What are some of the risk factors for breast cancer?

Genetics:

Five to ten percent of all breast cancers can be attributable to familial risk. However, even in patients with a strong family history, a specific genetic mutation is only detected in < 30% of cases. The most common mutations associated with breast cancer are the Breast cancer genes (BRCA) 1 and 2. Mutations in these genes are thought to cause 1-2% of all breast cancer diagnoses in Australia. Due to their aberrancy, these tumour suppressor genes fail to repair double-stranded DNA breaks, resulting in mutation accumulation eventually leading to breast cancer.

The rates of developing breast cancer, by age 80, in BRCA1 and BRCA2 are 55-72% and 45-69%, respectively. This far exceeds the lifetime risk of 14.3% for the baseline population. There are other genetic mutations that have been identified as increasing breast cancer risk and include PALB2 ATM and Chek2. All gene mutations can have variable penetrance and surveillance recommendations are modified according to the risk they confer.

Jewish heritage:

The Ashkenazi-Jewish population have an increased risk of carrying a BRCA1 or 2 mutations. Approximately 1 in 40 Ashkenazi Jewish women have a BRCA mutation, compared to 1 in 400 in the general population. There are three specific BRCA1/2 pathogenic variants, referred to as BRCA-Jewish founder mutations (B-JFM), accounting for more than 90% of the pathogenic variants in this sub-population. JeneScreen is an active project in which any Ashkenazi-Jewish women, regardless of their family history can test for the B-JFM, in Sydney and Melbourne. This has facilitated the detection of high risk individuals who would have been otherwise been ineligible for public testing.

Family history:

Often patients present with concerns of developing breast cancer due to a family member’s recent diagnosis. In cases where there is no identified genetic mutation, assessing familial risk can be difficult. The iPrevent tool is available to help assess a patient’s risk. In patients with a 10 year, or life-time risk of breast cancer, that is ≥ 3-fold compared to the population, we strongly recommend genetic referral as there is a possibility that they carry an unrecognised gene mutation. Genetic testing is Medicare rebatable for this group of patients. EviQ is a free online NSW resource providing evidence-based, consensus driven cancer treatment protocols and information to help guide patient care.