New Zealand has one of the highest rates of breast cancer diagnosis in the world, according to a recent survey of 185 countries. On the other hand, our rates of death from the disease are at the lower end of the scale and continue to fall. Partly, that is thanks to the Breastscreen Aotearoa programme. Since it was launched in 1998, we have got better at diagnosing breast cancer in its earlier and more treatable stages.
Breastscreen Aotearoa offers free mammograms every two years to women aged 45 to 69. This is being extended up to age 74, while women under 45 who are deemed high risk may also qualify.
Around 45% of the 3500 New Zealand women diagnosed each year will find out through routine screening before any symptoms have been noticed. The remaining 55% will have visited their GP, very often after discovering a breast lump. For them the outcomes may be poorer, particularly if they are Māori or Pacific women, who tend to be diagnosed with more advanced disease that requires more invasive treatments.
University of Waikato public health expert Professor Ross Lawrenson was involved with the original breast screening pilot in 1991, and has recently authored a paper looking at how we could be doing an even better job of catching breast cancer early.
“When we started there was no digital mammography,” he recalls. “We had films covered in acetate that we held up to the light and there were no specialist radiographers. The system has increasingly got better and better, so I was interested in looking at what is on the horizon now.”
The role of artificial intelligence is likely to expand, for instance. Currently, mammograms are read by two expert radiologists but studies are showing that AI assistance has the potential to detect cancerous tissue more quickly and accurately, plus reducing workload. In the US, some breast-imaging clinics already offer women the option of adding an AI-assisted reading to their mammograms.
“We know that training and machine learning for X-rays and mammography is going to keep getting better,” says Lawrenson. “To the extent that rather than it being an aid to the radiologist, it may be that the radiologist becomes an aid to the machine.”
More sophisticated mammography tools will also become available. Digital breast tomosynthesis, also known as 3D mammography, provides a more detailed, layered view of breast tissue compared with traditional mammography. In New Zealand, this can be accessed only in private clinics.
Another approach being used in some countries is reporting on breast density. Around 10% of women have very dense breast tissue and 30% moderately dense. Not only does this increase the risk of breast cancer, it makes it more difficult to detect on a mammogram.
Last year, in the US, the Food and Drug Administration issued a mandate that all women who go for screening should be routinely informed about their breast density. So far, New Zealand hasn’t followed suit, mainly because there aren’t the resources for the additional imaging that would be required, whether that is MRI, ultrasound or 3D mammography.
Lawrenson believes that in the future we will see a more personalised approach to screening.
“Not every woman has the same risk of breast cancer, so is screening everybody, every two years, the right answer?” he asks, adding high-risk women may need to be screened every year, while those at low risk could be screened every three years.
Factors that make up personal risk are not routinely recorded, and these include breast density, age and family history. “Then there are things like body weight, how many children you’ve had, whether you breastfed. Alcohol and smoking also increase risk. AI could be used to help inform people what their personal risk is and what their screening programme should be,” Lawrenson says.
While blood tests can be used as an aid in diagnosis and in monitoring treatment, it doesn’t seem likely that they will replace mammography as a diagnosis tool any time soon.
“I think that’s much more likely for other cancers involving internal organs like pancreatic and lung. But we will have better technologies with faster and more accurate diagnosis, and fewer false positives,” he promises.
While he sees room for improvement, Lawrenson has no doubt that screening has been beneficial.
“Our survival rates from breast cancer are remarkably good and a large part of that is because of the screening programme picking it up early.”
