Dr Michael Brada
Royal Marsden Hospital, London

Dr Brada is a radiation oncologist who specialises in the treatment of benign tumours. He evaluates current methods of treatment, aiming to make them more effective, with fewer side-effects.

Current treatment

The Pituitary gland lies adjacent to the brain, optic chiasm and carotid arteries. Surgery is normally the first line of treatment, but due to the surrounding structures and the size of the tumour, total excision is difficult. With incomplete removal re-growth is possible; at this point repeat surgery or Radiotherapy may be offered. So when is the best time to offer radiotherapy? Some retrospective studies have been carried out, and they demonstrate the radiotherapy's effectiveness in controlling tumours, but not when it is best to be treated with radiotherapy.

Conventional irradiation is administered from three directions, entering the head at the hairline of each temple and the hairline of the forehead. Each treatment lasts a few minutes, and the whole course is daily for a 5-week period. Side-effects during treatment include temporary hair loss (only at the three points mentioned), tiredness (especially towards the end) and an altered sense of taste and smell. These should resolve within a 2-month period.

Factors determining tumour control after radiotherapy include whether the tumour is treated after initial diagnosis and surgery or at the time of recurrence, its size, and the level of hormone secreted. Retrospective data from the Royal Marsden Hospital demonstrate that radiotherapy at the time of presentation gives better results. It may take months or years for Growth hormone (GH) to drop to what is considered normal range. The levels of GH prior to radiotherapy determine the time taken to reach normal levels.

Side-effects

The potential side-effects of radiotherapy are to the pituitary gland itself and the surrounding structures, the optic chiasm and the brain. Most patients have no visual impairment following radiotherapy; 1-2% may have some impairment, due to irradiation of the optic nerves and chiasm. Small doses of irradiation in each treatment minimise side-effects, as the risk of damage to normal brain is associated with high single doses.

Cognitive impairment means difficulty in the processes of comprehension, judgement, memory and reasoning. One study compared two groups with pituitary tumours: one received radiotherapy while the other had none. A third control group had no pituitary complaints. There was no difference in cognitive impairment between the two groups of patients with pituitary tumours, whether they had radiotherapy or not. There was, however, a significant difference between the control group and the groups with pituitary tumours. The Pituitary tumour and the overall package of treatment, rather than radiotherapy, appeared to be a factor in mild cognitive impairment. With correctly administered radiotherapy at conventional doses there is no or negligible risk of serious damage to normal brain.

Radiotherapy can reduce levels of the remaining hormones being secreted by the pituitary gland. Approximately 10 years after radiotherapy, 10-30% of patients who have normal pituitary function will require hormone replacement therapy due to deficiency.

Radiation is associated with an increased incidence of developing other tumours in the brain: a risk of 2% at 10-20 years after radiotherapy, and a relative risk of 9 compared with a 'normal' population. It is not clear whether these figures relate to an increased predisposition to development of tumours within this group of people.

Developments

There are new developments in the way irradiation is administered. Stereotactic irradiation is a high precision, localised method, using three-dimensional treatment planning. A head frame is used rather than a mask, allowing more precise immobilisation. Stereotactic irradiation is given in small repeated doses, as conventional radiotherapy. Occasionally treatment has been given in one dose (described as radiosurgery). This is experimental and, on current evidence, potentially more damaging, without any information that it is more effective.

Radiotherapy is an effective method of management but not without side-effects. The results of having radiotherapy must be weighed against the outcome of not having treatment.