Ask the Doctor: January Lopez, M.D.

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januaryLopezQ. I have heard that contrast used in MRIs may be harmful. Is this true?

A. Unfortunately, a rumor is starting to take hold that the contrast dye used in MRIs for breast cancer screenings is harmful. In some people who have multiple injections of MRI contrast dye gadolinium, trace amounts of the gadolinium can be deposited into areas of the body, including the brain. However, there is no evidence at this time that the gadolinium deposits do anything harmful in people with normal kidney function.

There are two classes of gadolinium contrast with differing chemical structure, called linear and macrocyclic agents. The data shows that linear agents deposit more than macrocyclic agents. Some people misinterpret this to mean that macrocyclic agents are “safer.” At this time, all agents are considered safe. Hoag uses the macrocyclic agents, which deposit less gadolinium, but, again, both are considered safe.

Unlike mammography, an MRI looks at blood-flow patterns in the breast, and is a powerful tool in detecting certain types of breast cancer before they would show up on a mammogram or ultrasound. The earlier a cancer is detected, the more treatable and the better the outcome.

If you were to look at 1,000 patients, on average, a mammogram will detect two to 10 breast cancers in asymptomatic patients. However, when looking at high-risk patients undergoing MRI, detection across 1,000 patients can be as high as 18 to 20. This illustrates the benefit of MRI for those who are at higher risk.

The decision to undergo an MRI for high risk breast cancer screening is an individual one. Balancing the risk versus benefit of any test, procedure or treatment, is integral to everything we do in medicine. Partnering with a team of skilled, knowledgeable specialty-trained breast radiologists, breast surgeons, oncologists and other service providers like we have at Hoag not only helps to create the most successful medical plan, but it also gives our patients the confidence to make the best decisions for themselves.

January Lopez, M.D. is a dedicated breast radiologist and director of Breast Imaging at Hoag Breast Centers.