Do I need any blood tests while taking Xalkori?
Yes, you will need blood tests while you take Xalkori to help monitor your liver and kidney function, red and white blood cell counts, and in some cases, your electrolytes or blood sugar levels. These tests are done to help follow your response to treatment, look for possible side effects, and adjust your drug dose, if needed.
Your doctor may also order a blood test to determine if you are pregnant. Xalkori can cause harm to an unborn baby.
Two of the most common types of blood tests ordered in patients being treated for cancer are:
- Complete Blood Count (CBC): helps to monitor your red and white blood cell counts and types. The CBC can help to alert your doctor to problems like anemia (low red blood cells) or infections (low white blood cells).
- Metabolic profile (blood chemistry panel): measures fats (lipids), proteins, sugar (glucose), electrolytes (such as potassium, magnesium, sodium, and calcium), and certain enzymes. These tests can help monitor the function of organs such as your liver, kidney or heart.
Why do I need blood tests for Xalkori treatment?
Based on your blood test results, your doctor may need to reduce your Xalkori (crizotinib) dose, or temporarily or permanently stop treatment. This will help to minimize any dangerous side effects. Do not change the dose or stop treatment unless your healthcare provider tells you to.
Here are some of the tests your doctor may order:
Complete Blood Count (CBC)
Red blood cells, white blood cells, platelets
Your doctor may order a blood test known as a complete blood count (CBC) with a differential. This test looks at the number and types of blood cells. You may require this blood test weekly, monthly or more often, especially if you develop a fever or infection.
- It can help to tell your healthcare provider if you have low red blood cells (RBC), which can lead to anemia. A low RBC count can mean that adequate oxygen is not being delivered to the tissues throughout your body.
- Low platelet counts, also known as thrombocytopenia, may cause trouble with blood clotting and lead to bleeding. Platelets help stop bleeding by plugging up blood vessel injuries. The risk of bleeding increases when platelet levels drop below a certain number.
- A low number of white blood cells may increase your risk for infections. The types of WBC’s monitored may include neutrophils, lymphocytes, monocytes, basophils, and eosinophils. Neutrophils are very important and if they drop too low (absolute neutrophil count < 500) your risk of infection is much higher.
Blood Chemistry Panel (metabolic profile)
In some people, Xalkori can cause liver toxicity that can be very severe or deadly. Your doctor will order tests to monitor your liver function every 2 weeks during the first 2 months of treatment, then once a month, or more, as needed. Tell your doctor before you start treatment if you have any liver problems.
These liver function tests look at liver enzymes known as ALT (alanine transaminase) and AST (aspartate aminotransferase), total bilirubin and alkaline phosphatase levels.
Tell your doctor if you have any type of liver problems before you start treatment. If you have moderate or severe liver disease, your doctor may decide to lower your dose of Xalkori. Your doctor may look at your aspartate aminotransferase (AST) and total bilirubin levels to decide if a dose adjustment is needed.
Tell your healthcare provider right away if you get any of the following new or worsening symptoms, which may indicate liver toxicity:
- yellowing of your skin or the whites of your eyes
- severe tiredness (fatigue)
- dark or brown (tea color) urine
- nausea or vomiting
- decreased appetite
- pain on the right side of your stomach
- bleeding or bruising more easily than normal
Tell your doctor before treatment if you have any type of kidney problems. If you have severe kidney disease you might need to take a lower dose of Xalkori.
Your doctor may order these blood tests to assess your kidney function.
- The glomerular filtration rate (GFR) is a number that can tell your doctor how well your kidneys are removing wastes and fluid from the blood.
- High levels of serum creatinine can indicated worsening kidney function. Creatinine is a waste by-product from muscles and is excreted through the kidneys.
- When Blood Urea Nitrogen (BUN) levels rise in the blood, it suggests that your kidney function is declining and cannot excrete urea nitrogen which comes from the breakdown of protein in foods.
Your doctor will use a calculated number called the creatinine clearance (CrCl) to determine if you need dose adjustments of Xalkori for kidney disease. CrCl is calculated using inputs such as your age, weight, height, sex and serum creatinine level.
Your doctor may order blood chemistry tests that measure the electrolytes in your body like sodium, potassium, chloride, magnesium, as well as bicarbonate. These substances help to keep your body’s fluid levels normal and help the function of your organs such as your heart, muscles, and other organs. Your doctor may also check your glucose (blood sugar) levels.
Tell your doctor right away if you have trouble with swallowing, vomiting, or diarrhea during treatment with Xalkori. Severe nausea, vomiting and diarrhea can occur with Xalkori and may lead to dehydration. Dehydration can lower your levels of electrolytes and can be dangerous. Your doctor will give you medicine to help lower nausea and vomiting when you start Xalkori treatment.
If you have significant vomiting or diarrhea, your doctor may order oral or intravenous rehydration solutions to help replace your fluids and electrolytes.
Tell your healthcare provider right away if you feel dizzy or faint or have abnormal heartbeats or if you take any heart or blood pressure medicines. Also let them know if you have heart problems, including a condition called long QT syndrome.
If needed, your doctor will determine if you are pregnant before starting treatment with Xalkori. They can determine your pregnancy status by ordering a blood test or a urine test. Xalkori can cause harm to an unborn baby when given to a pregnant woman.
Talk to your doctor about effective contraception (birth control) for both you and your partner during treatment.
How long until I get my lab tests with Xalkori?
Unclear or delayed test results can cause worry for anyone. You should be able to see your lab test results online from the lab as soon as they are available. This usually does not take longer than one week, but can vary. Ask your doctor how long until your lab tests are back.
- Ask for a copy of your lab results and go over these with your doctor to better understand your progress.
- Your lab results will show what your number is and what the normal range is for that particular test (and lab).
- If you have questions about any lab results, contact your healthcare team right away.
This is not all the information you need to know about Xalkori (crizotinib) for safe and effective use and does not take the place of your doctor’s directions. You may need different tests than the ones listed here. Review the full Xalkori information and discuss this information and any questions you have with your doctor or other health care provider.
- Xalkori (crizotinib) prescribing inforamtion. Revised Sept. 2021. Pfizer Inc. New York, NY. Accessed March 4, 2022 at https://labeling.pfizer.com/ShowLabeling.aspx?id=676#S2.5
- Understanding Your Lab Test Results. American Cancer Society. Accessed March 4, 2022 at https://www.cancer.org/treatment/understanding-your-diagnosis/tests/understanding-your-lab-test-results.html
- National Kidney Foundation. Tests to Measure Kidney Function, Damage and Detect Abnormalities. Accessed March 4, 2022 at https://www.kidney.org/atoz/content/kidneytests
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