What is breast cancer?
Breast cancer is the abnormal growth of the cells lining the breast ducts or lobules. These abnormal cells have the potential to spread to other parts of the body. Most breast cancers are invasive. This means the cancer has spread from the breast ducts or lobules into the surrounding breast tissue. Invasive breast cancer can be early, locally advanced or advanced (metastatic). Breast cancer is the most common cancer among Victorian females.
You can access further information about breast cancer, including risk factors, symptoms, diagnosis and treatment from Cancer Council Victoria. You can also call our trusted cancer nurses on 13 11 20 for support and to learn about our range of services for people affected by cancer.
The Victorian Cancer Registry also operates an interactive web portal, Data Explorer, which provides more trends and statistics than published here.
How common is breast cancer?
In 2021, 4954 Victorians were diagnosed with breast cancer. Of these, there were 46 males and 4907 females, representing 0.9% and 99.1% of the total Victorian breast cancer diagnoses, respectively. There were 1 cases where sex was reported as neither male or female, not known, established or defined. Currently, breast cancer is diagnosed at a rate of 0.7 per 100,000 males and 92 per 100,000 females. The median age at diagnosis of breast cancer is 69 years in males and 61 in females. Figure 1 and 2 show the distribution of breast cancer among Victorian females. Due to low numbers of cases when single years of data are displayed, Figure 1 and 2 do not include data for males. Accounting for 13.4% of all cancers diagnosed and 6.7% of all cancer-related deaths in 2021, breast cancer was the most commonly diagnosed cancer among females and the 30th most commonly diagnosed cancer among males. It is the 2nd most common cause of cancer-related deaths in Victorian females and the 35th most common cause of cancer-related deaths in Victorian males.
Trends in breast cancer over time
Figure 3 shows data for both males and females diagnosed with breast cancer. It indicates that since 1982 incidence of breast cancer has increased by an average of 0.9% per year in females. Over the past 39 years, mortality from breast cancer has decreased by 2% per year in females. With a much lower age-standardised rate than females, incidence of breast cancer has increased by an average of 0.9% per year in males and mortality has decreased by 2.9% per year in males.
Breast cancer morphology
Figure 4 provides a summary of the different types of cells (morphology) which have caused breast cancer for males and females combined. Most breast cancer tumours, 74.7%, present as Breast carcinoma, no special type.
Breast cancer subtypes
A tissue biopsy of breast cancer tissue enables the molecular makeup of the tumour to be further examined. This is undertaken to determine the best treatment path. Some tumours may have cells with hormone receptors which help cancers to grow. Cancers which receive signals from oestrogen are referred to as oestrogen receptor positive (ER+) and those receiving progesterone signals are progesterone receptor positive (PR+) cancers. Breast cancer tissue is also examined to assess whether the presence of the protein human epithelial growth factor receptor 2 (HER2) that appears on the surface of the breast cancer cells and may stimulate cancer cells to grow. Breast cancer tissue with high levels of HER2 protein is referred to as HER2 positive (HER2+) or HER2 amplified.
Luminal tumours are hormone-positive (ER+ and/or PR+) and HER2 negative.
Non-luminal tumours are HER2+ but both ER and PR negative. Triple negative tumours refers to breast cancer tissue which does not contain oestrogen receptors, progresterone receptors or HER2 (TNBC). People diagnosed with TNBC are usually treated with chemotherapy, because the tumour does not respond to drugs specifically developed to target oestrogen or progesterone or HER2.
Figure 5 provides a summary of the hormone status of tumours diagnosed in 2021 among both males and females.
Geographical variance in breast cancer by local government area
Figure 6 demonstrates variation in age-standardised incidence rates of breast cancer, by local government areas. Darker shading indicates areas with higher rates of breast cancer.
Breast cancer in people born overseas
Figure 7 shows the age standardised incidence rates of breast cancers in Australian-born Victorians compared to other major migrant groups, over the five-year period 2017 to 2021. The highest age standardised incidence rate for breast cancers was 0.9 for males born in the Southern and Central Asia region and the lowest rate of 0.2 was observed in males born in the South-East Asia region. The highest age standardised incidence rate of breast cancers was 98.6 for females born in the North America region and the lowest rate of 65.7 was observed in females born in the North-East Asia region.
Breast cancer distribution by stage at diagnosis
Figure 8 shows distribution of breast cancer by stage of disease at diagnosis in 2021. In females, Stage 1 accounted for the largest proportion (40.2%) of new diagnoses and Stage 4 accounted for the lowest proportion (4%) of new breast cancer diagnoses. Because of low numbers, data are not presented for males or those where sex is not recorded, or is recorded as indeterminate.
Breast cancer five-year relative survival
Figure 9 shows the change in 5-year survival for breast cancer among males and females, and the 5-year survival trend for all cancers over the same time period. It shows that 5-year relative survival has increased for breast cancer between 1986-1990 and 2016-2020 from 73% to 92%.