MRI safety in breast cancer screening

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The numbers are scary: The average woman has a 12 percent risk of developing breast cancer at some point in her life. For women with certain genetic mutations or risk factors, lifetime risk can climb to 85 percent.

Even more terrifying than the numbers, however, are the rumors; rumors that the contrast dye used in MRIs for breast cancer screenings is harmful; rumors that are driving women away from an adjunctive screening tool that could save their life.

So what is fact and what is speculation? At this time, we know that some people who have had multiple injections of MRI contrast dye gadolinium show trace amounts of the gadolinium deposited into areas of the body, including the brain. This can remain for prolonged periods of time (several months to years), however, there is no evidence at this time that the gadolinium deposits do anything harmful in people with normal kidney function. This was acknowledged by the FDA in a Safety Announcement concluding “the benefit of all approved GBCAs [gadolinium based contrast agents] continues to outweigh any potential risks.”

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.

As far as breast cancer screening goes, the gold standard remains mammography, though for women at higher risk for breast cancer – particularly those with dense breast tissue – supplemental screening with breast MRIs might be recommended.

I recently spoke with a patient who decided to undergo a screening MRI, despite the Internet’s fervent warnings, because her lifetime risk of developing breast cancer is 42 percent. Weighing her risks, the options available to her and the advice of the experts she had gathered into her corner, this patient decided that her risk of developing cancer was far greater than the unknown risks of potentially retaining trace amounts of MRI contrast dye.

She wanted to undergo the MRI because, unlike mammography, a breast MRI looks at the blood-flow pattern which is an important clue in detecting certain types of breast cancer before they show up on a mammogram or ultrasound. And even in 2019, this tenet remains true: the earlier cancer is detected, the more treatable and better the outcome.

For every 1,000 asymptomatic patients, mammograms detect an average of two to 10 breast cancers. However, in 1,000 high-risk patients, breast MRI detects upwards of 18 to 20 breast cancers. This illustrates the benefit of MRI for those who, like this particular patient, are at higher risk.

Balancing the risks versus benefits of any test, procedure, or treatment is integral to everything we do in medicine. I always encourage people to do their research, but watch out for websites or acquaintances (and even some doctors) who fan the flames of fear. Before succumbing to myths and rumors, I advise patients to ask their doctors the hard questions and weigh the risks versus benefits of any plan of action.

January Lopez is a director of breast imaging, Hoag Memorial Hospital Presbyterian, Newport Beach, CA.

Image credit: Shutterstock.com

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