New blood test may quickly predict if palbociclib is working, say researchers

London-based scientists have found a new blood test that may be able to quickly predict if a female patient is responding to the breast cancer drug, palbociclib, earlier that is possible with currently available tests.

This work, published in the journal Nature Communications, was performed by researchers from The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust, and was mostly funded by the Medical Research Council (MRC).

In testing women with oestrogen receptor positive breast cancer who were already taking part in a clinical trial for palbociclib in advanced breast cancer, the scientists found that their blood test could detect if the drug was working or not in about two to three weeks.

Palbociclib was approved by the National Institute for Health and Care Excellence (NICE) for use on the NHS in November last year (2017). Currently, women are required to wait about two to three months after commencing treatment with the drug before they can be scanned to see if the treatment is actually working.

This new blood test looks for DNA fragments within the sample that have been shed by the tumour. In particular, the team looked at the amount of gene PIK3CA in the blood samples both before treatment had started and then 15 days afterwards to be able to predict if the drug was working. If there was a large decrease in this gene, the scientists found that there was a significant improvement in the median progression-free survival.

“Palbociclib is one of a new class of drugs that delays cancer progression for patients with advanced breast cancer, but it's not effective for everybody,” explained Professor Nicholas Turner, senior author and Professor of Molecular Oncology at The Institute of Cancer Research, London, and Consultant Medical Oncologist at The Royal Marsden NHS Foundation Trust. “The problem is we have to wait for two to three months before doing a scan to see if the therapy is working. Our new study found that a blood test for cancer DNA in the first two weeks of treatment indicated whether the drug was likely to be effective. Having an early indication of how likely a treatment is to work might allow us to adapt treatment — switching some patients to an alternative drug that is more likely to benefit them.”

“It is exciting to see that using advances in diagnostic techniques, such as genetic tests for circulating tumour DNA, we may be able to more accurately define groups of patients and help us deliver the right treatment to the right patient sooner,” added Dr Nathan Richardson, Head of Molecular and Cellular Medicine at the MRC. “This study provides early evidence that might help us understand sooner when a drug is successfully treating breast cancer, and if not, it can be discontinued and better approaches pursued.”