Wellington radiologist investigating link between dense breast tissue and interval cancer

A Wellington breast radiologist is investigating whether having dense breast tissue puts women at a higher risk of developing cancer between mammogram screenings, which are Government funded for women aged 45-69 every two years.

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Now a radiologist is investigating the link between dense tissue and the disease. Source: 1 NEWS

Dr Monica Saini has received $75,000 from the Breast Cancer Foundation New Zealand for the study to be completed.

“We have a very different ethnic population mix and so because of that it's hard to look at other countries and say how does that reflect on New Zealand,” Saini said.

Women with increased dense breast tissue are at a higher risk of cancer and fibrous tissue can also mask cancer from being detected in a mammogram, as both appear as white tissue in imaging.

Factors such as ethnicity and family history will also be examined in the study.

The study will include reviewing the data of 200 women in the Wellington region with cancer that was detected between screenings, known as interval cancer, and 200 women from the same time who didn’t develop cancer.

“Our goal here is to actually collect data from the Wellington region and perhaps also with another DHB in the North where we would have higher Māori and Pasifika numbers so we could have statistically significant conclusions that we could draw,” Saini said.

Dr Saini said she aims to determine if breast density is one of the reasons Māori and Pasifika women have a higher rate of cancer that’s found between screening and higher breast cancer occurrence overall.

“It’s more comprehensive to look at as many risk factors as we can because then we can advise policy as to what would be the best screening regimen and how can we identify the women who are at highest risk.”

Breast Cancer Foundation New Zealand chief executive Evangelia Henderson said the study will provide much-needed knowledge about breast density and interval cancers.

"We need to know which women are more likely to develop interval cancers, so we can improve our screening programme," Ms Henderson said in a statement.

Saini is aiming to use the information from the study for a second investigation in the future, examining which screening tool is the most effective, in terms of the cost of the test and cancer detection rate, for screening these women found to be at high-risk.

“We need to start doing that research so that we would have that solution in hand and we're not just waiting five to ten years from now seeing what other countries are doing,” she said.

“Cost is certainly something but I think you have to start with the fact that we don't know just how many women would be eligible,” she said.

Saini said the Netherlands have used magnetic resonance imaging, or MRI, to decrease the country’s rate of cancers detected between screenings, but that tool is one of the most expensive, whereas ultrasounds are cheaper but have a higher rate of incorrect detections.

She said 40 to 50 per cent of women in the United States have dense breasts.

It’s not known how widespread increased dense tissue is in New Zealand, as the Ministry of Health doesn’t measure density as part of the national screening programme.

The Ministry of Health declined to be interviewed but said in a statement density isn’t measured because there isn’t enough evidence that additional testing for women with dense breasts would save lives.

It also said there isn’t agreement internationally about the most effective way to measure breast density.

"New Zealand has followed the approach taken in most of Australia and the UK, which is that until there is evidence for clinical best practice for how breast density should be assessed and managed we will not routinely assess and record breast density or provide supplemental screening for women with dense breasts," it stated.

“I don’t think we need to wait and see what other countries do, I think we need to take the lead and get going,” Saini said.

Breast cancer survivor Nikki Slade Robinson is welcoming Saini’s research project after not being aware she had dense breasts, that density was a cancer risk or that it made mammograms less effective, when her cancer was detected between screenings.

“I was really angry that currently the system in New Zealand does not give women that information… We have a right to that information about our own body,” Ms Slade Robinson said.

She hopes the study’s findings will provide “enough proof” for the Ministry of Health’s screening programme to be updated.

“I ultimately would love to see the public screening programme include in the results you have 'x' density so women know.”

Saini said being transparent with medical issues is important.

“In Western Australia, for example, for 10 years they have been informing women about their mammographic breast density and what they have found through their research is that women aren’t considerably more anxious by knowing this information – they’re more informed and as a result, compliance in attending regular screening mammography has gone up,” she said.

Women who get mammograms in private clinics are more likely to be told their density.

Dr Saini said detecting cancer in a very dense breast is like “finding a snowball in a snowstorm.”

Ms Slade Robinson said if her cancer was detected earlier, her treatment wouldn’t have been so invasive.

“I wouldn’t have needed chemo, maybe I would have only needed a lumpectomy but I’ve had a mastectomy.”

She said she’s sharing her experience because she wants other women to be screened more effectively.

“In the Eastern Bay of Plenty, we've got a high Māori population and Māori women are more pre-disposed to high density in their breasts so I'm fighting for them too.”

The Ministry of Health is considering providing pamphlets with general information about breast density to women at mammograms.

Ms Slade Robinson is urging women to be aware of the risk of breast density.

“Have your mammograms, do your self-examination; that’s really important, don’t stop but know your density as well and get an ultrasound as well if you’re in that really dense group.”