Effect of stereotactic radiosurgery before bilateral adrenalectomy for Cushing's disease on the incidence of Nelson's syndrome

Genetically engineered human pituitary corticotroph tumor organoids exhibit divergent responses to glucocorticoid receptor modulators

Cushing's disease (CD) is a serious endocrine disorder attributed to an adrenocorticotropic hormone (ACTH)-secreting pituitary neuroendocrine tumor (PitNET) that that subsequently leads to chronic hypercortisolemia. PitNET regression has been reported following treatment with the investigational selective glucocorticoid receptor (GR) modulator relacorilant, but the mechanisms behind that effect remain unknown. Human PitNET organoid models were generated from induced human pluripotent stem cells (iPSCs) or fresh tissue obtained from CD patient PitNETs (hPITOs). Genetically engineered iPSC derived organoids were used to model the development of corticotroph PitNETs expressing USP48 (iPSCUSP48) or USP8 (iPSCUSP8) somatic mutations. Organoids were treated with the GR antagonist mifepristone or the GR modulator relacorilant with or without somatostatin receptor (SSTR) agonists pasireotide or octreotide. In iPSCUSP48 and iPSCUSP8 cultures, mifepristone induced a predominant expression of SSTR2 with a concomitant increase in ACTH secretion and tumor cell proliferation. Relacorilant predominantly induced SSTR5 expression and tumor cell apoptosis with minimal ACTH induction. Hedgehog signaling mediated the induction of SSTR2 and SSTR5 in response to mifepristone and relacorilant. Relacorilant sensitized PitNET organoid responsiveness to pasireotide. Therefore, our study identified the potential therapeutic use of relacorilant in combination with somatostatin analogs and demonstrated the advantages of relacorilant over mifepristone, supporting its further development for use in the treatment of Cushing's disease patients.

Nelson's Syndrome: A Narrative Review

Nelson's syndrome (NS) is an uncommon disease occurring as a complication of bilateral adrenalectomy (BLA) in patients with persistent Cushing's disease (CD) due to an adrenocorticotropin-producing pituitary tumor. The first reports of this syndrome were done in the 50s, although its pathophysiology is still not understood. Every year, between 1.8 and 2.6 cases are thought to occur per million people. It is characterized by hyperpigmentation, elevated adrenocorticotropic hormone (ACTH) plasma levels, and typical signs and symptoms related to pituitary adenomas, such as visual deficits due to optic pathway compression or decreased hormone production from the adenohypophysis. NS represents a challenge due to the lack of accepted diagnostic criteria and the complexity of its treatment. Moreover, the development of stereotactic radiosurgery (SRS) in the last few years has become an essential but controversial strategy for this syndrome. This review presents a comprehensive overview of NS.

Corticotroph tumor progression speed after adrenalectomy

OBJECTIVES

After bilateral adrenalectomy in Cushing's disease, corticotroph tumor progression occurs in one-third to half of patients. However, progression speed is variable, ranging from slow to rapid. The aim was to explore corticotroph progression speed, its consequences and its risk factors.

DESIGN

A retrospective single-center observational study.

METHODS

In total,103 patients with Cushing's disease who underwent bilateral adrenalectomy between 1990 and 2020 were included. Clinical, biological, histological and MRI features were collected. Median duration of follow-up after bilateral adrenalectomy was 9.31 years.

RESULTS

In total,44 patients progressed (43%). Corticotroph tumor progression speed ranged from 1 to 40.7 mm per year. Progression speed was not different before and after bilateral adrenalectomy (P = 0.29). In univariate analyses, predictive factors for rapid corticotroph tumor progression included the severity of Cushing's disease before adrenalectomy as the cause of adrenalectomy, high ACTH in the year following adrenalectomy and high Ki67 immunopositivity in the tumor. During follow-up, early morning ACTH absolute variation was associated with corticotroph tumor progression speed (P-value = 0.001). ACTH measurement after dynamic testing did not improve this association.

CONCLUSION

After adrenalectomy, corticotroph progression speed is highly variable and manageable with MRI and ACTH surveillance. Progression speed does not seem related to bilateral adrenalectomy but rather to intrinsic properties of highly proliferative and secreting tumors.

Development of Human Pituitary Neuroendocrine Tumor Organoids to Facilitate Effective Targeted Treatments of Cushing's Disease

(1) Background: Cushing's disease (CD) is a serious endocrine disorder caused by an adrenocorticotropic hormone (ACTH)-secreting pituitary neuroendocrine tumor (PitNET) that stimulates the adrenal glands to overproduce cortisol. Chronic exposure to excess cortisol has detrimental effects on health, including increased stroke rates, diabetes, obesity, cognitive impairment, anxiety, depression, and death. The first-line treatment for CD is pituitary surgery. Current surgical remission rates reported in only 56% of patients depending on several criteria. The lack of specificity, poor tolerability, and low efficacy of the subsequent second-line medical therapies make CD a medical therapeutic challenge. One major limitation that hinders the development of specific medical therapies is the lack of relevant human model systems that recapitulate the cellular composition of PitNET microenvironment. (2) Methods: human pituitary tumor tissue was harvested during transsphenoidal surgery from CD patients to generate organoids (hPITOs). (3) Results: hPITOs generated from corticotroph, lactotroph, gonadotroph, and somatotroph tumors exhibited morphological diversity among the organoid lines between individual patients and amongst subtypes. The similarity in cell lineages between the organoid line and the patient's tumor was validated by comparing the neuropathology report to the expression pattern of PitNET specific markers, using spectral flow cytometry and exome sequencing. A high-throughput drug screen demonstrated patient-specific drug responses of hPITOs amongst each tumor subtype. Generation of induced pluripotent stem cells (iPSCs) from a CD patient carrying germline mutation CDH23 exhibited dysregulated cell lineage commitment. (4) Conclusions: The human pituitary neuroendocrine tumor organoids represent a novel approach in how we model complex pathologies in CD patients, which will enable effective personalized medicine for these patients.

Pituitary adenomas

Pituitary adenomas produce a complex collection of disorders. Some are incidental findings. Some distort local anatomical structures which can lead to disorders of vision or hormone production. Some produce excesses of hormones which can be either life threatening or clinically distressing. The management requires the expertise of a variety of experts who plan together. No single treatment is universally successful in controlling these conditions. Medical, biochemical, surgical and radiosurgical management can all have parts to play. Coordinate co-operation between specialists will provide patients with the best available treatment.

Prevalence of Nelson's syndrome after bilateral adrenalectomy in patients with cushing's disease: a systematic review and meta-analysis

PURPOSE

Bilateral adrenalectomy (BA) still plays an important role in the management of Cushing's disease (CD). Nelson's syndrome (NS) is a severe complication of BA, but conflicting data on its prevalence and predicting factors have been reported. The aim of this study was to determine the prevalence of NS, and identify factors associated with its development.

DATA SOURCES

Systematic literature search in four databases.

STUDY SELECTION

Observational studies reporting the prevalence of NS after BA in adult patients with CD.

DATA EXTRACTION

Data extraction and risk of bias assessment were performed by three independent investigators.

DATA SYNTHESIS

Thirty-six studies, with a total of 1316 CD patients treated with BA, were included for the primary outcome. Pooled prevalence of NS was 26% (95% CI 22-31%), with moderate to high heterogeneity (I² 67%, P < 0.01). The time from BA to NS varied from 2 months to 39 years. The prevalence of NS in the most recently published studies, where magnet resonance imaging was used, was 38% (95% CI 27-50%). The prevalence of treatment for NS was 21% (95% CI 18-26%). Relative risk for NS was not significantly affected by prior pituitary radiotherapy [0.9 (95% CI 0.5-1.6)] or pituitary surgery [0.6 (95% CI 0.4-1.0)].

CONCLUSIONS

Every fourth patient with CD treated with BA develops NS, and every fifth patient requires pituitary-specific treatment. The risk of NS may persist for up to four decades after BA. Life-long follow-up is essential for early detection and adequate treatment of NS.

Gamma knife radiosurgery in patients with Nelson's syndrome

PURPOSE

Nelson's syndrome (NS) is a long-term complication of bilateral adrenalectomy in patients with Cushing's disease. The best therapeutic strategy in NS has not been well defined. Gamma knife radiosurgery (GKRS) is very effective to stop the growth of the pituitary adenoma, which is the main goal of the treatment of patients with NS. We report the largest series of patients with NS treated by GKRS at a single center.

METHODS

The study was an observational, retrospective analysis of 28 consecutive patients with NS treated by GKRS in our department between 1995 and 2019. All patients had a growing ACTH-secreting pituitary adenoma. The main outcome of the study was to assess by the Kaplan-Meier method the risk of tumor progression after GKRS.

RESULTS

The median follow-up after GKRS treatment was 98 months (IQR 61-155 months, range 7-250 months). Two patients (7.1%) had a recurrence of disease during follow-up. The 10-year progression-free survival was 91.7% (95% CI 80.5-100%). No patient had deterioration of visual function or oculomotor function after GKRS. New onset of hypogonadism and hypothyroidism occurred in 18.8% and 14.3% of the patients at risk.

CONCLUSION

Our study confirms that GKRS may stop the tumor growth in the majority of patients with NS, even though very aggressive adenomas may ultimately escape this treatment. Safety of GKRS was good in our experience, but due attention must be paid to planning the distribution of radiation to critical structures, especially in patients previously treated by radiation.

Stereotactic radiosurgery before bilateral adrenalectomy is associated with lowered risk of Nelson's syndrome in refractory Cushing's disease patients

BACKGROUND

Nelson's syndrome is a rare but challenging sequelae of Cushing's disease (CD) after bilateral adrenalectomy (BLA). We sought to determine if stereotactic radiosurgery (SRS) of residual pituitary adenoma performed before BLA can decrease the risk of Nelson's syndrome.

METHODS

Consecutive patients with CD who underwent BLA after non-curative resection of ACTH secreting pituitary adenoma and had at least one follow-up visit after BLA were studied. Nelson's syndrome was diagnosed based on the combination of rising ACTH levels, increasing volume of the pituitary adenoma and/or hyperpigmentation.

RESULTS

Fifty patients underwent BLA for refractory CD, and 43 patients (7 men and 36 women) had at least one follow-up visit after BAL. Median endocrine, imaging, and clinical follow-up were 66 months, 69 months, and 80 months, respectively. Nine patients (22%) were diagnosed with the Nelson's syndrome at median time after BLA at 24 months (range: 0.6-119.4 months). SRS before BLA was associated with reduced risk of the Nelson's syndrome (HR = 0.126; 95%CI [0.022-0.714], p=0.019), while elevated ACTH level within 6 months after BLA was associated with increased risk for the Nelson's syndrome (HR = 9.053; 95%CI [2.076-39.472], p=0.003).

CONCLUSIONS

SRS before BLA can reduce the risk for the Nelson's syndrome in refractory CD patients requiring BLA and should be considered before proceeding to BLA. Elevated ACTH concentration within 6 months after BLA is associated with greater risk of the Nelsons' syndrome. When no prior SRS is administered, those with a high ACTH level shortly after BLA may benefit from early SRS.

Corticotroph tumor progression after bilateral adrenalectomy (Nelson's syndrome): systematic review and expert consensus recommendations

BACKGROUND

Corticotroph tumor progression (CTP) leading to Nelson's syndrome (NS) is a severe and difficult-to-treat complication subsequent to bilateral adrenalectomy (BADX) for Cushing's disease. Its characteristics are not well described, and consensus recommendations for diagnosis and treatment are missing.

METHODS

A systematic literature search was performed focusing on clinical studies and case series (≥5 patients). Definition, cumulative incidence, treatment and long-term outcomes of CTP/NS after BADX were analyzed using descriptive statistics. The results were presented and discussed at an interdisciplinary consensus workshop attended by international pituitary experts in Munich on October 28, 2018.

RESULTS

Data covered definition and cumulative incidence (34 studies, 1275 patients), surgical outcome (12 studies, 187 patients), outcome of radiation therapy (21 studies, 273 patients), and medical therapy (15 studies, 72 patients).

CONCLUSIONS

We endorse the definition of CTP-BADX/NS as radiological progression or new detection of a pituitary tumor on thin-section MRI. We recommend surveillance by MRI after 3 months and every 12 months for the first 3 years after BADX. Subsequently, we suggest clinical evaluation every 12 months and MRI at increasing intervals every 2-4 years (depending on ACTH and clinical parameters). We recommend pituitary surgery as first-line therapy in patients with CTP-BADX/NS. Surgery should be performed before extrasellar expansion of the tumor to obtain complete and long-term remission. Conventional radiotherapy or stereotactic radiosurgery should be utilized as second-line treatment for remnant tumor tissue showing extrasellar extension.

Gamma Knife radiosurgery for the treatment of Nelson's syndrome: a multicenter, international study

OBJECTIVE

Nelson's syndrome is a rare and challenging neuroendocrine disorder, and it is associated with elevated adrenocorticotrophic hormone (ACTH) level, skin hyperpigmentation, and pituitary adenoma growth. Management options including resection and medical therapy are traditional approaches. Ionizing radiation in the form of Gamma Knife radiosurgery (GKRS) is also being utilized to treat Nelson's syndrome. In the current study the authors sought to better define the therapeutic role of stereotactic radiosurgery (SRS) in Nelson's syndrome.

METHODS

Study patients with Nelson's syndrome were treated with single-fraction GKRS (median margin dose of 25 Gy) at 6 different centers as part of an International Radiosurgery Research Foundation (IRRF) investigation. Data including neurological function, endocrine response, and radiological tumor response were collected and sent to the study-coordinating center for review. Fifty-one patients with median endocrine and radiological follow-ups of 91 and 80.5 months from GKRS, respectively, were analyzed for endocrine remission, tumor control, and neurological outcome. Statistical methods were used to identify prognostic factors for these endpoints.

RESULTS

At last follow-up, radiological tumor control was achieved in 92.15% of patients. Endocrine remission off medical management and reduction in pre-SRS ACTH level were achieved in 29.4% and 62.7% of patients, respectively. Improved remission rates were associated with a shorter time interval between resection and GKRS (p = 0.039). Hypopituitarism was seen in 21.6% and new visual deficits were demonstrated in 15.7% of patients.

CONCLUSIONS

GKRS affords a high rate of pituitary adenoma control and improvement in ACTH level for the majority of Nelson's syndrome patients. Hypopituitarism is the most common adverse effect from GKRS in Nelson's syndrome patients and warrants longitudinal follow-up for detection and endocrine replacement.

Long-term outcome after bilateral adrenalectomy in Cushing's disease with focus on Nelson's syndrome

OBJECTIVE

We analyzed the clinical, biochemical, and imaging findings of adrenalectomized patients with Cushing's disease (CD) in order to compare the characteristics of those who developed Nelson's syndrome (NS) versus those who did not develop this complication (NNS), aiming to identify possible predictive factors for its occurrence.

SUBJECTS AND METHODS

We performed a retrospective review of the clinical records of a group of patients with CD who underwent TBA between 1974 and 2011.

RESULTS

Out of 179 patients with CD, 13 (7.3%) underwent TBA. NS occurred in 6 of them (46%) after a mean of 24 months from the total bilateral adrenalectomy (TBA). Age at diagnosis, duration of Cushing's syndrome (CS) until TBA, and steroid replacement doses were similar in both groups. Initial urinary cortisol levels (24-hour urinary free cortisol [UFC]) were significantly higher in the NS group than in the NNS group (p = 0.009). Four patients in the NS group and three of those in the NNS group received radiotherapy before TBA (p = 0.26). Three patients in the NS group presented residual tumors before TBA, compared with none in the NNS group (p = 0.04). At 1 year after TBA, the median ACTH level was 476 ng/L (240-1500 ng/L) in the NS group and 81 ng/L (48-330 ng/L) in the NNS group (p = 0.0007).

CONCLUSION

In conclusion, a residual tumor before TBA, higher 24-hour UFC at diagnosis, and increasing ACTH levels within 1 year after TBA emerged as predictive factors of development of NS.

Functioning Pituitary Adenomas - Current Treatment Options and Emerging Medical Therapies

Pituitary adenomas are benign tumours comprising approximately 16% of all primary cranial neoplasms. Functioning pituitary adenomas (prolactinomas, somatotroph, corticotroph, thyrotroph and rarely gonadotroph adenomas) cause complex clinical syndromes and require prompt treatment to reduce associated morbidity and mortality. Treatment approaches include transsphenoidal surgery, medical therapy and radiation. Medical therapy is the primary therapy for prolactinomas, and surgery by a skilled neurosurgeon is the first-line approach for other functioning pituitary adenomas. A multimodal treatment is frequently necessary to achieve biochemical and clinical control, especially, when surgery is not curative or when medical therapy fails. Several emerging, novel, medical treatments for acromegaly, Cushing's disease and prolactinomas are in phase II and III clinical trials and may become effective additions to the current drug armamentarium. The availability of various management options will allow an individualised treatment approach based on the unique tumour type, clinical situation and patient preference.

Management of hormone-secreting pituitary adenomas

Pituitary adenomas are one of the most common primary central nervous system tumors and have an estimated prevalence of 17%. Approximately half of pituitary adenomas secrete distinct pituitary hormones (most often prolactin, growth hormone, or adrenocorticotropic hormone). While these tumors are histologically benign, they have potent endocrine effects that lead to significant morbidity and shortened lifespan. Because of their pathophysiologic endocrine secretion and anatomic location near critical neural/vascular structures, hormone-secreting pituitary adenomas require defined management paradigms that can include relief of mass effect and biochemical remission. Management of hormone-secreting pituitary adenomas involves a multidisciplinary approach that can incorporate surgical, medical, and/or radiation therapies. Early and effective treatment of hormone-secreting pituitary adenomas can reduce morbidity and mortality. Consequently, understanding clinical features as well as therapeutic options in the context of the specific biological features of each type of hormone-secreting pituitary adenoma is critical for optimal management.

AN INDIVIDUALIZED APPROACH TO THE EVALUATION OF CUSHING SYNDROME

Cushing syndrome (CS) is caused by chronic exposure to excess glucocorticoids. Early recognition and treatment of hypercortisolemia can lead to decreased morbidity and mortality. The diagnosis of CS and thereafter, establishing the cause can often be difficult, especially in patients with mild and cyclic hypercortisolism. Surgical excision of the cause of excess glucocorticoids is the optimal treatment for CS. Medical therapy (steroidogenesis inhibitors, medications that decrease adrenocorticotropic hormone [ACTH] levels or glucocorticoid antagonists) and pituitary radiotherapy may be needed as adjunctive treatment modalities in patients with residual, recurrent or metastatic disease, in preparation for surgery, or when surgery is contraindicated. A multidisciplinary team approach, individualized treatment plan and long-term follow-up are important for optimal management of hypercortisolemia and the comorbidities associated with CS.

ABBREVIATIONS

ACTH = adrenocorticotropic hormone; BIPSS = bilateral inferior petrosal sinus sampling; CBG = corticosteroid-binding globulin; CD = Cushing disease; CRH = corticotropin-releasing hormone; CS = Cushing syndrome; Dex = dexamethasone; DST = dexamethasone suppression test; EAS = ectopic ACTH syndrome; FDA = U.S. Food & Drug Administration; HDDST = high-dose DST; IPS/P = inferior petrosal sinus to peripheral; MRI = magnetic resonance imaging; NET = neuroendocrine tumor; PET = positron emission tomography; UFC = urinary free cortisol.

A Long-Term Study of the Treatment of Nelson's Syndrome With Gamma Knife Radiosurgery

BACKGROUND

Nelson's syndrome may be a devastating complication for patients with Cushing's disease who underwent a bilateral adrenalectomy. Previous studies have demonstrated that stereotactic radiosurgery (SRS) can be used to treat patients with Nelson's syndrome.

OBJECTIVE

To report a retrospective study of patients with Nelson's syndrome treated with Gamma Knife radiosurgery to evaluate the effect of SRS on endocrine remission and tumor control.

METHODS

Twenty-seven patients with Nelson's syndrome treated with Gamma Knife radiosurgery after bilateral adrenalectomy were included in this study. After radiosurgery, patients were followed with serial adrenocorticotropic hormone (ACTH) levels and MRI sequences to assess for endocrine remission and tumor control. Cox proportional hazards regression analysis was used to evaluate the relationship between the time to remission and potential prognostic factors.

RESULTS

In 21 patients with elevated ACTH prior to SRS and endocrine follow-up data, 14 (67%) had decreased or stable ACTH levels, and 7 achieved a normal ACTH level at a median of 115 mo (range 7-272) post-SRS. Tumor volume was stable or reduced after SRS in 92.5% of patients (25/27) with radiological follow-up. Time to remission was not significantly associated with the ACTH prior to SRS (P = .252) or with the margin dose (P = .3). However, a shorter duration between the patient's immediate prior transsphenoidal resection and SRS was significantly associated with a shorter time to remission (P = .045).

CONCLUSION

This retrospective analysis suggests that SRS is an effective means of achieving endocrine remission and tumor control in patients with Nelson's syndrome.

STEREOTACTIC RADIATION THERAPY IN PITUITARY ADENOMAS, IS IT BETTER THAN CONVENTIONAL RADIATION THERAPY?

Pituitary radiotherapy (RT) has undergone important progress in the last decades due to the development of new stereotactic techniques which provide more precise tumour targeting with less overall radiation received by the adjacent brain structures. Pituitary surgery is usually first-line therapy in most patients with nonfunctioning (NFPA) and functioning adenomas (except for prolactinomas and large growth hormone (GH) secreting adenomas), while RT is used as second or third-line therapy. The benefits of RT (tumour volume control and, in functional tumours, decreased hormonal secretion) are hampered by the long latency of the effect and the potential side effects. This review presents the updates in the efficacy and safety of the new stereotactic radiation techniques in patients with NFPA, GH-, ACTH- or PRL-secreting pituitary adenomas.

Methods

A systematic review was performed using PubMed and articles/abstracts and reviews detailing RT in pituitary adenomas from 2000 to 2017 were included.

Results

Stereotactic radiosurgery (SRS) and fractionated stereotactic RT (FSRT) provide high rates of tumour control i.e. stable or decrease in tumour size, in all types of pituitary adenomas (median 92 - 98%) at 5 years. Endocrinological remission is however significantly lower: 44-52% in acromegaly, 54-64% in Cushing's disease and around 30% in prolactinomas at 5 years. The rate of new hypopituitarism varies from 10% to 50% at 5 years in all tumour types and as expected increases with the duration of follow-up (FU). The risk for other radiation-induced complications is usually low (0-5% for new visual deficits, cranial nerves damage or brain radionecrosis and extremely low for secondary brain tumours), however longer FU is needed to determine rates of secondary tumours. Notably, in acromegaly, there may be a higher risk for stroke with FSRT.

Conclusion

Stereotactic radiotherapy can be an effective treatment option for patients with persistent or recurrent pituitary adenomas after unsuccessful surgery (especially if residual tumour is enlarging) and/or resistance or unavailability of medical therapy. Comparison with conventional radiation therapy (CRT) is rather difficult, due to the substantial heterogeneity of the studies. In order to evaluate the potential brain-sparing effect of the new stereotactic techniques, suggested by the current data, long-term studies evaluating secondary morbidity and mortality are needed.

Cushing's disease: pathobiology, diagnosis, and management

Cushing's disease (CD) is the result of excess secretion of adrenocorticotropic hormone (ACTH) by a benign monoclonal pituitary adenoma. The excessive secretion of ACTH stimulates secretion of cortisol by the adrenal glands, resulting in supraphysiological levels of circulating cortisol. The pathophysiological levels of cortisol are associated with hypertension, diabetes, obesity, and early death. Successful resection of the CD-associated ACTH-secreting pituitary adenoma is the treatment of choice and results in immediate biochemical remission with preservation of pituitary function. Accurate and early identification of CD is critical for effective surgical management and optimal prognosis. The authors review the current pathophysiological principles, diagnostic methods, and management of CD.

Update on the management of recurrent Cushing's disease

After transsphenoidal surgery, Cushing's disease (CD) shows excellent long-term remission rates, but it may recur and pose a therapeutic challenge. Findings in recent published reports on the treatment of recurrent adrenocorticotropic hormone (ACTH)-secreting tumors suggest that repeat resection, radiation-based therapies such as Gamma Knife surgery and proton-beam radiosurgery, pharmacotherapy, and bilateral adrenalectomy all have important roles in the treatment of recurrent CD. Each of these interventions has inherent risks and benefits that should be presented to the patient during counseling on retreatment options. Radiation-based therapies increasingly appear to have efficacies similar to those of repeat resection in achieving biochemical remission and tumor control. In addition, an expanding retinue of medication-based therapies, several of which are currently being evaluated in clinical trials, has shown some promise as tertiary adjunctive therapies. Lastly, bilateral adrenalectomy may offer durable control of refractory recurrent CD. An increasing number of published studies with long-term patient outcomes highlight the evolving treatment patterns in the management of recurrent CD.

Re-examining Nelson's syndrome

PURPOSE OF REVIEW

Nelson's syndrome is a rare complication that can occur during the course of management of Cushing's disease. This article summarizes the recent literature on the diagnosis, monitoring and treatment of this potentially life-threatening outcome.

RECENT FINDINGS

Nelson's syndrome, with rising adrenocorticotropin hormone levels and corticotroph tumor progression on diagnostic imaging, can develop following treatment of refractory Cushing's disease with total bilateral adrenalectomy with/without radiotherapy. However, data showing that radiotherapy prevents Nelson's syndrome is inconsistent. In addition to the treatment of Nelson's syndrome with neurosurgery with/without adjuvant radiotherapy, selective somatostatin analogs and dopamine agonists, as well as other novel agents, have been used with increasing frequency in treating cases of Nelson's syndrome with limited benefit. The risk-benefit profile of each of these therapies is still not completely understood.

SUMMARY

Consensus guidelines on the evaluation and management of Nelson's syndrome are lacking. This article highlights areas in the surveillance of Cushing's disease patients, and diagnostic criteria and treatment regimens for Nelson's syndrome that require further research and review by experts in the field.

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.

Cushing's syndrome: epidemiology and developments in disease management

Cushing’s syndrome is a rare disorder resulting from prolonged exposure to excess glucocorticoids. Early diagnosis and treatment of Cushing’s syndrome is associated with a decrease in morbidity and mortality. Clinical presentation can be highly variable, and establishing the diagnosis can often be difficult. Surgery (resection of the pituitary or ectopic source of adrenocorticotropic hormone, or unilateral or bilateral adrenalectomy) remains the optimal treatment in all forms of Cushing’s syndrome, but may not always lead to remission. Medical therapy (steroidogenesis inhibitors, agents that decrease adrenocorticotropic hormone levels or glucocorticoid receptor antagonists) and pituitary radiotherapy may be needed as an adjunct. A multidisciplinary approach, long-term follow-up, and treatment modalities customized to each individual are essential for optimal control of hypercortisolemia and management of comorbidities.

Update on radiation therapy in patients with Cushing's disease

INTRODUCTION

Radiation therapy is an important therapy for patients with Cushing's disease who are not in remission or relapse after transsphenoidal pituitary surgery and are not considered surgical candidates. The development of stereotactic radiation therapy, using gamma knife, linear accelerators or proton beam based methods, has enabled selective radiation delivery to the target while minimizing exposure of healthy tissues. In patients whose tumors are sufficiently distant from the optic apparatus, stereotactic radiation therapy can be delivered in a single session, a procedure termed radiosurgery, which significantly improves patient convenience.

METHODS

Original articles on radiation therapy in Cushing's disease, published during the past 12 months (2013-2014), were identified and pertinent data extracted.

RESULTS

Recent studies have reported on the outcomes of patients with Cushing's disease who received mostly stereotactic radiation therapy. While tumor control has been excellent, biochemical remission was less consistently achieved. Some studies suggested that stereotactic radiation may lead to biochemical remission faster than conventional radiation therapy. In addition, retrospective data have suggested that withdrawing medical therapy around the time stereotactic radiation therapy is administered might lead to a faster biochemical response. Regardless of the radiation therapy method, biochemical recurrences may develop and these patients are at long-term risk of developing anterior hypopituitarism and require lifelong periodic endocrine follow-up. Other, less frequent complications may include cranial neuropathies, secondary tumor formation or temporal lobe necrosis. It is plausible that complications may be less frequent after stereotactic radiation therapy, but this requires confirmation.

CONCLUSIONS

Radiation therapy is an effective second line therapy in patients with Cushing's disease. Ongoing refinements in delivery of radiation therapy are anticipated to lead to improved patient outcomes, but long-term follow-up data, including adequate control groups, are needed to fully investigate this possibility.

Bilateral adrenalectomy for Cushing's disease

PURPOSE

Review the indications, outcomes, and consequences of bilateral adrenalectomy (BLA) in patients with Cushing's disease.

METHODS

A literature review was performed.

RESULTS

The primary therapy for Cushing's disease is surgery, with medical therapy and radiation therapy relegated to an adjuvant role. BLA is indicated in cases of persistent disease following pituitary surgery or in situations where rapid normalization of hypercortisolism is required. When performed via the laparoscopic approach, BLA is associated with a significantly reduced morbidity compared to the traditional, open approach. Following BLA, patients are at risk for adrenal crisis and the concern of Nelson's syndrome. However, BLA leads to a rapid resolution of the signs and symptoms of CS and leads to an improved long-term quality of life.

CONCLUSION

BLA should be considered in the treatment algorithm for patients with persistent CD after failed pituitary surgery, especially in patients who have severe consequences of hypercortisolism or desire pregnancy.

Changes in plasma ACTH levels and corticotroph tumor size in patients with Cushing's disease during long-term treatment with the glucocorticoid receptor antagonist mifepristone

CONTEXT

Pituitary effects of long-term therapy with mifepristone, a glucocorticoid receptor antagonist, in Cushing's disease (CD) patients are not well understood.

OBJECTIVE

Our objective was to report changes in ACTH and pituitary magnetic resonance imaging (MRI) findings during long-term use of mifepristone in CD patients.

DESIGN AND SETTING

The Study of the Efficacy and Safety of Mifepristone in the Treatment of Endogenous Cushing's Syndrome (SEISMIC) was a 24-week, open-label study of mifepristone, and its long-term extension (LTE) is a multicenter U.S. study.

PATIENTS

Forty-three CD patients (mean age 45.3 years) were enrolled in SEISMIC with 27 continuing into the LTE study.

INTERVENTIONS

Mifepristone (300-1200 mg) was administered once daily.

MAIN OUTCOME MEASURES

ACTH and pituitary MRI were assessed at baseline and at regular intervals during treatment.

RESULTS

A ≥2-fold increase in ACTH was observed in 72% of patients treated for a median duration of 11.3 months. The mean peak increase in ACTH was 2.76 ± 1.65-fold during SEISMIC, and mean ACTH concentrations remained stable during the LTE. ACTH was directly correlated with mifepristone dose and declined to near baseline levels after mifepristone discontinuation. Tumor regressed in 2 patients and progressed in 3 patients with macroadenomas. An additional microadenoma was identified after 25 months of treatment after a baseline tumor-negative MRI.

CONCLUSIONS

In the largest prospective study to date, long-term mifepristone treatment increased ACTH in approximately two-thirds of patients with CD. ACTH elevations were observed within the first few weeks of treatment, were dose-dependent, and generally remained stable over time. Corticotroph tumor progression and regression may occur over time, but patients may have significant increases in ACTH levels without evidence of tumor growth.

Whole-Sellar Stereotactic Radiosurgery for Functioning Pituitary Adenomas

BACKGROUND:

Functioning pituitary adenomas (FPAs) can be difficult to delineate on postoperative magnetic resonance imaging, making them difficult targets for stereotactic radiosurgery (SRS). In such cases, radiation delivery to the entire sella has been utilized as a radiosurgical equivalent of a total hypophysectomy.

OBJECTIVE:

To evaluate the outcomes of a cohort of patients with FPA who underwent SRS to the whole-sellar region.

METHODS:

This is a retrospective review of patients who underwent whole-sellar SRS for FPA between 1989 and 2012. Sixty-four patients met the inclusion criteria: they were treated with whole-sellar SRS following surgical resection for persistently elevated hormone levels, and (1) no visible lesions on imaging studies and/or (2) tumor infiltration of dura or adjacent venous sinuses observed at the time of a prior resection. The median radiosurgical volume covering sellar structures was 3.2 mL, with a median margin dose of 25 Gy.

RESULTS:

The median endocrine follow-up was 41 months; 22 (68.8%) patients with acromegaly, 20 (71.4%) patients with Cushing disease, and 2 (50.0%) patients with prolactinoma achieved endocrine remission. The 2-, 4-, and 6-year actuarial remission rates were 54%, 78%, and 87%, respectively. New-onset neurological deficit was found in 4 (6.3%) patients following treatment. New-onset hypopituitarism was observed in 27 (43.5%) patients, with panhypopituitarism in 2 (3.2%). Higher margin/maximum dose were significantly associated with a higher remission rate and development of post-SRS hypopituitarism.

CONCLUSION:

Whole-sellar SRS for invasive or imaging-negative FPA following failed resection can offer reasonable rates of endocrine remission. Hypopituitarism following whole-sellar SRS is the most common complication.