The trial of a new drug to treat a form of breast cancer has been hailed as “groundbreaking”, with results said to show a strong trend towards improved overall survival.

Pharmaceutical company AstraZeneca said Enhertu demonstrated a 72% reduction in the risk of disease progression or death in women with HER2-positive metastatic breast cancer compared to a different medicine.

The results were presented in a Presidential Symposium at the European Society for Medical Oncology (ESMO) Congress 2021.

The trial involving around 500 patients at multiple sites in Asia, Europe, North America, Oceania and South America found there was “a strong trend towards improved overall survival” with Enhertu.

But it was pointed out that this analysis is “not yet mature and is not statistically significant”.

AstraZeneca said that despite initial treatment with trastuzumab and a taxane, people with HER2-positive metastatic breast cancer will often experience disease progression.

The company said nearly all patients treated with Enhertu were alive at one year (94.1%) compared to 85.9% of patients treated with trastuzumab emtansine (T-DM1).

Susan Galbraith, executive vice president, Oncology R&D, said: “Today’s results are ground-breaking.”

She said Enhertu tripled progression-free survival as assessed by investigators, and provided a disease control rate exceeding 95% compared to 77% for trastuzumab emtansine.

“These unprecedented data represent a potential paradigm shift in the treatment of HER2-positive metastatic breast cancer, and illustrate the potential for Enhertu to transform more patient lives in earlier treatment settings,” she added.

Javier Cortes, from the International Breast Cancer Centre in Barcelona, said patients with previously treated HER2-positive metastatic breast cancer will typically experience disease progression in less than a year with available HER2-directed treatments.

He said the the “high and consistent benefit” seen across efficacy endpoints and key subgroups of patients receiving Enhertu is “remarkable and supports the potential of Enhertu to become the new standard of care for those who have previously been treated for HER2-positive metastatic breast cancer”.

Ken Takeshita, global head of R&D at Daiichi Sankyo, said: “These landmark data will form the basis of our discussions with global health authorities to potentially bring Enhertu to patients with previously treated HER2-positive metastatic breast cancer as a more effective treatment option as soon as possible.”

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