HER2-Targeted Therapy

HER2-targeted therapy treats cancers with excess HER2 activity by blocking growth signals or delivering medicine to HER2-bearing cells. HER2 is a protein on the surface of some cells; some cancers have too much of it or too many copies of its gene. Testing tumour tissue helps the oncology team decide whether a HER2 medicine is suitable. These medicines may be used alone or alongside chemotherapy, hormone therapy, surgery, or radiotherapy, depending on the cancer and its stage.

A treatment plan may include an antibody medicine, a small tablet that enters cells, or an antibody-drug conjugate that carries a cancer medicine toward HER2-bearing cells. Infusions are given through a vein or sometimes by injection; tablets follow a prescribed schedule. Before and during treatment, clinicians review symptoms, blood tests, heart function when relevant, and how the tumour is responding. The schedule changes when treatment is combined with other medicines or used before or after surgery.

Common effects vary by medicine and may include tiredness, nausea, diarrhoea, reduced appetite, rash, infusion reactions, or changes in blood counts. Tell the treatment team promptly about breathlessness, new swelling, faintness, chest discomfort, a fast heartbeat, severe diarrhoea, fever, or a sudden allergic-type reaction. Some HER2 medicines can affect heart pumping or the lungs, so scheduled checks matter. Do not stop a medicine or delay an infusion without contacting the oncology team.

Outcomes depend on the cancer type, HER2 test result, stage, previous treatment, and general health. HER2-targeted medicines can slow or shrink HER2-driven cancer and may reduce the chance of cancer returning when used as part of treatment for an earlier cancer. In advanced disease, the aim may be control, symptom relief, and maintaining daily function. Your team uses scans, examinations, blood tests, and symptoms to judge benefit and decide whether to continue, change, or combine treatments.

HER2 status is a tumour feature, not a symptom. A biopsy or surgical sample is usually tested before treatment is selected. Different medicines act at different points in the HER2 pathway, and a cancer can change its treatment response over time.

It may be considered when testing shows HER2-positive breast cancer or another HER2-driven cancer, including some stomach cancers. The choice depends on whether treatment is intended before surgery, after surgery, or for cancer that has spread. Ask how the test result, treatment goal, heart history, pregnancy plans, and other medicines affect your options. Read more about [HER2-Positive Breast Cancer](/conditions/her2-positive-breast-cancer/) and [Stomach Cancer](/conditions/stomach-cancer/).

The first visit commonly includes confirmation of the treatment plan, medication review, observations, and any baseline heart or blood testing. A nurse gives the medicine and watches for an infusion reaction, especially during an early dose. Later visits usually include a symptom check and tests before treatment. Keep a record of new symptoms, medicines, and questions so the team can adjust supportive care quickly.

Most people return home after an infusion or injection, unless the team recommends observation for longer. Fatigue, bowel changes, or an infusion reaction can appear during or after a dose, while other effects build over several visits. Rest, hydration, gentle activity, and the prescribed anti-sickness or bowel medicines may help. Contact the team if an effect interferes with eating, drinking, sleep, or ordinary activity.

Potential risks include allergic or infusion reactions, infection risk from low blood counts, heart function changes, lung inflammation, liver changes, and effects from medicines given at the same time. The exact risk profile depends on the drug. Report fever, breathing difficulty, chest symptoms, jaundice, severe weakness, or persistent diarrhoea urgently using the contact route supplied by your cancer centre.

Depending on the diagnosis, options may include surgery, radiotherapy, chemotherapy, hormone therapy, immunotherapy, another targeted medicine, or symptom-focused care. Some people receive a combination; others need a different plan because the tumour lacks HER2, has stopped responding, or another health condition changes the balance of benefits and risks. [Antibody Drug Conjugates](/materials/antibody-drug-conjugates/) and [HER2 Antibody Drugs](/materials/her2-antibody-drugs/) explain two medicine groups.

Choose an oncology service that can confirm HER2 testing, administer the selected medicine, manage infusion reactions, and arrange the needed heart, blood, and scan monitoring. Bring pathology reports, imaging, current medicines, allergies, and a list of previous cancer treatments to the consultation. [Breast Cancer](/conditions/breast-cancer/) provides related condition information.