Desmoid Tumors

Desmoid tumors, also called aggressive fibromatosis or desmoid-type fibromatosis, are rare and often debilitating and disfiguring soft-tissue tumors. They are characterized by a growth pattern that can invade surrounding healthy tissues, including joints, muscle and viscera. While they can arise in any part of the body, the most common sites are the upper extremities (arm, forearm, and hand), lower extremities (hip, thigh, leg, and foot), abdominal wall, thoracic areas, and the head and neck.

The severity of a desmoid tumor can vary based on the location of the tumor and the aggressiveness of its growth pattern. Desmoid tumors can cause significant morbidities, including severe pain, internal bleeding, incapacitating loss of range of motion, and, in rare cases, death.

desmoid tumors in head neck hands abdominal wall leg

While desmoid tumors can occur in people between 15 and 60 years of age, they are most commonly diagnosed in young adults between 30-40 years of age. Women are also 2 to 3 times more likely to develop them than men. It is estimated that there are 1,000 to 1,500 new cases diagnosed each year in the United States.


While the cause of most desmoid tumors is unknown, most desmoid tumors have mutations in a gene called catenin beta-1, which controls activity of other genes; promotes growth, activity, and division of cells; and helps cells stick together to form tissues. Other desmoid tumors are caused by mutations in a gene called APC that causes Familial Adenomatous Polyposis (FAP). People with FAP are at high risk of developing abdominal desmoid tumors.

Current Treatments

There are currently no medicines approved for the treatment of desmoid tumors. Historically, desmoid tumors were treated with surgical resection, but this approach has become less favored due to a high recurrence rate after surgery. Doctors may also use systemic therapies, including chemotherapies, off-label to treat desmoid tumors.

Our Investigational Therapy

Nirogacestat is an oral, small molecule, gamma-secretase inhibitor that has been investigated in 24 patients with desmoid tumors across Phase 1 and Phase 2 clinical trials. SpringWorks is conducting the Phase 3 “DeFi” (Desmoid/Fibromatosis) trial, a double-blind, randomized, placebo-controlled, global clinical trial in adults with progressing desmoid tumors. Additionally, in collaboration with Children’s Oncology Group (COG), a Phase 2 clinical trial is evaluating nirogacestat in children and adolescents with progressive, surgically unresectable desmoid tumors.

The FDA granted Orphan Drug Designation for nirogacestat for the treatment of desmoid tumors and Fast Track and Breakthrough Therapy Designations for nirogacestat for the treatment of adult patients with progressive, unresectable, recurrent or refractory desmoid tumors or deep fibromatosis.

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Patient Foundation:

Image of Desmoid Tumor Research Foundation logo

The mission of The Desmoid Tumor Research Foundation is to aggressively fund research to accelerate the development of improved therapies, and ultimately find a cure for desmoid tumors. The foundation collaborates with dedicated researchers and clinicians worldwide to improve the lives of patients through education, awareness, and support.