Breast cancer: Could breast density be as much risk as family history?
- Breast cancer accounts for 1 in 8 cancer diagnoses worldwide; hence it is important that people know how to mitigate their own risk.
- A new study has found that many women are unaware of the risk factors and how they can help reduce their breast cancer risk.
- The study identified breast density as a risk factor that few women were aware of.
Breast cancer is the most commonly diagnosed cancer globally, with cases predicted to rise to 3 million by 2040, according to researchers from the International Agency for Research on Cancer. They also note that 1 in 8 cancer diagnoses is for breast cancer, and 2.3 million cases were diagnosed worldwide in 2020.
There are some risk factors, such as genetic predisposition, that a person cannot change, but lifestyle changes can help reduce the risk of breast cancer. These include being physically active, maintaining a healthy weight, limiting alcohol consumption, and not smoking.
New research, published in JAMA Network Open, has found that many women are unaware of, or underestimate the importance of, risk factors for breast cancer, particularly breast density.
And almost one-third of those surveyed believed there was nothing they could do to reduce their personal risk.
What is breast density?
Most participants in the study were aware that having a first-degree relative increases the risk of breast cancer, but few knew that breast density was a risk factor.
High breast density may increase breast cancer risk by 1.2 to 4 times, whereas having a close relative with breast cancer doubles risk.
Dr. Arif Kamal, chief patient officer for the American Cancer Society, was unsurprised by this finding:
“[Breast density] a term we have not used for a long period of time, and I can’t remember a decade back that we would be talking to women about breast density, so as a risk factor, it’s relatively newly understood.”
Denser breasts contain more glandular and fibrous tissue than fatty tissue. About half of women have more dense breasts, generally those who are younger or have lower body mass.
Dr. Kamal explained to Medical News Today breast anatomy and where cancerous cells from in the breast:
“Breast tissue is made up of simply two things; one is the glandular tissue, the gland that makes the milk and holds the milk and expresses the milk, and the other is the fatty tissue around that. The part that can turn into cancer, in about one in eight women, is the glandular part. It’s the milk machinery that can turn into cancer. The fat part does not, with some rare exceptions.”
“When we’re talking about breast density what we’re saying is, relative to each other, how much glandular milk tissue [y]ou have as compared to fat tissue,” he added.
Comparing cancer risk factors
The study surveyed women between the ages of 40 to 76 with no previous history of breast cancer and who had recently had a mammogram. A total of 1,858 women completed the survey.
They were asked to compare five different risk factors to breast density:
- having a first-degree relative with breast cancer,
- being overweight or having obesity,
- drinking more than one alcoholic beverage per day,
- never having children,
- having a prior breast biopsy.
Of the respondents, 93% thought that having a close relative with breast cancer increased your risk more than high breast density.
The researchers then interviewed women who reported knowing their breast density about the different risk factors and what they knew about mitigating breast cancer risk. Few of them noted breast density as a breast cancer risk factor.
Breast density and cancer risk
“While having denser breasts does increase the risk of cancer, this is not something we can check for ourselves or something we can change.”
— Claire Knight, senior health information manager, Cancer Research UK
Breast density changes over a woman’s lifetime and, Dr. Kamal advised, cannot be assessed by self-examination.
“What they end up feeling can be areas of density but oftentimes those areas of density are fluctuating because if they are premenopausal, then it will be just cyclical changes, it can be [a] cyst and other things too, and so really we’re talking about a radiologic observation,” he explained.
So breast density must be assessed from a mammogram. However, Dr. Kamal reassured that higher breast density alone is not generally a reason to undergo further investigations.
“If breast density is the only risk factor, we still consider them to be in the lower risk category. If there are also other factors, that would mean higher risk,” he said.
He suggested one possible approach to screening breast density:
“Maybe […] at 35 [people] could potentially have a mammogram particularly to look at this issue. So what you’re then doing is an individualized risk assessment […] if at 35 you have high breast density and a strong family history […] maybe you would approach that differently so, I think it remains an ongoing important area of study.”
Reducing breast cancer risk
The women interviewed rated family history and genetics as the most important risk factors for breast cancer. Women with a family history of breast cancer tended to overestimate their risk, and women with no such background underestimated their risk.
And roughly one-third (28%) thought that there was nothing they could do to reduce their risk of breast cancer.
When asked about reducing risk, many women cited detection methods, such as self-examination and mammograms, rather than measures they could take to reduce the risk of developing cancer.
“There are things we can do to lower our risk of breast cancer, such as keeping a healthy weight, being physically active, and drinking less alcohol.”
— Claire Knight, CRUK
The CDC recommends the following to help reduce breast cancer risk:
- Maintain a healthy weight
- Keep physically active
- Drink alcohol in moderation or not at all
- If you are taking hormone replacement therapy or the birth-control pill, ask your doctor about the risks
- Breastfeed your children if you can
And Dr. Kamal noted that “the leading lifestyle risk [is] weight, particularly rapid weight gain, or postmenopausal weight gain.”
The study authors suggest that better information about the meaning of breast density should form part of communications to ensure greater understanding and awareness of breast cancer risks. This would allow people to make more informed choices about screening and prevention.
Meanwhile, Claire Knight gave general advice:
“Breast cancer is more common as we get older. But whatever your age, if you notice any unusual or persistent changes to your breasts, speak to your doctor.”
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