Nghiem Lab: UW Medicine, South Lake Union Campus
May 2, 2014
Ryan DoumaniDownload PDF
Pazopanib is a cancer medication in a family of drugs called tyrosine kinase inhibitors. A tyrosine kinase is a protein on the surface of a cell that transmits signals to the cell’s control center. Specifically, pazopanib targets vascular endothelial growth factor receptor (VEGFR) and platelet-derived growth factor receptor (PDGFR). In the setting of cancer, VEGFR and PDGFR can facilitate tumor cells to grow and divide. These two receptors help form new blood vessels (by a process called angiogenesis), which feed the tumor. This process of tumor angiogenesis is a hallmark feature of cancer as the human body loses control over the formation of new blood vessels. Pazopanib helps stop this process; it inhibits tumor growth by cutting off the fuel supply to the growing tumor cells. Without a supply of fresh blood and nutrients, the tumor cells cannot continue to grow and multiply.
Pazopanib is approved by the US-FDA for treatment of advanced renal cell carcinoma (kidney cancer) and soft tissue sarcoma, but not MCC. However, pazopanib has been reported in the medical literature to be successful in treating Merkel cell carcinoma in one patient. Based on this report, we have prescribed pazopanib for treatment of stage IV metastatic MCC either as monotherapy, or sometimes in combination with other treatments.
Pazopanib is a very expensive drug; a one-month supply usually costs around $10,000. Because this medication is not FDA-approved for the treatment of MCC, insurance companies may not readily cover it. Patients and their physicians often have to undergo a difficult and lengthy appeal process with their insurance companies to petition for pazopanib coverage. Although the appeal process can be laborious and time-consuming, petitions are often successful in obtaining coverage for at least a portion of the medication costs.
Several patients have been treated with pazopanib for advanced Merkel cell carcinoma. Formal analysis of data for outcomes is ongoing. Some people may see benefit from this treatment, although there is a clear subset of patients in which no clinical benefit was observed. While it has not been successful in all patients, a proportion of patients have had shrinkage and/or control of their disease, sometimes for several months to over a year.
Yes – as mentioned above, pazopanib may sometimes be used in combination with other medications and treatment regimens. However, because pazopanib blocks the formation of new blood vessels and thus would impair wound healing, pazopanib should not be taken while a patient is receiving radiation treatment. The medication should be stopped several days prior to and after any concurrent radiation treatment. Always consult your local oncologist before starting a new medication while on pazopanib, as this treatment may interact with some drugs.
Yes, we recommend that you be seen by your local oncologist every two weeks for the first two months, and then at least monthly afterwards. Because pazopanib can affect liver function, serum transaminases (ALT, AST) must be closely monitored during the course of treatment. Liver function can be checked with a simple blood draw at your physician’s office. ALT and AST should be monitored before initiation of treatment with pazopanib, and at weeks 3, 5, 7, 9. Thereafter, monitor at month 3 and month 4; periodic monitoring should then continue as clinically indicated. Your blood pressure should be checked regularly during treatment with this medicine. Your doctor may need to treat you if you develop high blood pressure while you are using this medicine. Symptoms of high blood pressure are blurred vision, dizziness, nervousness, headache, pounding in the ears, or a slow or fast heartbeat.
Pazopanib is taken in pill form by mouth as prescribed by your doctor. The usual starting dose is 800 mg/day, but this dose may be altered as recommended by your physician. Take pazopanib on an empty stomach, at least one hour before or two hours after a meal. Do not crush a pazopanib tablet. Swallow the whole pill. Crushing the pill may cause your body to absorb too much of the drug at one time.
Pazopanib is generally well tolerated in patients. We know of no evidence that pazopanib suppresses the immune system, unlike some other cancer treatments that are known to suppress immunity. The most common side effects of pazopanib include mild nausea and vomitting, diarrhea, fatigue, loss of appetite, weight loss, changes in hair or skin color, joint or muscle pain, and unusual or unpleasant taste in your mouth. Because pazopanib blocks the formation of new blood vessels, it inhibits normal wound healing. Thus, please notify your oncologist before you start pazopanib if you have any open or persistent wounds, or develop any during the course of your treatment.
Patients can remain on this medication for as long as there is ongoing clinical benefit. Clinical benefit will usually need to be assessed by your oncology team and will take into account both the effectiveness and the tolerability of the drug. The course of treatment is tailored to the patient on a case-by-case basis.
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September 13, 2019