What does radiotherapy do?

Radiotherapy is sometimes used as part of the overall treatment for pituitary tumours (also called pituitary adenomas).

The aim of radiotherapy treatment for patients with pituitary tumours is to control the growth of the tumour (or any remaining tumour after surgery) and prevent it enlarging. In some cases, radiotherapy also results in shrinkage of the tumour, but this can take many months or years to happen.

Although radiotherapy treatment is most often used for patients with cancer, people with pituitary tumours do not have cancer; their tumours are benign.

Pituitary tumours grow very slowly and tend to respond to radiotherapy slowly as well. Because of this, if radiotherapy treatment is required, it does not need to be given urgently within days or weeks of surgery and can safely be given months after the operation.

What exactly is radiotherapy?

Radiotherapy uses X-rays to treat disease and it works by damaging the DNA in the nucleus of any cells that it passes through.

Although cells can continue to live for some time with damaged DNA, eventually cells either repair the damage and survive, or, if the damage is too great, the cell dies. This cell death happens sometime after the radiation is delivered, often after the cell has divided a few times, many weeks, months or years after the treatment.

Normal body cells are better able to repair radiation damage than tumour cells and by delivering the radiotherapy using repeated small dose treatments; the chance of permanent damage to your own normal body cells is reduced.

In addition, by giving many small treatments, the total dose that can safely be delivered to the tumour is higher, thus increasing the chances of success.

Radiotherapy is delivered using high-energy X-ray machines, called linear accelerators (Linacs) which are similar to CT scanners. They focus an X-ray beam onto the pituitary tumour and surrounding area, from several different angles, one at a time.

Because the radiotherapy source is external, it does not make you radioactive. It is perfectly safe for you to be with other people, including children, throughout your weeks of treatment (although not during the radiotherapy itself).

External radiotherapy is usually given as an outpatient. It is planned and supervised by a clinical oncologist (a cancer specialist with training in radiotherapy treatment).

Why would I need to have radiotherapy?

It is not always possible to remove the whole of the pituitary tumour during surgery without running the risk of damaging surrounding structures, such as the optic nerves (the nerves that come from the eye and enable us to see) or major blood vessels. This is particularly true of larger tumours. Although pituitary tumours are normally benign (non-cancerous), they do tend to grow and if even a few cells remain after surgery, they can be the seed for a recurrence of the tumour in the same area.

Following surgery, you will undergo further scanning (MRI or CT) and blood tests. The multidisciplinary team (including an endocrinologist, neurosurgeon and radiotherapist) looking after you will then review your case and decide if radiotherapy is necessary.

In general, radiotherapy is considered for people:

  • Who have evidence of persisting tumour outside the pituitary fossa (the space where the pituitary gland sits) following surgery
  • Whose tumour is secreting a hormone that continues to be raised in blood tests following surgery despite treatment with drugs
  • Whose pituitary tumour re-grows (this would be some time after surgery, perhaps following a second operation)

If your post-surgery scan shows minimal persistent tissues within the pituitary fossa only, then you would not require radiotherapy. You will be followed up with annual scans, blood tests and visual field checks.