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What is Panitumumab: Uses, Dosage, Side Effects and More

Created at:1/13/2025

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Panitumumab is a targeted cancer medication that helps fight colorectal cancer by blocking specific proteins that help cancer cells grow. It's given through an IV infusion at a hospital or cancer treatment center, where your medical team can monitor you closely throughout the process.

This medicine belongs to a group called monoclonal antibodies, which work like guided missiles that target cancer cells while leaving most healthy cells alone. Your doctor will typically recommend panitumumab when other treatments haven't worked as well as hoped, or alongside other cancer medications to make treatment more effective.

What is Panitumumab?

Panitumumab is a laboratory-made antibody that mimics your body's natural immune system proteins. It specifically targets and blocks a protein called EGFR (epidermal growth factor receptor) that sits on the surface of cancer cells and helps them multiply and spread.

Think of EGFR as a lock on cancer cells, and panitumumab as the key that fits into that lock and stops it from working. When this protein gets blocked, cancer cells can't receive the signals they need to grow and divide rapidly.

This medication is completely synthetic, meaning it's created in a laboratory rather than derived from human or animal sources. The manufacturing process ensures consistency and safety in every dose you receive.

What is Panitumumab Used For?

Panitumumab treats metastatic colorectal cancer, which means cancer that started in your colon or rectum and has spread to other parts of your body. Your doctor will only prescribe this medication if your cancer cells have a specific genetic makeup that makes them likely to respond well.

Before starting treatment, you'll need a special genetic test called KRAS testing to check whether your cancer cells have certain mutations. This test is crucial because panitumumab only works effectively in people whose cancer cells don't have these specific KRAS mutations.

Your oncologist might recommend panitumumab as a single treatment or combine it with other chemotherapy drugs like FOLFOX or FOLFIRI. The combination approach often helps improve treatment outcomes by attacking cancer cells through multiple pathways simultaneously.

Sometimes doctors prescribe panitumumab when other treatments have stopped working effectively, giving you another option to fight the cancer. It's also used as a first-line treatment in certain situations where genetic testing shows your cancer is likely to respond well.

How Does Panitumumab Work?

Panitumumab works by attaching itself to EGFR proteins on cancer cell surfaces, essentially blocking the signals that tell cancer cells to grow and multiply. This targeted approach makes it a relatively precise treatment compared to traditional chemotherapy that affects both healthy and cancerous cells.

When cancer cells can't receive growth signals through EGFR, they become much less aggressive and may even start dying off naturally. This process doesn't happen overnight, which is why you'll need multiple treatments over several months to see the full benefits.

The medication is considered a moderately strong cancer treatment, more targeted than traditional chemotherapy but still powerful enough to cause significant side effects. Your body's immune system may also start recognizing and attacking cancer cells more effectively once panitumumab disrupts their growth patterns.

Unlike chemotherapy drugs that work throughout your entire body, panitumumab primarily affects cells that have high levels of EGFR proteins. This selective targeting helps explain why it can be effective against certain cancers while causing fewer widespread side effects.

How Should I Take Panitumumab?

Panitumumab is always given as an IV infusion at a hospital, cancer center, or specialized clinic where trained medical staff can monitor you closely. You cannot take this medication at home or as a pill, as it needs to be delivered directly into your bloodstream.

Your healthcare team will insert a small needle into a vein in your arm, or you might have a central line or port if you're receiving multiple cancer treatments. The infusion typically takes about 60 to 90 minutes, during which you'll sit comfortably in a reclining chair.

Before each infusion, you'll usually receive premedication to help prevent allergic reactions. These might include antihistamines, steroids, or other medications that help your body tolerate the treatment better.

You don't need to avoid food before treatment, but eating a light meal beforehand can help prevent nausea. Staying well-hydrated by drinking plenty of water in the days leading up to your infusion also helps your body process the medication more effectively.

Plan to spend about 3 to 4 hours at the treatment center for each visit, including preparation time, the actual infusion, and a brief observation period afterward. Bringing a book, tablet, or having a family member accompany you can help make the time pass more comfortably.

How Long Should I Take Panitumumab For?

The duration of panitumumab treatment varies greatly depending on how well your cancer responds and how your body tolerates the medication. Most people receive infusions every two weeks, but your specific schedule will depend on your individual treatment plan.

Your oncologist will continue treatment as long as your cancer is responding well and you're not experiencing severe side effects that outweigh the benefits. Some people receive panitumumab for several months, while others may need it for a year or longer.

Regular scans and blood tests will help your medical team determine whether the treatment is working effectively. If scans show that tumors are shrinking or remaining stable, you'll likely continue with the current schedule.

Treatment might be paused or stopped if you develop serious side effects that don't improve with supportive care, or if scans show that the cancer is growing despite treatment. Your doctor will discuss these possibilities with you and help you understand what to expect.

What Are the Side Effects of Panitumumab?

Panitumumab can cause various side effects, with skin-related problems being the most common and often the most noticeable. Understanding what to expect can help you manage these effects and communicate effectively with your healthcare team.

The most frequent side effects you might experience include skin reactions that can be quite uncomfortable but are usually manageable with proper care:

  • Acne-like rash on your face, chest, and back that may appear within the first few weeks of treatment
  • Dry, cracked skin that might become painful or infected if not properly moisturized
  • Changes in your hair texture, making it dry, brittle, or curly
  • Nail changes including pain, swelling, or infections around your fingernails and toenails
  • Increased sensitivity to sunlight, making you burn more easily
  • Fatigue that might make daily activities more challenging
  • Diarrhea that can range from mild to severe
  • Nausea and occasional vomiting

These common side effects often improve as your body adjusts to treatment, and your healthcare team can provide medications and strategies to help manage them effectively.

Some people experience more serious side effects that require immediate medical attention, though these are less common:

  • Severe allergic reactions during or shortly after infusion, including difficulty breathing, chest tightness, or swelling
  • Serious skin infections that develop from scratching or inadequate care of rashes
  • Severe dehydration from persistent diarrhea or vomiting
  • Eye problems including severe dryness, pain, or vision changes
  • Electrolyte imbalances that can cause weakness, confusion, or heart rhythm problems
  • Lung problems including shortness of breath or persistent cough

Your medical team will monitor you closely for these serious effects and provide immediate treatment if they occur. Most side effects are manageable with proper medical support and don't require stopping treatment permanently.

Who Should Not Take Panitumumab?

Panitumumab isn't suitable for everyone, and your doctor will carefully evaluate whether it's the right choice for your specific situation. Certain conditions and circumstances make this treatment inappropriate or potentially dangerous.

You should not receive panitumumab if you have KRAS-mutated colorectal cancer, as genetic testing has shown this medication is ineffective in these cases. Your doctor will always order this genetic test before recommending treatment.

People with severe heart, lung, or liver problems may not be good candidates for panitumumab, as these conditions can make it harder for your body to process the medication safely. Your medical team will review your complete medical history before making treatment decisions.

If you've had severe allergic reactions to other monoclonal antibodies or similar medications, panitumumab might not be appropriate for you. Your doctor will discuss your allergy history in detail to assess the risks.

Pregnant women should not receive panitumumab, as it can harm the developing baby. If you're of childbearing age, you'll need to use effective contraception during treatment and for several months afterward.

People with active, severe infections may need to wait until these are fully treated before starting panitumumab, as the medication can affect your immune system's ability to fight infections.

Panitumumab Brand Names

Panitumumab is sold under the brand name Vectibix in the United States and most other countries. This is the only commercially available form of this medication, manufactured by Amgen.

Unlike some medications that have multiple brand names or generic versions, panitumumab is only available as Vectibix. This ensures consistency in dosing and quality, as all patients receive the same formulation regardless of where they receive treatment.

Your insurance company and healthcare providers will refer to this medication by either name - panitumumab or Vectibix - and they mean exactly the same thing. Some medical staff prefer using the generic name, while others use the brand name more frequently.

Panitumumab Alternatives

Several other medications work similarly to panitumumab for treating colorectal cancer, though each has its own specific uses and side effect profiles. Your oncologist will choose the best option based on your cancer's characteristics and your overall health.

Cetuximab (Erbitux) is the most similar alternative, as it also targets EGFR proteins on cancer cells. Like panitumumab, it only works in people whose cancer cells don't have KRAS mutations, but it's given weekly instead of every two weeks.

Bevacizumab (Avastin) works through a different mechanism by blocking blood vessel growth that feeds tumors. This medication can be used regardless of KRAS mutation status, making it an option for people who can't receive panitumumab.

Newer medications like regorafenib (Stivarga) and TAS-102 (Lonsurf) are oral options that might be considered when IV treatments like panitumumab are no longer effective. These work through different pathways and are typically used later in treatment sequences.

Immunotherapy drugs like pembrolizumab (Keytruda) might be options for people whose colorectal cancer has specific genetic features called microsatellite instability. Your doctor will test for these features to determine if immunotherapy is appropriate.

Is Panitumumab Better Than Cetuximab?

Panitumumab and cetuximab are both effective treatments for colorectal cancer, and research shows they work similarly well in most situations. The choice between them often depends on practical factors like dosing schedule and side effect differences rather than one being definitively better.

Panitumumab has a slight advantage in that it's given every two weeks instead of weekly, which means fewer trips to the treatment center. This can be particularly helpful if you live far from your cancer center or have transportation challenges.

Some studies suggest panitumumab may cause slightly fewer severe allergic reactions compared to cetuximab, though both medications can cause significant skin side effects. The overall effectiveness in shrinking tumors and extending survival appears to be very similar between the two drugs.

Your oncologist will consider factors like your other medications, treatment schedule preferences, and insurance coverage when choosing between these options. Both are considered excellent treatments when used in the right patients.

Frequently asked questions about Panitumumab (intravenous route)

Panitumumab can be used in people with heart disease, but requires careful monitoring and possibly dose adjustments. Your cardiologist and oncologist will work together to ensure your heart condition remains stable during treatment.

The medication can occasionally cause changes in electrolyte levels, particularly magnesium and potassium, which can affect heart rhythm. Your medical team will check these levels regularly and provide supplements if needed to keep your heart functioning properly.

If you have severe heart failure or recent heart attacks, your doctors may recommend alternative treatments or delay panitumumab until your heart condition is more stable. Each situation is evaluated individually to balance cancer treatment benefits with heart health risks.

If you miss a scheduled panitumumab infusion, contact your oncology team immediately to reschedule as soon as possible. Don't wait until your next regularly scheduled appointment, as maintaining consistent treatment timing is important for effectiveness.

Your healthcare team will typically try to reschedule you within a few days of your missed appointment. They may also adjust your future scheduling slightly to get back on track with your treatment plan.

Missing one dose occasionally won't ruin your treatment, but try to keep missed appointments to a minimum. Your medical team understands that emergencies happen and will work with you to maintain the best possible treatment schedule.

If you experience symptoms like difficulty breathing, chest pain, severe skin reactions, or dizziness during your panitumumab infusion, alert your nurse immediately. Treatment centers are well-equipped to handle these situations and will stop the infusion right away.

Your medical team will likely give you medications like antihistamines, steroids, or epinephrine to counteract the reaction. Most infusion reactions can be managed effectively when caught early and treated promptly.

After a reaction, your doctor may recommend premedications before future infusions or might slow down the infusion rate to help your body tolerate the treatment better. Some people can continue treatment successfully after adjusting the approach.

You can stop panitumumab when your doctor determines that the benefits no longer outweigh the risks, or when scans show that your cancer is no longer responding to treatment. This decision is always made collaboratively between you and your oncology team.

Some people choose to stop treatment if side effects become too difficult to manage, even if the cancer is still responding. Your quality of life is an important consideration in these decisions, and your medical team will support whatever choice you make.

Never stop panitumumab on your own without discussing it with your oncologist first. They can help you understand the implications and ensure you have alternative treatment options if needed.

Most other medications can be taken safely with panitumumab, but you should always inform your oncologist about any new prescriptions, over-the-counter drugs, or supplements you want to start. Some medications may interact or require dose adjustments.

Blood thinners, heart medications, and drugs that affect your immune system may need special monitoring when combined with panitumumab. Your medical team will coordinate with your other doctors to ensure all your medications work well together.

Always bring a complete list of all medications and supplements to every appointment, including doses and timing. This helps your healthcare team provide the safest and most effective treatment possible.

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