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Six Months Seems Optimal for Follow-Up Imaging of 'Probably Benign' Breast Lesions

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Breast lesions found by mammogram and classified as probably benign by BI-RADS should have follow-up imaging at or before 6 months after the lesions are found to ensure that the lesions are not cancer, according to a study.

The research was published online on May 19, 2020, by the journal Radiology.

Read “Cancer Yield and Patterns of Follow-up for BI-RADS Category 3 after Screening Mammography Recall in the National Mammography Database.”

What is BI-RADS?

The Breast Imaging Reporting and Database System, or BI-RADS as it is commonly called, is a standardized way for breast imaging — mammograms, MRIs, and ultrasounds — to be reported. BI-RADS classifies mammogram results into one of six categories:

  • category 1 negative: no lesions found and there is 0% risk of cancer
  • category 2 benign: the lesion is benign and there is 0% risk of cancer
  • category 3 probably benign: the lesion is probably benign and there is a 2% or lower risk of cancer
  • category 4 suspicious is broken down into three subcategories:
    • 4A low suspicion for malignancy: the risk of cancer is 2% to 10%
    • 4B moderate suspicion for malignancy: the risk of cancer is 10% to 50%
    • 4C high suspicion for malignancy: the risk of cancer is 50% to 95%
  • category 5 highly suggestive of malignancy: the risk of cancer is 95% or higher
  • category 6 known biopsy-proven malignancy: a biopsy has confirmed the suspicious area is cancer

Why this study was done

The timing of follow-up procedures for all the categories is clear, except for category 3, lesions that are probably benign. Some earlier research suggested that the risk of cancer was so low for category 3 lesions that follow-up imaging could safely wait until a year later, rather than 6 months. Still, much of that research was done before the National Mammography Database was created in 2008. The National Mammography Database is a registry of U.S. mammogram information, including results, recalls, and outcomes.

"I thought that we should really look at this again now that we've got this large database we can work with and try to find out what happened with these patients," said lead author Wendie A. Berg, M.D., professor of radiology at the University of Pittsburgh School of Medicine.

How the study was done

The researchers looked at the records of 45,202 women with BI-RADS category 3 mammogram results. All the women were age 25 or older and had never been diagnosed with breast cancer.

Overall, 1,574 women had a biopsy when the BI-RADS category 3 lesion was detected, which resulted in 72 cancers being diagnosed.

The other 43,628 women opted to have surveillance instead of immediate biopsy:

  • 1.07% of the women were diagnosed with cancer as a result of imaging 6 months after the BI-RADS 3 lesion was found
  • 1.60% of the women were diagnosed with cancer as a result of imaging 12 months after the BI-RADS 3 lesion was found
  • 1.86% of the women were diagnosed with cancer as a result of imaging 24 months after the BI-RADS 3 lesion was found

Overall, 810 cancers were diagnosed, which means 1.9% of the women with a BI-RADS category 3 lesion were ultimately diagnosed with cancer. About 33% of the cancers were DCIS, which is stage 0, non-invasive cancer. The other 66% were invasive breast cancer, and 12% of the invasive cancers had spread to the lymph nodes.

So for the BI-RADS category 3 lesions looked at in this study, 468 of 810 cancers (57.8%) were diagnosed at or before 6-month follow-up.

"The majority of cancers were diagnosed at or right after the six-month follow-up, so it actually is important to get these patients back in that six-month time frame," Berg said. "The important thing about this paper is that these data come from a wide number of facilities across the United States, so it really brings to bear that, yes, this is the appropriate practice and yes, you still need to see these patients in six months."

What this means for you

If your mammogram results say that you have a BI-RADS category 3 lesion, it makes sense to talk to your doctor about this study. It also makes sense to ask how you will be monitored for cancer and when you should have your next mammogram. If your doctor suggests follow-up more than 6 months after your BI-RADS category 3 results, it’s a good idea to ask why and point out that the results of this study suggest that follow-up should happen within 6 months. Together, you and your doctor can make the best decision for your unique situation.

For more information, visit the Mammograms pages.

Written by: Jamie DePolo, senior editor

Reviewed by: Brian Wojciechowski, M.D., medical adviser

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