HER2 positive breast cancer is a type of breast cancer characterized by higher than normal levels of the HER2 protein or increased activity of the HER2 gene. This protein can encourage cancer cells to grow and divide rapidly. Advances in targeted therapies have expanded treatment options for people diagnosed with this subtype. Treatment may involve targeted medicines, chemotherapy.
HER2 positive breast cancer accounts for a significant proportion of breast cancer diagnoses. HER2 stands for human epidermal growth factor receptor 2, a protein involved in cell growth. When cancer cells produce excessive amounts of this protein, the disease may grow more quickly than some other breast cancer types. However, HER2 targeted treatments have substantially improved outcomes for many patients. Treatment planning depends on the cancer stage, hormone receptor status, previous treatments, overall health, and whether the disease is confined to the breast or has spread to other parts of the body.
Treatment for HER2 positive breast cancer often combines different approaches to control cancer growth, remove tumors, and reduce the risk of recurrence. The treatment plan may differ between early-stage disease and advanced or metastatic cancer. Doctors use pathology reports, HER2 testing, imaging, and other clinical findings to determine which treatments are appropriate.
Common treatment approaches include:
HER2 targeted therapy: Medicines such as trastuzumab and pertuzumab attach to or interfere with HER2-related signaling, helping control cancer growth. These treatments may be combined with chemotherapy in appropriate cases.
Chemotherapy: These medicines destroy cancer cells or prevent them from multiplying. Chemotherapy may be given before surgery to shrink a tumor or after surgery to reduce the risk of recurrence.
Surgery: Lumpectomy removes the cancerous area while preserving much of the breast, whereas mastectomy removes the breast. The choice depends on tumor characteristics and individual circumstances.
Radiation therapy: High-energy radiation destroys remaining cancer cells in a targeted area. It may be recommended after breast-conserving surgery and in certain other situations.
Hormone therapy: If the cancer is also estrogen receptor positive or progesterone receptor positive, hormone therapy may be used to reduce the influence of hormones on cancer growth.
Treatment may begin with medicines before surgery, known as neoadjuvant therapy, particularly when the tumor is larger or lymph nodes are involved. Following surgery, additional treatment depends partly on how the cancer responds to the initial therapy and the risk of recurrence.
For advanced or metastatic HER2 positive breast cancer, targeted medicines and antibody drug conjugates may help control the disease. These treatments deliver targeted effects against cancer cells or interfere with pathways involved in tumor growth. The choice of medicine depends on previous therapies, disease progression, treatment eligibility, and potential side effects.
Examples of treatments used in selected clinical situations include:
Trastuzumab deruxtecan: An antibody drug conjugate used in certain HER2 positive breast cancer settings, including some cases of advanced disease.
Ado trastuzumab emtansine: Also known as T DM1, this medicine combines HER2 targeting with a chemotherapy agent and may be used in specific treatment settings.
Tucatinib: A targeted medicine that inhibits HER2 signaling and may be combined with trastuzumab and capecitabine in eligible patients, including certain cases involving brain metastases.
Neratinib: An oral medicine that inhibits signaling through HER family proteins and may be considered in selected treatment situations.
Supportive care and monitoring: Regular examinations, imaging when indicated, and management of treatment-related effects help clinicians assess response and maintain quality of life.
Potential side effects vary by medicine and may include fatigue, nausea, diarrhea, hair loss, or changes in blood counts. Some HER2 targeted medicines can affect heart function, while trastuzumab deruxtecan carries a risk of interstitial lung disease or pneumonitis. Healthcare teams may recommend heart monitoring, blood tests, and prompt assessment of new respiratory symptoms.
The most appropriate treatment depends on individual clinical findings and current treatment guidelines. Patients can discuss the expected benefits, risks, duration, and alternatives with an oncology team. Clinical trials may also provide access to investigational treatments for eligible participants. Ongoing follow-up helps evaluate treatment effectiveness, identify side effects, and guide decisions if the cancer changes or returns.