About Metastatic Breast Cancer

Metastatic breast cancer (MBC) can be difficult to understand. This page explains what MBC is and outlines common steps in care. Everyone’s situation is different, and treatment and care plans are tailored to each person.

What is metastatic breast cancer

Metastatic breast cancer means the breast cancer has spread (metastasised) beyond the breast and nearby lymph nodes to other parts of the body. The most common places that breast cancer spreads to are the bones, liver, lungs and brain.

You may also hear metastatic breast cancer called stage IV (4) breast cancer, advanced breast cancer or secondary breast cancer.

Unlike early breast cancer (stage I or II) or locally advanced breast cancer (stage III) metastatic breast cancer isn’t considered curable. However, it can be treated and managed, often for many years.

Most people stay on some form of treatment long-term, for as long as it helps. Treatments aim to control the cancer, manage symptoms and help you live as well as possible for as long as possible. New treatment options are being researched and discovered every day.

It’s estimated that about 21,000 people in Australia are living with metastatic breast cancer (AIWH, 2025).

How MBC is classified

Metastatic breast cancer may be described in a few different ways:

• De novo metastatic: “De novo” means “from the beginning”. This means that the first time your breast cancer was diagnosed, it was already metastatic. In other words, you did not have an earlier diagnosis of early breast cancer.
• Recurrence: The breast cancer was previously treated as early breast cancer and has come back in other parts of the body.
• Oligometastatic: “Oligo” means “few” in Greek. Oligometastatic describes breast cancer that has spread to only a small number of sites in the body.

Cancer subtypes and why they matter

Breast cancer is not just one disease. There are different subtypes and knowing your cancer’s subtype will help you and your treating team understand which treatments are most likely to work for you.

The subtypes are based on whether your cancer cells have certain protein ‘receptors’ on the outside of the cells. The three receptors are oestrogen, progesterone and HER2.

Below is a brief explanation of the main subtypes. You can click on each option to learn more.

HR+ (Hormone Receptor Positive) – The breast cancer cells have the receptors for oestrogen and/or progesterone on their surface. This means the breast cancer cells grow in response to these hormones. HR+ is the most common subtype.

HER2+ (HER2 Positive) – The breast cancer cells have high levels of the HER2 receptor on their surface, due to an increase in the number of HER2 genes in the cancer cells.

HER2-low and HER2-ultralow – These are newer categories. These cancers were once grouped as HER2-negative, but we now know that some HER2-negative cancers actually have small amounts of HER2 on the surface of the cells. Some newer treatments, such as certain antibody-conjugate drugs, can work for HER2-low and HER2-ultralow breast cancers.

Triple Negative (TNBC) – The breast cancer cells don’t have the oestrogen, progesterone or the HER2 receptors. Because of this they are considered to be “triple negative”.

Triple Positive – The breast cancer cells have all three receptors – oestrogen, progesterone and HER2.

Understanding your subtype helps you and your medical team find the right treatment for you. It also explains why your treatment plan may look very different from someone else’s.

A common care pathway (timeline overview)

Everyone’s care pathway is different. It can be shaped by your cancer’s subtype, the treatments available and where you live.

Here’s a general timeline to help you plan and talk with your family and care team. Timeframes are approximate and may move faster or slower:

• Diagnosis (Weeks 1-2) - Scans, biopsies and blood tests help confirm the diagnosis and understand your cancer – where it is, whether it has certain receptors, and gene changes. This can look different if you’re diagnosed de novo (metastatic from the start) or after a distant recurrence following treatment of early breast cancer.TIP: ask how long results will take and who to contact with questions.
• Treatment planning (Weeks 2-4) – You’ll meet your oncology team to talk through goals, options, and supports and decide on your first treatment. Sometimes extra tests are needed to choose the best starting option for your breast cancer.TIP: bringing a support person and a written list of questions can help.
• Starting treatment (Week 4+) - Beginning your treatment plan. This may include systemic therapy (such as endocrine therapy, targeted therapy, chemotherapy or immunotherapy) and sometimes radiation or surgery to help with the symptoms.TIP: ask about likely side-effects and what to do if they happen.
• Ongoing monitoring (Every 2-3 months) Regular scans and tests check how well treatment is working. Early on you may have appointments a little more often.TIP: ask when and how results of your scans and tests will be shared.
• Treatment adjustments (as needed) – Your team may adjust doses, manage side-effects, add supportive care or change treatments if the cancer stops responding or if a better option becomes available. TIP: you can ask about clinical trials at any time.

Throughout this pathway, you should have access to support services, symptom management, and wellbeing resources. Access can be harder in outer suburban, regional and remote areas, but many services now offer phone or telehealth options – your care team and MBCAA can help you find what’s available to you.