Biological agents are also known as targeted therapies. They are treatments that recognise a specific protein on a cancer cell wall and act against it.
In breast cancer targeted therapies are often aimed at a protein known as Human Epidermal Growth Factor receptor 2. This protein is called HER-2 for short and all invasive breast cancers are tested for levels of HER-2. The levels are scored as 0, +, ++, and +++. If the score is +++ the breast cancer is referred to as ‘HER-2 positive’. If the level is ++ a further, more accurate test is carried out to decide whether the cancer is HER-2 positive or not. Levels of 0 or + are low and considered ‘HER-2 negative’.
Only about 1 in 5 breast cancers will be HER-2 positive and it is only in these cases that the drugs to target HER-2 will be effective. Your Doctor and Breast Care Nurse will explain to you if this is the case for you. If it is you may be recommended to have a drug known as trastuzumab (‘Herceptin’), which is the most commonly used biological agent for breast cancer. Trastuzumab is given as an injection, usually once every 3 weeks. It is given in the Chemotherapy unit as an out-patient treatment. It is not in itself a chemotherapy drug, and although it has side effects these are not usually as noticeable as for the chemotherapy drugs. However, it is usually recommended that if you are having trastuzumab it is given alongside chemotherapy drugs to start with. The trastuzumab is continued by itself after the chemotherapy treatments are complete.
There are other biological agents which are used less commonly but which also act against the HER group of proteins; these are pertuzumab and trastuzumab emtansine (Kadcyla). If we think you would benefit from these we will discuss this with you and explain why.