MRI Better at Finding DCIS Than Mammograms

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DCIS (ductal carcinoma in situ) is the earliest type of breast cancer. DCIS is found only in the milk duct where the cancer started. DCIS is also called Stage 0 breast cancer. DCIS can be small and hard to see on a routine screening mammogram and usually can't be felt during breast self-exam (BSE). Doctors sometimes call DCIS "precancerous" because it's non-invasive. But DCIS is associated with an increased risk of invasive breast cancer as well as cancer that spreads beyond the breast.

A study showed that MRI (magnetic resonance imaging) was better than mammography at finding DCIS. About 90% percent of DCIS was found by MRI, while only 56% was found by a mammogram. MRI uses magnetic fields to highlight different kinds of tissues, both normal and abnormal. Mammograms use x-rays to image breast tissue.

The goal of DCIS treatment is to reduce the risk of invasive cancer in the future. In most cases, the treatment for DCIS is lumpectomy. To further lower the risk of invasive cancer, most doctors recommend radiation therapy after DCIS surgery. The risk of DCIS coming back depends on the size and "personality" of the DCIS, as well as the type of treatment. Doctors use the terms high-grade and non-high-grade to describe the "personality" of DCIS. High-grade DCIS poses a greater risk for future invasive cancer. The treatment your doctor recommends will take into account the grade of DCIS.

Since MRI appears to be better than mammograms at detecting DCIS, more women who get screening MRIs will be diagnosed and treated for DCIS. This will reduce their risk of invasive breast cancer in the future. This is why this Research News story is titled "MRI scans might prevent breast cancer, study shows."

The results of this study add to the evidence that says MRI, in some circumstances, can screen for breast cancer better than routine mammograms. Another study also showed that MRI was better than mammography at finding DCIS — particularly high-grade DCIS.

The American Cancer Society recommends using MRI for screening instead of mammography in certain women at high risk for breast cancer. This doesn't mean that screening mammograms will be replaced by MRI in all women. But your doctor may decide that your particular circumstance mean an MRI should be done instead of (or in addition to) a mammogram.

You might be wondering why MRI is not routinely recommended to screen for breast cancer in all women. There are several good reasons. First, MRI is a very sensitive test that can lead to false alarms. Past research has shown that most suspicious breast abnormalities found by MRI were NOT breast cancer. Second, an MRI for breast cancer screening is much more expensive than a mammogram. Finally, there's still much to learn about the role of MRI in routine breast cancer screening. It's quite possible that some day MRI will replace mammography, when the understanding of MRI for breast cancer screening improves and the cost of MRI decreases.

To learn more about MRI, visit the Breastcancer.org Screening and Testing section. To learn more about DCIS, visit the Breastcancer.org DCIS pages.

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