Pazopanib (Votrient) is a targeted therapy used to treat specific advanced cancers. It is classified as a Tyrosine Kinase Inhibitor (TKI), meaning it blocks the activity of certain enzymes called tyrosine kinases within cells. These enzymes act like switches, sending signals that tell cancer cells to grow, divide, and form new blood vessels. By inhibiting these switches, Pazopanib interferes with molecular pathways that fuel cancer growth and survival, helping to slow the progression of advanced or metastatic disease.
How Pazopanib Targets Cancer Growth
Pazopanib is a multi-targeted receptor tyrosine kinase inhibitor that blocks multiple signaling pathways simultaneously. It achieves its therapeutic effect primarily by preventing angiogenesis, the formation of new blood vessels that tumors rely on for oxygen and nutrients. It acts by binding to and inhibiting several receptors on the surface of cancer cells and surrounding blood vessel cells.
The main targets include all three Vascular Endothelial Growth Factor Receptors (VEGFR-1, VEGFR-2, and VEGFR-3). Blocking these VEGFRs prevents the chemical signals that trigger new blood vessel growth toward the tumor mass. Pazopanib also inhibits the Platelet-Derived Growth Factor Receptors (PDGFR-alpha and PDGFR-beta) and the c-Kit receptor, which promote cancer cell proliferation and survival.
By blocking this spectrum of targets, Pazopanib starves the tumor by cutting off its blood supply and hindering growth signals. This mechanism leads to a reduction in tumor blood flow, increased cancer cell death, and inhibition of tumor growth.
Primary Medical Uses
Pazopanib is approved for treating two types of advanced cancer. The primary indication is for advanced Renal Cell Carcinoma (RCC), the most common form of kidney cancer. Pazopanib is often used as a first-line therapy or following other treatments for patients whose disease has spread or cannot be surgically removed.
The second established use is for advanced Soft Tissue Sarcoma (STS). These cancers develop in supportive tissues like muscle, fat, and nerves. For STS, Pazopanib is typically indicated for patients who have already received prior chemotherapy.
The Treatment Protocol
Pazopanib is administered orally as a tablet once daily. The standard starting dose is 800 milligrams (mg) per day, taken continuously until disease progression or unacceptable side effects occur. Tablets must be swallowed whole and never crushed, broken, or chewed.
The timing relative to food is critical for absorption. Pazopanib must be taken on an empty stomach: at least one hour before or two hours after a meal. Taking the medication with food significantly increases drug exposure, heightening the risk of severe side effects. If a dose is missed, it should only be taken if the next scheduled dose is more than 12 hours away; otherwise, the dose should be skipped.
Regular medical monitoring is necessary because Pazopanib affects several body systems. Liver function tests (LFTs) are checked weekly for the first month, then every two to four weeks for the next few months, and periodically thereafter.
Blood pressure must be well-controlled before starting therapy and monitored weekly during the first cycle due to the risk of hypertension. Cardiac monitoring, including baseline and periodic electrocardiograms (ECGs), is also recommended to watch for potential QT prolongation.
Understanding and Handling Side Effects
Patients frequently experience a range of side effects, some common and manageable, others requiring immediate medical attention. Fatigue is often reported; patients are advised to prioritize rest and light activity. Gastrointestinal issues are also prevalent, including nausea and vomiting, which can often be controlled with prescribed anti-sickness medications.
Diarrhea is a common side effect requiring proactive management to prevent dehydration. Dietary adjustments, such as avoiding high-fiber or greasy foods, are recommended, and anti-diarrheal medications like loperamide may be necessary after consulting a healthcare provider. A noticeable, non-harmful cosmetic side effect is a change in hair color, often lightening or graying.
More serious side effects necessitate immediate communication with the oncology team. Signs of liver toxicity, such as yellowing of the skin (jaundice), dark urine, or significant upper abdomen pain, require urgent evaluation and LFTs.
Severe or persistent hypertension, sudden chest pain, shortness of breath, or unexplained bleeding (indicating a blood clot or hemorrhage) are serious concerns. Timely communication about any new or worsening symptoms is essential for safely managing Pazopanib therapy.