What is Phesgo?

Phesgo is a medication used to treat HER2-positive breast cancer. It combines two medications—pertuzumab and trastuzumab—that target the HER2 protein on cancer cells. HER2 is a protein that helps cancer cells grow and divide. By blocking the HER2 receptor, Phesgo helps prevent cancer cell growth and may shrink tumors.

How Does Phesgo Work?

Phesgo contains two monoclonal antibodies:

1. Pertuzumab: This antibody binds to the HER2 receptor and prevents it from sending signals that tell cancer cells to grow.
2. Trastuzumab: This antibody also targets the HER2 receptor, preventing cancer cells from growing and helping your immune system to attack the cancer cells.

Together, these antibodies work to stop the HER2-positive cancer cells from growing and spreading.

How is Phesgo Given?

• Form: Phesgo is given as a subcutaneous (under the skin) injection.
• Administration: Phesgo is injected into the subcutaneous tissue (usually in the thigh or abdomen). It is administered by a trained healthcare professional.
• Dosage: The exact dosage of Phesgo will be determined by your healthcare provider based on your individual treatment plan. Typically, you will receive an initial loading dose, followed by regular maintenance doses.
• Schedule: After the initial dose, Phesgo is usually given once every 3 weeks.

Possible Side Effects

Phesgo can cause side effects, some of which can be serious. It is important to discuss any side effects you experience with your healthcare provider.

Common Side Effects:

• Injection Site Reactions: Some patients experience pain, redness, swelling, or itching at the site of the injection. This is usually temporary.
• Fatigue: You may feel tired or weak. Rest and conserve your energy, but let your healthcare provider know if fatigue is severe or affects your daily activities.
• Hair Loss: Some people may experience hair thinning or hair loss during treatment. Hair typically regrows after treatment ends.
• Diarrhea: Diarrhea is a common side effect. Stay hydrated and let your doctor know if diarrhea becomes severe or persistent.
• Nausea and Vomiting: Some people may feel nauseous or vomit, especially in the early stages of treatment. Anti-nausea medications can help manage these symptoms.

Serious Side Effects:

• Heart Problems: Phesgo can cause heart problems, including a decrease in heart function. Your doctor will monitor your heart with regular tests. Contact your doctor immediately if you experience shortness of breath, swelling in your ankles or legs, or chest pain.
• Infections: Phesgo can lower your immune system’s ability to fight infections. If you develop a fever, chills, sore throat, or other signs of infection, contact your healthcare provider right away.
• Severe Allergic Reactions: Although rare, Phesgo can cause allergic reactions. Symptoms may include difficulty breathing, swelling of the face or throat, rash, or itching. If you notice any of these symptoms, seek medical help immediately.
• Lung Problems: In rare cases, Phesgo can cause lung problems, such as difficulty breathing or a persistent cough. Let your healthcare provider know if you experience these symptoms.

Precautions Before Taking Phesgo

Before starting treatment with Phesgo, it is important to inform your healthcare provider about the following:

• Heart Conditions: If you have a history of heart disease, including heart failure or irregular heartbeats, tell your doctor, as Phesgo can affect heart function.
• Lung Conditions: If you have a history of lung disease, inform your doctor, as Phesgo can occasionally cause lung-related side effects.
• Pregnancy and Breastfeeding: Phesgo may harm an unborn baby. If you are pregnant, plan to become pregnant, or are breastfeeding, let your doctor know. Effective birth control is recommended during treatment, and you should not breastfeed while receiving Phesgo.
• Other Medications: Inform your healthcare provider about any other medications you are taking, including prescription, over-the-counter drugs, vitamins, and herbal supplements. Some medications may interact with Phesgo.
• Allergies: If you are allergic to pertuzumab, trastuzumab, or any of the ingredients in Phesgo, tell your doctor before starting treatment.

What to Avoid While Taking Phesgo

• Infections: Since Phesgo can lower your immune system’s ability to fight infections, avoid close contact with people who have infections or illnesses. Wash your hands frequently and practice good hygiene.
• Live Vaccines: Phesgo can weaken your immune system. Avoid live vaccines during treatment unless your doctor advises otherwise.
• Grapefruit: Avoid grapefruit and grapefruit juice, as they may affect how Phesgo is processed by your body.

Regular Monitoring

Your healthcare provider will regularly monitor your health throughout your treatment with Phesgo. This may include:

• Heart function tests: Your doctor will check your heart regularly using tests like echocardiograms to monitor for potential heart problems.
• Blood tests: You may need blood tests to check for infections, changes in blood counts, and other potential side effects.
• Infusion monitoring: Your healthcare team will monitor you during the injection to check for any immediate reactions or side effects.

When to Contact Your Doctor

Contact your healthcare provider if you experience:

• Fever, chills, sore throat, or other signs of infection
• Shortness of breath, swelling in your legs or ankles, or chest pain (possible heart problems)
• Difficulty breathing, persistent cough, or new lung-related symptoms
• Swelling of the face or throat, rash, difficulty breathing, or signs of an allergic reaction
• Severe diarrhea, nausea, vomiting, or any other side effects that concern you

Disclaimer:

This handout is for educational purposes only and should not be considered medical advice. Always follow the instructions provided by your healthcare provider regarding treatment and care. For personalized advice, consult your healthcare provider or pharmacist.