Dr P N Plowman
St Bartholomew's Hospital, London

Conventionally fractionated modern Radiotherapy has a long and established good track record at controlling both the endocrine (hormonal) and tumourous growth problems associated with pituitary adenoma. Such radiotherapy is commonly used following incomplete surgical resection or instead of surgery. Control of the endocrine effects may be slow (say, two years plus) but long-term control results are good.

Such conventional radiotherapy takes places over a period of five weeks in a standard radiotherapy department. The patient is immobilised in a non-claustrophobic plastic mask such that beams from several directions (usually through the forehead and through both temporal regions) crossfire on the pituitary, thus concentrating the dose just on the pituitary adenoma and any extensions it may have. The reason that patients come up every weekday for five weeks treatment is that small daily doses are 'kindest' to the surrounding, normal nervous system. Complications of this conventionally fractionated radiotherapy are few. Optic nerve problems are very rare indeed now that modern knowledge of the radiation tolerance of the optic apparatus is known. Other neural complications are few. Late endocrine dysfunction of the pituitary can occur and is more likely where the patient has had a large tumour (which in itself has compromised pituitary hormonal function) or additional surgery has further jeopardised normal endocrine function. The risk of the radiotherapy itself causing a tumour within the skull is a controversial issue but is probably not more than 1% risk and maybe less.

Problems involving recurrent pituitary adenomas, particularly those with extensions out of the pituitary fossa (for example into the cavernous sinuses), are commonly treated by the new technique of stereotactic radiosurgery. Of the three possible radiosurgical methods - charge particle beams, Gamma Knife and X-Knife - we at St Bartholomew's Hospital have experience of over a decade in the photon methods. Specifically, we have compared the Gamma Knife with the linear accelerator (X-Knife) technology for treating difficult pituitary adenomas.

Our conclusion at present is that, for 'first time around' pituitary radiotherapy, conventional radiotherapy is usually best. However, for recurrent tumours and particularly extensions into the cavernous sinus, stereotactic radiosurgery (perhaps optimally performed using the Gamma Knife/Unit facilities) is optimal therapy.