Endocrine Abstracts

Introductıon

Recent studies suggest temozolomide as an effective treatment modality in invasive pituitary adenomas that did not respond to conventional treatments. In this case series, we present three cases of invasive pituitary adenomas that did not respond to conventional medical treatments and radiotherapy and were subsequently treated with temozolomide.

Cases

The first patient had an invasive prolactinoma that did not respond to the maximum doses of cabergoline, the patient underwent trans-frontal surgery and conventional radiotherapy. On immunohistochemical staining, methylguanine DNA methyltransferase ( MGMT) was negative. The treatment with temozolomide 150 mg/m² for five days every 28 days was started. Three and 20 months later, a significant decrease in prolactin level and a 50 and 95% decrease in tumor size were observed, respectively, and remained unchanged after five years of treatment. The second patient with acromegaly that could not be controlled by 2 transsphenoidal surgeries, conventional radiotherapy, and 40 mg octreotide LAR. Treatment with 150 mg/m² of temozolomide for five days every 28 days was started. However, despite a small decrease in serum IGF-1 and GH levels, a reduction in tumor size did not ensue. The third patient had a non-functioning pituitary adenoma and underwent 2 transsphenoidal and one transcranial surgery and subsequent gamma knife radiosurgery, she developed 3. and 6. cranial nerve palsies, so temozolomide treatment was started at a dose of 150 mg/m² for five days every 28 days. However, temozolomide treatment was discontinued due to the absence of response after 3 months. Nevertheless, MGMT immunostaining was not performed in both cases.

Dıscussıon

Studies suggest temozolomide treatment as an effective treatment modality in invasive pituitary adenomas non-responsive to currently available conventional treatments. However, most of the information regarding the effect of temozolomide in invasive non-functional adenomas and GH secreting adenomas are sparse. Low tumoral expression of MGMT was suggested as a sign of favorable response to temozolomide. Although most GH-secreting adenomas are reported to express low levels of MGMT, our patients with acromegaly did not respond to temozolomide treatment. On the other hand, the patient with non-functioning pituitary adenoma did not respond to temozolomide as well. Therefore, temozolomide treatment may not be effective in cases with acromegaly and non-functioning invasive pituitary adenomas.