Understanding breast cancer – risk factors

WELCOME to part two of the Understanding Breast Cancer series. In this article we will dive deep into the risk factors associated with breast cancer.

Breast cancer is the most prevalent cancer among Jamaican women, comprising one-third of all annual cancer diagnoses in our female population. On average, Jamaican women face a seven per cent lifetime risk of developing breast cancer, which translates to one in 15 women. The number of new cases of breast cancer is predicted to increase due to certain social, cultural, economic, and lifestyle changes that often accompany the transitioning of developing nations such as Jamaica.

A common question posed to oncologists by their patients with breast cancers is what caused them to have the disease? Many patients feel that there must be some direct identifiable trait, factor, or event which, by itself, resulted in their diagnosis.

There are many factors that may be associated with the development of breast cancer, but these are more correctly referred to as risk factors rather than direct causations. These risk factors can be classified as:

1) Genetic/hereditary

2) Hormonal/reproductive history

3) Lifestyle

4) Environmental exposure.

The risk of developing breast cancer generally increases with age, and most Jamaican women with breast cancer are diagnosed between 40 and 70 years. The average age of diagnosis in Jamaican women is 54 years, which is much earlier than the average age of diagnosis in Western Europe or North America.

Family history/Genetics

Most women who go on to develop breast cancer have no known risk factors and while knowledge of risk factors is important to stratify the timing of commencement and the use of appropriate imaging for breast cancer screening, women with no known risk factors must never be neglected because most of the new breast cancers will develop in this group. A woman with a single first degree relative with breast cancer (parent, sibling, or offspring) has twice the risk of developing breast cancer as the average woman. It is very important for families to discuss the health histories, especially as it relates to breast, ovarian, and prostate cancers.

Highly penetrant genetic mutations such as BRCA1/2 account for five-10 per cent of all female breast cancers and a woman with this mutation has an estimated 70 per cent lifetime risk of developing breast cancer. These genetic mutations may be more common in women of African descent, but due to the expense and limited access, not many Jamaica women with breast cancers or a strong family history of breast cancer undergo this genetic testing.

Environmental – Hair dyes and relaxers

A study from the National Institute of Health in the USA showed that women who regularly used permanent hair dyes had a higher risk of developing breast cancer. The association between permanent hair dyes and breast cancer was greatest in African American women with a 45 per cent increased risk compared to seven per cent for white women. They also found an association between the use of hair relaxers/straighteners and breast cancer risk, especially in black women. Other studies have found no association between breast cancer risks and the use of hair dyes. More research is required in this area.

Environmental – Radiation exposure

Many patients ask if doing mammograms or other medical imaging may lead to breast cancer? While we are always cautious about radiation exposure in general, the evidence doesn’t support that exposure to low levels of radiation increases breast cancer risk. To put it into perspective, a typical screening mammogram uses 0.4 millisieverts of radiation, while increased cancer risks have been found only with dose exposure more than 100 millisieverts. Most of our yearly radiation exposure comes from natural background radiation, which is more than 15 times the exposure from a single mammogram.

Hormonal/reproductive

The risk of breast cancer is higher in women who have never given birth when compared to women who have. Women with first pregnancy at a later age are also at a relatively higher risk of developing breast cancer compared to women having first pregnancy at an earlier age. These are some of the factors contributing to increasing breast cancer incidence in developing countries. Earlier onset of regular menstruation and the late attainment of menopause (after age 55 years) are also associated with increased breast cancer risk. The use of oral hormone replacement therapy for menopausal women and combined hormonal birth control also increases breast cancer risk.

Lifestyle

Breast cancer is associated with potentially modifiable risk factors, especially as it relates to hormone positive breast cancer subtypes in postmenopausal women. As fat tissue is the largest source of oestrogen in postmenopausal women, weight gain and obesity in adult women doubles the risk of postmenopausal hormone positive breast cancers. Conversely, regular physical exercise and weight loss in adulthood reduces the risk.

Alcohol consumption increases the risk of breast cancer, with women who have two to three drinks per day having their breast cancer risk increase by 20 per cent .

Ultimately, the development of breast cancer in any population depends on many factors which may be hormonal, lifestyle, environmental, and familial/genetics. Some of these risk factors are modifiable and may decrease the overall developmental of breast cancer in our population by up to 15 per cent.

Table 1: Showing modifiable changes to decrease breast cancer risk

Join us again next week as we conclude our series by exploring breast cancer in younger populations.

Dr Jason Copeland is a fellowship trained breast surgeon, breast surgical oncologist (Roswell Park, Buffalo, New York) and consultant general surgeon.

He is the founder and clinical director of the Breast Health & Oncology Care Centre at Andrews Memorial Hospital. He is the clinical director of the Kingston Public Hospital Breast Oncology Clinic and is an associate lecturer at the University Hospital of the West Indies.