What are the recommended treatment fields for desmoid tumors?

There is great clinical equipoise on how to treat desmoid tumors with radiotherapy. I apply general sarcoma princples to the CTV expansions for desmoids depending on their location. I find it helpful to obtain an MR to delineate the extent of infiltration (I am lucky in that I have access to an MR simulator). I usually apply a 3 cm margin longitudinally and a 1.5 cm margin axially to the GTV trimming off uninvolved structures such as bone and hollow viscus for the CTV in extremities. For the abd...