A new three-drug combination could help women with a common form of aggressive breast cancer live longer, a study has suggested.
The trial, which included 325 patients from across 28 countries, showed the treatment more than doubled the time before the cancer “progressed or worsened”, according to the lead author, and could delay the need for chemotherapy.
The combination may become the “new go-to option” for women with PIK3CA-mutated hormone receptor positive (HR+) human epidermal growth factor receptor 2 negative (HER2-) breast cancer, said the researchers.
This mutation in the PIK3CA gene causes cells to divide and replicate uncontrollably.
More than half of the patients in the trial had metastatic breast cancer that had spread to three or more organs and the majority had already had chemotherapy.
Researchers used a blood test known as a liquid biopsy, which detects tumour DNA in the blood, to test for the PIK3CA mutation.
What is the three-drug therapy?
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Some 161 patients were given a three-drug combination made up of two targeted drugs – palbociclib, a type of cancer growth blocker, and a new drug called inavolisib, which blocks the activity of the PI3K protein – as well as the hormone therapy fulvestrant.
The placebo group, which included 164 patients, was given a dummy pill plus palbociclib and fulvestrant. The median overall survival in the inavolisib group was 34 months, compared with 27 months in the placebo group.
The three-drug therapy also delayed disease progression by 17.2 months, compared with 7.3 months in the placebo group, with patients also able to delay chemotherapy treatment by nearly two years longer.
The combined therapy of inavolisib, palbociclib and fulvestrant is not approved in the UK. However, the combination of palbociclib and fulvestrant has been available as an option for patients with certain types of breast cancer on the NHS since 2022.
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‘More time before needing chemotherapy’
Lead author Nick Turner, a professor of molecular oncology, said: “The key findings from this study showed that the inavolisib-based therapy not only helped patients live longer but it more than doubled the time before their cancer progressed or worsened.”
The final results of the trial, by experts at the Institute of Cancer Research and the Royal Marsden NHS Foundation Trust in London, have been published in the New England Journal of Medicine and presented at the American Society of Clinical Oncology (ASCO) annual meeting in Chicago.
About 55,000 women are diagnosed with breast cancer in the UK every year, some 70% of whom will have HR+, HER2- breast cancer. PIK3CA mutations are found in 35-40% of HR+ breast cancers.
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Prof Kristian Helin, chief executive of the Institute of Cancer Research, London, said: “One of the challenges with combination therapies is ensuring the right drug dosages and understanding their individual effects.
“It is extremely encouraging that this study not only demonstrates the effectiveness of this approach but also shows that the therapy was generally well tolerated by patients.”
Dr Simon Vincent, from Breast Cancer Now, called the findings “a significant breakthrough”.
