Mammography has been the gold standard for breast-cancer screening for decades now, and the technique hasn't developed much in that time. Women aged 45-69 who participate in the free public programme, BreastScreen Aotearoa, will be familiar with the process of having their breasts compressed in two different positions so that X-ray images can be captured and any early signs of cancer hopefully detected.
In women aged over 50, traditional two-dimensional mammograms find 85 per cent of unsuspected breast cancers. But if you go to a private radiology clinic, you might be offered an alternative, possibly at extra cost depending on your insurer.
Tomosynthesis is the latest generation of digital screening. A similar procedure, it also involves the breasts being compressed between two plates, but offers a more three-dimensional view as the scanner takes several images, or "slices", of each breast, reducing the amount of overlapping tissue. Research has shown that this can improve detection and reduce the need for those anxiety-inducing call-backs, particularly for women with denser breast tissue.
"Tomosynthesis is really good for dense breasts that are not too dense," says Adèle Gautier, of the Breast Cancer Foundation NZ.
Dense breasts have relatively high amounts of glandular and fibrous connective tissue and relatively low amounts of fatty tissue. This can make it harder for radiologists to identify any concerning changes as the denser tissue may obscure the often tiny calcifications they are looking for.
About 40 per cent of women have heterogeneously dense breasts, which means there are some areas of fatty tissue, but the majority is dense.
"For them, tomosynthesis is going to give a better read," says Gautier. "Unfortunately, it's not the solution for the really vexing problem of people with very dense breasts, which is around 10 per cent of women."
The other commonly used diagnostic tools for breast cancer are MRI (magnetic resonance imaging), which is a way of looking for areas of increased blood supply that can indicate tumour growth, and ultrasound. The challenge is that, for each of these tests, the breast is placed in a different position and, since it is a soft organ, it changes shape, making it difficult for clinicians to identify the exact spot that needs further investigation or treatment.
AdvertisementAdvertise with NZME.
"For an MRI, the person is lying on their tummy and the breast is hanging down into specialised imaging coils," says Professor Martyn Nash, of the University of Auckland Bio-
engineering Institute. "In ultrasound, the patient is lying on their back and the breast is relatively flat. And in mammography it is compressed. What clinicians are doing is taking all these very different-looking images and bringing the information together in their heads to get a three-dimensional view of the breast. They're trying to solve this three-dimensional problem all the time, and they're pretty good at it, but there are a number of cases where it's difficult to do. As engineers, we can make it a whole lot easier for them."
Nash and his team have received $1.05 million in philanthropic funding to develop an automated analysis technique that merges information from different medical images of the breast, making it easier to find abnormalities. They are using biomechanics to predict the movements of the suspicious tissues so the surgeon can be given a much better idea of where to find them.
The new three-dimensional visualisation technology is in the clinical research phase and, with feedback from doctors at Auckland City Hospital, the computer software is being developed all the time. "As bioengineers, we know how to predict how the body moves. We're using the laws of physics to predict how the breast changes shape; that's the crux of it," says Nash.
Other new technologies are on the way to help revolutionise breast screening. In the UK, researchers from the University of Nottingham are working on a blood test to detect breast cancer up to five years before any obvious clinical signs. The test identifies the body's immune response to substances produced by tumour cells and will hopefully provide an easier, cheaper screening method in the near future.
In the meantime, if you want to choose tomosynthesis rather than traditional 2D mammography, you will have to go private. It is a low-radiation procedure – Gautier describes it as being about the same as taking a flight to Christchurch. But it requires extra equipment, the scan takes slightly longer and the images are larger, so take up more storage space, and all these factors are barriers to BreastScreen Aotearoa being able to offer it.
"Integrating new technology into a population-wide screening programme is a massive undertaking," says Gautier.