Classification: Monoclonal Antibody
Trastuzumab is a type of monoclonal antibody, which is a group of medications that are designed to target a specific type of cell (in this case, a Her2 positive breast or gastric cancer cell). Her2 is overexpressed on about 25-30% of all breast cancers and in about 20% of gastric cancers. Her2 receptors on cells send signals telling the cell to grow and divide. Cancers that overexpress Her2 have too many receptors, which cause the cells to grow and divide more quickly. Trastuzumab is thought to block these receptors, preventing them from turning on cell growth.
How to Take Trastuzumab
Trastuzumab is given by intravenous (IV, into a vein) infusion. The initial infusion generally takes about 90 minutes, and subsequent treatments may take 30-90 minutes. The dose is based on your body size and type of cancer. The frequency of doses and adjuvant chemotherapy depends on the regimen used. Because trastuzumab is indicated only for treatment of HER2 positive cancer, a sample of your tumor will be tested in a lab to determine if it is HER2 positive prior to starting treatment.
Possible Side Effects of Trastuzumab
There are a number of things you can do to manage the side effects of trastuzumab. Talk to your doctor or nurse about these recommendations. They can help you decide what will work best for you. These are some of the most common side effects:
Infusion-Related Side Effects
Some patients experience chills and fever within 24 hours of the first infusion. The first trastuzumab infusion can also cause the patient to have nausea/vomiting, pain at the tumor site, headache, dizziness and rash. For these reactions, the infusion will be stopped, acetaminophen and/or diphenhydramine given to lessen the reactions, and the infusion restarted at a slower rate once symptoms resolve. This typically does not happen with subsequent infusions.
More serious reactions can occur, but are rare. Symptoms of a serious reaction include: shortness of breath, wheezing, low blood pressure, and increase in heart rate. The infusion will be stopped if this happens and the doctor will determine whether or not it is safe to restart the infusion. Notify your nurse right away if you develop any concerning symptoms.
Low White Blood Cell Count (Leukopenia or Neutropenia)
White blood cells (WBC) are important for fighting infection. While receiving treatment, your WBC count can drop, putting you at a higher risk of getting an infection. You should let your doctor or nurse know right away if you have a fever (temperature greater than 100.4), sore throat or cold, shortness of breath, cough, burning with urination, or a sore that doesn't heal.
Tips to preventing infection:
Low Red Blood Cell Count (Anemia)
Your red blood cells are responsible for carrying oxygen to the tissues in your body. When the red cell count is low, you may feel tired or weak. You should let your doctor or nurse know if you experience any shortness of breath, difficulty breathing or pain in your chest. If the count gets too low, you may receive a blood transfusion.
Fatigue is very common during cancer treatment and is an overwhelming feeling of exhaustion that is not usually relieved by rest. While on cancer treatment, and for a period after, you may need to adjust your schedule to manage fatigue. Plan times to rest during the day and conserve energy for more important activities. Exercise can help combat fatigue; a simple daily walk with a friend can help. Talk to your healthcare team for helpful tips on dealing with this side effect.
Nausea and/or Vomiting
Talk to your doctor or nurse so they can prescribe medications to help you manage nausea and vomiting. In addition, dietary changes may help. Avoid things that may worsen the symptoms, such as heavy or greasy/fatty, spicy or acidic foods (lemons, tomatoes, oranges). Try antacids, (e.g. milk of magnesia, calcium tablets such as Tums), saltines, or ginger ale to lessen symptoms.
Call your doctor or nurse if you are unable to keep fluids down for more than 12 hours or if you feel lightheaded or dizzy at any time.
Your oncology team can recommend medications to relieve diarrhea. Also, try eating low-fiber, bland foods, such as white rice and boiled or baked chicken. Avoid raw fruits, vegetables, whole grain breads, cereals and seeds. Soluble fiber is found in some foods and absorbs fluid, which can help relieve diarrhea. Foods high in soluble fiber include: applesauce, bananas (ripe), canned fruit, orange sections, boiled potatoes, white rice, products made with white flour, oatmeal, cream of rice, cream of wheat, and farina. Drink 8-10 glasses on non-alcoholic, un-caffeinated fluid a day to prevent dehydration.
Trastuzumab can cause heart problems, or worsen pre-existing heart problems, including congestive heart failure. Your heart function will be tested using a echocardiogram or MUGA scan prior to starting treatment with trastuzumab, and every couple of months while on treatment and after completion of treatment. Notify your healthcare provider if you have a sudden weight gain or swelling in the ankles or legs. If heart function decreases, trastuzumab will be stopped. The risk of heart problems is greater when trastuzumab is given in combination with anthracycline chemotherapy medications.
Trastuzumab use can also result in toxicity to the lungs, including swelling, fluid and/or scarring within the lungs. You should report any new or worsening shortness of breath, trouble breathing, cough, or fever, as these may be signs of lung toxicity.
Other Side Effects
Some less common side effects that have been reported include: headache, changes in taste and insomnia.
Exposure of an unborn child to this medication could cause birth defects, so you should not become pregnant or father a child while on this medication. Effective birth control is necessary during treatment and for at least 7 months after treatment. Even if your menstrual cycle stops or you believe you are not producing sperm, you could still be fertile and conceive. If you become pregnant within 7 months of receiving this medication, talk with your provider about the pregnancy registry for pregnancies after exposure to trastuzumab. You should not breastfeed while receiving this medication.
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