‘Interval’ cancers
Commenting further on the study, Dr. Kuhl pointed out that from 25% to 45% of cancers that occur in women who have undergone screening mammography are diagnosed as “interval” cancers, even among women who participate in the best mammography programs. “For a long time, people argued that these interval cancers developed only after the last respective mammogram, but that’s not true at all, because we know that with MRI screening, we can reduce the interval cancer rate down to zero,” Dr. Kuhl emphasized.
This is partially explained by the fact that mammography is “particularly blind” when it comes to detecting rapidly growing tumors. “The fact is that mammography has a modality-inherent tendency to preferentially detect slow-growing cancers, whereas rapidly growing tumors are indistinguishable from ubiquitous benign changes like cysts. [This] is why women who undergo screening mammography are frequently not diagnosed with the cancers that we really need to find,” she said.
Although there is ample talk about overdiagnosis when it comes to screening mammography, the overwhelmingly important problem is underdiagnosis. Even in exemplary mammography screening programs, at least 20% of tumors that are diagnosed on mammography have already advanced to a stage that is too late, Dr. Kuhl noted.
This means that at least half of women do not benefit from screening mammography nearly to the extent that they – and their health care practitioners – believe they should, she added. Dr. Kuhl underscored that this does not mean that clinicians should abandon screening mammography.
What it does mean is that physicians need to abandon the one-size-fits-all approach to screening mammography and start stratifying women on the basis of their individual risk of developing breast cancer by taking a family or personal history. Most women do undergo screening mammography at least once, Dr. Kuhl pointed out. From that mammogram, physicians can use information on breast density and breast architecture to better determine individual risk.
“We have good ideas about how to achieve risk stratification, but we’re not using them, because as long as mammography is the answer for everybody, there isn’t much motivation to dig deeper into the issue of how to determine risk,” Dr. Kuhl said.
“But we have to ensure the early diagnosis of aggressive cancers, and it’s exactly MRI that can do this, and we should start with women with very dense breasts because they are doubly underserved by mammography,” she said.
The study was supported by the University Medical Center Utrecht, Bayer HealthCare Medical Care, Matakina, and others. Ms. Geuzinge, Dr. Heijnsdijk, and Dr. Kuhl have disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.