Agree there is benefit in sparing serial structures in situations like chordoma… but this is where failing to account for the range uncertainties and biology can be most dangerous. We see this with brainstem necrosis in ependymoma. Additionally, conformality is better with photons in a lot of cases , depending on spot size and the need for robust optimization. Hubris and weak physics support are most dangerous trying to get cute with high gradients with protons… and these indications tend to be very specific and rare diseases. The low/intermediate dose sparing matters the same times it matters with photons (v20, heart dose, brain dose with large meningioma, retroperitoneal sarcoma abdominal dose, liver dose with B8 HCC etc…). These applications are more generalizable. While there are certainly cases where they are helpful with high dose near a serial organ, I don’t think this will be the most common application of this technology