Cushing’s disease: A single centre’s experience using the linear accelerator (LINAC) for stereotactic radiosurgery and fractionated stereotactic radiotherapy

Recurrent Cushing Disease: An Extensive Review on Pros and Cons of Different Therapeutic Approaches

OBJECTIVE

Recurrent Cushing disease (CD) is characterized by the reappearance of clinical and hormonal aspects of hypercortisolism that occur more than 6 months after an initial post-treatment remission.

METHODS

We performed a systematic review and meta-analysis to synthesize the evidence about remission and complication rates after transsphenoidal surgery (TSS) radiotherapy (RT) and medical therapy (MT) in recurrent CD patients. A quantitative systematic review was performed. Article selection was performed by searching MEDLINE (using PubMed), and Cochrane electronic bibliographic databases through 2020.

RESULTS

We noted 61 articles described therapeutic management of recurrent CD patients with representative outcome. A total of 723 patients received different therapeutic modality for their recurrent CD. The remission rates were 0.65 (95% confidence interval [CI] 0.60-0.70), 0.57 (95% CI 0.51-0.63), and 0.75 (95% CI 0.60-0.86) in the TSS, RT, and MT subgroups, respectively. The total remission rate after therapeutic approaches on recurrent CD patients was 0.64 (95% CI 0.60-0.68). A test for subgroup differences revealed there was a statistically significant difference between different subgroups (P = 0.01). The post hoc test showed that in comparison with RT, TSS (P = 0.0344) and MT (P = 0.0149) had a higher rate of remission. However, there was no statistically significant difference between separate therapeutic modalities in terms of complications including diabetes insipidus (P = 1.0) and hypopituitarism (P = 0.28).

CONCLUSIONS

Compared MT and TSS, RT has a statistically lower rate of remission. Although there is robust superiority of surgery over RT, interpretation of MT data must considered with caution due to the small number of included cases and wide CI range.

Stereotactic radiosurgery for secretory pituitary adenomas: systematic review and International Stereotactic Radiosurgery Society practice recommendations

OBJECTIVE

A systematic review was performed to provide objective evidence on the use of stereotactic radiosurgery (SRS) in the management of secretory pituitary adenomas and develop consensus recommendations.

METHODS

The authors performed a systematic review of the English-language literature up until June 2018 using the PRISMA guidelines. The PubMed (Medline), Embase, and Cochrane databases were searched. A total of 45 articles reporting single-institution outcomes of SRS for acromegaly, Cushing's disease, and prolactinomas were selected and included in the analysis.

RESULTS

For acromegaly, random effects meta-analysis estimates for crude tumor control rate, crude endocrine remission rate, and any new hypopituitarism rates were 97.0% (95% CI 96.0%-98.0%), 44.0% (95% CI 35.0%-53.0%), and 17.0% (95% CI 13.0%-23.0%), respectively. For Cushing's disease, random effects estimates for crude tumor control rate, crude endocrine remission rate, and any new hypopituitarism rate were 92.0% (95% CI 87.0%-95.0%), 48.0% (95% CI 35.0%-61.0%), and 21.0% (95% CI 13.0%-31.0%), respectively. For prolactinomas, random effects estimates for crude tumor control rate, crude endocrine remission rate, and any new hypopituitarism rate were 93.0% (95% CI 90.0%-95.0%), 28.0% (95% CI 19.0%-39.0%), and 12.0% (95% CI 6.0%-24.0%), respectively. Meta-regression analysis did not show a statistically significant association between mean margin dose with crude endocrine remission rate or mean margin dose with development of any new hypopituitarism rate for any of the secretory subtypes.

CONCLUSIONS

SRS offers effective tumor control of hormone-producing pituitary adenomas in the majority of patients but a lower rate of endocrine improvement or remission.

CyberKnife for the management of Cushing's disease: our institutional experience and review of literature

INTRODUCTION

Surgery is the primary treatment for Cushing's disease(CD). In cases with no biochemical remission after surgical resection or when recurrence occurs after a period of remission stereotactic radiosurgery (SRS) is used as alternative/adjuvant treatment. The aim of this study is to demonstrate the effectiveness of SRS and FSRS(Fractionated stereotactic radiosurgery) for the treatment of CD in a long term follow up.

METHODS

This is a retrospective study in which 41 patient (36 females and 5 males) who underwent surgery for CD from 2009 to 2019 were included. Out of 41 cases, 34 cases had microadenomas while 7 had macroadenomas. These patients had recurrence or persistence of hypercortisolism post-operatively. After multidisciplinary evaluation, these patients were treated by CyberKnife (SRS & FSRS).

RESULTS

Remission rate in our study was 60.97% with a median follow up period of 79.03 months. The median time to biochemical remission was 14 months. Tumour growth control was achieved in 95.12%. Hypopituitarism of different axes was seen in 34.14% patients. Secondary hypothyroidism was the most common pituitary insufficiency (34%) followed by secondary hypogonadism in 17%.

CONCLUSION

CyberKnife radiosurgery and hypofractionated radiosurgery can be used as an adjuvant treatment in patient with active disease and no biochemical remission after one or multiple surgical resections. Risk of radiation induced hypopituitarism and other complication is relatively low 34.14% and tumour growth control is significantly higher.

Updates in the outcomes of radiation therapy for Cushing's disease

External radiation therapy (RT) directed to the pituitary gland is generally recommended in patients with Cushing's disease (CD) as adjuvant to transsphenoidal surgery, among other second-line therapies offered to patients with residual or recurrent hypercortisolism (i.e., medical treatment, repeat surgery or bilateral adrenalectomy). RT is effective for the control of tumor growth, even in invasive tumors and in Nelson's syndrome. Progress in radiation stereotactic techniques lead to improved tumor targeting and radiation delivery, thus sparing the adjacent brain structures. Stereotactic RT is associated with a 55-65% rate of cortisol normalization after several months to a few years and potentially with a lower risk of long-term complications, compared with conventional RT. Cortisol-lowering medical therapy is recommended while awaiting the radiation effects. Hypopituitarism is the most frequent side-effect, damage to optic or cranial nerves or second brain tumors are rarely reported. This review presents the updates in the efficacy and safety of the stereotactic radiation techniques in CD patients. Practical points which should be considered by the clinician before recommending RT are also presented.

Early versus late Gamma Knife radiosurgery for Cushing's disease after prior resection: results of an international, multicenter study

OBJECTIVE

The optimal time to perform stereotactic radiosurgery after incomplete resection of adrenocorticotropic hormone (ACTH)-producing pituitary adenoma in patients with Cushing's disease (CD) remains unclear. In patients with persistent CD after resection of ACTH-producing pituitary adenoma, the authors evaluated the association of the interval between resection and Gamma Knife radiosurgery (GKRS) with outcomes.

METHODS

Pooled data from 10 institutions participating in the International Radiosurgery Research Foundation were used in this study.

RESULTS

Data from 255 patients with a mean follow-up of 65.59 ± 49.01 months (mean ± SD) were analyzed. Seventy-seven patients (30%) underwent GKRS within 3 months; 46 (18%) from 4 to 6 months; 34 (13%) from 7 to 12 months; and 98 (38%) at > 12 months after the resection. Actuarial endocrine remission rates were higher in patients who underwent GKRS ≤ 3 months than when treatment was > 3 months after the resection (78% and 65%, respectively; p = 0.017). Endocrine remission rates were lower in patients who underwent GKRS at > 12 months versus ≤ 12 months after the resection (57% vs 76%, respectively; p = 0.006). In multivariate Cox regression analyses adjusted for clinical and treatment characteristics, early GKRS was associated with increased probability of endocrine remission (hazard ratio [HR] 1.518, 95% CI 1.039-2.218; p = 0.031), whereas late GKRS (HR 0.641, 95% CI 0.448-0.919; p = 0.015) was associated with reduced probability of endocrine remission. The incidence of some degree of new pituitary deficiency (p = 0.922), new visual deficits (p = 0.740), and other cranial nerve deficits (p = 0.610) was not significantly related to time from resection to GKRS.

CONCLUSIONS

Early GKRS is associated with an improved endocrine remission rate, whereas later GKRS is associated with a lower rate of endocrine remission after pituitary adenoma resection. Early GKRS should be considered for patients with CD after incomplete pituitary adenoma resection.

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.

Pituitary Adenomas: What Are the Key Features? What Are the Current Treatments? Where Is the Future Taking Us?

Pituitary tumors are a heterogeneous group of lesions (usually benign) and proper understanding of the anatomy, physiology, and pathology of the hypothalamic/pituitary region is essential to make an accurate diagnosis and define the essential treatment options (i.e., surgery, medical therapies, and radiotherapy, alone or in combination). Surgery is the primary treatment for acromegaly, Cushing disease, thyroid-stimulating hormone-secreting adenomas, resistant prolactinomas, and nonfunctioning pituitary adenomas causing mass effect. Medical and radiation therapy are reserved in cases in which surgery is not possible or does not provide a complete cure. In the last decades, tremendous innovations (i.e., targeted drugs and refined surgical tools and techniques) have expanded the treatment strategies for pituitary adenomas. We herein report the current indications for and depiction of the surgical techniques in pituitary surgery, review current medical treatments, and provide a glimpse of future possibilities.

Medical Management of Cushing's Syndrome: Current and Emerging Treatments

Endogenous Cushing's syndrome is a chronic disease associated with increased morbidity and mortality if not appropriately treated. Recurrence and/or persistence of hypercortisolemia after surgical treatment, especially for Cushing's disease, are high, and long-term medical treatment is used to decrease cortisol levels and risk of metabolic comorbidities. Medical treatment is also often required while waiting for radiation effects to take place. In some cases, severe or life-threatening hypercortisolism must be urgently and medically treated, via intravenous medications or with combination therapy, before patients can undergo surgery. In the last decade, medical treatment has progressed from a few steroidogenesis inhibitors to three novel drug groups: new inhibitors for steroidogenic enzymes with possibly fewer side effects, pituitary-directed drugs that aim to inhibit the pathophysiological pathways of Cushing's disease, and glucocorticoid receptor antagonists that block cortisol's action. Understanding the pathophysiology of Cushing's syndrome has also led to the identification of potential targets that may decrease adrenocorticotrophic hormone and/or cortisol excess, and/or decrease tumor cell proliferation, and induce senescence or apoptosis. We provide here a review of current and near-future medical options to treat Cushing's syndrome, and discuss updates on clinical trials and the efficacy and safety of novel or in-development drugs, as well as future potential targets.

Current management of Cushing's disease

Cushing's disease (CD) is caused by a pituitary tumour that secretes adrenocorticotropin (ACTH) autonomously, leading to excess cortisol secretion from the adrenal glands. The condition is associated with increased morbidity and mortality that can be mitigated by treatments that result in sustained endocrine remission. Transsphenoidal pituitary surgery (TSS) remains the mainstay of treatment for CD but requires considerable neurosurgical expertise and experience in order to optimize patient outcomes. Up to 90% of patients with microadenomas (tumour below 1 cm in largest diameter) and 65% of patients with macroadenomas (tumour at or above 1 cm in greatest diameter) achieve endocrine remission after TSS by an experienced surgeon. Patients who are not in remission postoperatively or those who relapse may benefit from undergoing a second pituitary operation. Alternatively, radiation therapy to the sella with interim medical therapy, or bilateral adrenalectomy, can be effective as definitive treatments of CD. Medical therapy is currently adjunctive in most patients with CD and is generally prescribed to patients who are about to receive radiation therapy and will be awaiting its salutary effects to occur. Available treatment options include steroidogenesis inhibitors, centrally acting agents and glucocorticoid receptor antagonists. Several novel agents are in clinical trials and may eventually constitute additional treatment options for this serious condition.

Successful reduction of ACTH secretion in a case of intractable Cushing's disease with pituitary Crooke's cell adenoma by combined modality therapy including temozolomide

Crooke's cell adenoma (CCA) is an aggressive subtype of corticotroph adenoma; however, CCA is associated with a high incidence of low expression of methyl guanine methyl transferase (MGMT), suggesting that temozolomide (TMZ) treatment might be effective for this tumor type. The case of a 56-year-old woman with Cushing's disease caused by a pituitary CCA is presented. At the age of 38 years, the patient presented to our hospital with polyuria and a visual field defect. MRI and laboratory studies showed a 4.5-cm-diameter pituitary tumor with plasma adrenocorticotropic hormone (ACTH) and serum cortisol levels of more than 500 pg/mL and 40 μg/dL, respectively. At 39 years of age, the patient underwent a craniotomy, and her plasma ACTH and cortisol levels decreased to less than 200 pg/mL and 10 μg/dL, respectively; however, these hormone levels increased gradually to 3,940 pg/mL and 70 μg/dL, respectively, by the time the patient was 56 years old. Histopathological re-examination of the previously resected specimen showed that the pituitary tumor was MGMT-negative CCA. TMZ treatment after the second operation decreased the plasma ACTH levels from 600-800 pg/mL to 70-300 pg/mL. No signs of recurrence were observed in the seven years following these treatments with added prophylactic radiation therapy. These clinical findings suggest that TMZ treatment to patients with CCA accompanied with elevated ACTH may be good indication to induce lowering ACTH levels and tumor shrinkage.

The risk/benefit ratio of radiotherapy in pituitary tumors

Radiation therapy (RT) is an effective treatment for patients with either nonfunctioning or secreting pituitary adenomas unsuccessfully treated by surgery and/or medical therapy, resulting in local control of 90-95% at 5-10 years and variable normalization of hormonal hypersecretion for patients with GH-, ACTH-, and prolactin-secreting adenomas in the range of 40-80% at 5 years; however, its use has been limited because of concerns regarding potential late toxicity of radiation and delayed efficacy in normalization of hormone hypersecretion. In the last decades, there have been advances in all aspects of radiation treatment, including more accurate immobilization, imaging, treatment planning and dose delivery. RT has evolved with the development of highly conformal stereotactic techniques and new planning and dose delivery techniques, including intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT). All these new techniques allow precise and sharply focused radiation delivery reducing the dose to surrounding critical neurovascular and brain structures, and potentially limiting the long-term consequences of radiation treatments. In this review, we present a critical analysis of the more recent available literature on the use of RT in patients with both nonfunctioning and secreting pituitary adenomas, focussing particularly on the risk/benefit ratio of modern radiation techniques.

Outcomes After Gamma Knife Stereotactic Radiosurgery in Pediatric Patients with Cushing Disease or Acromegaly: A Multi-Institutional Study

OBJECTIVE

Pituitary adenomas comprise about 3% of all intracranial tumors in pediatric patients. This study examines the role of stereotactic radiosurgery in the management of pediatric acromegaly or patients with Cushing disease (CD).

METHODS

From an international consortium, we retrospectively collected treatment and outcome data on pediatric adrenocorticotrophic hormone and growth hormone-secreting pituitary adenomas treated with Gamma Knife radiosurgery (GKRS). There were a total of 36 patients including 24 with CD and 12 with acromegaly. The data were analyzed to assess outcomes including tumor control, endocrine remission, and adverse effects. Statistical analysis was performed to determine correlation between clinical/treatment parameters and outcomes.

RESULTS

At the last follow-up after GKRS, endocrine remission rates for CD and acromegaly were 80% and 42%, respectively. Tumor control was achieved in 87.5% of patients with CD and in 42% of patients with acromegaly. New pituitary hormone deficiency occurred in 7 of the 36 patients at a median time of 18 months after GKRS (range, 12-81 months). The predictive factors for endocrine remission were age <15 years (P = 0.015) and margin dose (P = 0.042). The median endocrine follow-up was 63.7 months (range, 7-246 months).

CONCLUSIONS

GKRS affords reasonable rates of endocrine remission and tumor control in most pediatric patients with functioning adenomas. The most common post-GKRS complication was hypopituitarism, although this occurred in only a few patients. Given the larger at-risk period for pediatric patients, further study is required to evaluate for delayed recurrences and hypopituitarism.

Outcomes of Pituitary Radiation for Cushing's Disease

Achievement of biochemical remission with preservation of normal pituitary function is the goal of treatment for Cushing's disease. For patients with persistent or recurrent Cushing's disease after transsphenoidal resection, radiation therapy may be a safe and effective treatment. Stereotactic radiosurgery is favored over conventional fractionated external beam radiation. Hormonal recurrence rates range from 0% to 36% at 8 years after treatment. Tumor control rates are high. New pituitary hormone deficiency is the most common adverse effect after stereotactic radiosurgery and external beam radiation. The effects of radiation planning optimization and use of adjuvant medication on endocrine remission rates warrant investigation.

Target delineation and optimal radiosurgical dose for pituitary tumors

Stereotactic radiosurgery (SRS) delivered as either single-fraction or multi-fraction SRS (2–5 fractions) is frequently employed in patients with residual or recurrent pituitary adenoma. The most common delivery systems used for SRS include the cobalt-60 system Gamma Knife, the CyberKnife (CK) robotic radiosurgery system, or a modified conventional radiotherapy machine (linear accelerator, LINAC). Tumor control and normalization of hormone hypersecretion have been reported in 75–100 % and 25–80 % of patients, respectively. Hypopituitarism is the most commonly reported late complication of radiation treatment, whereas other toxicities occur less frequently. We have provided an overview of the recent available literature on SRS in patients with a pituitary adenoma. Critical aspects of pituitary irradiation, including target delineation and doses to organs at risk, optimal radiation dose, as well as the long-term efficacy and toxicity of SRS for either nonfunctioning or secreting pituitary adenomas are discussed. Single-fraction SRS represents an effective treatment for patients with a pituitary adenoma; however, caution should be used for lesions > 2.5–3 cm in size and/or involving the anterior optic pathway. Future studies will be necessary to optimize target doses and critical organ dose constrains in order to reduce the long-term toxicity of treatments while maintaining high efficacy.

Curative effects of head γ-SRT for the treatment of functional pituitary macroadenoma

The aim of the study was to examine the curative effects and proper radiotherapy plan of head γ-stereotactic radiotherapy (γ-SRT) for the treatment of functional pituitary macroadenoma. Clinical samples of 30 patients that underwent γ-SRT (radiotherapy group) and 26 patients that underwent pituitary adenoma resection via single nasal-sphenoidal approach (surgery group) were analyzed retrospectively and their curative effects were compared. The results showed that in the radiotherapy group, 12 cases accepted single fraction irradiation, with an average maximum diameter of tumor body of 1.8±0.6 cm, average volume of 0.6±0.4 cm³, average dose of the central point of 52.6±18.7 Gy, average dose of the peripheral point of 24.7±10.2 mGy, and isodose curve of 50–70%. The remaining 18 cases accepted multiple fraction irradiation, with an average irradiation of 3.7±1.6 times, maximum average diameter of tumor body of 4.3±1.8 cm, average volume of 4.8±2.7 cm³, average dose of the central point of 24.6±12.5 Gy, average dose of the peripheral point of 13.6±7.4 mGy, and isodose curve of 50–70%. Following treatment, the tumor volumes of patients in the radiotherapy group that received single and multiple irradiation were significantly reduced and the visual acuity and visual field were improved (p<0.05). The two groups were followed up for an average of 3.8 years, and the follow-up results showed that differences of the two groups on the tumor control, mortality and hypopituitarism rates were not statistically significant (p>0.05). In addition, the incidence of complications of the radiotherapy group was significantly decreased as compared to that of the surgery group (p<0.05). In conclusion, γ-SRT was safe and effective for the treatment of functional pituitary adenomas. Its curative effects were equivalent to that of the microscopic single nasal-sphenoidal approach with fewer complications.

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.

Nelson's syndrome: a review of the clinical manifestations, pathophysiology, and treatment strategies

Nelson's syndrome is a rare clinical manifestation that occurs in 8%-47% of patients as a complication of bilateral adrenalectomy, a procedure that is used to control hypercortisolism in patients with Cushing's disease. First described in 1958 by Dr. Don Nelson, the disease has since become associated with a clinical triad of hyperpigmentation, excessive adrenocorticotropin secretion, and a corticotroph adenoma. Even so, for the past several years the diagnostic criteria and management of Nelson's syndrome have been inadequately studied. The primary treatment for Nelson's syndrome is transsphenoidal surgery. Other stand-alone therapies, which in many cases have been used as adjuvant treatments with surgery, include radiotherapy, radiosurgery, and pharmacotherapy. Prophylactic radiotherapy at the time of bilateral adrenalectomy can prevent Nelson's syndrome (protective effect). The most promising pharmacological agents are temozolomide, octreotide, and pasireotide, but these agents are often administered after transsphenoidal surgery. In murine models, rosiglitazone has shown some efficacy, but these results have not yet been found in human studies. In this article, the authors review the clinical manifestations, pathophysiology, diagnostic criteria, and efficacy of multimodal treatment strategies for Nelson's syndrome.

The role of bilateral adrenalectomy in the treatment of refractory Cushing's disease

Cushing's syndrome (CS) results from sustained exposure to excessive levels of free glucocorticoids. One of the main causes of CS is excessive adrenocorticotropic hormone (ACTH) secretion by tumors in the pituitary gland (Cushing's disease [CD]). Cushing's disease and its associated hypercortisolism have a breadth of debilitating symptoms associated with an increased mortality rate, warranting urgent treatment. Currently, the first line of treatment for CD is transsphenoidal surgery (TSS), with excellent long-term results. Transsphenoidal resections performed by experienced surgeons have shown remission rates ranging from 70% to 90%. However, some patients do not achieve normalization of their hypercortisolemic state after TSS and continue to have persistent or recurrent CD. For these patients, various therapeutic options after failed TSS include repeat TSS, radiotherapy, medical therapy, and bilateral adrenalectomy (BLA). Bilateral adrenalectomy has been shown to be a safe and effective treatment modality for persistent or recurrent CD with an immediate and definitive cure of the hypercortisolemic state. BLA was traditionally performed through an open approach, but since the advent of laparoscopic adrenalectomy, the laparoscopic approach has become the surgical method of choice. Advances in technology, refinement in surgical skills, competency in adrenopathology, and emphasis on multidisciplinary collaborations have greatly reduced morbidity and mortality associated with adrenalectomy surgery in a high-risk patient population. In this article, the authors review the role of BLA in the treatment of refractory CD. The clinical indications, current surgical and endocrinological results reported in the literature, surgical technique (open vs laparoscopic), drawbacks, and complications of BLA are discussed.

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.

Treatment of Cushing's Syndrome: An Endocrine Society Clinical Practice Guideline

OBJECTIVE

The objective is to formulate clinical practice guidelines for treating Cushing's syndrome.

PARTICIPANTS

Participants include an Endocrine Society-appointed Task Force of experts, a methodologist, and a medical writer. The European Society for Endocrinology co-sponsored the guideline.

EVIDENCE

The Task Force used the Grading of Recommendations, Assessment, Development, and Evaluation system to describe the strength of recommendations and the quality of evidence. The Task Force commissioned three systematic reviews and used the best available evidence from other published systematic reviews and individual studies.

CONSENSUS PROCESS

The Task Force achieved consensus through one group meeting, several conference calls, and numerous e-mail communications. Committees and members of The Endocrine Society and the European Society of Endocrinology reviewed and commented on preliminary drafts of these guidelines.

CONCLUSIONS

Treatment of Cushing's syndrome is essential to reduce mortality and associated comorbidities. Effective treatment includes the normalization of cortisol levels or action. It also includes the normalization of comorbidities via directly treating the cause of Cushing's syndrome and by adjunctive treatments (eg, antihypertensives). Surgical resection of the causal lesion(s) is generally the first-line approach. The choice of second-line treatments, including medication, bilateral adrenalectomy, and radiation therapy (for corticotrope tumors), must be individualized to each patient.

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.

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.

Stereotactic radiotherapy and radiosurgery for non-functioning and secreting pituitary adenomas

Radiotherapy (RT) is frequently employed in patients with residual or recurrent pituitary adenoma with excellent rates of tumor control and remission of hormonal hypersecretion. Advances in RT have improved with the use of stereotactic techniques either as fractionated stereotactic radiotherapy (FSRT) or stereotactic radiosurgery (SRS), all aiming to improve the dose distribution to the tumor while reducing the amount of normal brain receiving significant doses of radiation. We provide an overview of the recent published literature on the long-term efficacy and adverse effects of stereotactic irradiation in nonfunctioning and secreting pituitary adenomas. Both techniques are associated with excellent clinical outcomes; however, advantages and drawbacks of each of these techniques in terms of local control, hormonal excess normalization, and radiation-induced toxicity remain a matter of debate. In clinical practice, single-fraction SRS may represent a convenient approach to patients with small and medium-sized pituitary adenoma away at least 2 mm from the optic chiasm, whereas FSRT is preferred over SRS for lesions >2.5-3 cm in size and/or involving the anterior optic pathway.

Unyielding progress: recent advances in the treatment of central nervous system neoplasms with radiosurgery and radiation therapy

In the past decade, our understanding of the roles of external beam radiotherapy (EBRT) and stereotactic radiosurgery (SRS) in the management of brain tumors has dramatically improved. To highlight the changes and contemporary treatment approaches, we review the indications and outcomes of ionizing radiation for benign intracranial tumors and brain metastases. For nonfunctioning pituitary adenomas, SRS is able to achieve radiographic tumor control in at least 90 % of cases. The rate of SRS-induced endocrine remission for functioning pituitary adenomas depends on the tumor subtype, but it is generally lower than the rate of radiographic tumor control. The most common complications from pituitary adenoma SRS treatment are hypopituitarism and cranial neuropathies. SRS has become the preferred treatment modality for vestibular schwannomas and skull base meningiomas less than 3 cm in size. Large vestibular schwannomas and meningiomas remain best managed with initial surgical resection or EBRT for surgically ineligible patients. For small to moderately sized brain metastases, there has been a shift toward treatment of newly diagnosed patients with SRS alone due to similar local control rates compared with surgical resection. RCTs have shown combined SRS and whole brain radiation therapy (WBRT) for brain metastases to decrease rates of local and distant intracranial recurrence compared to SRS alone. However, the improved intracranial control comes at the expense of poorer neurocognitive outcomes and without prolonging overall survival. Therefore, WBRT is generally reserved for salvage therapy. While EBRT has been frequently supplanted by SRS for the treatment pituitary adenomas and brain metastases, it still proves useful in selected cases of large lesions which are not amenable to surgical debulking or for those with widespread disease, poor performance status, and short life expectancy. In recent years, the scope of SRS has extended beyond the intracranial space to include extradural and intradural spinal tumors.