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 2023, 5197 Victorians were diagnosed with breast cancer. Of these, there were 52 males and 5145 females, representing 1% and 99% of the total Victorian breast cancer diagnoses, respectively. Currently, breast cancer is diagnosed at a rate of 1.3 per 100,000 males and 128.5 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 are displayed, Figure 1 and 2 do not include data for males. Accounting for 13.2% of all cancers diagnosed and 6.8% of all cancer-related deaths in 2023, breast cancer was the most commonly diagnosed cancer among females and the 38th most commonly diagnosed cancer among males. It is the 2nd most common cause of cancer-related deaths in Victorian females and the 42nd most common cause of cancer-related deaths in Victorian males.

Trends in breast cancer over time

For females between 2014 to 2023 the age standardised incidence rate of breast cancer declined by an average of 0.1% per year. However this result wasn’t statistically significant, meaning the change cannot be confidently considered real and may be due to random fluctuations.

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, 75.5%, 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 2023 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 for females, 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 2018 to 2022. The highest age standardised incidence rate for breast cancers was 4.4 for males born in the North America region and the lowest rate of 0 was observed in males born in the South and Central America region. The highest age standardised incidence rate of breast cancers was 138.8 for females born in the UK and Ireland region and the lowest rate of 89.4 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 2023. In females, Stage 1 accounted for the largest proportion (38.2%) 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 1983-1987 and 2018-2022 from 72% to 93%.