By Mayo Clinic Staff

Monoclonal antibody medicines are treatments that use the body's germ-fighting immune system against diseases, including cancer.

If your healthcare professional recommends a monoclonal antibody medicine as part of your cancer treatment, find out what to expect from this therapy. Learn enough so that you feel comfortable asking questions and making decisions about your treatment. Work with your healthcare professional to decide whether a monoclonal antibody medicine may be right for you.

An antibody is a protein made by cells in the immune system. The immune system helps the body find and get rid of germs and other cells that shouldn't be in the body. The immune system is made up of cells, tissues and organs. The parts work together to fight germs and diseases.

When immune system cells find a germ or another cell that shouldn't be in the body, the immune system cells can make antibodies. The antibodies then find and stick to the diseased cells. When an antibody sticks to a diseased cell, it can damage the diseased cell. It also can attract other immune system cells to come and damage the diseased cell.

Monoclonal antibodies are proteins made in a lab. They work much like the antibodies made by the immune system. Monoclonal antibodies can be made so they stick to certain cells, such as cancer cells.

Monoclonal antibody medicines work by sticking to cancer cells and causing them to die. Exactly how the cells die depends on the type of medicine. There are different monoclonal antibody medicines for different types of cancer. The medicines work in different ways.

When a monoclonal antibody medicine sticks to cancer cells, it may:

• Damage the cancer cells and cause them to die.
• Stop the cancer cells from growing.
• Stop the cancer cells from making new blood vessels.
• Alert other immune system cells to kill the cancer cells.
• Mark the cancer cells so the immune system cells can find them.
• Bring cancer-killing medicine to the cancer cells.
• Bring radiation to the cancer cells.

Many monoclonal antibodies have been approved for treating different types of cancer. Clinical trials also are studying new medicines and new uses for existing monoclonal antibodies.

Most monoclonal antibodies are given through a vein. How often you have treatment depends on your cancer and the medicine you get. Some monoclonal antibody medicines may be used in combination with other treatments, such as chemotherapy or hormone therapy.

Some monoclonal antibody medicines are a part of standard treatment plans. Others are experimental and are used only when other treatments have not been successful.

Monoclonal antibody treatment for cancer can cause side effects. Some side effects are rare but can be serious. Talk to your healthcare professional about what side effects are linked to the medicine you're getting. Discuss the potential benefits and side effects to decide whether this is the right treatment for you.

More common side effects caused by monoclonal antibody medicines include:

• Allergic reactions.
• Flu-like symptoms, including chills, tiredness, fever, and muscle aches and pains.
• Nausea and vomiting.
• Diarrhea.
• Skin rashes.

Rare but serious side effects of monoclonal antibody medicines may include:

• Infusion reactions. Severe allergy-like reactions can happen. Very rarely, they can lead to death. You may receive medicine to block an allergic reaction before you start treatment. Infusion reactions usually happen while treatment is being given or soon after. Your healthcare team watches you closely for a reaction.
• Heart conditions. Certain monoclonal antibodies increase the risk of high blood pressure, congestive heart failure and heart attacks.
• Lung conditions. Some monoclonal antibodies are linked to a higher risk of inflammatory lung disease.
• Skin conditions. Sores and rashes on your skin can lead to serious infections in some cases. Serious sores also can happen in the mouth.

Discuss your cancer treatment options with your healthcare team. Together you can weigh the benefits and risks of each treatment and decide whether a monoclonal antibody treatment is right for you.

Questions to ask your healthcare team include:

• Have my cancer cells been tested to see if a monoclonal antibody medicine might help? Tests of your cancer cells can often tell if monoclonal antibody treatments might help your specific cancer.
• Has the monoclonal antibody medicine shown a clear benefit? Ask about evidence of the treatment's effect in studies. Did it slow cancer growth? Did it shrink the cancer? Is this a first line of treatment? Or is it only used when others don't work?
• What are the likely side effects of monoclonal antibody treatment? With your healthcare team, you can decide whether the potential side effects of treatment are worth the likely benefit.
• Do the potential benefits outweigh the risks? Also consider asking what might happen if you choose not to have monoclonal antibody treatment.
• How much will monoclonal antibody treatment cost? Monoclonal antibody treatments can be expensive.
• Is monoclonal antibody treatment available in a clinical trial? Clinical trials, which are studies of new treatments and new ways to use existing treatments, may be available to you. A clinical trial may give you a chance to try new monoclonal antibody medicines. Ask whether any clinical trials may be open to you.