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Approaches to Treating Pituitary Tumors

Posted Aug 24 2008 1:49pm
ANNOUNCER: Acromegaly is a disease characterized by high levels of growth hormone in the body.

LAURENCE KATZNELSON, MD: Over 95 percent of cases of acromegaly are due to a tumor, which is a benign growth of the pituitary gland.

ANNOUNCER: The elevated levels of growth hormone in acromegaly lead to changes in soft tissues throughout the body. Other symptoms are related to the size of the tumor itself.

LAURENCE KATZNELSON, MD: The pituitary gland sits in a bony cavity at the base of the skull called the sella turcica. This sits about two inches behind the nasal bridge at the base of the brain. They tend to grow outwards and upwards. And upwards includes the area that controls the optic nerves. So if the tumor grows to the optic nerves, that can lead to visual disturbances. If the tumor grows outwards to the left and right, that can lead to changes in cranial nerve function called palsies.

ANNOUNCER: Headaches that can be disablingly painful, are also among the side effects from tumor growth.

LAURENCE KATZNELSON, MD: There are two major goals for the therapy. One is to reduce the tumor size in order to prevent the complications of the tumor on the local brain. The second goal is to lower the growth hormone levels, because it is the growth hormone that circulates through the blood and leads to the changes in the body. And we know that if you lower the growth hormone, we can improve many of these aspects of acromegaly.

ANNOUNCER: Surgery is often the first line of attack after a patient has been diagnosed with acromegaly. Success rates usually depend on the size of the tumor.

ANN DANOFF, MD: For the lucky people who have small tumors, there's a very good chance of having a surgical cure. Maybe as high as 80 percent or so. In contrast, in people who have larger tumors, and sometimes the tumors in addition to being big, they also spread out, in other directions. For those people the chance of having surgical cure are not so good. Maybe 50 or 60 percent. Certainly it can help by doing what we call debulking or simply decreasing the size of the mass

ANNOUNCER: Radiation is sometimes used when surgery does not cure the patient. But more typically, doctors turn to medicines. Drugs called dopamine agonists are sometimes used, especially when a tumor leads to increased secretion of the hormone prolactin, as well as growth hormone.

ANN DANOFF, MD: The place where they seem to have the best efficacy is in people who have a combination of growth hormone over-secretion and prolactin over-secretion, and that occurs in about 30 percent of people with acromegaly. And in those situations, you might have an effective tumor size reduction.

ANNOUNCER: More commonly, doctors use a drug called Sandostatin.

LAURENCE KATZNELSON, MD: When Sandostatin binds to the pituitary tumor, it has two effects. One is to normalize or lower the growth hormone secretion. The other one is the effect on the tumor size itself. Sandostatin usually prevents tumor growth; in fact, it is very uncommon that patients who receive Sandostatin will they have an increase in tumor size. What may happen in about 30 to 40% of patients is there is an actual reduction in tumor size, due to these direct effects from Sandostatin.

ANNOUNCER: Drugs in yet another category are called growth hormone receptor antagonists.

LAURENCE KATZNELSON, MD: These are molecules that bypass pituitary tumor altogether, circulate in the blood and go to everywhere that growth hormone will have its effects and block those effects, leading to improvement in the signs and symptoms of acromegaly. The medicine that is currently available in the United States is Somavert. This is a growth hormone receptor antagonist.

ANNOUNCER: Doctors say the growth hormone receptor antagonists can be effective in limiting the harmful effects of elevated growth hormone. However, in bypassing the tumor, the drug is not likely to suppress tumor growth.

ANN DANOFF, MD: I think the concern about the receptor antagonists are that it's unlikely that they will affect tumor shrinkage.

ANNOUNCER: Fighting acromegaly is a two-prong process. Doctors say they have good surgical and medical tools to counter elevations in growth hormone, and to limit the growth, or shrink, the tumors that are usually responsible for the disease.

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