Second-line treatment for Cushing's disease when initial pituitary surgery is unsuccessful

Ketoconazole as second-line treatment for Cushing's disease after transsphenoidal surgery: systematic review and meta-analysis

Introduction

The first-line treatment for Cushing's disease is transsphenoidal surgery for pituitary tumor resection. Ketoconazole has been used as a second-line drug despite limited data on its safety and efficacy for this purpose. The objective of this meta-analysis was to analyze hypercortisolism control in patients who used ketoconazole as a second-line treatment after transsphenoidal surgery, in addition to other clinical and laboratory criteria that could be related to therapeutic response.

Methods

We searched for articles that evaluated ketoconazole use in Cushing's disease after transsphenoidal surgery. The search strategies were applied to MEDLINE, EMBASE, and SciELO. Independent reviewers assessed study eligibility and quality and extracted data on hypercortisolism control and related variables such as therapeutic dose, time, and urinary cortisol levels.

Results

After applying the exclusion criteria, 10 articles (one prospective and nine retrospective studies, totaling 270 patients) were included for complete data analysis. We found no publication bias regarding reported biochemical control or no biochemical control (p = 0.06 and p = 0.42 respectively). Of 270 patients, biochemical control of hypercortisolism occurred in 151 (63%, 95% CI 50-74%) and no biochemical control occurred in 61 (20%, 95% CI 10-35%). According to the meta-regression, neither the final dose, treatment duration, nor initial serum cortisol levels were associated with biochemical control of hypercortisolism.

Conclusion

Ketoconazole can be considered a safe and efficacious option for Cushing's disease treatment after pituitary surgery.

Systematic review registration

https://www.crd.york.ac.uk/prospero/#searchadvanced, (CRD42022308041).

Behavioral and steroidogenic pharmacology of phenyl ring substituted etomidate analogs in rats

Background

Cushing’s syndrome is an endocrine disorder characterized by the overproduction of adrenocortical steroids. Steroidogenesis enzyme inhibitors are the mainstays of pharmacological treatment. Unfortunately, they produce significant side effects. Among the most potent inhibitors is the general anesthetic etomidate whose GABA_A receptor-mediated sedative-hypnotic actions restrict use. In this study, we defined the sedative-hypnotic and steroidogenesis inhibiting actions of etomidate and four phenyl-ring substituted etomidate analogs (dimethoxy-etomidate, isopropoxy-etomidate, naphthalene-etomidate, and naphthalene (2)-etomidate) that possess negligible GABA_A receptor modulatory activities.

Methods

In the first set of experiments, male Sprague-Dawley rats were assessed for loss of righting reflexes (LoRR) after receiving intravenous boluses of either etomidate (1 mg/kg) or an etomidate analog (40 mg/kg). In the second set of experiments, rats were assessed for LoRR and their abilities to produce adrenocortical and androgenic steroids after receiving 2-h infusions (0.5 mg kg^− 1 min^− 1) of either etomidate or an etomidate analog.

Results

All rats that received etomidate boluses or infusions had LoRR that persisted for minutes or hours, respectively. In contrast, no rat that received an etomidate analog had LoRR. Compared to rats in the vehicle control group, rats that received etomidate analog infusions had plasma corticosterone and aldosterone concentrations that were reduced by 80–84% and 68–94%, respectively. Rats that received etomidate infusions had plasma corticosterone and aldosterone concentrations that were also significantly reduced (by 92 and 96%, respectively). Rats that received etomidate or isopropoxy-etomidate had significant reductions (90 and 57%, respectively) in plasma testosterone concentrations whereas those that received naphthalene-etomidate had significant increases (1400%) in plasma dehydroepiandrosterone concentrations. Neither etomidate nor any etomidate analog significantly affected plasma androstenedione and dihydrotestosterone concentrations.

Conclusions

Our studies demonstrate that the four phenyl-ring substituted etomidate analogs form a novel class of compounds that are devoid of sedative-hypnotic activities and suppress plasma concentrations of adrenocortical steroids but vary in their effects on plasma concentrations of androgenic steroids.

Dimethoxy-etomidate: A Nonhypnotic Etomidate Analog that Potently Inhibits Steroidogenesis

Cushing's syndrome is characterized by the overproduction of adrenocortical steroids. Steroidogenesis inhibitors are mainstays of medical therapy for Cushing's syndrome; unfortunately, adverse side effects and treatment failures are common with currently available drugs. The general anesthetic induction agent etomidate is among the most potent inhibitors of adrenocortical steroidogenesis. However, its use as a treatment of Cushing's syndrome is complicated by its sedative-hypnotic activity and ability to produce myoclonus, central nervous system actions thought to be mediated by the GABA_A receptor. Here, we describe the pharmacology of the novel etomidate analog (R)-ethyl 1-(1-(3,5-dimethoxyphenyl)ethyl)-1H-imidazole-5-carboxylate (dimethoxy-etomidate). In contrast to etomidate, dimethoxy-etomidate minimally enhanced GABA-evoked GABA_A receptor-mediated currents even at a near-saturating aqueous concentration. In Sprague-Dawley rats, dimethoxy-etomidate's potency for producing loss of righting reflexes-an animal model of sedation/hypnosis-was 2 orders of magnitude lower than that of etomidate, and it did not produce myoclonus. However, similar to etomidate, dimethoxy-etomidate potently suppressed adrenocortical steroid synthesis primarily by inhibiting 11β-hydroxylase. [³H]etomidate binding to rat adrenocortical membranes was inhibited by dimethoxy-etomidate in a biphasic manner with IC₅₀ values of 8.2 and 3970 nM, whereas that by etomidate was monophasic with an IC₅₀ of 22 nM. Our results demonstrate that, similar to etomidate, dimethoxy-etomidate potently and dose-dependently suppresses adrenocortical steroid synthesis by inhibiting 11β-hydroxylase. However, it is essentially devoid of etomidate's GABA_A receptor positive modulatory and sedative-hypnotic activities and produces no myoclonus, providing proof of concept for the design of etomidate analogs without important central nervous system actions for the pharmacologic treatment of Cushing's syndrome.

Normalized Early Postoperative Cortisol and ACTH Values Predict Nonremission After Surgery for Cushing Disease

CONTEXT

Perioperative increases in adrenocorticotropic hormone (ACTH) and cortisol mimic results of corticotropin-releasing hormone (CRH) stimulation testing. This phenomenon may help identify patients with residual adenoma after transsphenoidal surgery (TSS) for Cushing disease (CD).

OBJECTIVE

To predict nonremission after TSS for CD.

DESIGN

Retrospective case-control study of patients treated at a single center from December 2003 until July 2016. Early and medium-term remission were assessed at 10 days and 11 months.

PATIENTS AND SETTING

Two hundred and ninety-one consecutive TSS cases from 257 patients with biochemical evidence of CD seen at a clinical center.

INTERVENTIONS

Normalized early postoperative values (NEPVs) for cortisol and ACTH were calculated as immediate postoperative cortisol or ACTH levels minus preoperative post-CRH-stimulation test levels.

MAIN OUTCOME MEASURES

Prediction of early nonremission was evaluated using logistic regression. Prediction of medium-term remission was assessed using Cox regression. Predictive ability was quantified by area under the receiver operating characteristic curve (AUROC).

RESULTS

NEPVs for cortisol and ACTH predicted early nonremission [adjusted odds ratio (OR): 1.1; 95% confidence interval (CI): 1.0, 1.1; P = 0.016 and adjusted OR: 1.0; 95% CI: 1.0, 1.0; P = 0.048, respectively]. AUROC for NEPV of cortisol was 0.78 (95% CI: 0.61, 0.95); for NEPV of ACTH, it was 0.80 (95% CI: 0.61, 0.98). NEPVs for cortisol and ACTH predicted medium-term nonremission [hazard ratio (HR): 1.1; 95% CI: 1.0, 1.1; P = 0.023 and HR: 1.0; 95% CI: 1.0, 1.0; P = 0.025, respectively].

CONCLUSIONS

NEPVs for cortisol and ACTH predicted nonremission after TSS for CD.

Update on medical treatment for Cushing's disease

Cushing's disease (CD) is the most common cause of endogenous Cushing's syndrome (CS). The goal of treatment is to rapidly control cortisol excess and achieve long-term remission, to reverse the clinical features and reduce long-term complications associated with increased mortality. While pituitary surgery remains first line therapy, pituitary radiotherapy and bilateral adrenalectomy have traditionally been seen as second-line therapies for persistent hypercortisolism. Medical therapy is now recognized to play a key role in the control of cortisol excess. In this review, all currently available medical therapies are summarized, and novel medical therapies in phase 3 clinical trials, such as osilodrostat and levoketoconazole are discussed, with an emphasis on indications, efficacy and safety. Emerging data suggests increased efficacy and better tolerability with these novel therapies and combination treatment strategies, and potentially increases the therapeutic options for treatment of CD. New insights into the pathophysiology of CD are highlighted, along with potential therapeutic applications. Future treatments on the horizon such as R-roscovitine, retinoic acid, epidermal growth factor receptor inhibitors and somatostatin-dopamine chimeric compounds are also described, with a focus on potential clinical utility.

Emerging drugs for Cushing's disease

INTRODUCTION

Considering the effects of uncontrolled hypercortisolism on morbidity and mortality, there is a clear need for effective medical therapy for patients with Cushing's disease (CD). Therefore, the search for new medical effective tools remains active, and already promising results have been obtained.

AREAS COVERED

The importance of the design and conduct of trials to validate old drugs or to test new compounds is discussed. The results of the ongoing clinical trials, targeting the specific properties of drugs, such as ketoconazole, LCI699, mifepristone, etomidate and pasireotide, are also reported. The authors also emphasise the advantages and drawbacks of each particular drug, and the potential combined use of agents with complementary mechanisms of action.

EXPERT OPINION

CD is an excellent example of a situation where effective therapy is essential, but where the balance of risk and benefit must be carefully judged. Metyrapone is the drug of choice when rapid control of the hypercortisolaemia is required, ketoconazole represents a good second-line drug, although in the future LCI699 may be a better alternative. Mifepristone can also be used in the rare situation when previous drugs are inappropriate. Etomidate is useful where immediate parenteral action is required. For drugs working directly on the pituitary, cabergoline is occasionally effective and pasireotide can be attempted in patients with mild CD.

Medical therapy for Cushing's disease: adrenal steroidogenesis inhibitors and glucocorticoid receptor blockers

Morbidity and mortality in Cushing's disease (CD) patients are increased if patients are not appropriately treated. Surgery remains the first line therapy, however the role of medical therapy has become more prominent in patients when biochemical remission is not achieved/or recurs after surgery, while waiting effects of radiation therapy or when surgery is contraindicated. Furthermore, use of preoperative medical therapy has been also recognized. In addition to centrally acting therapies (reviewed elsewhere in this special issue), adrenal steroidogenesis inhibitors, and glucocorticoid receptor antagonists are frequently used. A PubMed search of all original articles or abstracts detailing medical therapy in CD, published within 12 months (2013-2014), were identified and pertinent data extracted. Although not prospectively studied, ketoconazole and metyrapone have been the most frequently used medical therapies. A large retrospective ketoconazole study showed that almost half of patients who continued on ketoconazole therapy achieved biochemical control and clinical improvement; however almost 20% discontinued ketoconazole due to poor tolerability. Notably, hepatotoxicity was usually mild and resolved after drug withdrawal. Etomidate remains the only drug available for intravenous use. A new potent inhibitor of both aldosterone synthase and 11β-hydroxylase, following the completion of a phase II study LCI699 is being studied in a large phase III with promising results. Mifepristone, a glucocorticoid receptor antagonist, has been approved for hyperglycemia associated with Cushing's syndrome based on the results of a prospective study where it produced in the majority of patients' significant clinical and metabolic improvement. Absence of both a biochemical marker for remission and/or diagnosis of adrenal insufficiency remain, however, a limiting factor. Patient characteristics and preference should guide the choice between different medications in the absence of clinical trials comparing any of these therapies. Despite significant progress, there is still a need for a medical therapy that is more effective and with less adverse effects for patients with CD.

Medical treatment of Cushing disease: new targets, new hope

This article provides an update on current medical therapies for the treatment of Cushing disease. This information will be of value in determining patients' suitability for certain medical treatments. An approach of combining drugs from the same or different classes could potentially increase the number of patients in whom Cushing can be controlled while minimizing adverse effects, although larger studies are needed. Successful clinical management of patients with Cushing disease remains a challenge.

Treatment of Cushing's disease: a mechanistic update

Cushing's disease (CD) is characterized by an ACTH-producing anterior corticotrope pituitary adenoma. If hypothalamus-pituitary-adrenal (HPA) axis physiology is disrupted, ACTH secretion increases, which in turn stimulates adrenocortical steroidogenesis and cortisol production. Medical treatment plays an important role for patients with persistent disease after surgery, for those in whom surgery is not feasible, or while awaiting effects of radiation. Multiple drugs, with different mechanisms of action and variable efficacy and tolerability for controlling the deleterious effects of chronic glucocorticoid excess, are available. The molecular basis and clinical data for centrally acting drugs, adrenal steroidogenesis inhibitors, and glucocorticoid receptor antagonists are reviewed, as are potential novel molecules and future possible targets for CD treatment. Although progress has been made in the understanding of specific corticotrope adenoma receptor physiology and recent clinical studies have detected improved effects with a combined medical therapy approach, there is a clear need for a more efficacious and better-tolerated medical therapy for patients with CD. A better understanding of the molecular mechanisms in CD and of HPA axis physiology should advance the development of new drugs in the future.

Recent advances in the medical treatment of Cushing's disease

Cushing’s disease is a condition of hypercortisolism caused by an adrenocorticotropic hormone (ACTH)-secreting pituitary adenoma. While rare, it is associated with significant morbidity and mortality, which suggests that early and aggressive intervention is required. The primary, definitive therapy for patients with Cushing’s disease in the majority of patients is pituitary surgery, generally performed via a transsphenoidal approach. However, many patients will not achieve remission or they will have recurrences. The consequences of persistent hypercortisolism are severe and, as such, early identification of those patients at risk of treatment failure is exigent. Medical management of Cushing’s disease patients plays an important role in achieving long-term remission after failed transsphenoidal surgery, while awaiting effects of radiation or before surgery to decrease the hypercortisolemia and potentially reducing perioperative complications and improving outcome. Medical therapies include centrally acting agents, adrenal steroidogenesis inhibitors and glucocorticoid receptor blockers. Furthermore, several new agents are in clinical trials. To normalize the devastating disease effects of hypercortisolemia, it is paramount that successful patient disease management includes individualized, multidisciplinary care, with close collaboration between endocrinologists, neurosurgeons, radiation oncologists, and general surgeons. This commentary will focus on recent advances in the medical treatment of Cushing’s, with a focus on newly approved ACTH modulators and glucocorticoid receptor blockers.

Remission rate after transsphenoidal surgery in patients with pathologically confirmed Cushing's disease, the role of cortisol, ACTH assessment and immediate reoperation: a large single center experience

Postoperative serum cortisol is used as an indicator of Cushing's disease (CD) remission following transsphenoidal surgery (TSS) and guides (controversially) the need for immediate adjuvant treatment for CD. We investigated postoperative cortisol and adrenocorticotropic hormone (ACTH) levels as predictors of remission/recurrence in CD in a large retrospective cohort of patients with pathologically confirmed CD, over 6 years at a single institution. Midnight and morning cortisol, and ACTH at 24-48 h postoperatively (>24 h after last hydrocortisone dose) were measured. Remission was defined as normal 24-h urine free cortisol, normal midnight salivary cortisol, a normal dexamethasone-corticotropin releasing hormone (CRH) test or continued need for hydrocortisone, assessed periodically. Statistical analysis was performed using PASW 18. Follow up data was available for 52 patients (38 females and 14 males), median follow up was 16.5 month (range 2-143 months), median age was 45 years (range 21-72 years), 28 tumors were microadenomas and 16 were macroadenomas, and in eight cases no tumor was observed on magnetic resonance imaging. No patient with postoperative cortisol levels >10 mcg/dl were found to be in remission. Ten of the 52 patients with cortisol >10 mcg/dl by postoperative day 1-2 underwent a second TSS within 7 days. Forty-three patients (82.7%) achieved CD remission (36 after one TSS and 7 after a second early TSS) and six patients suffered disease recurrence (mean 39.2 ± 52.4 months). An immediate second TSS induced additional hormonal deficiencies (diabetes insipidus) in three patients with no surgical complications. Persistent disease was noted in nine patients despite three patients having an immediate second TSS. Positive predictive value for remission of cortisol <2 mcg/dl and ACTH <5 pg/ml was 100%. Cortisol and ACTH levels (at all postoperative time points and at 2 months) were correlated (r = 0.37, P < 0.001). Nadir serum cortisol of ≤2 mcg/dl and ACTH <5 pg/ml predicted remission (P < 0.005), but no level predicted lack of recurrence. Immediate postoperative ACTH/cortisol did not predict length of remission. No patients with postoperative cortisol >10 mcg/dl were observed to have delayed remission; all required additional treatment. There was no significant difference in age, body mass index, tumor size and length of follow-up between postoperative cortisol groups: cortisol ≤2 mcg/dl, cortisol >5 mcg/dl and cortisol >10 mcg/dl. Immediate postoperative cortisol levels should routinely be obtained in CD patients post TSS, until better tools to identify early remission are available. Immediate repeat TSS could be beneficial in patients with cortisol >10 mcg/dl and positive CD pathology: our combined (micro- and macroadenomas) remission rate with this approach was 82.7%. ACTH measurements correlate well with cortisol. However, because no single cortisol or ACTH cutoff value excludes all recurrences, patients require long-term clinical and biochemical follow-up. Further research is needed in this area.

A new therapeutic approach in the medical treatment of Cushing's syndrome: glucocorticoid receptor blockade with mifepristone

OBJECTIVE

Cushing's syndrome (CS) is a serious endocrine disorder caused by prolonged exposure to high cortisol levels. Initial treatment of this condition is dependent upon the cause, but is generally surgical. For patients whose hypercortisolism is not cured by surgery, medical therapy is often required. Drugs that have typically been used for CS medical therapy act by decreasing cortisol levels. Mifepristone is a glucocorticoid receptor antagonist now available for use in patients with CS. Unlike other agents, mifepristone does not decrease cortisol levels, but directly antagonizes its effects. Our objective is to review the pharmacology and clinical use of this novel agent and to discuss detailed guidance on the management of CS patients treated with mifepristone.

METHODS

We review the literature regarding mifepristone use in CS and recently published clinical trial data. Detailed information related to clinical assessment of mifepristone use, potential drug interactions, drug initiation and dose titration, and monitoring of drug tolerability are provided.

RESULTS

Clinical trial data have shown that mifepristone improves glycemic control and blood pressure, causes weight loss and a decrease in waist circumference, lessens depression, and improves overall wellbeing. However, adverse effects include adrenal insufficiency, hypokalemia, and endometrial thickening with vaginal bleeding. These findings are supported by the earlier literature case reports.

CONCLUSION

This article provides a review of the pharmacology and clinical use of mifepristone in Cushing's syndrome, as well as detailed guidance on the management of patients treated with this novel agent.

Mifepristone: is there a place in the treatment of Cushing's disease?

The purpose was to review the use of mifepristone in the treatment of Cushing's syndrome (CS) in the context of other recently published studies. We review the use of mifepristone, as published in the recent Study of the Efficacy and Safety of Mifepristone in the Treatment of Endogenous Cushing's Syndrome (SEISMIC). We also review the multiple case reports and case series of mifepristone use in CS. A review of other medications used in the treatment of Cushing's disease (CD), including pasireotide and cabergoline also provides context for the discussion of the role of mifepristone in the treatment of CD. The results show that the treatment of CD has been primarily surgical with medical therapy reserved for adjuvant therapy when primary treatment fails or other therapies require time for optimal efficacy. Two recent large prospective studies, using pasireotide and mifepristone provide new clinical insights to the medical treatment of CD in particular. Mifepristone has been used to treat excessive cortisol production by blocking the action of cortisol at the level of the glucocorticoid receptor. Until recently, the majority of clinical experience with mifepristone on the treatment of excess cortisol was derived from case reports and small case series. Based on the SEISMIC study, mifepristone was FDA approved for hyperglycemia associated with CS. In conclusion the role of mifepristone in the treatment of CD remains one of adjuvant therapy. Its place among other choices for medical therapy has yet to be firmly established and an evidenced-based approach toward the use of novel medications in the treatment of CD has not been made. Selection of medication depends on drug approval and availability in individual countries and requires cautious assessment of potential adverse effects, consideration of patient comorbidities, and efficacy.

Medical management of persistent and recurrent cushing disease

Recent evidence supports the notion that the incidence of Cushing disease is higher than previously thought. Transphenoidal surgery, in the hands of experienced neurosurgeons, is currently considered the first-line treatment of choice. However, an examination of remission and recurrence rates in long-term follow-up studies reveals that potentially up to 40% to 50% of patients could require additional treatment. If left untreated, the resultant morbidity and mortality are high. Successful clinical management of patients with Cushing disease remains a challenge. The development of new therapeutic agents has been eagerly anticipated. This article discusses the results of currently available and promising new therapeutic agents used to treat this challenging disease.

Medical management of Cushing's syndrome

Cushing's syndrome is a debilitating endocrine disorder which results from hypercortisolemia. While endogenous Cushing's syndrome can be caused by an adrenocorticotrophic hormone (ACTH)-dependent or ACTH-independent mechanism, it is most often a result of excess secretion of ACTH by a corticotroph adenoma (Cushing's disease). Untreated hypercortisolemia causes significant morbidity and increased mortality due to its metabolic effects including hypertension, osteoporosis, obesity, dyslipidemia, osteoporosis and glucose intolerance. Although primary therapy is surgical, a substantial portion of patients will go on to require second-line therapies including repeat surgery, radiotherapy or drug therapy. While medical therapy for Cushing's syndrome has been limited, several new agents are being investigated. This aim of this review is to analyze and present the available options for medical management of Cushing's syndrome as well as review potential new therapies and their role in the treatment of this disorder.

Medical management of Cushing's disease: what is the future?

Cushing's disease (CD) is caused by a corticotroph, adrenocorticotropic-hormone (ACTH)-secreting pituitary adenoma resulting in significant morbidity and mortality. Transsphenoidal surgery is the initial treatment of choice in almost all cases. Remission rates for microadenomas are good at 65-90 % (with an experienced neurosurgeon) but remission rates are much lower for macroadenomas. However, even after postoperative remission, recurrence rates are high and can be seen up to decades after an initial diagnosis. Repeat surgery or radiation can be useful in these cases, although both have clear limitations with respect to efficacy and/or side effects. Hence, there is a clear unmet need for an effective medical treatment. Currently, most drugs act by inhibiting steroidogenesis in the adrenal glands. Most is known about the effects of ketoconazole and metyrapone. While effective, access to ketoconazole and metyrapone is limited in many countries, experience with long-term use is limited, and side effects can be significant. Recent studies have suggested a role for a pituitary-directed therapy with new multireceptor ligand somatostatin analogs (e.g., pasireotide, recently approved in Europe for treatment of CD), second-generation dopamine agonists, or a combination of both. Mifepristone (a glucocorticoid receptor antagonist) is another promising drug, recently approved by the FDA for treatment of hyperglycemia associated with Cushing's syndrome. We review available medical treatments for CD with a focus on the two most recent compounds referenced above. Our aim is to expand awareness of current research, and the possibilities afforded by available medical treatments for this mesmerizing, but often frightful disease.

Pasireotide (SOM230): a novel pituitary-targeted medical therapy for the treatment of patients with Cushing's disease

Cushing's disease (CD) is a rare and debilitating condition resulting from extended exposure to excessive glucocorticoids caused by an adrenocorticotropic hormone-secreting pituitary adenoma. First-line treatment for most patients with CD is trans-sphenoidal adenomectomy. Postsurgical remission remains problematic; however, due to the difficulty of removing the tumor. Until recently, there were no approved medical treatments for Cushing's syndrome, but recent data on pasireotide (SOM230; a novel somatostatin analog) demonstrate restored hormone levels and improvements in quality of life, with a safety profile similar to that of other somatostatin analogs, except for incidence of hyperglycemia. Pasireotide represents an exciting, novel, pituitary-targeted medical therapy for patients with CD who are not surgical candidates, or for those who experience postsurgical recurrence.

Temozolomide for corticotroph pituitary adenomas refractory to standard therapy

To highlight the potential of temozolomide (TMZ) to induce rapid tumor regression in patients with aggressive corticotroph adenomas (CA) that are refractory to surgery and radiation therapy and to review use of TMZ in other pituitary tumors. We present a case of a 56-year-old male with a 3 cm CA treated with transphenoidal surgery (TSS) and conventional radiotherapy in the same year. His hypercortisolemia recurred 11 years later with rapid tumor growth (to 4.2 × 2.5 cm) and he underwent a second TSS with good resection. The tumor recurred 6 months later with ophthalmoplegia. Over 16 months he underwent an additional three surgeries (two TSS, one craniotomy) and repeated conventional radiotherapy. Ki67 staining index on surgical specimens was 5-6%. Temozolomide is an oral alkylating agent approved for glioblastoma multiforme treatment that has only recently shown promise in treating some pituitary tumors. In this patient TMZ was started at 150 mg/m²/day, titrated to 200 mg/m²/day, taken 5 days per month. The only significant side effect was moderate nausea. After 10 weeks, the tumor showed a remarkable 60% regression with objective improvement in ophthalmoplegia. Treatment of aggressive CAs represents a therapeutic challenge and in some cases surgical debulking and radiotherapy are of limited success. Few reports of CAs responsive to TMZ have been reported in the literature. To our knowledge, this case represents the most rapid robust CA shrinkage response reported to date. Further randomized clinical trials of TMZ in the treatment of aggressive pituitary adenomas are warranted.