ABOUT BREAST CANCER

The risk of breast cancer increases with age, with about 79% of all new breast cancer diagnosed in women aged 50 and over. The average age of first breast cancer diagnosis in Australia is 61 years.

Besides gender, aging is the most significant risk factor associated with breast cancer [4]. The older you get, the more your cells accumulate DNA damage (mutations) and are therefore more likely to progress to cancer. According to Cancer Australia, women who are 50 years old are approximately 10 times more likely to develop breast cancer compared to women who are 30 years old.

Alcohol consumption is associated with an approximate 30-50% increased risk in breast cancer risk [1]. Alcohol consumption is the most-established dietary risk factor of breast cancer thought to be due to the increase of endogenous oestrogen levels it causes [2]. 

Your relative risk of breast cancer is increased by 7% of each additional 10 grams, or one standard drink, of alcohol consumed per day [3]. One standard drink is equivalent to 100mL of wine, 285mL full strength beer, 425mL low strength beer or 30mL (one nip) of spirits.

Evidence shows there is no safe level of alcohol consumption in regard to breast cancer risk. A large meta-analysis of 222 articles finding even light drinking (up to one drink per day) increases the risk of breast cancer in women. The risk increases further with each extra drink.

A family history of breast cancer means having one or more blood relatives who have received a breast cancer diagnosis.

Studies have found that women with one first-degree relative with breast cancer have almost two times the risk of developing breast cancer compared to a woman without any affected relatives. Furthermore, this becomes a three times higher risk for women with two or more first-degree relatives with breast cancer [5]. 

Approximately 5-10% of breast cancers are due to a strong family history (two or more close relatives) of genetic mutation such as BRCA1 or BRCA2. There are also lesser known gene-mutations linked to a higher breast cancer risk such as TP53, PTEN, CDH1 and STK11 and some rare moderate-risk gene mutations such as PALB2, ATM and CHEK2. Some women with strong family histories receive genetic testing to see if they have one of these mutations. You can learn more about genetic testing in this Breast Cancer Trials podcast.

You can learn more about the genetic risks for developing breast cancer here.

Breast Cancer Trials currently has a breast cancer prevention trial for those with the BRCA1 gene mutation. You can learn more here.

Even though breast density is a lower risk than other risk factors such as family history, it is more common in the general population [6]. Mammographic density, or dense breasts, refers to the percentage of dense tissue of an entire breast and can be seen as the whiteness on your mammogram. Breast density cannot be felt or touched and can only be determined through x ray or mammograms.

Women with dense breasts face two challenges; a potential late diagnosis of breast cancer due to poor sensitivity of mammographic screening and having a higher risk for developing breast cancer [7]. Researchers are uncertain as to why having dense breasts increases your breast cancer risks, but believe it has some genetic links. It is hypothesized that the greater proportion of epithelial and non-epithelial cells in areas of high breast density, and the greater cumulative exposure to hormones and growth factors, may stimulate more cell division which increases breast cancer risk [8].

Breast density is just one risk factor and doesn’t mean you will be diagnosed with breast cancer. However, if you are aware of your mammographic density, you should talk with your doctor about regular screening. You can learn more about dense breasts in this podcast.

Being overweight or obese is a known breast cancer risk factor. Obesity is associated with a 20% to 40% increased risk of breast cancer in post-menopausal women. In patients diagnosed with breast cancer, obesity is associated with a 33% increased risk of cancer recurrence and of death from any cause [9].

Additionally, gaining weight as an adult is associated with an increased risk of post-menopausal breast cancer. The risk increases by about 6% for each 5 kg increase in a woman’s weight.

However, having a higher BMI before menopause is associated with a decreased risk of premenopausal breast cancer. For each 5-unit increase in BMI, the risk of premenopausal breast cancer is decreased by about 7% [10]. Importantly, obesity throughout life increases the risk of many other diseases such as heart disease and other cancers, leading to a higher rate of premature death.

You should aim to lead an active life-style, with the Australian Government guidelines recommending 150 to 300 minutes (2 ½ to 5 hours) of moderate intensity physical activity or 75 to 150 minutes (1 ¼ to 2 ½ hours) of vigorous intensity physical activity, or an equivalent combination of both moderate and vigorous activities, each week if aged between 18-64. For those aged 65 and older, the recommendation is to be physically active for 30 minutes every day. This should be balanced with a healthy diet full of nutritious wholefoods [11].

Previous exposure to radiation is a known breast cancer risk factor, which increased according to how much radiation you have been exposed to and when you were exposed. Age is an important factor, with females exposed before age 20 years having the highest risk and minimal risk for those exposed to radiation after menopause [12].

Usually, this exposure to radiation therapy for young people in the chest region is due to treatment for Hodgkin lymphoma or childhood cancers. Women who were treated for hodgkin lymphoma using radiation alone have about five times the risk of breast cancer as women who did not receive this treatment. The risk is higher for those treated at a younger age, particularly close to the age when periods started [13].

Researchers have found an increased risk of breast cancer for those who smoke, particularly among women who started smoking at adolescence or younger ages. The relative risk of breast cancer associated with smoking has been found to be greater for women with a family history of the disease [14]. 

The carcinogenic potential of tobacco smoke is unarguable and has been definitively linked to heart disease, lung cancer and many other cancers, therefore not smoking is the best choice for your health.