As doctors and scientists have learned more about desmoid tumors, they’ve developed new treatments. Targeted therapies work by targeting or blocking proteins in desmoid tumor cells. Several treatments are available, but only one has recently been approved by the United States Food and Drug Administration (FDA).

In this article, we’ll cover four facts about targeted therapies for desmoid tumors. We’ll discuss what these drugs are, how they work, and when you may be treated with one. To learn more about how a targeted therapy may fit into your desmoid tumor treatment plan, talk to your doctor.

1. Targeted Therapies Block Desmoid Tumor Cell Proteins

Targeted therapies are one of the most commonly used methods to treat cancer. Desmoid tumors aren’t cancerous. However, they are caused by gene changes (mutations) that make cells grow uncontrollably. You may hear desmoid tumors referred to as “aggressive fibromatosis” for this reason.

Scientists have developed targeted therapies to target or block proteins in desmoid tumor cells. Without these proteins, the cells no longer receive signals telling them to grow and divide. This lack of signaling causes the desmoid tumors to stop growing or shrink.

Targeted therapies are considered systemic therapies because they can affect the entire body. Although these drugs are systemic, they are designed to target desmoid tumor cells specifically. In theory, they leave your other healthy cells alone. This is why targeted therapies have the potential to have fewer side effects compared to chemotherapy drugs, which can affect healthy cells in addition to tumor cells.

Many people with desmoid tumors are watched carefully by their health care team. Before starting treatment, the team uses scans to see if the tumor grows. This approach is called active surveillance. Your desmoid tumor care team may recommend treatment with targeted therapy if your tumor progresses or is causing symptoms or other problems. If your tumor progresses, your health care team will help you understand if targeted therapies are a good option for you.

2. Nirogacestat Is the Only FDA-Approved Targeted Therapy for Desmoid Tumors

In November 2023, the FDA approved nirogacestat (Ogsiveo) as the first treatment specifically for adults with progressing desmoid tumors. Nirogacestat is known as a gamma-secretase inhibitor. It works by blocking the enzyme gamma-secretase, preventing it from activating another protein called Notch. Scientists believe desmoid tumor cells use Notch proteins to grow and divide.

Doctors prescribe nirogacestat to people with desmoid tumors who need systemic treatment and when surgery isn’t a good option. Nirogacestat is taken as a pill twice daily.

Researchers studied nirogacestat in large, regulated studies known as clinical trials. They found that nirogacestat slowed desmoid tumor progression compared to a placebo (inactive treatment used for comparison in clinical trials). Additionally, a study cited in The New England Journal of Medicine found that 41 percent of participants who took nirogacestat had significant desmoid tumor shrinkage (by at least 30 percent). Only 8 percent of those who took the placebo had significant tumor shrinkage.

When choosing a desmoid tumor treatment option, your doctor or oncologist (cancer specialist) will weigh the benefits and risks. It’s important to discuss possible side effects and how the medication may affect your quality of life. Be sure to talk to your oncology team if you’re concerned about starting a new treatment.

In clinical trials, the most commonly reported side effects of nirogacestat treatment included:

• Diarrhea
• Hair loss
• Abdominal pain and nausea
• Headache
• Cough, shortness of breath, and upper respiratory infections
• Fatigue
• Ovarian toxicity (for example, fertility issues)

3. Tyrosine Kinase Inhibitors Are Used Off-Label for Desmoid Tumors

Tyrosine kinase inhibitors (TKIs) are a widely used targeted therapy for treating tumors and cancers. They block kinases — proteins that cells use to send growth signals. Blocking these proteins with TKIs may prevent desmoid tumors from growing.

Doctors treat desmoid tumors with several TKIs. It’s important to note that the FDA hasn’t approved any TKIs specifically for desmoid tumors. Instead, doctors prescribe them off-label, meaning they’re used for conditions other than what they were originally approved for.

Below are some TKIs that are used to treat desmoid tumors. Your health care team can help you understand why a specific drug might be recommended and the benefits and risks of the available treatments.

Sorafenib

Sorafenib (Nexavar) is a TKI approved for treating certain thyroid, kidney, and liver cancers. One study cited in the journal Cancer Discovery found that 33 percent of desmoid tumors had significant shrinkage (at least 30 percent) with sorafenib treatment. However, the authors noted that 20 percent of people who received a placebo also had their tumors significantly shrink.

Potential side effects of sorafenib include:

• Diarrhea
• Loss of appetite, nausea, and vomiting
• High blood pressure
• Skin rashes or dry and itchy skin
• Mouth sores

Pazopanib

Another TKI, pazopanib (Votrient), is typically used to treat soft tissue sarcomas (cancers) and kidney cancer. One clinical trial from France assigned participants with desmoid tumors to pazopanib or the chemotherapy drugs vinblastine and methotrexate. The authors found that more than 80 percent of people who received pazopanib and 54 percent of those who received chemotherapy were progression-free at six months. This means that their cancer didn’t grow or spread during this time.

Common side effects of pazopanib include:

• Fatigue
• Diarrhea
• High blood pressure
• Loss of color in your skin and hair

Imatinib and Nilotinib

Doctors also prescribe imatinib (Gleevec) to treat certain soft tissue sarcomas. A study from the European Journal of Cancer found that imatinib treatment may slow and even stop disease progression for several months.

Side effects of imatinib treatment include:

• The buildup of fluid in your body
• Nausea
• Fatigue
• Diarrhea
• Muscle aches

Some participants were unsuccessful with imatinib treatment. The researchers gave them the TKI nilotinib (Tasigna). Overall, seven of the eight participants had slowed or stopped desmoid tumor progression.

Nilotinib may cause:

• Itchy skin or rashes
• Headaches
• Easy bruising and bleeding
• Muscle aches
• Abdominal pain
• Fatigue

Sunitinib

Sunitinib (Sutent) is a TKI used to treat a certain type of soft tissue sarcoma, known as a gastrointestinal stromal tumor (GIST), in people who can’t take or progress on imatinib. An older study cited in the journal Investigational New Drugs studied 19 people treated with sunitinib. They found that eight of the participants had stable disease. This means their desmoid tumors had only minor growth, minor shrinkage, or no change in growth.

Side effects of sunitinib include:

• Cough or shortness of breath
• Easy bruising and bleeding
• Loss of appetite
• Dizziness
• Headaches
• Diarrhea or constipation
• High blood pressure

4. New Targeted Therapies for Desmoid Tumors Are Currently in Clinical Trials

Researchers from the American Cancer Society are also studying new targeted therapies for treating desmoid tumors.

Around 85 percent of sporadic desmoid tumors (uninherited tumors) have mutations in the CTNNB1 gene. This gene provides instructions for making beta-catenin — a protein involved in cell growth. CTNNB1 mutations prevent the breakdown of beta-catenin. As the protein builds up inside cells, it tells them to keep growing. This buildup eventually causes desmoid tumors to form.

Tegavivint is a new drug in clinical trials for desmoid tumors. It works by blocking beta-catenin from binding to another protein known as TBL1. Researchers believe this may help stop tumors from growing.

If you’re interested in joining a clinical trial studying a new treatment for desmoid tumors, talk to your oncologist. Targeted therapies are a new way to treat desmoid tumors. These treatments focus on specific proteins that help the tumors grow, which can lead to fewer side effects compared to traditional chemotherapy. Always talk to your health care team to find out which treatment might be best for you.

Read more about specific medications in this list of treatments for desmoid tumor.

Talk With Others Who Understand

MyDesmoidTumorTeam is the social network for people with desmoid tumors and their loved ones. On MyDesmoidTumorTeam, members come together to ask questions, give advice, and share their stories with others who understand life with desmoid tumor.

Have you taken a targeted therapy for your desmoid tumor? What side effects did you experience? Share your story in the comments below, or start a conversation by posting on your Activities page.