Research we helped fund* has revealed the potential benefits of using a blood test to identify who benefits most from being given CDK4/6 inhibitors as a first-line treatment for secondary breast cancer. This is a promising step towards better tailoring treatments for people with secondary breast cancer.
In this section
Why timing matters for CDK4/6 inhibitors
CDK4/6 inhibitors, such as palbociclib, are targeted breast cancer drugs. They’re used alongside hormone therapy to treat locally advanced or secondary oestrogen receptor (ER) positive, HER2-negative breast cancer.
Researchers have been studying how to best time this treatment. A few years ago, a clinical trial called the SONIA trial showed that waiting until later to offer CDK4/6 inhibitors was just as effective as adding them from the beginning.
But, Dr Saskia Wilting and her team at the Erasmus University Medical Centre in Rotterdam wondered if this might be different on an individual level. In new research, published in Nature Medicine, they analysed results from the SONIA trial in more detail. Now, their work has revealed how a blood test could potentially identify people who would benefit from CDK4/6 inhibitors during their first-line treatment.
Could a blood test provide the answer?
Saskia and her team analysed blood samples from over 400 women with secondary breast cancer who took part in the trial. They looked for small fragments of cancer DNA in the blood, known as circulating tumour DNA (ctDNA). Using a special test, the researchers estimated the levels of ctDNA in the blood, which is linked to both tumour size and aggressiveness.
They found that for women with high estimated ctDNA levels, starting CDK4/6 inhibitors as a first-line treatment made a difference. Their cancer took much longer to grow again after first treatment - an average of 21.1 months compared to 8.9 months.
But for women with low estimated ctDNA levels, the picture was different. Delaying CDK4/6 inhibitors until later had a similar effect as starting them immediately, but they were exposed to side effects for a longer time.
What could this mean?
These results offer hope that in the future, a simple blood test like could help personalise treatment for some secondary breast cancer. For some women with high ctDNA levels, using CDK4/6 inhibitors early might offer valuable extra time before their cancer progresses. For others, it may be better to wait, sparing them side effects and saving treatment options for later.
More research is needed before this test could become part of routine care. But it’s an exciting step towards making treatment decisions more tailored and helping make sure the right person gets the right drug at the right time.
*This project was funded as part of the Breast Cancer Now Catalyst Programme. This programme promotes innovation and excellence in breast cancer research, through collaboration in the UK and across Europe. Pfizer has provided $15 million USD funding to Breast Cancer Now for the Catalyst Programme as an Independent Medical Research Grant. Where applicable, research organisations also had access to specific Pfizer compounds. Pfizer has no involvement in allocating the grants or conducting the research studies funded by the Catalyst Programme.
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Secondary breast cancer can be treated, but it can’t be cured. We urgently need to fund new research into this disease to offer people living with secondary breast cancer more precious time.