Radiation therapy for pituitary gland tumours

Radiation therapy uses high-energy rays or particles to destroy tumour cells. It is sometimes used to treat pituitary gland tumours. Your healthcare team will consider your personal needs to plan the type and amount of radiation, and when and how it is given. You will probably receive other treatments.

Radiation therapy is given for different reasons. You may have radiation therapy to:

• destroy tumour cells left behind after surgery (called adjuvant therapy)
• destroy tumour cells in the body when surgery can’t be done
• help control the symptoms of functional tumours, which are tumours that make too many hormones

The following types of radiation therapy are most commonly used to treat pituitary gland tumours.

During external radiation therapy, a machine directs radiation through the skin and skull to the tumour and some of the tissue around it. It may be used to treat pituitary gland tumours that are not completely removed by surgery or when the tumour comes back after surgery. It can also be used when surgery can’t be done.

External radiation therapy works slowly on pituitary gland tumours. It can take months or even years before tumour growth and hormone levels are completely controlled.

External radiation therapy can be given daily (5 days a week) for 5 or 6 weeks. This is also called conventional radiation therapy.

Stereotactic radiosurgery is a type of external radiation therapy that delivers a high dose of radiation to a very specific area of the brain. This is usually done in one treatment. Sometimes the radiation is given in a few treatments.

Stereotactic radiosurgery allows doctors to target the pituitary gland tumour more closely than conventional radiation therapy. It tends to cause less damage to the brain and any normal pituitary gland that remains. The effects of stereotactic radiosurgery are often seen sooner than with conventional radiation therapy, but it can still take a few months to see the full benefits.

Stereotactic radiosurgery is most often used for small tumours that are away from the optic nerves. The high doses of radiation used in stereotactic radiosurgery can damage the optic nerves if they are too close.

Intensity-modulated radiation therapy (IMRT) is a type of external radiation therapy called conformal radiation therapy. It uses a special device to shape and aim many radiation beams at the tumour from different angles. The strength (intensity) of the radiation beams can also be changed. This reduces the amount of radiation that reaches sensitive areas of the brain, such as the optic nerve, the brain stem and the pituitary gland, while allowing a higher dose to be given to the tumour.

Radioisotope therapy is a type of internal radiation therapy, which means that radioactive materials are placed in the body. In radioisotope therapy, the radioactive material used is called a radioisotope. It travels through the body. Cancer cells take up the radioactive material, and the radioactive material destroys the cancer cells. The radioactive material is usually combined with a substance (a radiopharmaceutical) that targets specific molecules on the surface of cancer cells. Using the radiopharmaceutical allows the radiation to be delivered directly to the cancer cells and limits the effects of radiation on normal cells. Radioisotope therapy may be called targeted radiation therapy, systemic radiation therapy or radionuclide therapy.

PRRT is a type of radioisotope therapy rarely used to treat pituitary carcinoma. It uses a radioactive material, usually lutetium-177 (Lu-177), combined with a somatostatin analogue (octreotide or octreotate). This radiopharmaceutical is given through a needle into a vein (intravenously).

PRRT may be used for pituitary carcinoma when:

• surgery can’t be done
• some cancer remains after surgery
• the cancer has continued to grow (progressed) and spread (metastasized)

PRRT is only available at a few cancer centres in Canada. It can only be used with special approval from Health Canada or by taking part in a clinical trial. Talk to your doctor about whether PRRT is right for you.

Side effects can happen with any type of treatment for pituitary gland tumours, but everyone’s experience is different. Some people have many side effects. Other people have few or none at all.

During radiation therapy, the healthcare team protects healthy cells in the treatment area as much as possible. But damage to healthy cells can happen and may cause side effects. If you develop side effects, they can happen any time during, immediately after or a few days or weeks after radiation therapy. Sometimes late side effects develop months or years after radiation therapy. Most side effects go away on their own or can be treated, but some side effects may last a long time or become permanent.

Side effects of radiation therapy will depend mainly on the size of the area being treated, the specific area or organs being treated, the total dose of radiation and the treatment schedule. Some side effects of radiation therapy used for pituitary gland tumours are:

• fatigue
• hair loss
• skin problems
• vision changes
• nausea and vomiting
• problems with memory or thinking
• less hormones made by the pituitary gland than normal (hypopituitarism)

Tell your healthcare team if you have these side effects or others you think might be from radiation therapy. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them.

Find out more about radiation therapy and side effects of radiation therapy. To make the decisions that are right for you, ask your healthcare team questions about radiation therapy.