Technical considerations for noncoplanar proton-beam therapy of patients with tumors proximal to the optic nerve.

Purpose: To investigate technical feasibilities of noncoplanar proton-beam therapy (PBT) on dose reduction to critical organs.

Material And Methods: The degree of mechanical precision, rotational limitations of the gantry and the treatment couch were evaluated, and dose-volume histograms were compared for noncoplanar and coplanar PBT. Following these studies, three patients with tumors proximal to the optic nerve underwent noncoplanar PBT.

Results: Noncoplanar PBT offered advantage in dose reduction to the optic nerve when compared to coplanar therapy. This advantage was more significant if the tumor reduced in size during treatment. None experienced radiation injury to the optic nerve during a short follow-up time of 7-12 months.

Conclusion: Noncoplanar PBT appears to reduce doses to organs at risk.