How HER2 status shapes breast cancer drug choices across the US

Human epidermal growth factor receptor 2, known as HER2, is one of the main markers doctors use to tailor breast cancer treatment in the United States. Whether a tumor is classified as HER2 positive, HER2 low, or HER2 negative can determine which drug combinations are recommended, how long targeted therapies are continued, and which newer medicines may be considered if cancer returns or spreads.

HER2 is a protein that can sit on the surface of breast cancer cells. Tumors with high levels of HER2 tend to grow and divide more quickly. For many years that meant a worse outlook, but the development of HER2 targeted drugs has significantly changed outcomes for many people. Today, pathologists use standardized tests to measure HER2 levels, and those results play a central role in discussions between patients and oncology teams about treatment options.

HER2 breast cancer treatments and testing

HER2 status is typically determined using immunohistochemistry, which measures how strongly HER2 shows up on the tumor surface, and sometimes in situ hybridization tests, which look at HER2 gene copies. In the US, most pathology reports now sort tumors into HER2 positive, HER2 negative, or more recently, HER2 low categories. Getting an accurate reading is essential, because small differences in test results can mean access to very different sets of drugs.

Once HER2 status is known, treatment planning can begin. For early stage HER2 positive breast cancer, standard care often includes chemotherapy plus a HER2 targeted antibody such as trastuzumab, sometimes combined with pertuzumab, followed by a period of continued HER2 therapy. In metastatic disease, oncologists sequence multiple HER2 targeted options over time. For HER2 negative tumors, other approaches like endocrine therapy, chemotherapy, and certain antibody drug conjugates or immunotherapies may be used instead.

Drugs approved for breast cancer by HER2 status

In the US, the Food and Drug Administration has approved a wide range of drugs for breast cancer, many of them linked directly to HER2 test results. For HER2 positive disease, there are monoclonal antibodies, antibody drug conjugates, and small molecule tyrosine kinase inhibitors. For HER2 low metastatic disease, newer antibody drug conjugates expand options. Meanwhile, HER2 negative tumors are more likely to be treated with endocrine therapies, chemotherapy, or other targeted agents that focus on hormone receptors or specific gene changes rather than HER2.

Several HER2 targeted and related agents are now commonly used across the country, from major academic centers to community oncology clinics. While dosing and combinations vary based on stage, prior therapies, and overall health, the same core drugs appear in treatment guidelines and insurance coverage policies. The table below summarizes selected drugs used in HER2 positive or HER2 low breast cancer, their manufacturers, key features, and very approximate monthly cost ranges in the US.

---

Product or Service Name	Provider	Key Features	Cost Estimation (if applicable)
Trastuzumab (Herceptin and biosimilars)	Genentech and multiple biosimilar makers	Monoclonal antibody targeting HER2; backbone of many regimens in early and metastatic HER2 positive disease	Roughly 5,000 to 10,000 USD per month depending on weight and schedule
Pertuzumab (Perjeta)	Genentech	Monoclonal antibody that blocks HER2 dimerization; often combined with trastuzumab and chemotherapy	Often 5,000 to 7,000 USD per cycle at loading doses
Ado trastuzumab emtansine (Kadcyla)	Genentech	Antibody drug conjugate delivering chemotherapy directly to HER2 positive cells; used after prior HER2 therapy	Commonly in the range of 9,000 to 12,000 USD per month
Trastuzumab deruxtecan (Enhertu)	Daiichi Sankyo and AstraZeneca	Antibody drug conjugate active in HER2 positive and HER2 low metastatic disease after prior treatment	Frequently estimated at 13,000 to 20,000 USD per month
Tucatinib (Tukysa)	Seagen	Oral small molecule HER2 kinase inhibitor often combined with trastuzumab and capecitabine, including for brain metastases	Around 15,000 to 20,000 USD per month for the oral drug alone

Prices, rates, or cost estimates mentioned in this article are based on the latest available information but may change over time. Independent research is advised before making financial decisions.

HER2-targeted therapies in different US settings

Because oncology guidelines are widely used across the United States, recommended HER2 related regimens are surprisingly consistent from one region to another. Most centers follow evidence based protocols for early stage HER2 positive disease, often including chemotherapy combined with trastuzumab, with or without pertuzumab. After surgery, many people continue HER2 targeted therapy for up to a year, and some with higher risk features may receive an additional agent such as ado trastuzumab emtansine. In metastatic settings, oncologists commonly move from an antibody based combination in the first line to an antibody drug conjugate or other targeted options if the disease progresses.

HER2 low and HER2 negative tumors require different strategies. HER2 low status, usually defined by limited HER2 staining without gene amplification, has become important mainly in metastatic disease, where trastuzumab deruxtecan can be considered after prior chemotherapy. HER2 negative cancers that are hormone receptor positive are more likely to be managed with endocrine therapy plus targeted agents such as CDK4 6 inhibitors, while triple negative tumors are approached with chemotherapy, immunotherapy in some cases, and other targeted options tied to specific gene changes.

Evolving HER2-targeted therapies and access

When choosing among HER2 directed drugs, US oncologists consider more than just HER2 status. Heart health is a major concern because trastuzumab and some related drugs can affect cardiac function, so echocardiograms or other heart tests are done regularly. The presence of brain metastases, prior exposure to certain agents, side effect profiles, and other medical conditions also guide whether an antibody, an antibody drug conjugate, or an oral kinase inhibitor is the most appropriate next step.

Access to HER2 targeted treatments can still vary. Insurance coverage, co pay structures, and availability of infusion centers may differ between urban and rural areas, and between private insurance, Medicare, and Medicaid plans. Many manufacturers and nonprofit groups offer financial assistance programs, and large cancer centers often have staff to help patients navigate these resources. Clinical trials across the US continue to test new HER2 targeted drugs and combinations, which may be an option for some people depending on location and eligibility criteria.

Across the United States, HER2 status has become a central organizing factor in breast cancer treatment planning. Accurate testing, careful interpretation of pathology reports, and close coordination between medical oncologists, surgeons, radiation oncologists, and primary care teams all help ensure that people receive therapies that match the biology of their tumors. As testing methods and drug options continue to evolve, HER2 will likely remain a key marker shaping how breast cancer drugs are selected and sequenced.

This article is for informational purposes only and should not be considered medical advice. Please consult a qualified healthcare professional for personalized guidance and treatment.