Radiation therapy for Cushing's disease: a review

Pathway-based analyses of gene expression profiles at low doses of ionizing radiation

Radiation exposure poses a significant threat to human health. Emerging research indicates that even low-dose radiation once believed to be safe, may have harmful effects. This perception has spurred a growing interest in investigating the potential risks associated with low-dose radiation exposure across various scenarios. To comprehensively explore the health consequences of low-dose radiation, our study employs a robust statistical framework that examines whether specific groups of genes, belonging to known pathways, exhibit coordinated expression patterns that align with the radiation levels. Notably, our findings reveal the existence of intricate yet consistent signatures that reflect the molecular response to radiation exposure, distinguishing between low-dose and high-dose radiation. Moreover, we leverage a pathway-constrained variational autoencoder to capture the nonlinear interactions within gene expression data. By comparing these two analytical approaches, our study aims to gain valuable insights into the impact of low-dose radiation on gene expression patterns, identify pathways that are differentially affected, and harness the potential of machine learning to uncover hidden activity within biological networks. This comparative analysis contributes to a deeper understanding of the molecular consequences of low-dose radiation exposure.

Management of patients with persistent or recurrent Cushing's disease after initial pituitary surgery

INTRODUCTION

Treatment options for persistent and recurrent Cushing's disease (CD) include an individualized approach for repeat surgery, medical treatment, radiation therapy (RT), and bilateral adrenalectomy (BLA).

AREAS COVERED

In this expert opinion perspective, the authors review the latest treatment(s) for persistent/recurrent CD. A PubMed search was undertaken (English articles through May 2020) and relevant articles discussed. Repeat pituitary surgery should be considered in most patients with proven hypercortisolism; there is potential for cure with low risk of major complications. Medical therapy is valuable either alone, while awaiting the effects of RT, or in preparation for BLA. Medical therapy includes steroidogenesis inhibitors, agents that act at the pituitary or glucocorticoid receptor level, and novel agents in development. Radiation therapy has been used successfully to treat CD, but hypopituitarism risk and delayed efficacy (improved with radiosurgery) are major drawbacks. Laparoscopic BLA is safe and effective in patients with severe, difficult-to-manage hypercortisolism, but long-term follow-up is required as corticotroph tumor progression can develop.

EXPERT OPINION

Treatment of persistent/recurrent CD is challenging. Most patients require >1 therapy to achieve long-lasting remission. There is currently no ideal single treatment option that provides high and rapid efficacy, low adverse effects, and preserves normal pituitary-adrenal axis function.

Persistent Cushing's Disease after Transsphenoidal Surgery: Challenges and Solutions

Transsphenoidal surgery remains the primary treatment for Cushing's disease (CD). However, despite the vast improvements in pituitary surgery, successful treatment of CD remains a great challenge. Although selective transsphenoidal removal of the pituitary tumor is a safe and effective procedure, the disease persists in around 22% of CD patients due to incomplete tumor resection. The persistence of hypercortisolism after pituitary surgery may also be the consequence of a misdiagnosis, as can occur in case of ectopic ACTH secretion or pseudo-Cushing. Considering the elevated mortality and morbidity characterizing the disease, a multidisciplinary approach is needed to minimize potential pitfalls occurring during the diagnosis, avoid surgical failure and provide the best care in those patients who have undergone unsuccessful surgery. In this review, we analyze the factors that could predict remission or persistence of CD after pituitary surgery and revise the therapeutic options in case of surgical failure.

The use of yttrium in medical imaging and therapy: historical background and future perspectives

Yttrium presents a wide palette of isotopes with interesting coordination and radiochemical properties. We review its most prominent isotopes and their diverse medical uses in therapy and imaging.

[Retrospective analysis to evaluate efficacy and safety of stereotactic radiosurgery in Cushing's disease: 24 cases and a review]

BACKGROUND

In the past few years, stereotactic radiosurgery (SRS) has been suggested as a good alternative, second line therapy for the management of patients with ACTH-secreting pituitary adenomas. A retrospective study has been conducted in order to evaluate the efficacy and safety of this treatment in these patients.

MATERIAL AND METHODS

Data were collected on all patients treated with SRS for an ACTH-secreting pituitary adenoma between 1996 and 2008, and with at least one year of follow-up. An analysis was carried out by analysing the return to normal of the hormone levels and clinical improvement rates (including Cushing signs, arterial hypertension), as well as adverse effects, and disease relapse. A return to normal of the 24 hour urinary free cortisol (24-UFC) levels (<100 μg/day) without any ACTH-secretion suppressor drug treatment, was considered as cure or improvement.

RESULTS

A total of 30 patients were treated with SRS, of which 24 were included in the analysis. They all had high 24-UFC levels before the treatment. Cure was achieved in 12 (50%) in a mean of 28 months, and in other 3 patients 24-UFC levels returned to normal with treatment with ketoconazole after the SRS. Cushing signs improved in all cases, as well as arterial hypertension in 13 out of 14 cases. There were relapses after cure consolidation. As far as adverse effects, it should be mentioned that there were 9 cases of new pituitary hormonal dysfunction (the most frequent being hypothyroidism), one radionecrosis, and one case of visual field defect impairment. Radiation-related neoplasm was not detected in any of the cases.

CONCLUSIONS

SRS is an effective treatment for those patients with ACTH-secreting pituitary adenoma in whom surgery has failed, or in those that are not good candidates for it. It showed good rates of hormone levels returning to normal, as well as clinical disease control and a low level of adverse effects.

The Treatment of Cushing's Disease

Cushing's disease (CD), or pituitary-dependent Cushing's syndrome, is a severe endocrine disease caused by a corticotroph pituitary tumor and associated with increased morbidity and mortality. The first-line treatment for CD is pituitary surgery, which is followed by disease remission in around 78% and relapse in around 13% of patients during the 10-year period after surgery, so that nearly one third of patients experience in the long-term a failure of surgery and require an additional second-line treatment. Patients with persistent or recurrent CD require additional treatments, including pituitary radiotherapy, adrenal surgery, and/or medical therapy. Pituitary radiotherapy is effective in controlling cortisol excess in a large percentage of patients, but it is associated with a considerable risk of hypopituitarism. Adrenal surgery is followed by a rapid and definitive control of cortisol excess in nearly all patients, but it induces adrenal insufficiency. Medical therapy has recently acquired a more important role compared to the past, due to the recent employment of novel compounds able to control cortisol secretion or action. Currently, medical therapy is used as a presurgical treatment, particularly for severe disease; or as postsurgical treatment, in cases of failure or incomplete surgical tumor resection; or as bridging therapy before, during, and after radiotherapy while waiting for disease control; or, in selected cases, as primary therapy, mainly when surgery is not an option. The adrenal-directed drug ketoconazole is the most commonly used drug, mainly because of its rapid action, whereas the glucocorticoid receptor antagonist, mifepristone, is highly effective in controlling clinical comorbidities, mainly glucose intolerance, thus being a useful treatment for CD when it is associated with diabetes mellitus. Pituitary-directed drugs have the advantage of acting at the site responsible for CD, the pituitary tumor. Among this group of drugs, the dopamine agonist cabergoline and the somatostatin analog pasireotide result in disease remission in a consistent subgroup of patients with CD. Recently, pasireotide has been approved for the treatment of CD when surgery has failed or when surgery is not an option, and mifepristone has been approved for the treatment of Cushing's syndrome when associated with impairment of glucose metabolism in case of the lack of a surgical indication. Recent experience suggests that the combination of different drugs may be able to control cortisol excess in a great majority of patients with CD.

Managing Cushing's disease: the state of the art

Cushing's disease is a rare chronic disease caused by a pituitary adenoma, which leads to excess secretion of adrenocorticotropic hormone (ACTH). The over-production of ACTH leads to hyperstimulation of the adrenal glands and a chronic excess of cortisol, resulting in the signs and symptoms of a severe clinical state (Cushing's syndrome) that leads to significant morbidity, negative impacts on the patient's quality of life, and, if untreated, increased mortality. The management of patients with Cushing's disease is complicated by the heterogeneity of the condition, with signs and symptoms that overlap with those of other diseases, and high subclinical incidence rates. Controversies surrounding the tests used for screening and identifying patients with Cushing's disease add to the challenge of patient management. Surgical intervention to remove the adenoma is the first-line treatment for patients with Cushing's disease, but medical therapies are useful in patients who relapse or are unsuitable for surgery. The recent introduction of pasireotide, the first pituitary-directed medical therapy, expands the number of treatment options available for patients with Cushing's disease. This state-of-the-art review aims to provide an overview of the most recent scientific research and clinical information regarding Cushing's disease. Continuing research into improving the diagnosis and treatment of Cushing's disease will help to optimize patient management.

Complete surgical removal of a very enlarged pituitary corticotroph adenoma in a dog

A 13 yr old castrated male vizsla was referred to the authors' institute because of polyuria, polydipsia, polyphagia, and weight loss. Pituitary-dependent hypercortisolism (PDH) was diagnosed by hormone testing and adrenal and pituitary imaging. Computed tomography (CT) revealed a pituitary mass measuring 21 mm in width. Medical therapy was initiated with trilostane. Despite adequate control of the hypercortisolemia, the polyuria and polydipsia persisted and the dog developed neurologic signs due to the pituitary mass effect. Pituitary transsphenoidal debulking surgery was performed and immunocytochemistry confirmed a corticotroph adenoma. The dog survived for 13 mo after surgery. Postmortem examination revealed an empty fossa without pituitary remnants and the presence of a malignant pheochromocytoma in the right adrenal gland. This case report demonstrates, for the first time, that a large pituitary adenoma in the dog may be treated successfully by pituitary surgery.

An approach to the evaluation and treatment of Cushing’s disease

Cushing's syndrome is an uncommon disorder involving dysregulation of the hypothalamic-pituitary-adrenal axis resulting in endogenous hypercortisolemia. It has multiple causes, but most commonly is due to hypersecretion of corticotropin from the pituitary gland, called Cushing's disease. The diagnosis of Cushing's syndrome remains a challenge to clinicians because routine hormonal assays can have significant overlap in pathological and normal states. We will review an approach to evaluating patients with suspected cortisol excess. We will also discuss treatment options and post-surgical assessment for those diagnosed with Cushing's disease.

Mitotane reduces human and mouse ACTH-secreting pituitary cell viability and function

Medical therapy for Cushing's disease (CD) is currently based on agents mainly targeting adrenocortical function. Lately, pituitary-directed drugs have been developed, with limited efficacy. Mitotane, a potent adrenolytic drug, has been recently investigated for the treatment of CD, but the direct pituitary effects have not been clarified so far. The aim of our study was to investigate whether mitotane may affect corticotroph function and cell survival in the mouse pituitary cell line AtT20/D16v-F2 and in the primary cultures of human ACTH-secreting pituitary adenomas, as an in vitro model of pituitary corticotrophs. We found that in the AtT20/D16v-F2 cell line and in primary cultures, mitotane reduces cell viability by inducing caspase-mediated apoptosis and reduces ACTH secretion. In the AtT20/D16v-F2 cell line, mitotane reduces Pomc expression and blocks the stimulatory effects of corticotropin-releasing hormone on cell viability, ACTH secretion, and Pomc expression. These effects were apparent at mitotane doses greater than those usually necessary for reducing cortisol secretion in Cushing's syndrome, but still in the therapeutic window for adrenocortical carcinoma treatment. In conclusion, our results demonstrate that mitotane affects cell viability and function of human and mouse ACTH-secreting pituitary adenoma cells. These data indicate that mitotane could have direct pituitary effects on corticotroph cells.

Stereotactic radiosurgery for treatment of Cushing disease: an Australian experience

Stereotactic radiation therapy has emerged as an alternative to conventional radiotherapy for treatment of Cushing disease. The aim of this study was to investigate the efficacy and safety of this treatment. Records of patients with Cushing disease treated with stereotactic radiation were reviewed. Seventeen patients underwent stereotactic radiosurgery. Ten achieved remission after a mean of 23 (95% confidence interval, 15-31) months, and two developed hormone deficiencies.

Treatment of pituitary adenomas using radiosurgery and radiotherapy: a single center experience and review of literature

Fractionated radiotherapy (FRT) and gamma knife stereotactic radiosurgery (GKSRS) are used as adjuvant therapies to surgical resection for functional and non-functional pituitary adenomas, although their optimum role in the treatment algorithm, as well as long-term safety and efficacy, still awaits further study. We report a single center experience with 33 patients with non-functional (16 patients), ACTH- (five patients), GH- (four patients), or prolactin-secreting (eight patients) tumors treated with FRT or SRS. The median tumor diameter was 1.9 cm, and the median follow-up was 36 months. For GKSRS, the median dosage was 16 Gy for non-functional adenomas and 23 Gy for hormone-secreting tumors. The median total dose for FRT was 50.4 Gy over 28 fractions (median). Two patients (6%) demonstrated radiographic evidence of tumor progression, three patients (9%) demonstrated radiation-induced visual field deficits on neuro-ophthalmic evaluation, and two patients (6%) suffered from radiation-induced hypopituitarism. Biochemical control, defined as normalized hormone values in the absence of medical therapy, was achieved in five out of eight prolactinoma patients and two out of five patients with Cushing's disease, but none of the four patients with acromegaly. These results are presented with a review of the relevant literature on the differential characteristics of FRT versus SRS in the treatment of functional and non-functional pituitary adenomas and validate postoperative irradiation as a potentially safe and effective means for tumor control.

Surgical management of pediatric Cushing's disease: an analysis of 15 consecutive cases at a specialized neurosurgical center

OBJECTIVE: The aim of this study was to review the results of surgery for pediatric patients with Cushing's disease who were less than 18 years old and underwent transsphenoidal surgery in a specialized center during a 25-year period. SUBJECTS AND METHODS: Retrospective study, in which the medical records, histology and pituitary imaging of 15 consecutive pediatric patients with Cushing's disease (mean age: 13 years) were evaluated by the same team of endocrinologists and a neurosurgeon from 1982 to 2006. Patients were considered cured when there was clinical adrenal insufficiency and serum cortisol levels were below 1. 8 µg/dL or 50 nmol/L after one, two, three, or seven days following surgery; they therefore required cortisone replacement therapy. Follow-up was for a median time of 11.5 years (range: 2 to 25 years). RESULTS: Clinical and biochemical cure was achieved in 9/15 patients (60%) exclusively after transsphenoidal surgery. Hypopituitarism was observed in four patients; growth hormone deficiency, in two; permanent diabetes insipidus, in one case. CONCLUSIONS: Cushing's disease is rare in children and adolescents. Transsphenoidal surgery is an effective and safe treatment in most of these patients. Plasma cortisol level < 1. 8 µg/dL following surgery is the treatment goal and is a good predictive factor for long-term cure of Cushing's disease.

Efficacy of transsphenoidal surgery on endocrinological status and serum chemistry parameters in dogs with Cushing's disease

Postoperative changes in endocrinological status and serum chemistry during the 4 years after transsphenoidal surgery (TSS) in 25 dogs with Cushing's disease were investigated in a prospective study. In all 25 dogs, Cushing's disease was diagnosed from resected pituitary tissues as a corticotroph adenoma in the anterior lobe of the pituitary. Prior to TSS, all 25 dogs showed hypercortisolemia. After TSS, the ACTH stimulation test showed continued low serum cortisol concentrations in 21 dogs (84%). In addition, the serum thyroid stimulating hormone concentrations decreased sequentially, while the serum T4 concentrations tended to increase due to the postoperative hormone substitution therapy utilized to avoid secondary hypothyroidism. In regard to serum chemistry, alkaline phosphatase (ALP), alanine aminotransferase (ALT) and total cholesterol are commonly increased in canine Cushing's disease. In this study, ALP, ALT and total cholesterol were increased in 23 cases (92%), 19 cases (76%) and 20 cases (80%), respectively. However, postoperatively, these concentrations gradually decreased. The postoperative serum concentrations of ALP at 1 year, that of ALT at six months to 2 years and that of total cholesterol over the course of the 4 years decreased significantly compared with the concentrations before TSS. These results show that TSS is an effective treatment for canine Cushing's disease and for long-term improvement of hypercortisolemia. Moreover, TSS is effective in improvement of hypercortisolism, such as increased concentrations of serum ALP, ALT and total cholesterol.

Somatostatin and dopamine receptors as targets for medical treatment of Cushing's Syndrome

Somatostatin (SS) and dopamine (DA) receptors are widely expressed in neuroendocrine tumours that cause Cushing's Syndrome (CS). Increasing knowledge of specific subtype expression within these tumours and the ability to target these receptor subtypes with high-affinity compounds, has driven the search for new SS- or DA-based medical therapies for the various forms of CS. In Cushing's disease, corticotroph adenomas mainly express dopamine receptor subtype 2 (D(2)) and somatostatin receptor subtype 5 (sst(5)), whereas sst(2) is expressed at lower levels. Activation of these receptors can inhibit ACTH-release in primary cultured corticotroph adenomas and compounds that target either sst(5) (pasireotide, or SOM230) or D(2) (cabergoline) have shown significant efficacy in subsets of patients in recent clinical studies. Combination therapy, either by administration of both types of compounds separately or by treatment with novel somatostatin-dopamine chimeric molecules (e.g. BIM-23A760), appears to be a promising approach in this respect. In selected cases of Ectopic ACTH-producing Syndrome (EAS), the sst(2)-preferring compound octreotide is able to reduce cortisol levels effectively. A recent study showed that D(2) receptors are also significantly expressed in the majority of EAS and that cabergoline may decrease cortisol levels in subsets of these patients. In both normal adrenal tissue as well as in adrenal adenomas and carcinomas that cause CS, sst and DA receptor expression has been demonstrated. Although selected cases of adrenal CS may benefit from sst or DA-targeted treatment, its total contribution to the treatment of these patients is likely to be low as surgery is effective in most cases.

An approach to the management of patients with residual Cushing's disease

The evaluation and management of patients with residual Cushing’s disease is one of the more complex issues facing neurosurgeons and neuroendocrinologists in clinical practice. There is considerable controversy over several relevant issues such as the timing of the assessment of whether a patient is in remission, what biochemical parameters define remission, the most appropriate course of action to take after residual disease has been defined, etc. As a consequence of the controversies, treating physicians develop notions and fall into certain practice patterns based on evidence of varying levels, their anecdotal experiences, and information gleaned from scientific meetings. This practice pattern, we believe, constitutes the “art of medicine.” We conducted a PubMed literature search to identify manuscripts containing data relevant to Cushing’s disease, outcomes of various therapeutic modalities, and recurrences. Reference lists were used to identify additional relevant manuscripts. We focused our review on manuscripts that included reasonably large series of patients, those reflecting the experience of pituitary centers and physicians recognized as experts in the field, and those papers felt to represent seminal contributions to the literature. Furthermore, trends in the evaluation and management of relevant patients have been incorporated by the senior author who has seen and evaluated over 750 patients with documented Cushing’s syndrome over the past 18 years in clinical practice. An analysis of current evidence indicated that, despite advances in neurosurgical techniques and recent developments in adjuvant therapies, patients with residual Cushing’s disease present significant management challenges to treating physicians. In this era, however, it is indeed possible to gain control of the hypercortisolism in most patients. Despite the wide variability in research methodology designed to collect relevant data, a step-wise approach to the management of these patients can be achieved. A logical step-wise approach to the evaluation of postoperative patients with Cushing’s disease is essential. Patients with residual disease require the development of an individualized plan of management that takes into account numerous factors pertaining to status of disease, the experience of treating physicians, and available therapeutic modalities.

Stereotactic radiosurgery for pituitary adenomas: a comprehensive review of indications, techniques and long-term results using the Gamma Knife

OBJECT

This study reviews the long-term clinical results of stereotactic radiosurgery in the treatment of pituitary adenoma patients.

METHODS

We reviewed the outcomes of 298 patients who underwent Gamma Knife radiosurgery for recurrent or residual pituitary adenomas. These results are compared to other contemporary radiosurgical series.

RESULTS

Pituitary tumors are well-suited for radiosurgery, since radiation can be focused on a well circumscribed region, while adjacent neural structures in the suprasellar and parasellar regions are spared. The overall rate of volume reduction following stereotactic radiosurgery is 85% for non-secretory adenomas that are followed for more than 1-year. The rates of hormonal normalization in patients with hypersecretory adenomas can vary considerably, and tends to be higher in patients with Cushing's Disease and acromegaly (remission rate of approximately 53% and 54%, respectively) when compared with patients who have prolactinomas (24% remission) and Nelson's syndrome (29%) remission. Advances in dose delivery and modulation of adenoma cells at the time of radiosurgery may further improve results.

CONCLUSIONS

Although the effectiveness of radiosurgery varies considerably depending on the adenoma histopathology, volume, and radiation dose, most studies indicate that radiosurgery when combined with microsurgery is effective in controlling pituitary adenoma growth and hormone hypersecretion. Long-term follow-up is essential to determine the rate of endocrinopathy, visual dysfunction, hormonal recurrence, and adenoma volume control.

Cushing's disease: radiation therapy

The usual first treatment for Cushing's disease is surgical removal of the pituitary adenoma. In patients in whom surgery is unsuccessful or who decline an operation, radiation to the pituitary offers the possibility of remission. No form of radiation delivery results in immediate control of cortisol production. Thus, until radiation treatment becomes effective, medical therapy to lower cortisol production is indicated. The time to remission with radiation therapy cannot be predicted, medical therapy should be discontinued every 6 months to assess response to radiation treatment; a normal 24 h urine free cortisol being the optimal outcome. There are no prospective studies comparing the results among the different types of radiation delivery. The type of radiation delivery depends on several factors, including the availability of different treatment modalities and the size of the target area (focused high dose radiation with the Gamma knife is not suitable for a large lesion close to the optic nerves or optic chiasm). All types of radiation delivery cause loss of normal pituitary function and patients should be monitored regularly (every 6 months) for development of new hypopituitarism and appropriate hormone replacement(s). Complications of radiation therapy may include adverse effects on vision, normal brain tissue, and with older methods of fractionated radiation delivery, vasculopathy with an increased risk of cerebrovascular disease. Current use of more targeted methods of delivery will hopefully reduce this risk. If pituitary surgery is unsuccessful and the patient undergoes bilateral adrenalectomy, without pituitary radiation, there is a substantial risk, approximately 50% of patients, of development of Nelson's syndrome (growth of pituitary adenoma, increase in serum ACTH, hyperpigmentation). There is a role for pituitary radiation in the treatment of patients with Cushing's disease, most commonly as adjunctive therapy after unsuccessful pituitary surgery. Regular medical monitoring is necessary to determine the effectiveness of radiation therapy and development of new pituitary hormone deficiency.

Management of Cushing's disease: outcome in patients with microadenoma detected on pituitary magnetic resonance imaging

OBJECT

Outcomes of therapy for Cushing's disease (CD) vary depending on different aspects of presentation and diagnostic studies. The authors designed this study to verify the remission rate and outcomes after transsphenoidal surgery (TSS) for patients with CD who had positive findings on MR imaging.

METHODS

Patients who had presented with CD at the University of Virginia for initial treatment between July 1992 and December 2005 were retrospectively reviewed. The patients included in the study were considered to be optimal surgical candidates, defined as an adult (>18 years of age) with classic clinical features of CD, laboratory studies confirming a central (pituitary/hypothalamic) adrenocorticotropic hormone-dependent source of disease, and an MR imaging study revealing a microadenoma in the sella turcica.

RESULTS

A total of 167 patients fulfilled the criteria. Thirty were men (18%) and 137 were women (82%). The mean age was 42.3 years (range 18.2-77 years). All patients underwent TSS. Surgical remission was achieved in 148 patients (88.6%), which was correlated with the surgeon's intraoperative identification of an adenoma (p=0.03). Histopathological confirmation of an adrenocorticotropic hormone-secreting adenoma strongly correlated with remission (p=0.0001). Three patients (1.8%) had postoperative cerebrospinal fluid leaks, and 1 patient had meningitis. Transient diabetes insipidus was diagnosed and treated in 10 patients (6%), whereas permanent diabetes insipidus occurred in 8 patients (4.8%). Panhypopituitarism followed the surgery in 14 patients (8.3%), 13 of whom underwent total hypophysectomy (9 initially and 4 with early reoperations), and in 1 of 10 patients who underwent subtotal hypophysectomy. Nineteen patients (12.8%) who were initially in remission developed recurrent CD after an average of 50 months. The mean follow-up for the 167 patients was 39 months (range 6-157 months). Gamma Knife surgery was the most common modality of radiotherapy used to treat 31 patients (18.5%) who did not achieve remission or later presented with recurrent disease. Bilateral adrenalectomies were performed in 10 patients in the series (6%), 2 of whom developed Nelson's syndrome. The overall posttreatment remission rate was 95.8%.

CONCLUSIONS

Even in patients with ideal diagnostic criteria of CD, there remain a significant number of cases in which TSS alone is not adequate to assure long-lasting remission. A multidisciplinary approach is essential to the achievement of satisfactory overall remission rates.

Nelson syndrome: comprehensive review of pathophysiology, diagnosis, and management

Nelson syndrome (NS) is a rare clinical manifestation of an enlarging pituitary adenoma that can occur following bilateral adrenal gland removal performed for the treatment of Cushing disease. It is characterized by excess adreno-corticotropin secretion and hyperpigmentation of the skin and mucus membranes. The authors present a comprehensive review of the pathophysiology, diagnosis, and management of NS. Corticotroph adenomas in NS remain challenging tumors that can lead to significant rates of morbidity and mortality. A better understanding of the natural history of NS, advances in neurophysiology and neuroimaging, and growing experience with surgical intervention and radiation have expanded the repertoire of treatments. Currently available treatments include surgical, radiation, and medical therapy. Although the primary treatment for each tumor type may vary, it is important to consider all of the available options and select the one that is most appropriate for the individual case, particularly in cases of lesions resistant to intervention.

Outcomes and management of patients with Cushing's disease without pathological confirmation of tumor resection after transsphenoidal surgery

CONTEXT

Despite the success of transsphenoidal surgery (TSS) for the treatment of Cushing's disease, in a number of cases, an ACTH-staining pituitary adenoma is not identified histologically. The clinical significance of lack of histological confirmation remains unclear.

SETTING

This was a retrospective review of patients treated at the University of Virginia Medical Center.

PATIENTS

Of 490 TSS procedures for Cushing's disease between 1993 and 2004, we identified 111 cases without histological adenoma confirmation.

MAIN OUTCOME MEASURE

Remission and recurrence of Cushing's disease were measured.

RESULTS

Overall, 50% of these patients achieved remission, a figure lower than for our entire series (79%) and for patients with histological confirmation of an ACTH-staining adenoma (88%) (P < 0.001). Patients with a history of two prior TSS achieved remission less often than patients with a history of fewer TSS (P = 0.026). No other factors influenced remission rates. Although the overall recurrence rate (21%, seven of 33 evaluated) was not different from previously published long-term studies, in three of seven cases of recurrence, early recurrences were noted between 2 and 4 months after remission. In patients who did not achieve remission, the most common and effective treatment options were repeat TSS, gamma-knife radiosurgery, and bilateral adrenalectomy.

CONCLUSION

The lower remission rate in patients without histological evidence of an adenoma is most likely a result of a decreased rate of adenoma extirpation. The incidence of early recurrence may be a unique feature of this patient population; patients without histological confirmation of tumor resection therefore require close and consistent monitoring postoperatively.

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

PURPOSE OF REVIEW

Adenectomy via transsphenoidal surgery is considered the treatment of choice for Cushing's disease. It is successful in about 80% of patients in the hands of an experienced surgeon. When transsphenoidal surgery fails or is contraindicated, a second-line treatment must be chosen. The review focuses on second-line treatment options.

RECENT FINDINGS

Repeat pituitary surgery results in the cure of Cushing's disease in about 50% of cases. Bilateral adrenalectomy results in resolution of hypercortisolemia in almost all patients, but leaves the patient glucocorticoid and mineralocorticoid deficient. Nelson's syndrome, depending on the definition, occurs in up to 35% of these patients. Irradiation of the residual pituitary tumor typically takes several years before the full effect is realized; it can cause panhypopituitarism. Finally, pharmacologic treatment of persistent hypercortisolemia can be effective, but is often associated with untoward side effects. These side effects are a powerful deterrent to its use. Several new pharmacologic agents are being studied and show some promise.

SUMMARY

Each of the second-line treatments for Cushing's disease currently available can be effective at treating hypercortisolism, but each has significant limitations. New pharmacologic agents may soon offer some very exciting treatment options.

Pitfalls in the management of Cushing’s disease

Cushing's disease is caused by functional corticotroph adenomas of the pituitary gland, most commonly noninvasive microadenomas. Transsphenoidal microsurgery is an effective means of control for patients with adrenocorticotrophic hormone-producing microadenomas. However, a wide variation of clinical outcomes and recurrence rates has been reported. The major causes of surgical failure in the treatment of Cushing's disease lies in inadequate preoperative evaluation, unsuccessful identification of the adenoma and inexperience of the surgeon. Furthermore, appropriate use of combination therapy, including surgery, radiotherapy, radiosurgery and adrenalectomy can improve the outcome. For optimal results in this rare disease, endocrinological, radiological and surgical procedures should be co-ordinated in a specialized center. In this review, factors affecting preoperative evaluation, surgical success and outcome are outlined in the light of current knowledge.

Cushing's Syndrome: important issues in diagnosis and management

CONTEXT

The diagnosis, differential diagnosis, and treatment of Cushing's syndrome are challenging problems in clinical endocrinology. We focus on critical questions addressing screening for Cushing's syndrome, differentiation of Cushing's subtypes, and treatment options.

EVIDENCE ACQUISITION

Ovid's MEDLINE (1996 through April 2006) was used to search the general literature. We also relied on previously published reviews and a recent monograph and cite a mix of primary articles and recent reviews.

EVIDENCE SYNTHESIS

Although this article represents our opinion, it draws heavily on a recent consensus statement from experts in the field and a recent monograph on Cushing's syndrome.

CONCLUSIONS

We concluded that: 1) measurement of late-night or bedtime salivary cortisol is a useful approach to screen for Cushing's syndrome; 2) measurement of suppressed plasma ACTH by immunometric assay is useful to differentiate ACTH-dependent and -independent Cushing's syndrome; 3) inferior petrosal sinus sampling for ACTH should be performed in patients with ACTH-dependent hypercortisolism in whom a pituitary magnetic resonance imaging is normal or equivocal (in the absence of a pituitary ACTH gradient, prolactin levels should be measured to confirm the integrity of venous sampling); 4) computed tomography of the chest and abdomen and somatostatin receptor scintigraphy should be performed in patients with the occult ectopic ACTH syndrome; and 5) patients with Cushing's disease should be referred to a neurosurgeon with extensive experience operating on corticotroph microadenomas. Bilateral laparoscopic adrenalectomy should be considered in patients with Cushing's disease who fail therapies directed at the pituitary.

Hypertension in Cushing's syndrome

Cushing's syndrome can be exogenous, resulting from the administration of glucocorticoids or adrenocorticotrophic hormone (ACTH), or endogenous, secondary to increased secretion of cortisol or ACTH. Hypertension is one of the most distinguishing features of endogenous Cushing's syndrome, as it is present in about 80% of adult patients and in almost half of children and adolescents patients. Hypertension results from the interplay of several pathophysiological mechanisms regulating plasma volume, peripheral vascular resistance and cardiac output, all of which may be increased. The therapeutic goal is to find and remove the cause of excess glucocorticoids, which, in most cases of endogenous Cushing's syndrome, is achieved surgically. Treatment of Cushing's syndrome usually results in resolution or amelioration of hypertension. However, some patients may not achieve normotension or may require a prolonged period of time for the correction of hypercortisolism. Therefore, therapeutic strategies for Cushing's-specific hypertension (to normalise blood pressure and decrease the duration of hypertension) are necessary to decrease the morbidity and mortality associated with this disorder. The various pathogenetic mechanisms that have been proposed for the development of glucocorticoid-induced hypertension in Cushing's syndrome and its management are discussed.

Adrenocortical hypertension

Primary aldosteronism, congenital adrenal hyperplasia, Cushing's syndrome, glucocorticoid-remediable aldosteronism, and corticotropin-dependent forms of adrenal pathology can cause hypertension by excessive production of adrenocortical hormones. Although traditional biochemical assays continue to be used, genetic testing has simplified the diagnosis of glucocorticoid-remediable aldosteronism. Also new interventional radiologic approaches for the diagnosis and treatment of corticotropin-dependent forms of Cushing's syndrome are available. Medical and surgical approaches, however, still remain viable options for treatment.

Cushing's disease

Cushing's disease, i.e., pituitary ACTH-secreting adenoma causing excess glucocorticoid secretion, is a rare disease with significant mortality and morbidity. Timely diagnosis and appropriate treatment can alter the course of the disease and are therefore mandatory. First step of the diagnostic work-up is the endogenous glucocorticoid excess by measurement of urinary free cortisol, cortisol circadian rhythmicity or suppression by low doses of dexamethasone. In patients with equivocal results, second line tests, such as the dexamethasone-suppressed CRH test and desmopressin stimulation, usually enable the diagnosis to be confirmed. Measurement of plasma ACTH then allows the distinction between ACTH-dependent (e.g., pituitary or extrapituitary neuroendocrine tumors) and ACTH-independent causes (e.g., adrenal tumors). The last step in the diagnostic algorithm is often the most fraught with problems as the distinction between Cushing's disease and ectopic ACTH secretion relies on judicious interpretation of several diagnostic procedures. Positive responses to stimulation with CRH and inhibition by high doses of dexamethasone, if concurrent, enable a pituitary origin to be established whereas conflicting results call for inferior petrosal sinus sampling, the latter to be performed in experienced centres only. Visualisation of the tumor at pituitary imaging is helpful but not required for the diagnosis, as microadenomas often remain undectected by MRI and/or CT scan and, on the other hand, visualisation of a non-secreting incidentaloma may be misleading. Surgical removal of the pituitary tumor is the optimal treatment choice and should be attempted in every patient. Surgical failures as well as relapses can be treated by radiotherapy, medical therapy or, if necessary, bilateral adrenalectomy. Finally, patients cured of Cushing's disease require long-term monitoring given the risk of relapse and clinical burden of associated ailments.

Pituitary radiotherapy

This article includes general comments about pituitary radiation, outcomes in patients who have Cushing's disease and adverse effects of treatment.

Treatment of pituitary adenomas by fractionated stereotactic radiotherapy: A prospective study of 110 patients

PURPOSE

To optimize and reduce the toxicity of pituitary adenoma irradiation by assessing the feasibility and effectiveness of fractionated stereotactic radiotherapy (FSR).

METHODS AND MATERIALS

Between 1990 and 1999, 110 consecutive patients, 47 with a functioning adenoma, were treated according to a strategy of either early surgery and FSR (n = 89) or FSR only (n = 21). Of the 110 patients, 75 had persistent macroscopic tumor and 47 persistent hormonal secretions; 15 were treated in the prophylactic setting. The linear accelerator-delivered dose was 50.4 Gy (5 x 1.8 Gy weekly), with a 2-mm safety margin.

RESULTS

After a minimal follow-up of 48 months, only 1 patient had developed progression. Of the 110 patients, 27 (36%) had a complete tumor response, 67 (89.3%) had an objective tumor response, 20 (42%) had a hormonal complete response, and 47 (100%) had a hormonal objective tumor response. The proportion of patients without a complete tumor response, objective tumor response, complete hormonal response, and objective hormonal response was 85.1%, 62%, 83%, and 59.3% at 4 years and 49.3%, 9%, 59.3%, and 10.6% at 8 years, respectively. The sole unfavorable predictive factor was preoperative SSE >20 mm for tumor response (p = 0.01) and growth hormone adenoma for the hormonal response (p <0.001). No late complications, except for pituitary deficiency, were reported, with a probability of requiring hormonal replacement of 28.5% and 35% at 4 and 8 years, respectively. Nonfunctioning status was the sole unfavorable factor (p = 0.0016).

CONCLUSIONS

Surgery plus FSR is safe and effective. FSR focused to the target volume seems more suitable than standard radiotherapy, and standard fractionation reduces the risk of optic neuropathy sometimes observed after single-dose radiosurgery. Therefore, FSR allows us to consider combined transrhinoseptal surgery and early radiotherapy, with a curative goal without patient selection.

Stereotactic radiosurgery for pituitary adenomas: an intermediate review of its safety, efficacy, and role in the neurosurgical treatment armamentarium

OBJECT

Pituitary adenomas are very common neoplasms, constituting between 10 and 20% of all primary brain tumors. Historically, the treatment armamentarium for pituitary adenomas has included medical management, microsurgery, and fractionated radiotherapy. More recently, radiosurgery has emerged as a viable treatment option. The goal of this research was to define more fully the efficacy, safety, and role of radiosurgery in the treatment of pituitary adenomas.

METHODS

Medical literature databases were searched for articles pertaining to pituitary adenomas and stereotactic radiosurgery. Each study was examined to determine the number of patients, radiosurgical parameters (for example, maximal dose and tumor margin dose), duration of follow-up review, tumor growth control rate, complications, and rate of hormone normalization in the case of functioning adenomas. A total of 35 peer-reviewed studies involving 1621 patients were examined. Radiosurgery resulted in the control of tumor size in approximately 90% of treated patients. The reported rates of hormone normalization for functioning adenomas varied substantially. This was due in part to widespread differences in endocrinological criteria used for the postradiosurgical assessment. The risks of hypopituitarism, radiation-induced neoplasia, and cerebral vasculopathy associated with radiosurgery appeared lower than those for fractionated radiation therapy. Nevertheless, further observation will be required to understand the true probabilities. The incidence of other serious complications following radiosurgery was quite low.

CONCLUSIONS

Although microsurgery remains the primary treatment modality in most cases, stereotactic radiosurgery offers both safe and effective treatment for recurrent or residual pituitary adenomas. In rare instances, radiosurgery may be the best initial treatment for patients with pituitary adenomas. Further refinements in the radiosurgical technique will likely lead to improved outcomes.

The efficacy of linear accelerator radiosurgery in the management of patients with Cushing's disease

We identified 35 patients who had undergone stereotactic radiosurgery (SRS) for their biochemically proven Cushing's disease in order to assess the efficacy of SRS with regard to control of hypercortisolism, improvement of clinical features and prevention of tumor progression, and subsequent incidence of hypopituitarism. Seventeen (49%) patients achieved control of their cortisol levels following SRS; the mean time to normalization was 7.5 months (range: 1-33). Four (19%) patients experienced recurrent hypercortisolism at a mean time of 35.5 months following therapy (range: 17-64). Control of tumor progression was achieved in 91% patients. Fourteen (40%) patients demonstrated a new pituitary deficiency following SRS. Our results suggest that cortisol levels are normalized more efficiently and with a lower recurrence rate with SRS than with conventional fractionated external beam radiotherapy (EBT). We have confirmed the near 100% tumor control rate reported with SRS. The percentage of patients developing pituitary insufficiency following SRS is less than that of patients having undergone EBT; however, deficits occurred up to 10 years posttreatment. We advocate the use of SRS as the primary therapeutic modality in those patients who are poor surgical candidates, or as the adjunct treatment to microsurgery in eliminating residual tumor cells or disease that is not easily amenable to resection.

Adrenocortical hypertension

Primary aldosteronism, congenital adrenal hyperplasia, Cushing's syndrome, glucocorticoid-remediable aldosteronism, and corticotropin-dependent forms of adrenal pathology can cause hypertension by excessive production of adrenocortical hormones. Although traditional biochemical assays continue to be used, genetic testing has simplified the diagnosis of glucocorticoid-remediable aldosteronism. Also, new interventional radiologic approaches for the diagnosis and treatment of corticotropin-dependent forms of Cushing's syndrome are available. Medical and surgical approaches, however, still remain viable options for treatment.

The Nelson's syndrome... revisited

Adrenalectomy is a radical therapeutic approach to control hypercortisolism in some patients with Cushing's disease. However it may be complicated by the Nelson's syndrome, defined by the association of a pituitary macroadenoma and high ACTH secretion after adrenalectomy. This definition has not changed since the end of the fifties. Today the Nelson's syndrome must be revisited with new to criteria using more sensitive diagnostic tools, especially the pituitary magnetic resonance imaging. In this paper we will review the pathophysiological aspects of corticotroph tumor growth, with reference to the impact of adrenalectomy. The main epidemiological data on the Nelson's syndrome will be presented. More importantly, we will propose a new pathophysiological and practical approach to this question which attempts to evaluate the Corticotroph Tumor Progression after adrenalectomy, rather than to diagnose the Nelson's syndrome. We will discuss the consequences for the management of Cushing's disease patients after adrenalectomy, and will also draw some perspectives.