Planning for the future: 3D mammography with DBT

Earlier this year at the annual European Radiology Congress (ERC) in Vienna, Austria, Dr Alessia Milan, from the University of Turin, presented a paper that posited that digital breast tomosynthesis (DBT) provided a better view of lesion margins when compared with mammography, which was found to not be as effective in reducing re-excision rates.

The purpose of the study was to compare the re-excision rate for positive or close margins in patients who are undergoing breast cancer surgical treatment. Milan and her team conducted a retrospective observer study, which included patients with newly diagnosed breast cancer who consecutively underwent breast surgery.

Patients were divided into two groups: in the first, patients were staged with digital mammography (DM) and ultrasounds, while the second group comprised patients who were staged with a cocktail of DBT, DM and ultrasounds.

For 7.9% of patients with positive margins at definitive histology, the study found that the re-excision rate was 10.0% for group one, which was significantly higher than group two’s 5.0%. The re-excision planning was also less extensive for patients in the second group who received all three treatments, resulting in one in 20 patients getting mastectomies, compared with 20 in 53 for group one.

Dr Milan’s study concludes that the two groups did not differ significantly for breast cancer characteristics, age and risk factors, finding that using DBT, in conjunction with preoperative DM and ultrasound, drastically reduces the re-excision rate of breast cancer surgical treatment. Despite the result of this study not being randomised – and perhaps biased – it does, however, provide an interesting starting point for future studies that will include patients staged with breast MRI.

When discussing the framework for screening, Dr Milan stated that DBT shows a lot of promise for surgical planning because it enables medical professionals to have a clearer view of lesion margins; however, mammography and ultrasound are the most prevalent primary diagnostic and preoperative imaging methods for breast cancer.

But this is while her own study shows that DBT reduces breast surgery re-excision rates. So what exactly is DBT and how could it change the way hospitals diagnose cancer?

DBT mammograms use low-dose X-rays to create a 3D image of the breast that can be viewed in narrow slices, as in CT scans. In conventional 2D mammography, overlapping tissues can sometimes mask suspicious areas, while 3D images are able to eliminate this overlap and make abnormalities easier to recognise.

Several low-dose images are taken from different angles around the breast to create the 3D picture. A conventional mammogram creates a 2D image of the breast from two X-ray images of each breast. It is estimated that 50% of the facilities in the Breast Cancer Surveillance Consortium now offer 3D mammograms.

It is also expected that 3D DBT will replace conventional mammography within ten years. The main reasons behind this change stem from the technology’s reduction in the number of false positives, as well as several studies that have found that 3D mammograms locate more cancers than traditional 2D mammograms.

Rather than producing a single 2D planar view of multiple tissue layers, DBT systems use 3D technology to eliminate tissue interference by digitally removing overlying or underlying tissue in 1mm slices. This means that potential extensions of the cancer, radiating laterally or deep to the lesion, can be seen with greater clarity, helping to decrease the risk of positive margins and optimising the cosmetic outcome of the procedure.

During the treatment stage of breast cancer, digital tomosynthesis is the key to providing a 3D solution for 3D and wide-ranging problem.

Cultural changes

This is relevant to ideas surrounding cancer screening today. Several countries – including Denmark – have now dropped widespread cancer screening for women, whereas Switzerland and other countries have been recommended to follow suit by their governing health boards.

This was mainly because mammograms posed several problems: women were being treated for cancers that were insignificant and only required monitoring or were investigated for possible cancers through a mammogram after a scan had found dense tissue.

Over the past few decades, it has been a vital way to achieve a reliable scanning method while reducing mistakes and misdiagnoses. Perhaps this will increase following cultural changes and the introduction of huge government screening programmes globally.

A study that assessed three years of data from breast cancer screening with 3D mammograms has found that their benefits last over time, according to a recent report from the US charity BreastCancer.org, which provides information and support to women.

The charity reports that a study was published online in 2016 by the American Medical Association’s JAMA Oncology journal. Entitled ‘Effectiveness of digital breast tomosynthesis compared with digital mammography: outcomes analysis from three years of breast cancer screening’, it affirmed that 3D mammography was a better technique for screening breast cancer.

Emily Conant, chief of breast imaging at the Perelman School of Medicine, which is part of the University of Pennsylvania, was the study’s senior author and states that its results “are an important step towards informing policies so that all women can receive 3D mammography for screening”.

Conant’s study analysed 45,000 screening mammograms from 24,000 women who had never been diagnosed with breast cancer.

All of the women were screened with digital 2D mammograms only and for the next three years, the women were screened with 3D mammograms.

Conant and her team of researchers then compared the differences in screening outcomes between each 3D mammogram year and the 2D digital mammogram year for three years.

They also compared the differences in outcomes between women who had one, two or three 3D mammograms.

An interesting result from the study found that the rates of women who had to come back for more testing increased slightly year on year for women who had the 3D mammograms. It is clear from these results that many women may benefit from the process if it were more widespread.

These findings will hopefully help to make 3D mammography become part of routine breast cancer screening. Vikram Butani, CEO and founder of Kubtec Medical Imaging, agrees with Milan’s findings. “We all know tomosynthesis provides a better view of the anatomy when comparing with the 2D and 3D in mammography,” he explains from the company’s headquarters in Connecticut.

“They find the cancer, but in the operating room it is the surgeon who needs to make sure that they get the entire cancer out, which requires finding margins of the healthy tissue around the cancer – so it is equally important not just to find the cancer, but also to make sure you got all of it out the first time.”

He believes that Milan’s study on re-excision rates is important because women only want one procedure – anything else is too harmful.

“The flipside is that you don’t want to take out too much tissue because of trends where a woman wouldn’t want to go in for a mastectomy for a 1cm cancer,” he says.

“Today, you see the trends for early detection, more precise treatment, a focus on cosmesis and better oncological outcomes. Then, above all, there’s containment: if you do spot the cancer, but don’t entirely excise it the first time, then you have to redo the procedure.”

Butani adds, “studies have shown that, 60–70% of the time, if a women has to go back for another procedure within a few months of getting the first one, she just decides to have a mastectomy because having to go back and say ‘You didn’t get the cancer the first time?’ is traumatic and horrific.”

Treatment benefits

Kubtec’s MOZART system provides clear images of targeted lesions – even through dense tissue – and identifies the extent of these.

Butani also states that hospital costs are a large factor in this growth of acceptance towards DBT. “The hospital is not going to get paid twice if you have to re-excise, and that’s where the trends are in the US; you’re not going to get paid again for doing the same procedure, so you better get it right the first time.”

Adding DBT to preoperative DM and ultrasound reduces the re-excision rate of surgical treatment for breast cancer, which is great news for women and imaging centres that seek to render cost-effective care. Yet, expenditure and the invasiveness of procedures could act as barriers to introducing this change.

At the ERC, Milan stated that margin status is an important predictor of cancer recurrence following surgery. She added that accurate preoperative staging formulates the best surgical treatment methods and also reduces the consequences of re-excision, including emotional burden, an undesired cosmetic outcome and higher costs.

A new way

Many women may benefit from Milan’s study, which shows there is a way around re-excision as another tool in the fight against cancer. She concludes that her results prove that DBT can help to improve conventional imaging for preoperative breast cancer surgical treatment staging.