Dr Simon Vincent, director of research, support and influencing at Breast Cancer Now, said:
"This exciting study shows that adding pembrolizumab to chemotherapy before and after surgery could be more effective in eliminating cancer cells in patients with the most common type of breast cancer, ER-positive HER2-negative, regardless of age or menopausal status.
"The trial found that pembrolizumab led to more patients having no detectable cancer cells in their breast or lymph nodes when their treatment finished, although further research is needed to see whether this translates into improved survival rates and a lower likelihood of the cancer coming back.
"With over 1,000 people dying from breast cancer every month, we desperately need new and effective treatments for this disease.
"While pembrolizumab is currently used for the treatment of triple negative breast cancer, we hope the drug can be submitted to the MHRA for licensing and assessed by NICE as soon as possible so the treatment can reach NHS patients who may be able to benefit.
"Anyone affected by breast cancer can speak to Breast Cancer Now’s expert nurses by calling our free helpline on 0808 800 6000 for information and support.”