Lay Abstract
Desmoid tumors (DT) are aggressive tumors predominantly affecting young people. They can potentially cause significant pain, decreased limb mobility and invalidity. In certain individuals, DTs can even be life threatening. Although some tumors may spontaneously shrink or remain stable without any treatment, patients with growing tumors will require either surgery or chemotherapy. Over the last decades, a number of drugs including hormonal blockers like tamoxifen, intravenous chemotherapy like weekly methotrexate and vinblastine and doxorubicin and targeted therapy like imatinib have shown various degrees of success in treating DTs. Recently, two new targeted drugs, sorafenib and pazopanib, were approved to treat DTs. In clinical trials, DTs treated with either drug showed significant tumor shrinkage and control over time. Since their approval and routine use in practice, there remains many unknowns. Duration of treatment is still ill defined. Outcomes of patients who failed or stopped sorafenib or pazopanib are unknown. Predicting which patients may respond to these novel drugs is still a challenge. The main objective of this multicenter Canadian retrospective study is to collect real world data to better guide physicians in managing these rare tumors.
Scientific Abstract
Desmoid tumors (DT) are locally aggressive neoplasms affecting predominantly young adults and are associated with considerable morbidity ranging from functional limb impairment, chronic opioid use, anxiety and depression and rarely mortality. Although a minority of DTs will undergo spontaneous remission throughout their disease course, a significant proportion of patients will require either surgery or systemic therapy. Over the last decades, a number of agents have shown some evidence of activity ranging from hormonal blockers like tamoxifen to chemotherapy like weekly methotrexate and vinblastine and doxorubicin and to targeted agents like imatinib. However, no convincing high level data was ever produced with these agents. Sorafenib and pazopanib, two protein kinase inhibitors, were the first drugs to have shown activity in randomized phase II and phase III trials. For sorafenib and pazopanib, the reported objective response rates were 33% and 37% respectively and the 6-month progression-free survival rates were 89% and 86%. Both drugs were well tolerated and associated commonly with rashes (73%), fatigue (67%), hypertension (55%), and diarrhea (51%). Although these new agents are now widely used for the treatment of DTs, there remains many unknowns. Duration of treatment is still ill defined. Outcomes of pediatric patients or patients who failed or stopped TKIs are unknown. Predicting which patients may respond to these novel therapies is still a challenge. The main objective of this multicenter Canadian retrospective study is to collect real world data to better guide physicians in managing these rare tumors. Overall response, 6-month and 12-month progression free rates and adverse events will be evaluated. Outcomes of patients stopping or failing TKIs will also be assessed.
