Thousands more women with breast cancer could benefit from a blockbuster immunotherapy drug than previously thought, research suggests.
Pembrolizumab, sold under the brand name Keytruda, targets and blocks a specific protein on the surface of certain immune cells, which then seek out and destroy the cancer cells.
In England it is offered to people with triple-negative breast cancer, one of the most aggressive forms of the disease, accounting for around 15% of cases. However, new findings from a global study suggest it could be effective if used more widely.
The findings will be presented on Wednesday at the European Breast Cancer Conference in Milan.
Treating a common form of breast cancer with pembrolizumab, as well as chemotherapy, before and after surgery, can be effective regardless of the patient’s age or if they have gone through menopause, researchers found.
They tried the drug in women with early-stage breast cancer, which is at high risk of returning or spreading further, and who is estrogen receptor positive (ER positive) and HER2 negative.
According to Cancer Research UK, approximately 80 in 100 breast cancer diagnoses are ER positive.
The Keynote-756 study has been running internationally for eight years and includes 1,278 patients with invasive ductal carcinoma (IDC), which means cancer begins to spread from the milk ducts into the surrounding breast tissue.
Patients were treated before and after surgery with pembrolizumab and chemotherapy, or with a placebo. Researchers measured the lack of signs of cancer in tissue samples, also known as the pathological complete response rate (PCR).
Prof Javier Cortés, director of the International Breast Cancer Center in Barcelona, Spain, said there was a “statistically significant increase” in the PCR rate among those treated with pembrolizumab.
About 24.3% of patients had no cancer cells left in the breast or lymph nodes, compared with 15.6% of patients treated with a placebo.
Dr. Simon Vincent, director of research, support and advocacy at UK charity Breast Cancer Now, said: “This exciting study shows that adding pembrolizumab to chemotherapy before and after surgery could be more effective at eliminating cancer cells in women with the most common cancer cells. type of breast cancer, ER positive HER2 negative, regardless of their age or menopausal status.
“The study found that pembrolizumab led to more patients having no detectable cancer cells in their breast or lymph nodes when their treatment ended, although further research is needed to see if this translates into improved survival rates and a lower chance of the cancer returning.
“With more than 1,000 people dying from breast cancer every month in the UK, we urgently need new and effective treatments for this disease.
“Although pembrolizumab is currently used to treat triple negative breast cancer, we hope that the drug can be submitted to the MHRA (Medicines & Healthcare products Regulatory Agency) for licensing and assessed by Nice (National Institute for Health and Human Services) as soon as possible Care Excellence). so that patients with ER-positive HER2-negative breast cancer, who could also benefit from this treatment, can access it through the NHS.”
The conference will also hear how researchers have developed a genetic test that can identify how patients with early-stage triple negative breast cancer will respond to immunotherapy drugs. It means that patients who are unlikely to respond to these medications can avoid the adverse side effects associated with them and be treated with other therapies.