Pituitary adenoma treatment: drugs or surgery?

Medical management requires the collaboration of several specialists, namely a neurosurgeon, an otorhinolaryngologist (ENT), an endocrinologist and a radiation oncologist.

Effective treatment consists of either neurosurgery, medication and radiation to the tumour, or a combination of these methodologies. The aim of therapy is to remove the tumour and bring the body's hormones back into balance.

Surgical treatment

Neurosurgery is especially needed in situations where the pituitary tumor is pressing on the optic nerves or if it is a functional adenoma that produces large amounts of certain hormones.

Two main neurosurgical approaches are used.

Endoscopic transnasal transsphenoidal approach

The tumour is removed using a very special method where there is no need to perform a craniotomy, i.e. to open the patient's skull. The tumour is approached through the nose and sinuses.

The advantage of this operation is that no other part of the brain is damaged during the operation. The scar is so small that it is hardly visible.

The limitations of this procedure are adenomas that are too large or overgrow into the surrounding brain structures.

Classical open transcranial approach (craniotomy)

The tumor is surgically removed through a hole in the skull. The procedure is slightly riskier, but is the only solution for giant adenomas or other medical contraindication to the transsphenoidal approach.

Radiation

Radiation therapy is based on irradiating the tumor with a high-energy source of radioactive radiation. It is usually used after surgery to stabilize the bed after tumor removal or as a stand-alone treatment modality.

It is also used for recurrent tumors that regrow after surgical removal.

The therapeutic effect and complications of this form of treatment are not immediate. It takes years to take effect.

The methods of radiation therapy include:

• Stereotactic radiosurgery

This is a single application of a thin radioactive beam of very high energy. Using imaging techniques, the size, shape and volume of the tumour to be irradiated are precisely determined.

The precision of such a "cut" is very high, accurate to 1 mm. The advantage is that the surrounding healthy tissue is protected from the radiation. A high effective dose of radiation is sent to the tumour to stop its growth.

This therapy uses a special technique, namely a linear accelerator, cyberknife or gamma-knife, which are only available at some specialised centres.

• External radiotherapy

External radiotherapy also uses radioactive radiation from a linear accelerator, but the radiation is given in series and in smaller doses.

A complete series of treatments takes several weeks. It is given either on an outpatient basis or during hospitalisation.

The disadvantage is that with this type of radiation, surrounding organs, healthy pituitary cells and brain tissue or nerves near the tumour may be affected.

• Intensity modulated radiation therapy (IMRT)

In this type of radiation, the beams are specially shaped to hit as much of the tumor tissue as possible and spare the surrounding healthy cells.

In addition to the angle of the beams, the dose, i.e. the energy and power, to the tumour is adjusted. The advantage is that the surrounding organs are protected.

• Proton beam therapy

This type of irradiation uses positively charged ions, i.e. protons, which have the advantage that they lose their energy quickly after hitting the target. The tissue behind the tumour is therefore not affected by the strong radiation.

This method of therapy is not yet widely available. Patients are usually sent to specialised proton centres.

Medication

The aim of medication (i.e. treatment with drugs) is to block the increased secretion of certain hormones or, in their absence, to replace them. Some types of tumour may shrink after appropriate treatment.

Treatment of prolactinoma

Prolactinoma is the most common pituitary tumour ever. Normal prolactin levels range from 5-20 ng/ml. In prolactinoma, levels are elevated up to 150 ng/ml, but can be extremely elevated to 10,000 ng/ml.

The production of prolactin is blocked by another hormone, dopamine. Therefore, substances with a similar effect to dopamine, namely cabergoline and bromocriptine, are used to treat prolactinoma. After treatment, the tumour even shrinks to disappear.

Possible side effects are not serious and usually include drowsiness, dizziness, nausea, stuffy nose, vomiting, diarrhea or constipation, confusion and depression.

Treatment of ACTH overproduction (Cushing's disease)

When ACTH is overproduced, the body's secretion of the hormone cortisol is stimulated. A drug that controls the excessive secretion of cortisol from the adrenal glands is, for example, ketoconazole or osilodrostat.

The most common side effects include heart rhythm disturbances.

Treatment of growth hormone (STH) overproduction

Up to three types of drugs are available to treat STH-secreting adenomas.

The first type is a somatostatin analogue, such as octreotide. Its effect is to reduce growth hormone production and it can also shrink the tumour. It is injected, once a month.

There is also an oral formulation of octreotide which has similar effectiveness. It is not yet available in some countries.

Side effects include nausea, vomiting, diarrhoea, stomach pain, dizziness or headache. The treatment sometimes promotes the formation of gallstones and can also worsen diabetes mellitus.

The second type of treatment is somatostatin receptor antagonists. This means in practice that the effects that the hormone has on the cells of the body are blocked. One such drug is pegvisomant. Its serious side effect is liver damage.

A third possible drug is dopamine agonists, similar to prolactinoma therapy.

Pituitary hormone replacement

Sometimes the growth of the adenoma itself can cause reduced hormone production or hormone levels are low as a result of neurosurgery or radiotherapy.

For example, desmopressin is used as a substitute for vasopressin (ADH) in neurohypophysis.

Watch and wait method

For non-functioning or small tumors, doctors choose this watch and wait method.

Of course, the patient undergoes regular MRI scans and is followed up by an endocrinologist.