How would you approach radiotherapy planning for a pediatric patient with Ewing sarcoma of the spine (vertebral body primary)?

Per the recent AEWS 1031 protocol:

GTV1 is defined as the visible and/or palpable disease defined by physical examination, CT, MRI, and/or PET prior to any surgical debulking or chemotherapy.

GTV2 is defined as a residual visible or palpable tumor as assessed by CT, MRI, PET, or physical exam after induction chemotherapy with or without surgery. For unresected tumors, GTV2 includes the pre-chemotherapy extent of disease in bone, and the post-chemotherapy extent of disease in soft tissue.

At a minimum, CTV1 is defined as the entire vertebral body. PTV1 is the CTV1 volume with an institution-specific margin of approximately 0.5 cm to account for day-to-day variation in set-up and physiologic motion.

For the field-reduction boost, CTV2 is defin...