Feasibility of pre-operative mTOR inhibitor Sirolimus in children and young adults with desmoid tumor

Background: • Desmoid tumor represents an intermediate grade neoplasm with a striking predilection for locally invasive growth and recurrence following resection • More effective, well-tolerated non-surgical treatment options are needed • Current approaches • If feasible, watchful waiting is the preferred approach • 20-30% spontaneous regression • In situations where treatment is indicated, the following approaches are utilized • Surgery is the primary approach if minimal morbidity is anticipated • Medical therapies • Cytotoxic drugs • Tyrosine kinase inhibitors • Hydroxyurea • Gamma secretase inhibitors • mTOR Inhibitor Rationale • Desmoid tumor is well-known to be associated with deregulation of the APC/β-catenin pathway • Deregulation of the mTOR cell proliferation/survival pathway may play an important role in tumor biology when the APC/βcatenin pathway is disrupted • The mTOR inhibitor sirolimus is attractive as a potential targeted therapy for desmoid tumor • Well-tolerated in children and young adults • Can be given orally in tablet or liquid formulatio