Mammograms may not be the best way to screen for breast cancer
A mammogram is the gold standard for breast cancer detection... it always works, right?
Dianne Anderson, 55, knew she had dense breast tissue when she went for her annual mammogram a few years ago. The results showed that the Ohio resident had the dense tissue, but no signs of cancer. Her radiologist suggested that she should have a secondary screening test, something Dianne passed on, thinking that the mammogram would have showed cancer.
The next year, her mammogram did not show signs of cancer. This time, however, her radiologist suggested a molecular breast imaging (MBI) scan. This nuclear test and scan is designed to spot breast cancer specifically in those with dense breast tissue. Her insurance would cover it, so Dianne agreed to have it done.
Thankfully, she did — the scan detected that she had stage 2 breast cancer that had spread to her lymph nodes.
So, are mammograms enough?
Her story raises an important question that all women should ask themselves: Is a mammogram effective enough to detect breast cancer?
About 50 percent of women have dense breast tissue, which can mask cancer from traditional mammogram images. This is why we have to understand the risks that come with dense breast tissue — namely, that a mammogram could miss detecting cancer if you have it. If you’ve got dense breast tissue, it's important to know about the MBI.
The Mayo Clinic recently published a study that showed impressive results to using MBI as opposed to other methods of dense breast tissue detection. The MBI showed a sensitivity increase of 67 percent compared to 39 percent in ultrasound, 34 percent in tomosynthesis and 56 percent in MRI. Knowing that, and knowing if you have dense tissue, it seems like a good idea to consider an MBI.
More than 20 states require mammogram reports to state a woman’s breast density percentage — if you ask me, that’s not enough to give us the protection we need.
Breast density key to detection
Dr. Deborah Rhodes, who performed the study, explained that the commonality of misdetections like Dianne’s depends on the extent of breast density.
"Breast density has been found to be the most important factor in the failure of mammography to detect cancer," she said. According the her, the aforementioned study found that mammography missed three out of every 10 cancers in the dense breast.
"The problem is that cancers can be hidden for years in a dense breast, as it can be like searching for a snowball in a field of snow," she said.
The MBI process
Dianne said the doctors gave her an injection of a drug to enhance the images, then she sat in a chair and placed her breasts in a scanner that lightly compressed them.
"It was not painful," she recalls. "They had a video screen in front of me to watch nature scenes. In my case, there was a radiology and nuclear med tech with me during the scan so we enjoyed talking."
After the scan, the radiologist performed an ultrasound and then a biopsy.
"Not everyone has to do those last two steps; but the radiology tech told me in advance that might happen so I was prepared," Dianne said.
Based on all of this, you may want to ask yourself a few questions:
Do I have dense breast tissue?
Rhodes said that breast density is based on the mammographic appearance of the breast, not the way the breast looks or feels. Translation: The only way to know if you have dense breasts is to undergo a mammogram.
Should I have an MBI?
"Mammography remains the standard breast cancer screening tool for all women, as it is the only breast screening tool that has been associated with a reduction in breast cancer mortality," she said.
After an annual mammogram, you can choose to pursue additional screening if you have dense breasts (this is known as supplemental screening).
Rhodes said there is not a consensus among doctors as to whether all women with dense breasts should pursue supplemental screening or which method is the preferred supplemental screening tool.
"Women must decide for themselves after discussion of the risks and benefits with their care provider," she said. Risks include over-diagnosis of a breast cancer that wouldn't otherwise cause harm, and false positive findings, which can lead to more tests that do not detect a cancer and additional costs may be incurred.
What type of supplemental screening might I need?
Whole breast screening ultrasound, tomosynthesis and MBI are the options available if you want extra testing after a mammogram. Rhodes notes that an MRI scan is typically reserved for women at high risk for breast cancer due to the high expense.
She said that MBI has a much higher yield of additional cancers detected than tomosynthesis and ultrasound. But MBI also has a higher false positive rate than tomosynthesis. Ultrasound has a very high false positive rate. At Mayo Clinic, women who seek supplemental screening for dense breasts are offered either tomosynthesis or MBI.
"I see cases in my clinic every month of women who are diagnosed with breast cancers despite having had a recent negative mammogram," Rhodes said. It is usually always due to breast density.
Is an MBI safe?
The radiation dose used in MBI is considered safe for screening. There is a lot of concern about radiation exposure, but I think there is also a lot of misunderstanding about what constitutes a safe dose. The dose administered with an MBI is higher than for mammography, but still considered a low and safe dose, Rhodes said.
"I think the more important question is: What is the test that is most likely to find a cancer, which is ultimately the whole purpose of screening for breast cancer," she asked. “If MBI nearly quadruples the chance of finding a breast cancer relative to mammography, alone, then I think it is an important option for women to consider."
"It is important for women to know that they should pursue additional evaluation for any breast change, even if they have just had a normal mammogram," she said.
Clearly, Dianne agrees.
"For women with dense breast tissue, MBI is a very important diagnostic tool in addition to yearly mammograms," she said. "The MBI found my cancer and saved my life. Please go the extra step and do an MBI."