A powerful drug combination for breast cancer could save thousands of lives, according to new results from a long-term study. The drug Keytruda (also known as pembrolizumab), if given at the right time and in combination with chemotherapy, can stop the disease coming back in women with a type of aggressive breast cancer, driving up the chance of being cured. Keytruda is an immunotherapy that works by helping the immune system to kill cancer cells. It is already a treatment for a number of cancers. The drug is given via a drip into the bloodstream, with the number of sessions depending on the t…