Treatments for triple negative metastatic breast cancer

The treatment of triple negative metastatic breast cancer is complex. The main treatment is chemotherapy. Targeted therapies and immunotherapy are also options.

You will have a series of treatments over time. Each series works to control the cancer for a period of time.

First line treatment

Chemotherapy is offered as the initial or 'first line' treatment, either alone or with immunotherapy. Usually this starts within a few weeks of the diagnosis. It may be delayed a short time if you need radiotherapy or surgery.

Depending on the drug or drugs used, you have chemotherapy treatment in a ‘pattern’ such as:

• cycles of 3 to 4 weeks
• other sequences, such as 2 out of every 3 weeks.

Chemotherapy is given via tablet or intravenously (by drip). It continues until it no longer controls the cancer or the side effects are too much.

You will have regular blood tests when you are on treatment and, usually every 8 to 12 weeks, you have scans. This may be a CT scan, whole body bone scan, PET scan or MRI. These check how effective the treatment is. Your team uses the results to decide whether to continue or change to a different type of treatment.

Doctors will recommend you change to another treatment if the cancer becomes active or worse. This is called disease progression. This may be clear from your symptoms, scans or a physical examination.

Second and following lines of treatment

When you stop your first line of treatment, you often will start a new treatment within a few weeks.  Your doctor might talk to you about a clinical trial as the next treatment.

Either way, this next treatment is called 'second line' treatment. It continues in the same way as first line treatment, until the cancer progresses, or it causes too many side effects

When the second line treatment stops working, you may continue to 'third', 'fourth', 'fifth' line etc. treatment. This is a decision between you and your medical oncologist. The decision will depend on:

• how well the cancer responds to treatment
• how well you tolerate the treatment
• your wishes about treatment.

How long chemotherapy continues

You and your medical oncologist will discuss how long you continue with chemotherapy. It depends on:

• how well it is controlling the cancer
• how well you are coping with side effects
• whether side effects might cause longer-term problems, such as nerve-ending damage
• how you feel about continuing
• any specific commitments, such as a planned holiday or special event.

Generally, if the cancer is responding, you will have at least 6 cycles of treatment in the first instance.

Sometimes, you can continue some chemotherapy for 12 months and more with good cancer control. 

Having treatment for longer can make the benefits of treatment last longer. But you shouldn't continue if the side effects are affecting your ability to live well.

Find out more about chemotherapy treatment.

Targeted therapies

Sacituzumab govitecan (Trodelvy) is currently available on the PBS. Trodelvy directs chemotherapy into the cancer cells. It is a combined antibody and chemotherapy drug. These drugs are called antibody drug conjugates (ADCs).

It is approved for people who have had previous treatment for breast cancer.

Like most drugs, there are some side effects. The most common are:

• low white blood cells and red cells
• nausea and vomiting
• diarrhoea
• fatigue
• hair loss
• constipation
• rash
• decreased appetite
• abdominal pain.

Trodelvy also may cause serious side effects. Find out about Side effects and how to manage them.

You can ask your medical oncologist if Trodelvy is suitable for you.

Other targeted therapies

Triple negative breast cancer has a number of subtypes. These have different characteristics that provide different targets for treatment.

Research and clinical trials are developing new treatments for some of these targets.

If you are interested, ask your doctor if any clinical trials may be suitable.

PARP inhibitors

A PARP inhibitor is a medication that blocks the PARP enzyme in cells. In cancer treatment, blocking PARP may prevent damaged cells from repairing. This causes them to die. PARP inhibitors can be effective for BRCA mutation-related metastatic breast cancer.

Olaparib (Lynparza) is an oral medication that people generally cope well with. Side effects include low white cell count, anaemia, low platelets, fatigue, nausea and rash.

Availability: not on the PBS (Mar 2025).

Antibody drug conjugates (ADCs)

ADCs are a combination of chemotherapy and an antibody that targets a specific cancer cell.

The target cancer cell absorbs the ADC, so the chemotherapy is able to damage it. The chemotherapy may also damage or kill nearby cancer cells that do not have the target. This is called the 'bystander effect'.

As an ADC is targeted, it often has fewer side effects than non-targeted chemotherapies. 

Trastuzumab deruxtecan (Enhertu) is used in HER2-positive and HER2-low metastatic breast cancer.

Side effects include nausea, vomiting, low white cell count, anaemia, low platelets and fatigue.

Androgen blocking therapies

Some breast cancers have oestrogen receptors (ER). Some cases of triple negative breast cancer have androgen receptors (AR). Trials are investigating androgen blocking treatments in this subtype of breast cancer.

Immunotherapy

Triple negative breast cancer is one of the subtypes most likely to respond to immunotherapy.

Immunotherapy uses the body's own immune system to fight against cancer cells. 

To find out how immunotherapy works, read About immunotherapy.

Pembrolizumab (Keytruda) is an immunotherapy (checkpoint inhibitor) drug that targets PD-1. By blocking PD-1, this drug boosts the immune response against breast cancer cells.

Approx. 30% to 40% of triple negative breast cancers are PD-L1 positive.

Keytruda can improve survival by more than six months for people whose tumours express higher levels of the PD-L1 protein.

Availability: available on the PBS as first line treatment for triple negative metastatic breast cancer.

Side effects can usually be controlled with steroids.

Access to new treatments

Clinical trials

Some new treatments are only available in clinical trials.

Before you decide to join a clinical trial, you should understand the benefits and risks. Talk to your medical oncologist and read About clinical trials.

Patient access programs

You might hear about drugs that are not subsidised through the PBS. Some pharmaceutical companies make these available at a lower cost, or even free.

Ask your doctor to:

• check the Medicines Access Portal
• contact the relevant pharmaceutical company.

For information about access programs, go to Ways to access new treatments.