Digital Breast Tomosynthesis Reduces Benign Biopsy Rate 

Becky McCall

March 19, 2019

Digital breast tomosynthesis (DBT), also known as 3-D mammography, reduces the benign biopsy rate, compared to full-field digital mammography (FFDM), while maintaining the cancer detection rate, shows a single centre, prospective study from Leeds.

All women in the study had been recalled after routine screening as part of the National Health Service Breast Screening Programme (NHSBSP). DBT was then performed during the diagnostic workup stage.

The key benefit found in the study was a reduction in biopsy rate from 69.0% (571 of 827) to 36.0% (298 of 827) if DBT had been used compared to FFDM. Cancer detection rate was the same with or without DBT. Effectively, 273 biopsies could have been avoided if DBT had been used.

Dr Nisha Sharma, is director of breast screening at Leeds Teaching Hospital NHS Trust. "Our study validates that DBT can help in the diagnostic workup of mammographic abnormalities and reduce harm to women through fewer false positive biopsies without any reduction in the cancer detection rate," she said in an interview with Medscape News UK.

She added that: "DBT increases your confidence as a radiologist to conclude that there is nothing to worry about and no biopsy is needed."

The study is published in 19th March edition of Radiology.

Standard of Care Plus DBT Reduces Benign Biopsy Rate 

DBT acquires multiple images to produce a set of reconstructed thin-section images, viewed as three-dimensional information. The thin-section images of the breast minimise tissue overlap that can lead to a false positive recall or to a cancer being missed when FFDM is used. DBT has the potential to improve the sensitivity and specificity of mammography.

The study aimed to compare the use of DBT versus no DBT in women recalled for screening assessment after routine breast screening within the NHSBSP programme. Benign biopsy rate

and cancer detection rate were the primary outcomes assessed. Dr Sharma intended for the study to help overcome a paucity of studies on whether the benign biopsy rate will be lower with DBT.

After routine screening of 30,933 women local to Seacroft Hospital, Leeds, 4.8% were recalled due to an abnormal finding. After exclusions, 827 women were included in the study. All women received standard triple assessment (clinical examination of the breast, imaging with two-dimensional [2D] mammography and ultrasound of the area of abnormality, and biopsy if needed). DBT examination was performed in women who consented to take part in the study. Women had a mean age of 56.7 years. The researchers read the DBT images blinded to the original FFDM screening results to determine whether DBT images would have influenced the biopsy recommendation.

Effectively, two screening protocols were compared: triple assessment with no DBT, versus triple assessment with DBT. The number of biopsies required after each protocol, and the number of cancers detected were recorded.

In the protocol without DBT, a total of 571 biopsies were performed (69% biopsy rate), and 429/571 of these were benign (a 75% benign biopsy rate); 142 malignant cancers were diagnosed. In the hypothetical protocol that included DBT, 298 biopsies (biopsy rate 36%, benign biopsy rate of 52%) would have been performed and 142 cancers would have been diagnosed.

"In total, the study identified 145 cancers," explained Dr Sharma. Of these, 142 were seen on the standard triple assessment, one through MRI (family history screening), but two cancers were not picked up on standard assessment but would have been if DBT was used. DBT missed two cancers but these were both non-invasive cancers.

Reflecting on the usefulness of DBT in the diagnostic work-up process for breast cancer, Dr Sharma said: "Abnormal findings that a radiologist might have been indecisive about before [DBT], you can now be reassured that they are normal and do not need a biopsy."

Important in Diagnostic Workup, but for Routine Screening? 

"I feel that DBT is an important imaging tool in the diagnostic workup of mammographic abnormalities in women who have been recalled," said Dr Sharma, adding that, "there is also some discussion around whether tomosynthesis should be used as a routine screening tool. A UK study called PROSPECTS is looking at this but currently within the UK, DBT can only be used in the diagnostic workup and not screening.

"At the moment, for recalled women, DBT is an important aspect of the diagnostic workup because it helps to reduce the number of women needing a biopsy."

DBT is increasingly widely available, she says: "I think around half of clinics have tomosynthesis available."

In an editorial accompanying the study, Dr Per Skaane from the Department of Radiology and Nuclear Medicine, Oslo University Hospital, said: "The study by Sharma et al is important, as they have clearly shown that DBT can reduce the benign biopsy rate at assessment. The extent of their findings is limited to screening programs that have not implemented DBT as a screening test."

Published in 19th March edition of Radiology.

COI: Dr Sharma has declared no conflicts of interest.

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