Pituitary Adenoma: Classification and Treatment

What is classification for pituitary adenoma?

Pituitary adenomas, which are benign tumors, are classified but not staged like most cancers are. Classification explains how much tumor is in your body and what treatment can be used. Classification looks at the size of the tumor, where it is, and if it has grown into other areas near the pituitary gland. Tests like vision tests, checking your hormone levels, urine testing, biopsy, CT, and MRI scans may be done to help classify your tumor. Your providers need to know about your tumor and your health so that they can plan the best treatment for you.

How is pituitary adenoma classified?

Most pituitary adenomas are benign, meaning they are not cancer. Malignant (cancerous) tumors in the pituitary gland are very rare and can be called carcinoma. Only about 100 cases of pituitary cancer have been reported in medical literature. Often, pituitary adenomas are classified as:

• Macroadenomas- Greater than or equal to 1 centimeter (cm) in size. These can grow into the bony areas near the pituitary gland (like to the bones of the skull).
• Microadenomas- Less than 1 cm in size.

They are also classified as:

• Secreting- Adenomas that make hormones, also called functional.
• Non-secreting- Adenomas that do not make hormones, also called non-functional.

Other types of tumors (both benign and malignant) can start in the pituitary gland. These include teratomas, germinomas, and choriocarcinomas.

Staging and classification of pituitary adenomas is based on:

• The size of your tumor on imaging tests and what is found after surgery.
• If there is spread to other organs (metastasis).
• If the tumor is secreting or non-secreting.
• If it is secreting, and which hormone it is releasing.
• If the tumor is causing any symptoms, like changes to your sight.

How are pituitary adenomas treated?

Treatment for pituitary adenomas depends on things like it's classification, your age, overall health, and testing results. Your treatment may include:

• Surgery.
• Radiation Therapy.
• Stereotactic Radiosurgery.
• Treatment with Medications.
• Clinical Trials.

Malignant pituitary adenomas are often treated with surgery and radiation therapy.

Surgery

Surgery is the common treatment for pituitary adenomas.

• Surgery for non-secreting macroadenomas: Removes excess tissue and relieves pressure from the adenoma on nearby tissues.
• Surgery for hormone-secreting adenomas: Surgery often helps slow down the amount of hormone being made.

Surgery for pituitary tumors can be done in a few ways:

• Transsphenoidal surgery: This is the most common surgery for pituitary adenomas. An incision (cut) is made on the inside of the upper lip just above the teeth or along the septum (bridge) of the nose. The surgeon makes a cut through the base of the sphenoid sinus to get to the pituitary gland.
  • For microadenomas, this surgery has high cure rates with few side effects. Sometimes, this surgery can lead to less hormone being made by the pituitary gland, cerebral spinal fluid (CSF) leaks leading to meningitis, and loss of vision. These side effects are rare and happen in less than 1 out of 100 surgeries done by an experienced neurosurgeon.
  • This type of surgery does not work as well for larger tumors, especially macroadenomas that are very fibrous or are too far toward the back of the head.
• Endoscopic surgery: Uses a fiberoptic camera (an endoscope) to make a small incision or hole. The surgeon can get to the pituitary fossa through the nostril (nose). Small instruments are passed through the small hole to remove the pituitary adenoma. This surgery works well for small tumors. It is less invasive than a transsphenoidal surgery, with quicker recovery time and a low chance of side effects. This procedure may not be helpful for larger tumors or tumors that are not in a good spot.
• Craniotomy: This is used for larger tumors that go beyond the normal pituitary gland. The neurosurgeon makes cuts through the bones of the skull to get to the pituitary gland. There is a higher risk of neurologic side effects and a longer recovery time compared to the other surgeries.

Central diabetes insipidus is a common side effect of any surgery for the pituitary gland. In diabetes insipidus, the pituitary gland does not make enough anti-diuretic hormone (ADH), which causes a loss of water in the urine. In most cases of diabetes insipidus after surgery, the problem goes away by itself after one to two weeks. Sometimes this problem can be permanent (long-term). To treat it, you need to take an ADH replacement (also known as vasopressin), often as a nasal spray.

Radiation Therapy

Radiation treatment is the use of high-energy x-rays to kill tumor cells. Pituitary tumors can be well controlled with radiation therapy. Radiation does not stop the pressure that macroadenomas place on nearby structures like surgery does, and hormone levels fall more slowly after radiation therapy than they do after surgery. In most cases, radiation therapy is only given:

• To patients who have tumor left behind after surgery.
• For patients who have their pituitary adenoma come back after surgery (recurrence).
• For patients whose adenomas are not in a good place for surgery.
• In patients who would not tolerate surgery.

Stereotactic Radiosurgery

Stereotactic radiosurgery delivers radiation therapy to brain tumors in a very precise (exact) way. This method treats a tumor with large doses of radiation over a few days, or even in a single treatment, instead of spreading the treatment out over weeks. This kind of radiation can give high doses of radiation to a specific area of the brain while lowering the amount of radiation that is given to healthy brain tissue.

Stereotactic radiosurgery has been tested in the treatment of pituitary adenomas. Stereotactic radiosurgery helps lower hormone levels of secreting adenomas quickly. However, since higher doses are given with each treatment, more side effects have been seen with stereotactic radiosurgery, like damage to the optic nerves. For this reason, stereotactic radiosurgery is not often used to treat pituitary adenomas. Sometimes, stereotactic radiosurgery can be used when a pituitary adenoma has recurred (come back after treatment).

Treatment with Medications

For some pituitary adenomas that secrete hormones (functional adenomas), treatment with medication instead of surgery or radiation can be helpful. In these cases, medications are often the first treatment.

• For pituitary adenomas that make the hormone prolactin, the medications most used are bromocriptine (Parlodel) and cabergoline (Dostinex). Lisuride and pergolide mesylate have also been used. These medications are similar to a chemical made in the brain called dopamine, which normally stops the pituitary gland from making prolactin until it is needed. This causes less prolactin to be made in the pituitary adenoma, which can shrink the tumor. The shrinking takes days to months. If the medication is stopped, the adenoma will go back to making prolactin and can grow again. Medication therapy for a prolactin-secreting pituitary adenoma is a lifelong treatment.
• Pituitary adenomas that make growth hormones can be treated with drugs such as octerotide, lanreotide, pasireotide (somatostatin analogs), or pegvisomant (growth hormone antagonist). In general, these medications work to slow down or stop the body from making certain hormones. 

Clinical Trials

You may be offered a clinical trial as part of your treatment plan. To find out more about current clinical trials, visit the OncoLink Clinical Trials Matching Services.

Making Treatment Decisions

Your care team will make sure you are part of choosing your treatment plan. This can be overwhelming as you may be given a few options to choose from. It feels like an emergency, but you can take a few weeks to meet with different providers and think about your options and what is best for you. This is a personal decision. Friends and family can help you talk through the options and the pros and cons of each, but they cannot make the decision for you. You need to be comfortable with your decision – this will help you move on to the next steps. If you ever have any questions or concerns, be sure to call your team.

You can learn more about pituitary adenoma at OncoLink.org.