Temozolomide treatment for aggressive pituitary tumors: correlation of clinical outcome with O(6)-methylguanine methyltransferase (MGMT) promoter methylation and expression

Treatment of invasive silent somatotroph pituitary adenoma with temozolomide. Report of a case and review of the literature

Improved imaging techniques have contributed to increased diagnosis of pituitary tumors. These tumor types can be microadenomas or macroadenomas and can either be functional or non-functional. Atypical or aggressive pituitary adenomas are tumors that rapidly increase in size and may invade into the suprasellar or parasellar regions. They are characterized by a Ki-67 nuclear labeling index greater than 10 %. Management of these tumors is difficult, and many recur after surgery. Temozolomide, a second generation alkylating agent, has been showing promising results in the treatment of these tumors. The patient was a 39-year-old male diagnosed with an invasive silent somatotroph pituitary macroadenoma treated with temozolomide after surgery. We present the case along with the review of the literature of the therapeutic effects of temozolomide in somatotroph macroadenomas.

Disulfiram sensitizes pituitary adenoma cells to temozolomide by regulating O6-methylguanine-DNA methyltransferase expression

O6-methylguanine-DNA methyltransferase (MGMT) activity is responsible for temozolomide (TMZ) resistance in patients harboring aggressive pituitary adenomas. Recently, disulfiram (DSF) has been shown to induce the loss of MGMT protein and increase TMZ efficacy in glioblastoma cells, while CD133+ nestin+ cells isolated from the cell population have been implicated as pituitary adenoma stem-like cells. However, whether DSF is able to potentiate the cytotoxic effects of TMZ on human pituitary adenoma cells has not been investigated to date. In the present study, CD133+ nestin+ phenotype cells were isolated from primary cultured human pituitary adenoma cells using microbeads. It was found that DSF reduced MGMT protein expression and sensitized human pituitary adenoma cells and stem-like cells to TMZ in vitro, while the proteasome inhibitor PS-341 abrogated the inhibitory effect of DSF on MGMT in vitro. The sensitizing effect of DSF was also verified in primary cultured human pituitary adenoma cells in vivo. The results of the present study suggested that DSF can increase the efficacy of the anti-tumor effect of TMZ on human pituitary adenoma cells and CD133+ nestin+ stem like cells via the ubiquitin-proteasomal MGMT protein elimination route. DSF combined with TMZ may be an effective therapeutic strategy against aggressive pituitary adenomas.

Temozolomide Therapy for Aggressive Pituitary Tumors: Results in a Small Series of Patients from Argentina

We evaluated results of temozolomide (TMZ) therapy in six patients, aged 34-78 years, presenting aggressive pituitary tumors. In all the patients tested O(6)-methylguanine-DNA methyltransferase (MGMT) immunoexpression in surgical specimens was absent. Patients received temozolomide 140-320 mg/day for 5 days monthly for at least 3 months. In two patients minimum time for evaluation could not be reached because of death in a 76-year-old man with a malignant prolactinoma and of severe neutro-thrombopenia in a 47-year-old woman with nonfunctioning pituitary adenoma. In two patients (a 34-year-old acromegalic woman and a 39-year-old woman with Nelson's syndrome) no response was observed after 4 and 6 months, respectively, and the treatment was stopped. Conversely, two 52- and 42-year-old women with Cushing's disease had long-term total clinical and radiological remissions which persisted after stopping temozolomide. We conclude that TMZ therapy may be of variable efficacy depending on-until now-incompletely understood factors. Cooperative work on a greater number of cases of aggressive pituitary tumors should be crucial to establish the indications, doses, and duration of temozolomide administration.

Aggressive pituitary tumors

Pituitary adenomas are common intracranial tumors that are mainly considered as benign. Rarely, these tumors can exhibit an aggressive behavior, characterized by gross invasion of the surrounding tissues, resistance to conventional treatment leading to early and frequent recurrences. Even more rarely, pituitary tumors can give rise to cerebrospinal or systemic metastases qualifying as pituitary carcinomas according to the latest WHO definition. In the same classification, a subset of tumors with relatively distinct histopathological features was identified and defined as atypical adenomas designated to follow a more aggressive clinical course. This classification, although clinically useful, does not provide an accurate correlation between histopathological findings and the clinical behavior of these tumors, neither is it adequate to convey the precise features of 'aggressive' tumors. Thus, 'aggressive' pituitary adenomas need to be properly defined with clinical, radiological, histological and molecular markers in order to identify patients at increased risk of early recurrence or subsequent tumor progression. At present, no single marker or classification system of pituitary tumor aggressiveness exists, and clinically useful information in the literature is insufficient to guide diagnostic and therapeutic decisions. Treatment of patients with aggressive pituitary tumors is challenging since conventional treatments often fail, necessitating multiple surgical procedures with additional radiotherapy. Although traditional chemotherapy applied in other neuroendocrine tumors has not been shown to be efficacious, newer agents, particularly temozolomide, have shown promising results and are currently used despite the lack of data from a randomized prospective trial. Molecular targeted therapies such as mTOR and epidermal growth factor inhibitors have also been applied and might prove to be useful in the management of these patients. In the present review, we provide information regarding the epidemiology and clinical, histopathological and molecular features of aggressive pituitary tumors using recent employed definitions. In addition, we review currently employed therapeutic means providing a therapeutic algorithm and highlight the need to identify more specific disease-related and prognostic markers and the necessity for central registration of these tumors.

Treatment of pituitary carcinomas and atypical pituitary adenomas: a review

Atypical pituitary adenomas (APAs) are aggressive tumors, harboring a Ki-67 (MIB-1) staining index of 3% or more, and positive immunohistochemical staining for p53 protein, according to the World Health Organization (WHO) classification in 2004. Pituitary carcinomas (PC) usually develop from progressive APAs and predominantly consist of hormone-generating tumors, defined by the presence of disseminations in the cerebrospinal system or systemic metastases. Most of the cases with these malignant pituitary adenomas underwent surgeries, irradiations and adjuvant medical treatments, nevertheless, the therapies are mainly palliative. Recently, the efficacy of temozolomide (TMZ), an orally administered alkylating agent, has been reported as an alternative medical treatment. However, some recent studies have demonstrated a significant recurrence rate after effective response to TMZ. Further clinical and pathological researches of malignant pituitary adenomas will be required to improve the outcome of patients with these tumors.

The role of temozolomide in the treatment of a patient with a pure silent pituitary somatotroph carcinoma

OBJECTIVE

To describe a case of a pure silent somatotroph pituitary carcinoma.

METHODS

We describe a 54-year-old female with a clinically nonfunctioning pituitary macroadenoma diagnosed 15 years earlier.

RESULTS

The patient underwent transsphenoidal surgery and no visible tumor remnant was observed for 6 years. A magnetic resonance imaging (MRI) detected the recurrence of a 1.2 × 1.5 cm macroadenoma. The patient was submitted to conventional radiotherapy (4500 cGy), and the tumor volume remained stable for 7 years. Then, an MRI revealed a slight increase in tumor size, and 2 years later, a subsequent MRI detected a very large, invasive pituitary mass. The patient was resubmitted to transsphenoidal surgery, and the histopathological examination showed diffuse positivity for growth hormone (GH). The nadir GH level during an oral glucose tolerance test was 0.06 ng/mL, and the pre- and postoperative insulin like growth factor type I (IGF-I) levels were within the normal range. Abdominal, chest, brain, and spine MRI showed multiple small and hypervascular liver and bone lesions suggestive of metastases. Liver biopsy confirmed metastasis of GH-producing pituitary carcinoma. The patient has been treated with temozolomide and zoledronic acid for 7 months and with octreotide long-acting release (LAR) for 4 months. The primary tumor and metastases are stable.

CONCLUSION

Despite being an extremely rare event, pituitary carcinoma may develop several years after the successful treatment of even a silent GH-producing pituitary adenoma, which suggests that close long-term follow-up is necessary.

The expression profile of Dopamine D2 receptor, MGMT and VEGF in different histological subtypes of pituitary adenomas: a study of 197 cases and indications for the medical therapy

BACKGROUND

To study the expression of D2R, MGMT and VEGF for clinical significance in pituitary adenomas, and to predict the potential curative medical therapy of dopamine agonists, temozolomide and bevacizumab on pituitary adenomas.

METHODS

Immunohistochemistry and western blot were performed to detect the expression of expression of D2R, MGMT and VEGF in pituitary adenoma tissue samples. The ratio of high expression of D2R, MGMT or VEGF in different subtypes of PA was compared by the use of chi-squared tests. The relationships between D2R, MGMT and VEGF expression were assessed by the Spearman rank correlation test. The association between their expression and clinical parameters was analyzed using a chi-squared test, or Fisher's exact probability test when appropriate.

RESULTS

The data showed that in 197 different histological subtypes of pituitary adenomas (PAs), 64.9% of them were D2R high expression, 86.3% were MGMT low expression and 58.9% were VEGF high expression. D2R high expression existed more frequently in PRL- and GH- secreting PAs. MGMT low expression existed in all PA subtypes. VEGF high expression existed more frequently in PRL, ACTH, FSH secreting and non-functioning PAs. The data of western blot also support the results. Spearman's rank correlation analysis showed that expression of MGMT was positively associated with D2R (r = 0.154, P = 0.031) and VEGF (r = 0.161, P = 0.024) in PAs, but no correlation was showed between D2R and VEGF expression (r = -0.025, P = 0.725 > 0.05). The association between their expression and clinical parameters was analyzed using a chi-squared test, or Fisher's exact probability test when appropriate, but the result showed no significant association.

CONCLUSIONS

PRL-and GH-secreting PAs exist high expression of D2R, responding to dopamine agonists; Most PAs exist low expression of MGMT and high expression of VEGF, TMZ or bevacizumab treatment could be applied under the premise of indications.

Metal-dependent conformational activation explains highly promutagenic replication across O6-methylguanine by human DNA polymerase β

Human DNA polymerase β (polβ) inserts, albeit slowly, T opposite the carcinogenic lesion O6-methylguanine (O6MeG) ∼30-fold more frequently than C. To gain insight into this promutagenic process, we solved four ternary structures of polβ with an incoming dCTP or dTTP analogue base-paired with O6MeG in the presence of active-site Mg²⁺ or Mn²⁺. The Mg²⁺-bound structures show that both the O6MeG·dCTP/dTTP–Mg²⁺ complexes adopt an open protein conformation, staggered base pair, and one active-site metal ion. The Mn²⁺-bound structures reveal that, whereas the O6Me·dCTP–Mn²⁺ complex assumes the similar altered conformation, the O6MeG·dTTP–Mn²⁺ complex adopts a catalytically competent state with a closed protein conformation and pseudo-Watson–Crick base pair. On the basis of these observations, we conclude that polβ slows nucleotide incorporation opposite O6MeG by inducing an altered conformation suboptimal for catalysis and promotes mutagenic replication by allowing Watson–Crick-mode for O6MeG·T but not for O6MeG·C in the enzyme active site. The O6MeG·dTTP–Mn²⁺ ternary structure, which represents the first structure of mismatched polβ ternary complex with a closed protein conformation and coplanar base pair, the first structure of pseudo-Watson–Crick O6MeG·T formed in the active site of a DNA polymerase, and a rare, if not the first, example of metal-dependent conformational activation of a DNA polymerase, indicate that catalytic metal-ion coordination is utilized as a kinetic checkpoint by polβ and is crucial for the conformational activation of polβ. Overall, our structural studies not only explain the promutagenic polβ catalysis across O6MeG but also provide new insights into the replication fidelity of polβ.

Management of endocrine disease: clinicopathological classification and molecular markers of pituitary tumours for personalized therapeutic strategies

Pituitary tumours, the most frequent intracranial tumour, are historically considered benign. However, various pieces of clinical evidence and recent advances in pathological and molecular analyses suggest the need to consider these tumours as more than an endocrinological disease, despite the low incidence of metastasis. Recently, we proposed a new prognostic clinicopathological classification of these pituitary tumours, according to the tumour size (micro, macro and giant), type (prolactin, GH, FSH/LH, ACTH and TSH) and grade (grade 1a, non-invasive; 1b, non-invasive and proliferative; 2a, invasive; 2b, invasive and proliferative and 3, metastatic). In addition to this classification, numerous molecular prognostic markers have been identified, allowing a better characterisation of tumour behaviour and prognosis. Moreover, clinical and preclinical studies have demonstrated that pituitary tumours could be treated by some chemotherapeutic drugs or new targeted therapies. Our improved classification of these tumours should now allow the identification of prognosis markers and help the clinician to propose personalised therapies to selected patients presenting tumours with a high risk of recurrence.

Implications of MGMT methylation status in pituitary adenoma

BACKGROUND

Very little literature exists on frequency of MGMT methylation status in pituitary adenoma. We assessed the frequency of MGMT methylation and protein expression in pituitary adenoma and correlated with patients' age group and prognosis.

METHODS

Tumor tissues from 30 patients with pituitary adenoma were evaluated for MGMT promoter methylation status by methylation specific PCR method. All tumors were also immunostained with MIB-1, anti-p53 and anti-MGMT antibodies.

RESULTS

MGMT methylation status was noted in 40% of cases (7/20 non-functioning adenomas and 5/10 functioning adenomas). MGMT protein expression on IHC was noted in 72.2% of unmethylated tumors, while only 41.6% of methylated tumors demonstrated protein expression. The mean labeling index of MGMT protein was higher in unmethylated tumors as compared to the methylated group, though the difference was not statistically significant (18.6% vs 8.8%; p=0.131). Tumor regrowth occurred in four unmethylated tumors as compared to none in methylated group. Even though there was no correlation between patient age and MGMT methylation status (p=0.823), we noted that the frequency of methylation in middle age patients (between 30 and 59 yrs) was 64.7%, which was higher compared to other age groups.

CONCLUSION

This is the first study from India showing MGMT promoter methylation status with protein expression in pituitary adenoma. We noted that tumor regrowth was higher in unmethylated tumors.

Pituitary carcinoma in situ

OBJECTIVE

Pituitary carcinomas are extremely rare tumors associated with poor prognosis despite surgery, radiation, and chemotherapy. The hallmark of diagnosis implies subarachnoid, brain, or systemic tumor spread.

METHODS

We report a case of rapid transformation of atypical nonfunctioning pituitary adenoma to a carcinoma.

RESULTS

A 64-year-old woman presented with sudden onset of ophthalmoplegia. Magnetic resonance imaging (MRI) scan showed a pituitary macroadenoma (2.2 x 2.1 cm) with invasion of the right cavernous sinus. Biochemical data was consistent with a nonfunctioning pituitary adenoma. Pathology showed a pituitary adenoma with negative immunohistochemistry for pituitary hormones. The patient returned a month later with weakness, lethargy, and a dilated nonreactive right pupil. MRI showed an invasive large mass (5 x 4.7 cm). After an emergent second transsphenoidal surgery, histopathologic examination revealed a widely infiltrative neoplasm invading the overlying mucosa and showing a high mitotic activity and necrosis and a very high Ki-67 (MIB-1) proliferation index (80%). MIB-1 retrospectively performed on the first specimen was also elevated (30%). Soon after the second surgery, MRI showed a 7.9 x 8.0 cm mass that metastasized to dura mater and extended into the right orbit, right middle cranial fossa, nasopharynx, clivus, posterior fossa, and along the right tentorium cerebelli, resulting in significant compression of the brainstem.

CONCLUSION

Development of a pituitary carcinoma from an adenoma is an exceptional occurrence and predictors of such course are currently lacking. A very high Ki-67 proliferation index should raise concern of a pituitary carcinoma in situ or premetastatic carcinoma.

Effect of combined bevacizumab and temozolomide treatment on intramedullary spinal cord tumor

STUDY DESIGN

C6 glioma cells and an intramedullary spinal cord tumor model were used to evaluate the effect of bevacizumab (Avastin) or temozolomide (TMZ).

OBJECTIVE

In this study, we hypothesized that treatment with bevacizumab accelerates the therapeutic effect of TMZ on intramedullary gliomas in an animal model.

SUMMARY OF BACKGROUND DATA

Recently therapies for the management of intramedullary malignant gliomas include surgery, chemotherapy, and radiotherapy. Concurrent or adjuvant TMZ has been considered an emerging new treatment for intramedullary malignant gliomas; however, high-dose application of TMZ has limitation of side effect.

METHODS

C6 glioma cells were injected into the T5 level of the spinal cord, and TMZ and bevacizumab were administered 5 days after C6 inoculation (n = 7 for each group). Tumor size was analyzed using histology and magnetic resonance imaging at 13 days after tumor inoculation.

RESULTS

Histological analyses and magnetic resonance imaging findings showed that combined treatment with TMZ and bevacizumab reduced tumor mass. The tumor volume of control group was 2.8-fold higher than combined therapy (P < 0.05). Neurological outcomes demonstrated that combined therapy improved hind limb function more than TMZ-alone group or control group (P < 0.05).

CONCLUSION

This study shows that bevacizumab could be useful in combination with TMZ to increase the therapeutic benefits of TMZ for intramedullary spinal cord tumors.

LEVEL OF EVIDENCE

N/A.

Management of endocrine disease: GH excess: diagnosis and medical therapy

Acromegaly is predominantly caused by a pituitary adenoma, which secretes an excess of GH resulting in increased IGF1 levels. Most of the GH assays used currently measure only the levels of the 22 kDa form of GH. In theory, the diagnostic sensitivity may be lower compared with the previous assays, which have used polyclonal antibodies. Many GH-secreting adenomas are plurihormonal and may co-secrete prolactin, TSH and α-subunit. Hyperprolactinaemia is found in 30-40% of patients with acromegaly, and hyperprolactinaemia may occasionally be diagnosed before acromegaly is apparent. Although trans-sphenoidal surgery of a GH-secreting adenoma remains the first treatment at most centres, the role of somatostatin analogues, octreotide long-acting repeatable and lanreotide Autogel as primary therapy is still the subject of some debate. Although the normalisation of GH and IGF1 levels is the main objective in all patients with acromegaly, GH and IGF1 levels may be discordant, especially during somatostatin analogue therapy. This discordance usually takes the form of high GH levels and an IGF1 level towards the upper limit of the normal range. Pasireotide, a new somatostatin analogue, may be more efficacious in some patients, but the drug has not yet been registered for acromegaly. Papers published on pasireotide have reported an increased risk of diabetes mellitus due to a reduction in insulin levels. Pegvisomant, the GH receptor antagonist, is indicated - alone or in combination with a somatostatin analogue - in most patients who fail to enter remission on a somatostatin analogue. Dopamine-D2-agonists may be effective as monotherapy in a few patients, but it may prove necessary to apply combination therapy involving a somatostatin analogue and/or pegvisomant.

Emerging drugs for acromegaly

INTRODUCTION

Acromegaly is a rare disease that severely impacts patients' health all the while, being a slowly progressing illness. In the past decades, advancements in treatment modalities, especially development of new drugs, as well as focused guidelines has improved management of acromegaly. Still, many patients are considered not sufficiently treated and there remains an ongoing need for further development.

AREAS COVERED

This article reviews new medical treatments currently under clinical investigation (such as pasireotide, oral octreotide and somatoprim) and under experimental development (such as octreotide implants, CAM2029 and ATL-1103).

EXPERT OPINION

As it seems unlikely that one single agent may achieve cure in 100% of cases, there is an urgent need for new agents that help patients where current medication fails. Imperatively, this means we have to improve our understanding of the underlying pathogenetic and molecular mechanisms.

Chemotherapy-induced regression of an adrenocorticotropin-secreting pituitary carcinoma accompanied by secondary adrenal insufficiency

Purpose. Adrenocorticotropin- (ACTH-) secreting pituitary carcinomas are rare and require multimodality treatment. The aim of this study was to report the response to various therapies and discuss the potential development of secondary adrenal insufficiency with cytotoxic chemotherapy. Methods. This report describes a man with a large silent corticotroph adenoma progressing to endogenous hypercortisolism and metastatic ACTH-secreting pituitary carcinoma over a period of 14 years. Results. Seven years after initial presentation, progressive tumor enlargement associated with the development of hypercortisolism mandated multiple pituitary tumor debulking procedures and radiotherapy. Testing of the Ki-67 proliferation index was markedly high and he developed a hepatic metastasis. Combination therapy with cisplatin and etoposide resulted in a substantial reduction in tumor size, near-complete regression of his liver metastasis, and dramatic decrease in ACTH secretion. This unexpectedly resulted in symptomatic secondary adrenal insufficiency. Conclusions. This is the first reported case of secondary adrenal insufficiency after use of cytotoxic chemotherapy for metastatic ACTH-secreting pituitary carcinoma. High proliferative indices may be predictive of dramatic responses to chemotherapy. Given the potential for such responses, the development of secondary adrenal insufficiency may occur and patients should be monitored accordingly.

Long-term remission in an aggressive Crooke cell adenoma of the pituitary, 18 months after discontinuation of treatment with temozolomide

Key Clinical Message

The clinical course of our patient, who sustained remission status for at least 18 months highlights the chance of long-term hormonal and tumor remission and demonstrates the efficacy and safety of discontinuation of temozolomide therapy. Prospective studies are required in order to define predictors of long-term remission of this promising therapeutic modality.

Molecular status of pituitary carcinoma and atypical adenoma that contributes the effectiveness of temozolomide

There have been several reports of temozolomide (TMZ) treatment of pituitary carcinomas and atypical adenomas. O(6)-methyl-guanine-DNA methyltransferase is not the sole molecule determining the sensitivity to TMZ in pituitary carcinomas and atypical adenomas. The Japan Society of Hypothalamic and Pituitary Tumors study suggests that MSH6, one of mismatch repair pathway enzyme, fulfills a contributory role to the efficacy of TMZ treatment for pituitary carcinomas and atypical adenomas. The preserved MSH6 function might be essential for the responsiveness to TMZ treatment in pituitary carcinomas and atypical adenomas.

New avenues in the medical treatment of Cushing's disease: corticotroph tumor targeted therapy

Cushing's disease (CD) is a condition of chronic hypercortisolism caused by an adrenocorticotropic hormone-secreting pituitary adenoma. First-line transsphenoidal surgery is not always curative and disease sometimes recurs. Radiotherapy often requires months or years to be effective, and is also not curative in many cases. Consequently, effective medical therapies for patients with CD are needed. Corticotroph adenomas frequently express both dopamine (D2) and somatostatin receptors (predominantly sstr5). Pasireotide, a somatostatin analog with high sstr5 binding affinity, has shown urinary free cortisol (UFC) reductions in most patients with CD in a large phase 3 trial, with UFC normalization and tumor shrinkage in a subset of patients. Adverse events were similar to other somatostatin analogs, with the exception of the degree and severity of hyperglycemia. Two small trials (one prospective and one retrospective) have suggested that cabergoline, a D2 receptor agonist, could be effective in normalizing UFC, but current long-term data results are conflicting. Combination treatment with pasireotide plus cabergoline and the adrenal steroidogenesis inhibitor ketoconazole has been successful, but further investigation in larger trials is necessary. Retinoic acid also showed interesting results in a recent very small prospective study. Glucocorticoid receptor blockade with mifepristone has recently demonstrated improvement in signs and symptoms of Cushing's and glycemic control; however, this modality does not address the etiology of the disease and has inherent adverse events related to its mechanism of action. Pituitary-targeted medical therapies will soon play a more prominent role in treating CD, and may potentially become first-line medical therapy when surgery fails or is contraindicated.

MGMT expression and pituitary tumours: relationship to tumour biology

Over the past half decade, temozolomide, an oral akylating chemotherapeutic agent, has been shown to have significant activity in the management of aggressive pituitary tumours. The expression of 06-methylguanine-DNA methyltransferase (MGMT), a DNA repair enzyme, is an important predictor of response to therapy. Low MGMT expression has been reported with a higher frequency amongst more aggressive pituitary tumours, suggesting MGMT may play a role in pituitary tumour progression. In this study, we performed a microarray analysis to determine whether there was a distinct gene expression profile between tumours with low MGMT and high MGMT expression. Overall, 1,403 differentially expressed genes were identified with raw p values less than 0.05. Gene set enrichment analysis (GSEA) revealed significant differences in the gene expression profile between high and low MGMT expressing pituitary tumours. High MGMT expressing pituitary tumours were found to have upregulation of components of the FGFR family and downstream signaling cascades such as PI3 K/Akt and MAPK pathways. Activation of genes involved in the DNA damage response and DNA repair pathways, as well as genes involved in transcription, were identified in pituitary tumours with low MGMT expression. These results form the basis of our proposed model to describe the role of MGMT in pituitary tumorigenesis.

Aggressive silent GH pituitary tumor resistant to multiple treatments, including temozolomide

Temozolomide (TMZ) has been proposed as a therapeutic option in aggressive pituitary tumors. Among the published cases, GH expressing tumors were rare. We describe a patient with initially benign silent GH adenoma that transformed into an aggressive GH secreting tumor resistant to usual therapy. MGMT expression was high and the MGMT promoter was unmethylated. Before this aggressive course, patient received three cycles of TMZ; no response was observed. Four cases of GH aggressive tumor treated by TMZ have been reported. Response to TMZ was observed in one of these four patients. Predictive factors of failure of TMZ remain unclear.

Management of large aggressive nonfunctional pituitary tumors: experimental medical options when surgery and radiation fail

Pituitary adenomas are generally considered benign tumors; however, a subset of these tumors displays aggressive behavior and are not easily cured. The protocol for nonsurgical treatment of aggressive pituitary lesions is less standardized than that of other central nervous system tumors. Aggressive surgical treatment, radiation, dopamine agonists, antiangiogenic drugs, and other chemotherapeutics all have roles in the treatment of aggressive pituitary tumors. More studies are needed to improve outcomes for patients with aggressive pituitary tumors.

DNA mismatch repair protein (MSH6) correlated with the responses of atypical pituitary adenomas and pituitary carcinomas to temozolomide: the national cooperative study by the Japan Society for Hypothalamic and Pituitary Tumors

CONTEXT

Temozolomide (TMZ) is an alkylating agent and was a first-line chemotherapeutic agent for malignant gliomas. Recently, TMZ has been documented to be effective against atypical pituitary adenomas (APAs) and pituitary carcinomas (PCs).

OBJECTIVE

The clinical and pathological characteristics of APAs and PCs treated with TMZ in Japan were surveyed and analyzed retrospectively.

DESIGN

Members of the Japan Society of Hypothalamic and Pituitary Tumors were surveyed regarding the clinical characteristics of APAs and PCs treated with TMZ. Stored tumor samples were gathered from the responders and were assessed by the immunohistochemistry of Ki-67, O(6)-methyl-guanine-DNA methyltransferase, p53, MSH6, and anterior pituitary hormones. Responses to TMZ treatment were defined as complete response (CR), partial response (PR), progressive disease (PD), and stable disease (SD) according to RECIST (Response Evaluation Criteria in Solid Tumors) version 2.0.

SUBJECTS

Three samples from 3 subjects with APA and 11 samples from 10 subjects with PC were available.

RESULTS

The 13 subjects had APAs and PCs consisting of 5 prolactin-producing tumors, 5 ACTH-producing tumors, and 3 null cell adenomas. The clinical response to TMZ treatment was as follows: 4 cases of CR and PR (31%), 2 cases of SD (15%), 6 cases of recurrence after CR and PR (46%), and 1 case of PD (8%). However, considerable subjects had recurrent disease after a response to TMZ. The immunohistochemical findings of Ki-67, O(6)-methyl-guanine-DNA methyltransferase, and p53 did not show any significant correlation with the efficacy of TMZ. However, the immunopositivity of MSH6 was positively correlated with TMZ response (P = .015, Fisher's exact test).

CONCLUSIONS

This study showed that preserving MSH6 function was contributory to the effectiveness of TMZ in malignant pituitary neoplasms. It is necessary to survey more cases and evaluate multifactor analyses.

ACTH-secreting Crooke cell carcinoma of the pituitary

PURPOSE

While pituitary adenomas are common, pituitary carcinomas are rare. It is unclear whether pituitary carcinomas arise de novo or evolve from adenomas.

METHODS

We studied the clinical characteristics and tissue samples from eight pituitary surgeries and the autopsy from a patient with pituitary carcinoma. A 16-year-old female patient was diagnosed with an aggressive Crooke cell macroadenoma. Following transsphenoidal surgery, clinical signs of Cushing disease quickly reappeared. During the 14-year course of the illness, eight pituitary surgeries, three courses of extracranial irradiation and two (90) Yttrium-DOTATOC treatments were undertaken. A bilateral adrenalectomy was performed. The patient died of metastatic disease and uncontrolled hypercortisolism due to an adrenal remnant. A systematic morphologic study (histologic staining, electron microscopy) of all available surgical and autopsy specimens was undertaken.

RESULTS

Brisk mitotic activity, high Ki-67 and p53 immunolabelling were present in the pituitary samples from the onset. High proportion of tumour cells showed irregular nuclei and large nucleoli, and gradual increase in MGMT staining was observed. The tumour remained of Crooke cell type throughout the course. Autopsy disclosed a postirradiation sarcoma in the pituitary area.

CONCLUSIONS

The question whether pituitary carcinomas arise de novo or transform from an adenoma cannot be answered at present with certainty.

Clinicopathological correlations in pituitary adenomas

Pituitary adenomas are common neuroendocrine neoplasms arising from adenohypophysial cells. Recent progress in our understanding of pituitary tumorigenesis as well as pathways involved in molecular cytodifferentiation of the adenohypophysis has impacted on the classification of pituitary adenomas. The detailed comprehensive classification of pituitary adenomas is now well recognized to reflect specific clinical features and genetic changes that predict targeted treatments, as well as prognostic information for patients with pituitary adenomas. Therefore, the clinical responsibility of pathologists is not only limited to the distinction of pituitary adenomas from other sellar lesions, but also to provide a comprehensive subtype classification using appropriate ancillary tools. In this article, we highlight an approach to clinical diagnosis and pitfalls in the classification of these common neoplasms.

A case of nonfunctioning pituitary carcinoma that responded to temozolomide treatment

Pituitary carcinoma is a rare malignancy and is difficult to manage. Pituitary carcinomas commonly produce either PRL or ACTH, but some do not produce pituitary hormones. The alkylating reagent temozolomide (TMZ) was recently shown to be effective as a treatment for pituitary carcinoma. Most of the published reports of TMZ use in pituitary carcinoma cases were against hormone-producing carcinomas. Only a few patients with a nonfunctioning pituitary carcinoma treated with TMZ have been reported. Here we describe our treatment of a patient with nonfunctioning pituitary carcinoma and a background of multiple endocrine neoplasia type 1. The pituitary carcinoma was accompanied by meningeal dissemination with cerebral and L1 spinal bone metastasis. The patient received continuous dosing of TMZ along with external radiation, followed by standard dosing of TMZ. There was an apparent antitumor response seen in MRI. MGMT, an enzyme antagonized by TMZ, was negative in the tumor. The therapeutic efficacy of TMZ and dosing schedules of TMZ in pituitary carcinoma are discussed.

Temozolomide responsiveness in aggressive corticotroph tumours: a case report and review of the literature

Pituitary carcinoma occurs in ~0.2% of resected pituitary tumours and carries a poor prognosis (mean survival <4 years), with standard chemotherapy regimens showing limited efficacy. Recent evidence suggests that temozolomide (TMZ), an orally-active alkylating agent used principally in the management of glioblastoma, may also be effective in controlling aggressive/invasive pituitary adenomas/carcinomas. A low level of expression of the DNA-repair enzyme O6-methylguanine-DNA methyltransferase (MGMT) predicts TMZ responsiveness in glioblastomas, and a similar correlation has been observed in the majority of aggressive pituitary adenomas/carcinomas reported to date. Here, we report a case of a silent pituitary corticotroph adenoma, which subsequently re-presented with Cushing's syndrome due to functioning hepatic metastases. The tumour exhibited low immunohistochemical MGMT expression in both primary (pituitary) and secondary (hepatic) lesions. Initial TMZ therapy (200 mg/m² for 5 days every 28 days-seven cycles) resulted in marked clinical, biochemical [>50% fall in adrenocorticotrophic hormone (ACTH)] and radiological [partial RECIST (response evaluation criteria in solid tumors) response] improvements. The patient then underwent bilateral adrenalectomy. However, despite reintroduction of TMZ therapy (further eight cycles) ACTH levels plateaued and no further radiological regression was observed. We review the existing literature reporting TMZ efficacy in pituitary corticotroph tumours, and highlight the pointers/lessons for treating aggressive pituitary neoplasia that can be drawn from experience of susceptibility and evolving resistance to TMZ therapy in glioblastoma. Possible strategies for mitigating resistance developing during TMZ treatment of pituitary adenomas/carcinomas are also considered.

Pituitary Centers of Excellence

Pituitary tumors and associated neuroendocrine disorders pose significant challenges in diagnostic and therapeutic management. Optimal care of the “pituitary patient” is best provided in a multidisciplinary collaborative environment that includes not only experienced pituitary practitioners in neurosurgery and endocrinology, but also in otorhinolaryngological surgery, radiation oncology, medical oncology, neuro-ophthalmology, diagnostic and interventional neuroradiology, and neuropathology. We provide the background and rationale for recognizing pituitary centers of excellence and suggest a voluntary verification process, similar to that used by the American College of Surgeons for Trauma Center verification. We propose that pituitary centers of excellence should fulfill 3 key missions: (1) provide comprehensive care and support to patients with pituitary disorders; (2) provide residency training, fellowship training, and/or continuing medical education in the management of pituitary and neuroendocrine disease; and (3) contribute to research in pituitary disorders. As this is a preliminary proposal, we recognize several issues that warrant further consideration including center and surgeon practice volume as well as oversight of the verification process.

Management Strategies for Aggressive Cushing's Syndrome: From Macroadenomas to Ectopics

Cushing's syndrome (CS) is a rare but severe clinical condition represented by an excessive endogenous cortisol secretion and hence excess circulating free cortisol, characterized by loss of the normal feedback regulation and circadian rhythm of the hypothalamic-pituitary axis due to inappropriate secretion of ACTH from a pituitary tumor (Cushing's disease, CD) or an ectopic source (ectopic ACTH secretion, EAS). The remaining causes (20%) are ACTH independent. As soon as the diagnosis is established, the therapeutic goal is the removal of the tumor. Whenever surgery is not curative, management of patients with CS requires a major effort to control hypercortisolemia and associated symptoms. A multidisciplinary approach that includes endocrinologists, neurosurgeons, oncologists, and radiotherapists should be adopted. This paper will focus on traditional and novel medical therapy for aggressive ACTH-dependent CS. Several drugs are able to reduce cortisol levels. Their mechanism of action involves blocking adrenal steroidogenesis (ketoconazole, metyrapone, aminoglutethimide, mitotane, etomidate) or inhibiting the peripheral action of cortisol through blocking its receptors (mifepristone “RU-486”). Other drugs include centrally acting agents (dopamine agonists, somatostatin receptor agonists, retinoic acid, peroxisome proliferator-activated receptor γ “PPAR-γ” ligands) and novel chemotherapeutic agents (temozolomide and tyrosine kinase inhibitors) which have a significant activity against aggressive pituitary or ectopic tumors.

Cushing's disease

Cushing’s disease, or pituitary ACTH dependent Cushing’s syndrome, is a rare disease responsible for increased morbidity and mortality. Signs and symptoms of hypercortisolism are usually non specific: obesity, signs of protein wasting, increased blood pressure, variable levels of hirsutism. Diagnosis is frequently difficult, and requires a strict algorithm. First-line treatment is based on transsphenoidal surgery, which cures 80% of ACTH-secreting microadenomas. The rate of remission is lower in macroadenomas. Other therapeutic modalities including anticortisolic drugs, radiation techniques or bilateral adrenalectomy will thus be necessary to avoid long-term risks (metabolic syndrome, osteoporosis, cardiovascular disease) of hypercortisolism. This review summarizes potential pathophysiological mechanisms, diagnostic approaches, and therapies.

Temozolomide in the management of dopamine agonist-resistant prolactinomas

BACKGROUND

The majority of prolactinomas respond to dopamine agonist therapy, but a proportion are resistant, requiring other treatments including surgery and/or radiotherapy. Temozolomide is an oral chemotherapy agent, which has been used as a salvage therapy to treat aggressive pituitary adenomas and carcinomas, including prolactinomas, unresponsive to all conventional treatment.

CASE SERIES

We report three patients where temozolomide was used in the treatment of refractory prolactinomas. Case 1 describes a patient with a highly invasive prolactinoma, resistant to all conventional therapy, which responded dramatically to temozolomide used as a salvage treatment. In case 2, temozolomide was used after incomplete surgical resection to relieve chiasmal compression and avoid chiasm exposure to radiotherapy. In case 3, temozolomide enabled radiotherapy to be deferred in a 16-year old with a resistant prolactinoma. In all three cases, the tumours were negative by immunostaining for methylguanine methyltransferase (MGMT).

LITERATURE REVIEW AND DISCUSSION

A review of the published literature reveals 51 reported cases of temozolomide treatment for pituitary tumours, including 20 prolactinomas. Fifteen of the 20 prolactinomas showed a good response to temozolomide. Our analysis demonstrates a strong association between MGMT-negative staining and a good response to temozolomide (OR 9.35, P = 0.0030). Current clinical practice is to use temozolomide as a salvage therapy after all conventional modalities of treatment have failed. We suggest that, in selected cases, consideration should be given to using temozolomide earlier in the treatment algorithm.

Pituitary carcinomas and aggressive pituitary tumours: merits and pitfalls of temozolomide treatment

Pituitary carcinomas are rare, accounting for about 0.2% of all pituitary tumours. They represent a challenge to clinical practice in both diagnosis and treatment. They may present initially as typical pituitary adenomas, with a delayed appearance of aggressive signs, or as aggressive tumours from the outset. Predicting the pituitary tumour behaviour remains difficult: increased mitotic, Ki-67 and P53 indices might be associated with tumour aggression. The treatment of pituitary carcinomas and aggressive pituitary tumours includes surgery, adjuvant medical treatment, external beam radiotherapy and chemotherapy. Until recently, the treatment of pituitary carcinomas was mainly palliative and did not seem to increase overall survival. Recent case reports have detailed the successful use of temozolomide, an orally administered alkylating agent used to treat malignant gliomas, in the management of pituitary carcinomas and aggressive pituitary tumours. The outcome of treatment might depend on the expression of O(6)-methylguanine-DNA methyltransferase (MGMT), a DNA repair enzyme that potentially interferes with drug efficacy. This review describes the clinical presentation and response to temozolomide in 44 patients with pituitary carcinomas or aggressive pituitary tumours reported in the literature. The results suggest that temozolomide should be considered a drug of major importance in the therapeutic algorithm of aggressive pituitary tumours and pituitary carcinomas. Because of the inconsistency of published data, MGMT expression should probably not be taken as a reason to deny these patients the potential benefit of temozolomide treatment, taking into account the paucity of other available treatments.

O-6-methylguanine-DNA methyltransferase (MGMT) immunohistochemical expression in pituitary corticotroph adenomas

BACKGROUND

O-6-methylguanine-DNA methyltransferase (MGMT) is a DNA repair enzyme that counteracts chemotherapeutic cytotoxicity of alkylating agents such as temozolomide. Low levels of MGMT expression have been shown to correlate with longer survival in glioma patients treated with temozolomide. The same is true in pituitary adenomas.

OBJECTIVE

We investigated the immunohistochemical expression of MGMT in a variety of corticotroph adenoma subtypes to determine the potential utility of temozolomide as a therapeutic agent.

METHODS

The tumors consisted of 40 cases of adrenocorticotropin-secreting pituitary tumors in Cushing disease, 12 Crooke cell adenomas, and 7 subtype I silent corticotroph adenomas. Staining for MGMT was assessed by light microscopy; nuclear reactivity was estimated semiquantitatively as present in < 10%, 10% to 25%, 25% to 50%, 50% to 75%, and > 75% of cells.

RESULTS

Immunoexpression showed no correlation with patient age, sex, tumor size, invasiveness, or recurrence in patients with Cushing disease. Among adrenocorticotropin-secreting adenomas associated with Cushing disease, most invasive (60%) and recurrent (86%) tumors showed low MGMT immunopositivity, defined as < 25%. Most (75%) Crooke cell adenomas exhibited an MGMT immunoreactivity of ≤ 50%. All subtype I silent corticotroph adenomas showed < 10% MGMT staining.

CONCLUSION

Our descriptive findings of low MGMT expression in adrenocorticotropin-producing pituitary adenomas, particularly aggressive tumors, suggest that they may be suitable candidates for temozolomide therapy.

New targeted therapies in pituitary carcinoma resistant to temozolomide

To evaluate the antitumoral efficacy of everolimus in pituitary carcinoma resistant to temozolomide, the correlation with mammalian target of rapamycin (mTOR) signaling in the tumor and to present recent advances and future treatments of pituitary carcinomas. Pituitary carcinomas are rare and largely unresponsive to current treatment options. Recent reports on the antitumoral efficacy of temozolomide in some such patients are encouraging, yet most patients appear to show resistance to its actions. As a potential alternative, the mTOR inhibitor, everolimus, has been shown to potently inhibit pituitary cell proliferation highlighting mTOR inhibition as a promising therapeutic approach for pituitary carcinomas. We described the tumoral effects of a combination therapy with everolimus (5 mg/day) and octreotide (30 mg/month) and the mTOR signalling expression in a patient with pituitary ACTH carcinoma, compared to 17 other ACTH adenomas. Clinical and biochemical evaluation were performed every month, and imaging after 3 month of treatment. mTOR signaling was assessed by microarray expression analysis of each of the 18 adenoma tissues. Combined therapy failed to control pituitary tumor growth and ACTH secretion. Slight activation of mTOR signaling was found in all ACTH tumors alongside important variations between tumors. Low antitumor efficacy shown by everolimus might be explained by the weak activation of mTOR pathway in ACTH tumors. Everolimus treatment was inefficient at controlling secretion and tumor growth of one ACTH pituitary carcinoma. More clinical cases, with mTOR signalling expression analysis of the tumor, must be published before any conclusions can be drawn.

Temozolomide in aggressive pituitary adenomas and carcinomas

Temozolomide is an alkylating agent used in the treatment of gliomas and, more recently, aggressive pituitary adenomas and carcinomas. Temozolomide methylates DNA and, thereby, has antitumor effects. O6-methylguanine-DNA methyltransferase, a DNA repair enzyme, removes the alkylating adducts that are induced by temozolomide, thereby counteracting its effects. A Medline search for all of the available publications regarding the use of temozolomide for the treatment of pituitary tumors was performed. To date, 46 cases of adenohypophysial tumors that were treated with temozolomide, including 30 adenomas and 16 carcinomas, have been reported. Eighteen of the 30 (60%) adenomas and 11 of the 16 (69%) carcinomas responded favorably to treatment. One patient with multiple endocrine neoplasia type 1 and an aggressive prolactin-producing adenoma was also treated and demonstrated a good response. No significant complications have been attributed to temozolomide therapy. Thus, temozolomide is an effective treatment for the majority of aggressive adenomas and carcinomas. Evidence indicates that there is an inverse correlation between levels of O6-methylguanine-DNA methyltransferase immunoexpression and therapeutic response. Alternatively, high-level O6-methylguanine-DNA methyltransferase immunoexpression correlates with an unfavorable response. Here, we review the use of temozolomide for treating pituitary neoplasms.

Clinical review: Pituitary carcinoma: difficult diagnosis and treatment

CONTEXT

Although pituitary tumors are common, pituitary carcinoma is very rare and is only diagnosed when pituitary tumor noncontiguous with the sellar region is demonstrated. Diagnosis is difficult, resulting in delays that may adversely effect outcome that is traditionally poor. Barriers to earlier diagnosis and management strategies for pituitary carcinoma are discussed.

EVIDENCE ACQUISITION

PubMed was employed to identify relevant studies, a review of the literature was conducted, and data were summarized and integrated from the author's perspective.

EVIDENCE SYNTHESIS

The available data highlight the difficulties in diagnosis and management and practical challenges in conducting clinical trials in this rare condition. They suggest that earlier diagnosis with aggressive multimodal therapy may be advantageous in some cases.

CONCLUSIONS

Although pituitary carcinoma remains difficult to diagnose and treat, recent developments have led to improved outcomes in selected cases. With broader use of molecular markers, efforts to modify current histopathological criteria for pituitary carcinoma diagnosis may now be possible. This would assist earlier diagnosis and, in combination with targeted therapies, potentially improve long-term survival.

Adrenocorticotropic hormone-producing pituitary carcinoma with intracranial metastases

BACKGROUND

Pituitary carcinomas are rare and challenging clinical entities. Because of the paucity of cases, there is limited information in the literature on how best to diagnose and treat pituitary carcinomas.

METHODS

We review the literature and describe a woman who presented with an adrenocorticotropic hormone (ACTH)-secreting pituitary macroadenoma that later evolved into a carcinoma with intracranial metastases.

RESULTS

A 39-year-old woman presented at age 27 with classic findings of Cushing's syndrome and a pituitary macroadenoma. Her initial treatment was transsphenoidal surgery, during which we confirmed an ACTH-secreting pituitary neoplasm. For 5 years, she was asymptomatic before her first recurrence. During the next 6 years, she underwent four transsphenoidal surgeries and two craniotomies. After each surgery, there was some reduction in the size of the macroadenoma but the residual tumor mass would rapidly enlarge. Immunochemical staining was positive for ACTH, and a stain for Ki-67 antigen showed a high mitotic index. Eleven years after her initial presentation, magnetic resonance imaging revealed bilateral hippocampal and tempero-occipital masses. The patient's health continued to deteriorate, largely from complications of severe hypercortisolemia, and she died from sepsis. At postmortem, the hippocampus and tempero-occipital lobe masses proved to be a pituitary tumor with positive ACTH staining.

CONCLUSIONS

Pituitary carcinomas are rare, may present many years after diagnosis of a primary pituitary adenoma, and should be suspected in patients with persistent or recurrent disease. Reliable histopathologic ways to distinguish between carcinoma and adenoma are difficult because the features of hypercellularity, nuclear pleomorphism, and mitotic figures are not always helpful.

Aggressive pituitary tumours: the role of temozolomide and the assessment of MGMT status

BACKGROUND

Aggressive pituitary tumours are associated with substantial morbidity and mortality. Treatment options are often limited, and chemotherapy has been reserved as salvage therapy although historically results have often been disappointing. However, temozolomide, an oral alkylating agent, has recently demonstrated significant activity against these tumours. A DNA repair protein, 06-methylguanine-DNA methyltransferase (MGMT) has been suggested as a biomarker to predict response to temozolomide in pituitary tumours.

MATERIALS AND METHODS

This paper will review the current literature on temozolomide and pituitary tumours and discuss the recent controversy surrounding the value of determining the MGMT status in this tumour group. A PubMed search was performed to retrieve articles, using the terms 'pituitary tumour' and 'temozolomide'.

RESULTS

Overall, 24/40 (60%) of the published cases demonstrated a response to temozolomide therapy. The highest response rates were seen amongst prolactinomas (73%) and ACTH-secreting tumours (60%), whilst nonfunctioning pituitary tumours exhibit lower response rates (40%). Responsivity is typically evident in the first 3 months of therapy and may be dramatic and sustained. Low MGMT expression, as determined by immunohistochemistry, is associated with a high response rate (76%), whilst high MGMT expression has not been associated with responses. MGMT promoter methylation does not correlate with temozolomide response.

CONCLUSIONS

Temozolomide is the first chemotherapeutic agent to show substantial response rates in aggressive pituitary tumours. MGMT immunohistochemistry, but not MGMT methylation analysis, shows promise as a predictive tool. Prospective clinical trials are now necessary to more accurately determine the efficacy of this agent in this patient group.

MGMT immunoexpression in growth hormone-secreting pituitary adenomas and its correlation with Ki-67 labeling index and cytokeratin distribution pattern

Recent publications suggest the utility of temozolomide (TMZ) in the management of aggressive pituitary adenomas and carcinomas, resistant to conventional treatments. The response to TMZ is inversely correlated with tumoral expression of O-6 methylguanine DNA methyl transferase (MGMT). Therefore, we aimed to assess MGMT immunoexpression in pure GH-secreting pituitary adenomas, in an effort to predict the likelihood of response to TMZ, and to correlate MGMT immunoexpression with Ki-67 LI and cytokeratin (CK) distribution pattern. Our material consisted of 36 GH-secreting pituitary adenomas (21 female,15 male, mean age 42.5±10.5), operated at our center between 2003 and 2010. Immunostaining for MGMT, Ki-67, and CK was performed using avidin-biotin-peroxidase complex method. Immunoreactivity for MGMT and Ki-67 was evaluated microscopically and recorded as percentages of positive nuclear immunostaining. CK distribution pattern was also evaluated microscopically and assoreted into dot-like and nondot-like pattern subtypes. MGMT immunoexpression scored as 0=none, 1=<10%, 2=<25%, 3=<50%, and 4=>50%. Staining for MGMT was <10% (score 1) in 30 (83.3%), 10-25% (score 2) in 3 (8.3%), 25-50% (score 3) in 2 (5.6%) and >50% (score 4) in 1 (2.8%) of the tumors, respectively. There was no correlation between Ki-67 LI and CK distribution pattern with MGMT immunoreactivity (P>0.05). Data from the current study suggest a large proportion of GH-secreting adenomas, including those with dot-like CK distribution pattern and high Ki-67 LI, demonstrate negative/low MGMT immunoreactivity and could be treated with TMZ, if conventional treatment fails.

Therapy of aggressive pituitary tumors

INTRODUCTION

Aggressive tumors of the pituitary gland are classically defined as pituitary tumors with a massive invasion of the surrounding anatomical structures and rapid growth. They are notoriously difficult to manage and are associated with poor prognosis because the therapeutic options are limited and the tumors are generally unresponsive to therapy.

AREAS COVERED

This review focuses on treatment options for aggressive pituitary tumors, including surgery, radiotherapy and medical treatment, as well as focusing on the promising therapeutic options for aggressive pituitary tumors, evaluating the literature of the last 15 years. With the exception of prolactinomas, surgery is the first-line option, but most aggressive pituitary tumors often require repeated surgery. Pharmacotherapies are useful when surgery is unlikely to improve symptoms, or as an adjunct therapy to surgery. In prolactinomas, dopamine agonists are the first-line treatment and normalize prolactin levels in most patients, even those with macroprolactinomas. Somatostatin analogs are effective agents for primary therapy, pre-operatively or post-operatively to control tumor re-expansion of pituitary adenomas. However, dopamine agonists and somatostatin analogs are not as effective as they are for the treatment of non-aggressive adenomas. When surgery and pharmacotherapy fail, radiotherapy is a useful third-line strategy. Conventional chemotherapy is poorly effective but recent case reports with the temozolomide, an alkylating agent, have provided better results in the short term.

EXPERT OPINION

Aggressive pituitary tumors are associated with poor prognosis as therapeutic options are limited. Moreover, they tend to recur quickly after initial treatment, are generally unresponsive to therapy, and are difficult to manage. To improve the overall response rate, the early application of current therapeutic approaches with the incorporation of new therapeutic developments is mandatory.

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.