HER2-Positive Breast Cancer Treatment: New FDA-Approved Options in 2026

"Enhertu gains new FDA approvals in 2026 for certain patients with early-stage HER2-positive breast cancer, expanding treatment options."

Illustration. A doctor explains cancer examination and treatment to a patient at a hospital.

In 2026, the U.S. Food and Drug Administration (FDA) expanded the approved use of fam-trastuzumab deruxtecan-nxki (Enhertu) to certain adults with HER2-positive early-stage breast cancer. 

The May 15, 2026, approval created two separate indications: one for neoadjuvant treatment of certain Stage II or III cancers and another for adjuvant treatment of patients who have residual invasive disease after neoadjuvant therapy.

Enhertu was already approved for certain patients with HER2-positive metastatic breast cancer, including a December 2025 FDA approval of Enhertu in combination with pertuzumab as first-line treatment for unresectable or metastatic HER2-positive breast cancer.

These approvals do not mean that every person with HER2-positive breast cancer should receive Enhertu.

The appropriate treatment depends on factors such as:

• cancer stage;

• HER2 test results;

• hormone receptor status;

• whether the cancer can be surgically removed;

• previous treatment;

• whether disease remains after preoperative treatment;

• overall health;

• and the specific FDA indication.

Medical information: This article is for educational purposes and does not replace individualized medical advice. Cancer treatment decisions should be made with a qualified oncology team familiar with the patient's pathology, stage, biomarkers and treatment history.

What Is HER2-Positive Breast Cancer?

HER2 stands for human epidermal growth factor receptor 2.

HER2 is a protein involved in cell growth and signaling.

Some breast cancers have unusually high levels of HER2 or amplification of the ERBB2 gene. These tumors are classified as HER2-positive when they meet established testing criteria.

HER2-positive breast cancer can grow differently from breast cancers without HER2 overexpression or amplification.

The important point for patients is that HER2 is not simply a descriptive label.

It can help doctors determine whether HER2-targeted treatment is appropriate.

How Is HER2 Status Determined?

HER2 status is determined through testing of the breast cancer tissue.

Testing may involve:

• immunohistochemistry (IHC) to measure HER2 protein;

• in situ hybridization (ISH) to evaluate HER2 gene amplification.

For the 2026 early-stage Enhertu indications, the FDA specifies HER2-positive disease as IHC 3+ or ISH-positive, determined by an FDA-authorized test.

This distinction matters because not every breast tumor described as having some HER2 expression meets the FDA definition of HER2-positive disease for these indications.

What Changed for HER2-Positive Breast Cancer in 2026?

On May 15, 2026, the FDA approved fam-trastuzumab deruxtecan-nxki, marketed as Enhertu, for two separate indications involving HER2-positive early-stage breast cancer.

The first indication involves neoadjuvant treatment.

The second involves adjuvant treatment after surgery for certain patients who still have residual invasive disease.

The FDA also approved companion diagnostic devices for identifying HER2-positive patients who may be eligible for the treatment.

This is significant because HER2-targeted therapy is now incorporated into treatment strategies for specific early-stage patients before and after surgery.

What Is Neoadjuvant Treatment?

Neoadjuvant treatment is treatment given before surgery.

For certain patients with HER2-positive Stage II or III breast cancer, the FDA-approved 2026 Enhertu regimen is:

Enhertu → followed by taxane + trastuzumab + pertuzumab (THP)

The FDA indication applies to adults with HER2-positive, IHC 3+ or ISH-positive Stage II or III breast cancer identified by an FDA-authorized test.

The purpose of neoadjuvant treatment can include:

• treating cancer systemically before surgery;

• potentially reducing tumor burden;

• allowing doctors to assess how the cancer responds to treatment;

• and helping determine subsequent treatment decisions.

The exact treatment plan depends on the patient's cancer and oncology team.

What Is Adjuvant Treatment?

Adjuvant treatment is therapy given after surgery to reduce the risk of recurrence.

Under the FDA's May 2026 approval, Enhertu is indicated for adults with HER2-positive breast cancer who have residual invasive disease after neoadjuvant treatment with trastuzumab, with or without pertuzumab, and taxane-based treatment.

This is an important distinction.

The approval is not simply:

"HER2-positive breast cancer = Enhertu after surgery."

Instead, the patient's previous treatment and whether invasive cancer remains after neoadjuvant therapy matter.

Who May Be Eligible for the 2026 Early-Stage Enhertu Indication?

The FDA-approved early-stage indications are specific.

For the neoadjuvant indication, the patient must be:

• an adult;

• diagnosed with HER2-positive breast cancer;

• have Stage II or III disease;

• have HER2 status confirmed as IHC 3+ or ISH-positive by an FDA-authorized test.

For the adjuvant indication, the patient must have:

• HER2-positive breast cancer;

• residual invasive disease after neoadjuvant treatment;

• previous neoadjuvant trastuzumab, with or without pertuzumab;

• and taxane-based treatment.

Eligibility should be determined by the oncology team using the patient's pathology and treatment history.

What About HER2-Positive Metastatic Breast Cancer?

The treatment landscape is different when breast cancer is unresectable or has spread to distant parts of the body.

In December 2025, the FDA approved Enhertu in combination with pertuzumab for the first-line treatment of adults with unresectable or metastatic HER2-positive breast cancer. The cancer must meet the FDA's HER2-positive definition, using an FDA-approved test.

Enhertu also has other approved uses in HER2-positive metastatic disease, including treatment of certain patients who have previously received anti-HER2 therapy.

Therefore, a patient with metastatic HER2-positive breast cancer may have different treatment options from someone with newly diagnosed Stage II or III disease.

Is Enhertu the Same as Herceptin?

No.

Both are HER2-targeted treatments, but they are different medicines.

Herceptin is the brand name for trastuzumab.

Enhertu is fam-trastuzumab deruxtecan-nxki.

Enhertu is an antibody-drug conjugate, meaning it combines a HER2-directed antibody with a chemotherapy component.

Trastuzumab is a HER2-targeted monoclonal antibody.

The two drugs can therefore have different roles in treatment.

The FDA's 2026 early-stage indication specifically incorporates Enhertu into a treatment sequence that can later include trastuzumab, pertuzumab and a taxane.

What Is an Antibody-Drug Conjugate?

An antibody-drug conjugate, or ADC, is designed to combine targeted recognition with delivery of a cytotoxic drug.

In simplified terms:

Antibody → recognizes the target

Drug component → provides the cancer-killing activity

Enhertu targets HER2 and carries a topoisomerase I inhibitor payload.

The concept is to deliver the drug to cells expressing the target while retaining systemic anticancer activity.

However, an ADC can still cause significant side effects and requires medical monitoring.

It should not be interpreted as a treatment that affects only cancer cells.

What Are the Common Side Effects of Enhertu?

Enhertu can cause significant adverse reactions.

The FDA prescribing information includes warnings and precautions for potentially serious problems, including:

• interstitial lung disease (ILD) or pneumonitis;

• neutropenia;

• decreased blood cell counts;

• nausea and vomiting;

• fatigue;

• reduced appetite;

• anemia;

• liver-related abnormalities;

• and other adverse reactions.

ILD or pneumonitis can be serious and, in some cases, life-threatening.

Patients receiving Enhertu should report new or worsening respiratory symptoms to their healthcare team promptly.

The specific side-effect profile depends on the treatment setting, dose, combination therapy and individual patient.

Why Is HER2 Testing So Important?

HER2 testing is directly connected to treatment eligibility.

The FDA's 2026 approval specifies HER2-positive disease using defined laboratory results.

The FDA also approved companion diagnostic devices for the early-stage Enhertu indications, including the PATHWAY anti-HER2/neu 4B5 antibody and the VENTANA HER2 Dual ISH DNA Probe Cocktail.

This is an example of precision oncology.

Instead of choosing treatment based solely on where the cancer originated, doctors increasingly use molecular and pathological characteristics to identify which therapies may be appropriate.

What Does IHC 3+ Mean?

IHC is a laboratory test that measures the amount of HER2 protein expressed on cancer cells.

An IHC result of 3+ is considered HER2-positive under the FDA's relevant Enhertu indications.

An IHC result of 0, 1+ or 2+ does not automatically mean the tumor qualifies as HER2-positive for these particular indications.

For IHC 2+, additional ISH testing may be used to determine whether the tumor is HER2-positive based on gene amplification.

The exact interpretation should come from the pathology report and oncology team.

Is HER2-Low the Same as HER2-Positive?

No.

This is an important distinction.

A breast cancer can have some HER2 expression without meeting the conventional definition of HER2-positive disease.

Terms such as:

• HER2-positive;

• HER2-low;

• HER2-ultralow;

• and HER2-negative

describe different biological and testing categories.

The FDA has separately approved Enhertu for certain patients with unresectable or metastatic hormone receptor-positive breast cancer that is HER2-low or HER2-ultralow and has progressed after endocrine therapy. That approval dates to January 2025.

Therefore, an article about HER2-positive breast cancer treatment should not automatically combine HER2-positive and HER2-low disease.

They can involve different treatment indications.

What Other Treatments Are Used for HER2-Positive Breast Cancer?

Enhertu is only one component of a broader HER2-directed treatment landscape.

Depending on stage and clinical circumstances, treatment may involve combinations or sequences involving:

• trastuzumab;

• pertuzumab;

• taxane chemotherapy;

• antibody-drug conjugates;

• other HER2-targeted therapies;

• endocrine therapy when the tumor is also hormone receptor-positive;

• radiation therapy;

• surgery;

• and other systemic treatments.

The appropriate combination depends on the clinical setting.

A patient newly diagnosed with early-stage HER2-positive breast cancer should not assume that the treatment used for metastatic disease is appropriate for them.

Does Hormone Receptor Status Matter?

Yes.

Breast cancer can be:

• HER2-positive and hormone receptor-positive;

• HER2-positive and hormone receptor-negative;

• or have other combinations of biomarker results.

Estrogen receptor (ER) and progesterone receptor (PR) status can influence treatment decisions.

For example, a patient whose cancer is both HER2-positive and hormone receptor-positive may have endocrine therapy incorporated into the overall treatment strategy.

HER2 status is therefore only one part of the pathology report.

What Does Stage II or III Mean?

The 2026 neoadjuvant Enhertu indication specifically applies to Stage II or III HER2-positive breast cancer.

Cancer stage describes how extensive the disease is.

Staging can consider factors such as:

• tumor size;

• lymph-node involvement;

• whether the cancer has spread to distant organs;

• and other pathological characteristics.

Stage II or III breast cancer is not the same as metastatic Stage IV disease.

This distinction is essential when interpreting an FDA drug approval.

Is HER2-Positive Breast Cancer Curable?

Some people with early-stage HER2-positive breast cancer can achieve long-term remission and may be cured.

However, an individual outcome cannot be predicted simply from HER2 status.

Prognosis depends on factors such as:

• stage;

• tumor characteristics;

• lymph-node involvement;

• response to treatment;

• hormone receptor status;

• overall health;

• and treatment received.

Metastatic breast cancer is a different clinical situation.

It is generally treated as advanced disease, and treatment aims can include controlling the cancer, prolonging survival and maintaining quality of life.

Patients should discuss their individual prognosis with their oncology team.

Does Everyone With HER2-Positive Breast Cancer Need Chemotherapy?

Not necessarily in the same way or with the same regimen.

HER2-positive breast cancer treatment can involve chemotherapy together with HER2-targeted therapy, particularly in early-stage disease.

But treatment decisions depend on:

• stage;

• tumor size;

• lymph-node status;

• hormone receptor status;

• patient's health;

• prior therapy;

• and treatment goals.

The FDA's 2026 approval itself illustrates this complexity: the approved neoadjuvant regimen uses Enhertu followed by taxane, trastuzumab and pertuzumab rather than treating Enhertu as a standalone universal therapy.

How Does Surgery Fit Into HER2-Positive Treatment?

For operable early-stage breast cancer, surgery can be an important part of treatment.

Depending on the clinical situation, systemic therapy may be given before surgery.

This is called neoadjuvant treatment.

After surgery, doctors examine the surgical specimen to determine whether invasive cancer remains.

That information can influence subsequent treatment.

This is particularly relevant to the 2026 Enhertu approval because residual invasive disease after neoadjuvant therapy is specifically part of the adjuvant indication.

What Questions Should You Ask Your Oncologist?

If you have been diagnosed with HER2-positive breast cancer, consider asking:

1. What exactly is my HER2 test result?

2. Was my HER2 status determined by IHC, ISH, or both?

3. What is my breast cancer stage?

4. Is my cancer ER-positive or PR-positive?

5. Is my cancer considered early-stage or metastatic?

6. Should treatment begin before surgery?

7. Is Enhertu appropriate for my specific diagnosis?

8. Why are you recommending this treatment sequence?

9. What are the major risks and side effects?

10. What symptoms should I report immediately?

11. How will we monitor my response to treatment?

12. What happens if cancer remains after neoadjuvant treatment?

13. Are there FDA-approved alternatives for my situation?

14. Are clinical trials appropriate?

15. What will my insurance cover?

How Much Does HER2-Positive Breast Cancer Treatment Cost?

There is no single national price for HER2-positive breast cancer treatment.

The total cost can depend on:

• the specific drug;

• dosage;

• treatment duration;

• infusion or administration costs;

• laboratory testing;

• imaging;

• surgery;

• radiation;

• hospital or outpatient facility;

• insurance coverage;

• deductible;

• coinsurance;

• and financial assistance.

The list price of a cancer drug should not be confused with the amount an individual patient ultimately pays.

For insured patients, the more useful question is:

"What is my estimated out-of-pocket cost for this treatment under my specific insurance plan?"

Patients should ask the oncology practice for an insurance benefits investigation or financial counseling when available.

Can Insurance Cover Enhertu?

FDA approval does not automatically mean that every patient will have identical insurance coverage.

Commercial insurers, Medicare and other payers can have their own coverage policies and requirements.

Coverage can depend on:

• the diagnosis;

• FDA-approved indication;

• medical necessity;

• treatment setting;

• insurance plan;

• prior authorization;

• and provider network.

Patients should ask the oncology practice and insurer whether prior authorization is required.

What Is the Difference Between FDA Approval and a Doctor's Recommendation?

An FDA approval means the agency has determined that a drug can legally be marketed for a specific indication based on the applicable regulatory standard.

It does not mean:

"Every patient with this cancer should receive this drug."

A doctor must still determine whether the approved treatment is appropriate for the individual patient.

The FDA's Enhertu approval illustrates this point clearly because the indications specify cancer stage, HER2 testing, treatment history and disease setting.

What Are the New HER2 Treatment Options in 2026?

The most important 2026 development for HER2-positive early-stage breast cancer is the FDA expansion of Enhertu into two specific early-stage settings.

Early-stage, Stage II or III

Enhertu followed by THP is approved for neoadjuvant treatment of adults with HER2-positive Stage II or III breast cancer.

Residual invasive disease after neoadjuvant treatment

Enhertu is approved as adjuvant treatment for adults with HER2-positive breast cancer who have residual invasive disease after specified neoadjuvant treatment.

Unresectable or metastatic disease

Enhertu also has FDA-approved uses in certain adults with HER2-positive unresectable or metastatic breast cancer, including in combination with pertuzumab as first-line therapy under the December 2025 approval.

The exact treatment choice depends on the clinical setting.

HER2-Positive Breast Cancer Treatment in 2026: Quick Guide

This is a simplified overview, not a treatment recommendation.

What Should Patients Know About the 2026 FDA Approval?

The biggest takeaway is that HER2-positive breast cancer treatment is becoming increasingly specific to disease setting and treatment response.

The 2026 FDA approval does not create one universal HER2 treatment.

Instead, it provides additional options for defined groups of patients:

Before surgery:
Certain adults with Stage II or III HER2-positive breast cancer may receive an FDA-approved Enhertu-based neoadjuvant regimen.

After surgery:
Certain patients who have residual invasive disease after specified neoadjuvant treatment may receive adjuvant Enhertu.

Advanced disease:
Patients with unresectable or metastatic HER2-positive breast cancer have separate FDA-approved treatment options.

The patient's HER2 test, stage and previous treatment therefore matter as much as the drug name.

The Bottom Line

HER2-positive breast cancer treatment in the United States has expanded significantly, and 2026 brought an important FDA development.

On May 15, 2026, the FDA approved Enhertu (fam-trastuzumab deruxtecan-nxki) for two specific early-stage HER2-positive breast cancer indications. One is a neoadjuvant indication for adults with HER2-positive Stage II or III disease, using Enhertu followed by taxane, trastuzumab and pertuzumab. The other is an adjuvant indication for certain patients with residual invasive disease after specified neoadjuvant treatment.

Enhertu also has FDA-approved uses in certain patients with HER2-positive unresectable or metastatic breast cancer.

The most important point is that HER2-positive does not automatically mean Enhertu is the right treatment.

Doctors must consider:

• HER2 test results;

• stage;

• hormone receptor status;

• whether the cancer is operable;

• response to previous treatment;

• residual disease;

• overall health;

• and the specific FDA-approved indication.

For patients newly diagnosed with HER2-positive breast cancer, the most useful question is not simply:

"What is the newest HER2 drug?"

Instead, ask:

"Based on my HER2 test, cancer stage and treatment history, which FDA-approved treatment is appropriate for me?"

Medical Sources

This article was fact-checked against:

• U.S. Food and Drug Administration

• FDA prescribing information for Enhertu

• FDA companion diagnostic information

• National Cancer Institute

Key FDA updates reviewed:

• May 15, 2026 — Enhertu approved for two early-stage HER2-positive breast cancer indications.

• December 15, 2025 — Enhertu plus pertuzumab approved for first-line treatment of certain unresectable or metastatic HER2-positive breast cancer.

• January 27, 2025 — Enhertu approved for certain HR-positive, HER2-low or HER2-ultralow unresectable or metastatic breast cancer.

Last reviewed for source accuracy: October 2026.

Medical disclaimer: This article is for general educational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. FDA approvals and treatment recommendations can change. Patients should discuss their pathology, biomarker results, treatment options, risks and benefits with a qualified oncology professional.