The news release does a generally good job presenting the main findings of the study. In particular, the release makes a compelling case for why current practices in breast cancer screening may be lacking, establishes the novelty of the research and presents the hypothesis that MRI screenings are helpful to women with average risk for breast cancer — and not just those at high risk. It’s a hypothesis that now needs to be confirmed.
These positives are offset, however, by a few unanswered questions. First, it is unclear what average risk really means. Digging through the study’s inclusion criteria, we found that the subjects were women aged 40–70 with “a calculated lifetime breast cancer risk of 6%–12% according to the Gail model.” Those percentages are probably not what the average reader has in mind when she hears “average risk.” Second, there is no mention of the specificity (the ability of the test to correctly rule out those without the disease) of MRI screening for average risk women. Lack of specificity can lead to false positives, which have been a concern with MRI screening. Knowing only the sensitivity (the ability of the test to correctly identify people who have the disease) does not allow us to see the complete picture.
This news release scored well on several of our criteria. For a discussion of another news releases on MRI screening for breast cancer that wouldn’t have scored as well, see a related post.
Mammograms are known to be less effective for dense breast tissue
. MRIs, though more effective in this setting, are avoided in practice for average risk patients due to higher costs. Research like this advances the discussion on the cost of breast cancer screening but it remains unclear whether MRI screening will be a cost savings down the road, especially since we don’t know how much overdiagnosis/overtreatment may be occurring with MRI screening.
Although the news release does not specify the exact price tag, it makes the reader aware that MRI screening is often avoided due to higher cost than other screening options:
“MRI screening has not been considered necessary for women at average risk, and there has been resistance to expansion of MRI into this population due, in part, to concern over higher costs.”
It would have been helpful if the release had stated whether or not this rapid MRI will have a lower cost than traditional breast MRI.
The supplemental cancer detection rate seems to be the main metric of success for the MRI screening. The news release does a good job presenting absolute benefits, not just relative benefits:
“Breast MRI detected 60 additional breast cancers, including 40 invasive cancers, for an overall supplemental cancer detection rate of 15.5 per 1,000 women. Of the 60 cancers detected in the study group over the observation period (7,007 screening rounds), 59 were found only using MRI, one was found also by mammography, and none by mammography or ultrasound alone.”
But the news release only reports sensitivity and begs the question on the matter of specificity. Sensitivity and specificity are two sides of the same coin when it comes to assessing any screening method. A bit of digging on our own reveals that the MRI screening had a low false-positive rate of 2.9%.
The news release does not state any potential harms of MRI screening. False positives from MRIs aren’t uncommon and can lead to anxiety and additional invasive testing. That’s harmful for patients.
We’d like to see news releases and stories start to acknowledge potential harms, particularly since the country is moving toward more universal breast cancer screening with MRI.
Over the past few years, studies have been coming out noting concerns about the gadolinium (a heavy metal) contrast material that is used during breast MRI. The contrast is necessary to demonstrate areas of increased tissue vascularity (the state of blood vessel development and functioning). Recent reports note that gadolinium may deposit in the brain. We do not know the long-term significance of this. The FDA is studying the effects — if any– on “repeated use of gadolinium-based contrast agents (GBCAs) for magnetic resonance imaging (MRI).”
The release provides a nice summary of the study protocol, noting that:
“Between 2005 and 2013, Dr. Kuhl and colleagues studied breast MRI’s impact on 2,120 women, ages 40 to 70, with less than a 15 percent lifetime risk of breast cancer. The women had normal screening mammograms and, in the case of those with dense breast tissue, normal screening ultrasound. Breast MRI detected 60 additional breast cancers, including 40 invasive cancers, for an overall supplemental cancer detection rate of 15.5 per 1,000 women. Of the 60 cancers detected in the study group over the observation period (7,007 screening rounds), 59 were found only using MRI, one was found also by mammography, and none by mammography or ultrasound alone.”
Unfortunately, the release isn’t clear about the limitations of the study. The study doesn’t show that MRI offers benefits that women really care about such as longer life and better quality of life. The only way to prove such benefits would be in a large-scale controlled trial that follows groups of women (those who do and don’t receive breast MRIs) for many years. The release also fails to mention the risk of over-diagnosis and over-treatment. Finding more cancer at an early stage is not always a good thing, because some cancers don’t progress to a point where they would cause harm. While the release suggests that many of the cancers that were found were aggressive in nature, it doesn’t say how many, nor does it caution that some of these cancers might never have caused a problem. It also doesn’t warn that some particularly aggressive cancers might not respond to treatment despite early detection.
The published research noted that the screening studies were read by specialized breast radiologists and that the results “may not be transferrable to a community level until more radiologists gain practical experience in reading breast MR screening studies.” That would have been a useful addition to the release as well.
Breast cancer’s prevalence in cancer-related deaths in women was highlighted but not overstated.
But we aren’t told whether the 20 cases of non-invasive cancer identified were ductal carcinoma in situ (DCIS). There’s wide debate on whether the presence of these types of abnormal cells should even be referred to as cancer. The lack of clarity on the types of cancer identified and the difference between them earns a Not Satisfactory rating.
The release doesn’t name the sponsors.
The news release includes a comparison with breast ultrasound. It found that supplemental MRI screening is useful for women with average risk of cancer who exhibit a range of breast densities and that it is superior to the alternative of breast ultrasound for this purpose.
It is clear that MRI screening is already available. The release notes that there’s been a resistance to expand MRI screening to average risk women because of the cost.
The news release establishes that the novelty of the study lies in its challenge of the conventional wisdom that supplemental MRI screening should be recommended to high-risk women but not average-risk women.
The release doesn’t rely on sensational language.
However, we find the opening sentence of the news release to be, if not unjustifiable, potentially misleading:
“MRI screening improves early diagnosis of breast cancer in all women-not only those at high risk-according to a new study from Germany published online in the journal Radiology.”
To our eyes, there is nothing in the study that supports this claim applied to all women. The cohort examined in this prospective observational study are characterized by women with average risk of breast cancer.