Trastuzumab

Approved Uses

Trastuzumab is primarily used to treat cancers that are HER2-positive, meaning the cancer cells have high amounts of a protein called human epidermal growth factor receptor 2. This medication is used for the following conditions:

Breast Cancer

• Early-stage breast cancer: It may be used after surgery (adjuvant treatment) or as part of a larger chemotherapy regimen to reduce the risk of the cancer returning.
• Metastatic breast cancer: It is used to treat breast cancer that has spread to other parts of the body. In these cases, it may be used alone or combined with other cancer medications.

Stomach Cancer

Trastuzumab is used to treat metastatic gastric (stomach) cancer or gastroesophageal junction adenocarcinoma. This application is specifically for patients whose tumors are HER2-positive and who have not received prior treatment for metastatic disease.

Testing Requirements

Before starting trastuzumab, healthcare providers must confirm the presence of HER2 protein overexpression or HER2 gene amplification using a specialized test. The medication is only effective in cancers that test positive for these specific markers.

Targeting HER2 Proteins

Some types of breast, stomach, and esophageal cancers are HER2-positive, meaning the cancer cells have an excess of a protein called human epidermal growth factor receptor 2 (HER2). These proteins act as receptors on the cell surface that send signals telling the cancer to grow and divide.

Mechanism of Action

Trastuzumab is a type of monoclonal antibody designed to interfere with the growth of these specific cancer cells. It works in two primary ways:

• Blocking Signals: The medication attaches to the HER2 receptors on the surface of the cancer cells. This prevents the receptors from receiving the signals that tell the cells to multiply, which can slow or stop the tumor's growth.
• Immune System Response: By binding to the cancer cells, trastuzumab may also help the body's immune system identify and destroy those cells.

This treatment is specifically targeted, meaning it is most effective against cancers that overexpress the HER2 protein.

Common Side Effects

Many people experience mild to moderate side effects while receiving trastuzumab. These often include:

• Fever and chills, especially during the first infusion
• Nausea, vomiting, or diarrhea
• Headache or dizziness
• Cough or shortness of breath
• Fatigue or weakness
• Muscle, joint, or bone pain
• Rash
• Trouble sleeping (insomnia)
• Cold-like symptoms such as a runny or stuffy nose

Serious Side Effects

Some side effects can be severe and require immediate medical attention. Contact your doctor right away if you experience:

• Heart problems: Symptoms may include new or worsening shortness of breath, cough, swelling in the ankles or legs, or a rapid heartbeat.
• Infusion reactions: These typically occur during or within 24 hours of a dose and may include fever, chills, dizziness, or fainting.
• Lung issues: Severe breathing problems, wheezing, or inflammation of the lungs.
• Low blood cell counts: Increased risk of infection due to low white blood cell levels.
• Severe allergic reactions: Swelling of the face or throat, hives, or difficulty breathing.

Heart Complications

Trastuzumab is associated with a risk of heart muscle damage and congestive heart failure. This risk is significantly increased when the drug is used in combination with anthracycline-based chemotherapy. Healthcare providers typically perform heart function tests, such as echocardiograms, before starting treatment and at regular intervals during therapy.

Lung Toxicity

Serious lung problems, including interstitial lung disease and pneumonitis, have been reported. These conditions can be life-threatening. Symptoms such as new or worsening shortness of breath, cough, or fever require immediate medical evaluation.

Infusion-Related Reactions

Severe reactions can occur during or shortly after the administration of trastuzumab. These may include fever, chills, nausea, vomiting, pain, headache, dizziness, and breathing difficulties. In rare cases, these reactions can be fatal.

Pregnancy and Fetal Harm

Using trastuzumab during pregnancy can cause serious harm to the fetus, including lung and kidney damage or death, due to a decrease in amniotic fluid. Effective contraception is necessary for individuals of childbearing potential during treatment and for at least seven months following the final dose.

Low White Blood Cell Counts

When administered with other chemotherapy drugs, trastuzumab may cause a significant drop in white blood cell counts (neutropenia). This can increase the risk of developing serious infections.

Pregnancy

Trastuzumab can cause fetal harm when used during pregnancy. Exposure to this medication is associated with low levels of amniotic fluid, a condition known as oligohydramnios. This can result in severe complications for the developing fetus, such as:

• Underdeveloped lungs
• Skeletal abnormalities
• Neonatal death

Patients who are able to become pregnant should use effective birth control while receiving trastuzumab and continue using it for 7 months after the final dose. If pregnancy is suspected or confirmed during this period, a healthcare provider should be notified immediately.

Breastfeeding

It is not known if trastuzumab is excreted in human breast milk. Due to the potential for serious side effects in a nursing infant, breastfeeding is generally not recommended during treatment and for 7 months following the last dose. Patients should consult with their healthcare team to determine the safest approach for their situation.

Dosage Forms

Trastuzumab is available in the following form:

• Powder for solution: A dry substance that must be mixed with a sterile liquid before use.

This medication is administered as an intravenous infusion, meaning it is delivered directly into a vein. It is given by a healthcare provider in a clinical setting, such as a hospital or infusion center.

FDA Approval and Indications

Trastuzumab is approved by the U.S. Food and Drug Administration (FDA) for the treatment of cancers that overexpress the HER2 protein. Its primary approved uses include:

• Adjuvant Breast Cancer: Used as part of a treatment regimen for HER2-overexpressing node-positive or node-negative breast cancer.
• Metastatic Breast Cancer: Used alone or in combination with chemotherapy for patients who have not received prior treatment for metastatic disease.
• Metastatic Gastric Cancer: Used in combination with chemotherapy for HER2-overexpressing metastatic gastric or gastroesophageal junction adenocarcinoma.

Boxed Warnings

The FDA has issued boxed warnings for trastuzumab due to the risk of severe and potentially fatal adverse reactions. These include:

• Cardiomyopathy: Trastuzumab can lead to heart failure or a significant decrease in heart function. Patients typically undergo heart function monitoring, such as an echocardiogram, before and during treatment.
• Infusion Reactions: Serious and sometimes fatal reactions can occur during or within 24 hours of the infusion. Symptoms may include fever, chills, and respiratory distress.
• Pulmonary Toxicity: The medication can cause severe lung issues, including interstitial pneumonitis and acute respiratory distress syndrome.
• Embryo-Fetal Toxicity: Exposure to trastuzumab during pregnancy can cause low amniotic fluid levels, which may result in permanent harm or death to the fetus.

Biosimilar Status

The FDA has approved several biosimilar versions of trastuzumab. These biosimilars are highly similar to the original reference product and have no clinically meaningful differences in safety, purity, or potency. These approvals provide additional treatment options for patients with HER2-positive malignancies.

Factors Influencing Cost

Trastuzumab is a specialty biological medication, which generally makes it more expensive than traditional drugs. Several factors can influence the total out-of-pocket cost:

• Brand vs. Biosimilar: Trastuzumab is available as the original brand-name drug and several biosimilar versions. Biosimilars are highly similar to the original product but are often available at a lower price point.
• Administration Fees: Because this medication is typically administered as an intravenous infusion or injection by a healthcare professional in a clinical setting, the total cost often includes facility fees and professional administration charges.
• Treatment Schedule: The frequency and duration of treatment, which vary based on the type and stage of cancer being treated, will affect the overall expense.

Insurance and Financial Assistance

Most insurance plans, including Medicare and Medicaid, provide coverage for trastuzumab when it is prescribed for FDA-approved uses. However, patients may still be responsible for copayments, coinsurance, or deductibles. Many manufacturers offer patient assistance programs or co-pay cards to help reduce the financial burden for eligible individuals. It is recommended to contact the insurance provider or the treatment facility's billing department for specific cost estimates.