Crizotinib, known by its brand name Xalkori, is a targeted therapy used in cancer treatment. This oral medication focuses on specific molecular pathways within cancer cells, distinguishing it from traditional chemotherapy.
Crizotinib’s Mechanism of Action
Crizotinib functions as a tyrosine kinase inhibitor (TKI), a drug class that blocks specific proteins called tyrosine kinases. In certain cancers, genetic alterations cause these proteins to become overactive, leading to uncontrolled cell growth and division.
Crizotinib specifically targets and inhibits the anaplastic lymphoma kinase (ALK) and ROS1 proteins. When abnormally active due to genetic rearrangements, ALK and ROS1 drive tumor growth. By blocking these proteins, crizotinib disrupts the signaling pathways cancer cells use for survival and multiplication.
Medical Uses for Crizotinib
Crizotinib is approved for treating specific cancers with particular genetic alterations. It is primarily used for non-small cell lung cancer (NSCLC) in adults whose tumors test positive for an ALK or ROS1 gene rearrangement.
It also treats ALK-positive anaplastic large cell lymphoma (ALCL) in pediatric and young adult patients when the cancer has returned or is unresponsive to other treatments. Additionally, crizotinib is indicated for ALK-positive inflammatory myofibroblastic tumor (IMT) in pediatric patients, especially when the tumor cannot be surgically removed or has recurred. A specific genetic test is required to identify these ALK or ROS1 gene rearrangements in a patient’s tumor, ensuring the cancer is likely to respond.
Common Side Effects and Management
Patients undergoing crizotinib treatment may experience common side effects. Vision disturbances are frequently reported, including flashes of light, floaters, or blurred vision. These effects are often mild.
Gastrointestinal issues are also prevalent, encompassing nausea, diarrhea, vomiting, and constipation. These can often be managed with dietary adjustments or over-the-counter medications. Fluid retention, or edema, can cause swelling in the hands, feet, or face. Lifestyle adjustments, such as reducing salt intake and elevating affected limbs, can help manage this.
Fatigue is another common side effect, often managed by balancing rest with gentle activity. Other reported effects include decreased appetite, upper respiratory infections, dizziness, and peripheral neuropathy, which is numbness or tingling.
Serious Health Warnings
Crizotinib treatment carries risks of serious adverse reactions requiring immediate medical attention. Liver problems can occur, and in rare cases, have been fatal.
Serious lung inflammation, known as interstitial lung disease (ILD) or pneumonitis, is another concern. This condition can manifest as new or worsening shortness of breath, cough, or fever. Patients with these symptoms should seek prompt medical evaluation, and if diagnosed, crizotinib should be permanently discontinued.
Heart-related issues, such as an irregular heartbeat (QT interval prolongation) and a slow heart rate (bradycardia), have also been observed. Report any new or severe symptoms, especially those affecting the heart or breathing, to a doctor immediately.
Administration and Monitoring
Crizotinib is administered orally, usually twice a day. Capsules should be swallowed whole. If a dose is missed, take it as soon as remembered, unless it is less than six hours until the next dose. If vomiting occurs after a dose, do not take an extra dose; continue the regular schedule.
Routine monitoring assesses the drug’s effects and the body’s response. This includes regular blood tests for liver function and blood cell levels. Electrocardiograms (EKGs) periodically monitor heart rhythm. Periodic eye exams are recommended, especially if new visual symptoms arise. Imaging scans also evaluate the cancer’s response to treatment.