A large new study by researchers at Karolinska Institutet in Sweden has revealed that nearly one-third of breast cancer cases are not detected during regular screening but are found in the time between two scheduled mammograms.
These cancers, known as interval cancers, are often more aggressive and harder to treat. The findings, published in JAMA Oncology, underline the need for more personalized breast cancer screening programs.
Mammography has long been proven to save lives by detecting breast cancer early, when it is easier to treat. However, it is not perfect. Some cancers are missed during the screening and are only found later when symptoms appear or during a medical checkup between routine screening visits.
These are called interval cancers, and they can grow quickly and spread faster than cancers caught during scheduled screenings.
The study looked at data from over 500,000 women in Stockholm between 1989 and 2020. Over this 30-year period, the researchers found that interval cancers made up about 30% of all breast cancer cases detected through screening. Surprisingly, this percentage has stayed the same, despite improvements in mammogram technology and screening practices.
According to lead author Yuqi Zhang, a postdoctoral researcher at the Department of Medical Epidemiology and Biostatistics at Karolinska Institutet, the findings suggest that the issue is not just about outdated machines or poor screening methods. Instead, certain individual risk factors may play a large role in why some cancers go undetected.
One major risk factor is high breast density. Dense breast tissue makes it harder to spot tumors on a mammogram because both appear white in the image, like looking for a snowball in a snowstorm. Women with high breast density were more likely to have cancers missed during screening.
Another factor is the use of hormone therapy, often taken by women during or after menopause. Hormone therapy can increase breast density and possibly influence cancer development. These women are also more likely to receive a false negative result during screening.
Other risk factors include older age at the birth of the first child and higher levels of education, although the reasons for the link between education and interval cancer are not fully understood.
Family history also plays a critical role. Women who had close relatives with breast cancer were 1.9 times more likely to develop interval cancer themselves. That risk increased to 2.9 times if the family history specifically involved interval cancers. This suggests a potential genetic influence, not just on cancer risk, but on the type of cancer and how quickly it grows.
“These fast-growing tumors often appear suddenly between scheduled mammograms,” Zhang explained. “It’s not always because the cancer was missed during screening. Many of them simply grow very quickly.”
The study highlights a clear need to move beyond the one-size-fits-all approach to breast cancer screening. Professor Kamila Czene, the senior author of the study, argues that screening programs should be tailored to individual risk levels.
This could involve more frequent mammograms, additional imaging techniques like contrast-enhanced mammography or ultrasound, or even genetic testing for women with a strong family history of breast cancer.
“By adjusting how and when we screen based on each woman’s risk, we can catch cancers earlier, when they’re easier to treat,” Czene said. “That means less invasive treatment, better survival, and less emotional stress for patients.”
Review and Analysis:
This study is important because it brings attention to a serious gap in current breast cancer screening programs. The fact that one in three cancers can still slip through regular screening—even after three decades of progress—is a call to action.
While mammography remains a life-saving tool, it’s not enough for every woman, especially those with high-risk factors like dense breasts, hormone use, or a strong family history.
The idea of personalizing screening may sound complex, but it could be the key to better outcomes. Just as we no longer treat every patient the same way after diagnosis, we may also need to screen people differently based on their risk profile. This research adds weight to the idea that more tailored health care is better health care.
In conclusion, breast cancer screening saves lives—but it can be improved. For women at higher risk of interval cancers, better and more frequent screening could make all the difference.
If you care about breast cancer, please read studies about a major cause of deadly breast cancer, and this daily vitamin is critical to cancer prevention.
For more information about cancer, please see recent studies that new cancer treatment could reawaken the immune system, and results showing vitamin D can cut cancer death risk.
The research findings can be found in JAMA Oncology.
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