When is chemotherapy recommended for HER2-positive breast cancer?

HER2 is a protein that can help some breast cancer cells grow. A HER2-positive result opens the possibility of HER2-targeted medicines, but it does not by itself decide whether chemotherapy is needed. The team considers tumour size, lymph nodes, hormone receptors, grade, surgery findings, general health and heart health. Before surgery, chemotherapy with HER2-targeted treatment may shrink the tumour and show how it responds. After surgery, it may treat microscopic cells that could remain. If disease returns or has spread, systemic treatment may be used to control it, with the combination chosen to match earlier treatment and current health.

HER2-targeted medicines and chemotherapy are different treatments and may have different monitoring needs. Your plan can change if side effects, heart test results, blood counts or other medical issues alter the balance of benefit and harm.

Ask whether treatment is planned before or after surgery and what each medicine is intended to do. Discuss heart testing, pregnancy or fertility plans, contraception, existing heart conditions, other medicines and practical help during infusion visits. Tell the team about fever, diarrhoea, numbness, breathlessness, swelling or unusual tiredness. Keep your appointment and symptom record so doses and supportive medicines can be reviewed safely.

Contact the oncology team promptly for fever, repeated vomiting, severe diarrhoea, unusual bleeding, a new rash or worsening numbness. Seek emergency care for chest pain, fainting, severe breathlessness, sudden swelling of the face or throat, or a severe allergic reaction during or after treatment.

What do my HER2, hormone-receptor and pathology results mean for chemotherapy? Is treatment before surgery or afterward? Which heart checks are needed? How will you manage side effects and decide whether the next dose is appropriate?