Why is this relevant? Because so many ACTH-secreting adenomas of the pituitary invade other structures. The study states:
Clinically significant pituitary tumours occur in approximately 1 in every 1000
individuals ...between 35-55% of adenomas demonstrate invasion into bone,
dura or adjacent structures such as the cavernous or sphenoid sinuses or
According to this article, some tumors display aggressive behavior and are resistant to current treatments. They can require the patient to have multiple operations and/or radiation therapy in order to control the growth.
Temozolomide works for some patients in the control of their tumors. Widely used for other brain tumors, its success has been mixed when applied to aggressive pituitary tumors. In this study, the relationship of "MGMT immunohistochemistry in two patients with aggressive pituitary tumours treated with temozolomide" is important. "[L]ow expression was demonstrated in a patient who responded to temozolomide whereas high expression was seen in another patient with no response to this agent 20."
When enlarging their study to 88 tissue samples from previous patients, the authors found their "work suggests that low MGMT protein expression, as assessed by immunohistochemistry, may be associated with a clinical response to temozolomide in aggressive pituitary tumours and supports the brief report of Kovacs et al."
The bottom line: MGMT immunohistochemistry is a promising technique for predicting the applicability of temozolomide for controlling aggressive pituitary tumors.
Ann I. McCormack, Kerrie L. McDonald, Anthony J. Gill, Susan J. Clark, Morton G. Burt, Kirsten A. Campbell, Wilton J. Braund, Nicholas S. Little, Raymond J. Cook, Ashley B. Grossman, Bruce G. Robinson, Roderick J. Clifton-Bligh (2008). Low 0(6)-methylguanine-DNA methyltransferase (MGMT) expression and response to temozolomide in aggressive pituitary tumours
Clinical Endocrinology DOI: 10.1111/j.1365-2265.2008.03487.x