Long-term follow up of a patient with a recurrent desmoid tumor that was successfully treated with proton beam therapy: A case report and literature review

Desmoid tumors are benign, but may have a locally invasive tendency that commonly results in local recurrence. Most occur on the body trunk or extremities, whereas a head and neck desmoid tumor is relatively rare. The efficacy of radiotherapy has been suggested and 50–60 Gy is used for unresectable or recurrent desmoid tumors, but there are few reports of use of particle beam therapy. However, since this tumor occurs more often in younger patients compared to malignant tumors and the prognosis is favorable, there may be an advantage of this therapy. We treated a male patient with a head and neck recurrent desmoid tumor with proton beam therapy (PBT) at a dose of 60 Gy (RBE). This patient underwent surgical resection as initial treatment, but the tumor recurred only six months after surgery, and resection was performed again. After PBT, the tumor gradually shrank and complete remission has been achieved for 10 years without any severe late toxicity. Here, we report the details of this case, with a review of the literature. We suggest that PBT may reduce the incidence of second malignant tumors by reducing the dose exposure around the planning target volume.