Temozolomide monotherapy and in combination
Temozolomide, an oral alkylating agent typically used in chemotherapeutic treatment of astrocytoma and melanoma, has shown promise as monotherapy [62, 63], and in combination with pasireotide [64], as a treatment for aggressive pituitary adenomas and carcinomas.
To date, ~30 cases of pituitary adenoma have been treated with temozolomide (including ten ACTH-secreting adenomas). Overall reported response rate is approximately 60 % [62, 63]; however, information on temozolomide treatment of pituitary adenomas is currently confined to individual case reports and three case series [65–67]. An inverse relationship between tumoral O6-methylguanine-DNA methyltransferase (MGMT) immunoexpression and response to temozolomide therapy has been suggested, but not confirmed in all studies [62, 65, 67, 68].
Temozolomide may represent a viable treatment option for aggressive corticotroph adenomas refractory to surgery, radiotherapy, or other medical treatment. In tumors that responded to temozolomide, the clinical response was associated with prompt reductions in ACTH, chiasmatic compression and mass effects. Thus, it is possible to evaluate response early in the course of treatment. Targeted modulation of MGMT expression may be useful in patients who may otherwise not respond to temozolomide therapy [63].