Adding a new targeted therapy to hormone therapy halts the growth of tumour cells in women with early-stage breast cancer, new research has shown.

Giving women palbociclib – already hailed as a major step forward in treating advanced breast cancer – alongside hormone therapy had a much greater effect on cell growth than the hormone treatment alone.

Palbociclib, alongside an aromatase inhibitor – a type of hormone treatment – shrank tumours in half of women with early-stage disease, a similar proportion to women who took the hormone therapy alone. But the drug combination led to a marked decrease in cell growth, stopping tumour growth entirely in 90 per cent of women, compared with 59 per cent given hormone therapy alone.

The large international trial was led by a team at The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust, in collaboration with researchers in America. It was funded by the drug’s manufacturer, Pfizer.

Longer-term clinical trials are ongoing to assess if giving palbociclib alongside hormone therapy after surgery can delay breast cancer coming back.

The results were presented at the San Antonio Breast Cancer Symposium in Texas, and published in the Journal of Clinical Oncology.

Hormone therapy is an effective treatment for hormone receptor-positive breast cancer, but the disease can return when tumours evolve to become resistant to treatment.
Combining hormone treatment with a targeted therapy such as palbociclib is one way of combating drug resistance – just as combination treatment is also used in diseases such as tuberculosis and HIV.

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