can be detected at an earlier stage when the cancer is easier to treat. Women who get yearly mammograms after age 50 are 30 percent less likely to die from breast cancer than their unscreened peers.

But what if you are one of those unlucky women with breast cancer scattered throughout your family tree? And what if some of those cancers occurred when your relatives were younger than 50? What about screening earlier? Unfortunately, mammography is not as accurate in younger women, whose breasts are dense and difficult to image.

Researchers in the Netherlands set out to see if they could devise a screening strategy for women who, based on their family history of breast cancer in first degree relatives (mother, sisters) and second degree relatives (grandmother, aunts, nieces), had at least a 15 percent lifetime risk (to age 90) of getting breast cancer. Perhaps 15 percent isn’t all that different from 11 percent, which is the average woman’s lifetime risk, but the key here is the family history. The Dutch researchers compared their results to two control groups. The first group consisted of all women who were diagnosed with breast cancer in the Netherlands during 1998. The second were a group of women with breast cancer who were participating in another study.

The researchers looked at three screening strategies: breast exams every six months with a trained clinician, mammography and magnetic resonance imaging (MRI). They screened 1,909 women whom they followed for an average of three years. During their study they detected 50 breast cancers and the MRI was the most sensitive test for finding cancer.

So is MRI the next big thing in cancer screening? Not hardly. It’s way too expensive for a general screening test. The MRI missed 18 tumors, 13 of which were identified on mammogram. One tumor wasn’t visible on either MRI or mammogram, but was detected by clinical breast exam. And the test with the most false positives—findings that could be cancer but turned out not to be—was the MRI. These women were subjected to even more testing, usually biopsy, before they found out they really didn’t have cancer. In this study, screening by MRI led to twice as many unneeded additional tests as did mammography and three times as many unneeded biopsies.

By far, the groups that benefited the most from this intensive screening strategy were the women who carried the gene mutations BRCA1 and BRCA2, and women who did not carry the mutation but because of family history had a lifetime risk of 30 percent to 49 percent for developing breast cancer. These women in the screened group had significantly smaller tumors and dramatically less spread to the lymph nodes at diagnosis than women in the control groups.

Some women in these very high risk groups elect to have their breasts removed rather than live with the increased odds of getting breast cancer. For those who want to keep them, intensive screening with breast exam, mammography and MRI may help. For the rest of us, yearly mammograms and regular breast exams are still the way to go.