Do We Really Need MRI for Women with Newly Diagnosed Breast Cancer?
The San Antonio Symposium is an interesting not just because of the new science that is presented, but for the overviews of topics of clinical interest to the patients and doctors in attendance.
This morning Dr. Monica Morrow, a surgical oncologist at the Memorial Sloanâ€”Kettering Cancer Center, did a terrific job summarizing the role of MRI in women with newly diagnosed breast cancerâ€”and her conclusions will undoubtedly surprise many women.
It is certainly true that MRI can find lesions that mammograms do not. Some of these lesions MRI can find will be cancers, but some will not. Common sense says that finding more tumors in the cancer-bearing breast as well as in the other breast and treating themâ€” even if it means bilateral mastectomiesâ€”would improve outcomes. But this is not true!
Dr. Morrow presented data showing that preoperative MRI not only had no influence on whether women needed a second surgery within six months. Moreover, it increased the delay of definitive surgery by three weeks and doubled the incidence of mastectomy.
Doctors hypothesize that removing all of the potential disease found on MRI will eliminate the risk of local recurrence (recurrence in the breast or mastectomy scar). Yet a study from the University of Pennsylvania showed that there was no difference. The local recurrence rate was the same: 3-4%. Based on multiple published studies of preoperative MRI, it appears that between 32 and136 women underwent inappropriate breast conservation because of MRI findings, as only 13 of the women actually had local recurrences. This was true for both lobular and ductal cancers.
How is it possible that finding additional cancers doesnâ€™t matter? We have always known that we were leaving small areas of cancer behind. Pathological studies of breasts that have been removed show that between 32 and 63% of women has disease elsewhere in their breasts. But radiation therapy after breast conservation takes care of it. In general, MRI finds one-third of this disease, misses one-third of it, and overestimates one-third.
The local recurrence rate after breast conservation is about the same as mastectomy (4-10%) in node-negative patients and 3-6% in node-positive patients. In women who are ER-positive it is 1.5%. It has more to do with the biology of the cancer than the extent of the surgery. The greatest impact on whether there is a local recurrence is the use of tamoxifen, not the surgery. What about the opposite breast? Isnâ€™t it important to see if there is a cancer there? Again the answer is no. The incidence of contralateral breast cancer found on MRI is 3.1%.
We used to do blind mirror image biopsies. These found an incidence of contralateral breast cancer of 6.1%. But the rate of development of contralateral breast cancer is less than 3% (0.7%/year). This means we are finding cancers that would never become clinically relevant. Also our adjuvant treatmentsâ€”tamoxifen, aromatase inhibitors, Herceptin, and chemotherapyâ€”all reduce the risk of cancers in the opposite breast. Finally MRI is not good at predicting who will get a second cancer. Women who have had an MRI on the opposite breast have the same risk of getting a second cancer (8% in 8 years) as women who do not.
A second presentation described a very large prospective trial that explored whether MRI decreased the need for second operations because of dirty margins. In other words, does preoperative MRI help the doctor plan the surgery better, so that the patient only needs to have one operation? Again, the answer is no. The group of women who had MRIs and the group who did not had the same number of second operations.
So what is the conclusion? There is no evidence that preoperative MRI is useful in planning surgery, decreasing local recurrence by finding multifocal disease, or preventing second cancers by finding lesions in the opposite breast. Meanwhile, it increases the amount of surgery, delays the definitive treatment, and doubles the rate of unnecessary mastectomies. We have very good data on breast conservation surgery done without the benefit of preoperative MRI showing excellent results compared to mastectomy. Expensive pretty pictures that have been shown to make no difference in cancer outcomes should not seduce us.
Stay tuned for my next update!