Targeted (also known as biological) therapies are antibodies which act by 'targeting' specific proteins on the surface of cancer cells.

They destroy the cancer cell by either:

• Blocking pathways which are essential for cancer cells to grow and spread
• Triggering the body’s immune system to attack the cancer cell
• Attaching a chemotherapy drug to an antibody which delivers the drug directly into the cancer cell.

Because these drugs only attach to specific cancer cell receptors they have very few effects on healthy cells and therefore cause minimal side effects.

They are often given initially in combination with chemotherapy and then continued alone, for up to one year post-operatively (or indefinitely in patients with secondary breast cancer).

About 15-20% of breast cancers have too many copies of the HER2 (Human Epidermal growth factor Receptor) on their cells. These are known as HER2 positive (HER2+) cancers. Too many HER2 receptors trigger the cells to grow and divide more rapidly.

Drugs which target the HER2 receptor:

Trastuzumab (Herceptin®)

• This is given as an injection under the skin, usually into the thigh, or into a vein
• Patients have an injection every 3 weeks for 12 months, running in parallel with chemotherapy for the first few treatments
• Regular cardiac monitoring is required because trastuzumab occasionally causes a decline in heart function, which is usually reversible on stopping the drug

Pertuzumab (Perjeta®)

• This drug, given intravenously, stops HER2 receptors joining other HER2 proteins on the cell surface and therefore prevents cell growth
• Pertuzumab works best when given in combination with trastuzumab, initially with chemotherapy
• It is used to treat secondary breast cancer or pre-operatively to shrink cancers before surgery

Trastuzumab emtasine (T-DM1 or Kadcyla®)

• This drug is a molecule of trastuzumab bound to a chemotherapy drug called emtasine (or DM1)
• The trastuzumab delivers the chemotherapy directly into the cancer cells, like a ‘magic bullet’. Consequently, it causes very few side effects
• It is used to treat secondary breast cancer.