Stereotactic radiosurgery. IX. Craniopharyngioma: durable complete imaging responses and indications for treatment

The previous literature on radiosurgical treatment for craniopharyngioma is sparse, because the involvement of the radiosensitive optic chiasm within the target volume (in most cases) precludes safe high single dosage. The relocatable frame, introduced at St Bartholomew's Hospital in 1989, utilizes the dosimetric advantages of stereotactic isodosimetry to treat with the safer fractionated therapy; this may well be the most advantageous methodology for larger and critically situated tumours around the chiasm. We believe that radical high dose radiosurgery (either single dose or fractioned) has a role in the treatment of selected craniopharyngiomas and our first six patients treated are presented here. There were two patients with discrete, small, solid lesions and both achieved complete responses that maintain at 1-2 years. The other four patients are more difficult to assess: one patient was treated for disease within the clivus and there is no evidence of disease progression at 18 months; one child, who was treated by fractionated radiosurgery to a solid component of a complex partly solid, partly cystic craniopharyngioma enveloping the chiasm, suffered tumour progression and died; one patient died of a hemisphere cerebovascular accident, which we believe was unrelated to the therapy, and one patient suffered malignant change 1 year after radiosurgery (a time point that we consider too early to ascribe to the radiation from this therapy). We discuss the indications for this technology in the multi-disciplinary therapy of this complex disease. It seems clear that, for low lying lesions, well below the optic apparatus, radiosurgery has an important role (possibly a primary radical radiotherapeutic role for small bulk solid masses). Where there is an inoperable solid tumour enveloping the chiasm the dosimetric advantages of the x-knife (10% internal dose gradient versus the 100% internal dose gradient of the gamma knife) plus the fractionation facility using the relocatable frame, argue for the x-knife (linear accelerator) as being the optimal radiosurgery system. These arguments also apply to acoustic neuroma therapy and preservation of hearing, the other clinical situation where a radiosensitive special sensory nerve lies within the target volume.