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Novel blood test could quickly predict breast cancer patient’s response to palbociclib

A novel blood test could predict if breast cancer patients are responding to the recently approved drug palbociclib, months earlier than current tests.

In this study researchers compared the amount of the gene PIK3CA in 73 women with oestrogen-receptor positive breast cancer who were taking part in a clinical trial of palbociclib for advanced breast cancer.

A blood test was administered both before treatment and 15 days after starting treatment. The researchers discovered that patients who had a small decrease in PIK3CA circulating DNA at 15 days had a median progression-free survival of only 4.1 months, whilst women with a large decrease in PIK3CA had a median progression-free survival of 11.2 months.

Currently, breast cancer patients must wait 2–3 months for a scan to find out if palbociclib is working. The novel blood test could help researchers detect whether palbociclib is working in just 2–3 weeks.

“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 Nicholas Turner, senior author from the The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust (both London, UK).

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“Our new study found that a blood test for cancer DNA in the first 2 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,” he added.

Sources: O’Leary B, Hrebien S, Morden JP et al. Early circulating tumor DNA dynamics and clonal selection with palbociclib and fulvestrant for breast cancer. ‎Nat. Commun. 9, 896; www.mrc.ac.uk/news/browse/blood-test-could-predict-if-palbociclib-will-help-breast-cancer-patients/