Who this is for
This page is for people with hormone receptor–positive, HER2-negative advanced or metastatic breast cancer whose cancer has grown after treatment with CDK4/6 inhibitors such as palbociclib, ribociclib or abemaciclib. If you have recently been told that your treatment is no longer working, this explains what that means and what options may still be available in Melbourne and across Australia.
If CDK4/6 treatment has stopped working:
• You may still have further targeted treatment options.
• Mutation testing becomes especially important.
• Chemotherapy is not always the immediate next step.
• Treatment decisions are individualised.
• A structured second opinion can help clarify sequencing.
When CDK4/6 treatment stops working
Being told that your cancer has progressed can feel like a major setback.
Many people immediately assume that chemotherapy is the only option left.
In most cases, that is not true.
Breast cancer evolves over time. When it becomes resistant to one therapy, it may still respond to another — particularly if we understand the biology driving that resistance.
The next decision should be calm, structured and informed by mutation testing, prior response to treatment and your overall health.
Targeted treatment options available in Australia
In Melbourne and across Australia, several targeted therapies may be considered before chemotherapy, depending on genomic testing and previous treatment exposure.
Capivasertib plus fulvestrant (CAPItello-291)
This treatment targets the AKT pathway, which can become active after resistance develops.
In a large international phase III study:
• Median progression-free survival: 7.2 months vs 3.6 months
• Hazard ratio: 0.60
For eligible patients, capivasertib is PBS-listed in Australia.
The most common side effect is diarrhoea, which is usually manageable with early recognition and dose adjustment.
Alpelisib plus fulvestrant (for PIK3CA-mutated cancer)
Some cancers develop a PIK3CA mutation. If identified through mutation testing, alpelisib may be appropriate.
In clinical trials:
• Median progression-free survival: 11.0 months vs 5.7 months
• Hazard ratio: 0.65
This treatment requires monitoring for elevated blood sugar, which can generally be managed.
It is registered in Australia but not currently PBS-subsidised.
Elacestrant (for ESR1 mutation)
Another resistance pathway involves ESR1 mutation. If detected, elacestrant may be considered.
In patients with ESR1-mutated disease:
• Median progression-free survival: 3.8 months vs 1.9 months
• Hazard ratio: 0.55
The most common side effect is nausea, typically manageable.
In Australia, access is mainly through clinical trials at present.
Most important thing is some patients benefit from these options significantly longer (even years) than others.
When chemotherapy is considered
Chemotherapy remains an effective and important treatment for advanced breast cancer.
If targeted therapies are not suitable, or if the cancer is progressing quickly, chemotherapy may be recommended.
Modern chemotherapy in Melbourne and across Australia is delivered with structured supportive care to reduce nausea, support blood counts and maintain quality of life.
Needing chemotherapy does not mean treatment has failed. It means the strategy has shifted.
How the next step is decided
After CDK4/6 inhibitors, decisions are individualised.
We consider:
• Response to previous treatments
• Mutation testing results, including PIK3CA and ESR1 where relevant
• Location and pace of disease
• General health and performance status
• Your treatment priorities
Two patients with similar scans may require very different plans depending on tumour biology.
International patients, including Sri Lanka
Patients from Sri Lanka and other countries sometimes seek an Australian second opinion when advanced breast cancer progresses after CDK4/6 therapy.
A structured review of imaging, pathology and molecular testing can help clarify sequencing options and treatment access within the Australian system.
Key Takeaway
• Progression after CDK4/6 therapy does not mean you have run out of options.
• Mutation testing helps guide personalised treatment decisions.
Next steps should be calm, structured and biologically informed.
• Some of these drugs are absolute game changers in controlling “Your Cancer”