Image-Guided Stereotactic Radiosurgery with the CyberKnife for Pituitary Adenomas

Applications of Frameless Image-Guided Robotic Stereotactic Radiotherapy and Radiosurgery in Pediatric Neuro-Oncology: A Systematic Review

BACKGROUND

CyberKnife-based robotic radiosurgery (RRS) is a widely used treatment modality for various benign and malignant tumors of the central nervous system (CNS) in adults due to its high precision, favorable safety profile, and efficacy. Although RRS is emerging in pediatric neuro-oncology, scientific evidence for treatment indications, treatment parameters, and patient outcomes is scarce. This systematic review summarizes the current experience and evidence for RRS and robotic stereotactic radiotherapy (RSRT) in pediatric neuro-oncology.

METHODS

We performed a systematic review based on the databases Ovid Medline, Embase, Cochrane Library, and PubMed to identify studies and published articles reporting on RRS and RSRT treatments in pediatric neuro-oncology. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were applied herein. Articles were included if they described the application of RRS and RSRT in pediatric neuro-oncological patients. The quality of the articles was assessed based on their evidence level and their risk for bias using the original as well as an adapted version of the Newcastle Ottawa Quality Assessment Scale (NOS). Only articles published until 1 August 2021, were included.

RESULTS

A total of 23 articles were included after final review and removal of duplicates. Articles reported on a broad variety of CNS entities with various treatment indications. A majority of publications lacked substantial sample sizes and a prospective study design. Several reports included adult patients, thereby limiting the possibility of data extraction and analysis of pediatric patients. RRS and RSRT were mostly used in the setting of adjuvant, palliative, and salvage treatments with decent local control rates and acceptable short-to-intermediate-term toxicity. However, follow-up durations were limited. The evidence level was IV for all studies; the NOS score ranged between four and six, while the overall risk of bias was moderate to low.

CONCLUSION

Publications on RRS and RSRT and their application in pediatric neuro-oncology are rare and lack high-quality evidence with respect to entity-related treatment standards and long-term outcomes. The limited data suggest that RRS and RSRT could be efficient treatment modalities, especially for children who are unsuitable for surgical interventions, suffer from tumor recurrences, or require palliative treatments. Nevertheless, the potential short-term and long-term adverse events must be kept in mind when choosing such a treatment. Prospective studies are necessary to determine the actual utility of RRS and RSRT in pediatric neuro-oncology.

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.

The rationale and development of a CyberKnife© registry for pediatric patients with CNS lesions

BACKGROUND

CyberKnife© Radiosurgery (CKRS) is a recognized treatment concept for CNS lesions in adults due to its high precision and efficacy beside a high patient comfort. However, scientific evidence for this treatment modality in pediatric patients is scarce. A dedicated registry was designed to document CyberKnife© procedures in children, aiming to test the hypothesis that it is safe and efficient for the treatment of CNS lesions.

METHODS

The CyberKnife© registry is designed as a retrospective and prospective multicenter observational study (German Clinical Trials Register ( https://www.drks.de ), DRKS-ID 00016973). Patient recruitment will be ongoing throughout a 5-year period and includes collection of demographic, treatment, clinical, and imaging data. Follow-up results will be monitored for 10 years. All data will be registered in a centralized electronic database at the Charité-Universitätsmedizin. The primary endpoint is stable disease for benign and vascular lesions at 5 years of follow-up and local tumor control for malign lesions at 1- and 2-year follow-up. Secondary endpoints are radiation toxicity, side effects, and neurocognitive development.

CONCLUSION

The CyberKnife© registry intends to generate scientific evidence for all treatment- and outcome-related aspects in pediatric patients with treated CNS lesions. The registry may define safety and efficacy of CKRS in children and serve as a basis for future clinical trials, inter-methodological comparisons and changes of treatment algorithms.

Stereotactic Radiosurgery for Residual and Recurrent Nonfunctioning Pituitary Adenomas: A Contemporary Case Series of GammaKnife and CyberKnife Radiosurgery

BACKGROUND

In patients with residual or recurrent nonfunctioning pituitary adenomas (NFPAs) after transsphenoidal resection, both GammaKnife (GKRS) and CyberKnife (CKRS) stereotactic radiosurgery (SRS) are viable treatment options.

OBJECTIVES

We report a retrospective single center series comparing assessing the effectiveness and complications from of these 2 commonly used SRS techniques.

METHODS

A total of 53 patients with prior surgical resection and residual or recurrent NFPAs who underwent GKRS or CKRS and minimum 3-month follow-up between January 2002 and February 2017 at a single center were identified.

RESULTS

A total of 34 patients underwent GKRS and 19 received CKRS. CKRS patients had a larger maximal tumor diameter (P = 0.005) and tumor volume treated (P = 0.001). Differences between GKRS and CKRS treatment parameters included target volume, target volume treated, prescribed dose, maximum dose, prescription isodose line, and conformity index (P < 0.05). The mean follow-up time was 53.74 months for GKRS and 41.48 months for CKRS patients. Tumor progression developed in 6% of cases after GKRS versus 5% after CKRS. The mean progression-free survival was 48.44 months after GKRS and 38.57 months after CKRS (P = 0.61). Five-year actuarial tumor control rates were 91% after GKRS versus 89% after CKRS (P > 0.99). There were no differences in worsened vision or rates of hypopituitarism.

CONCLUSIONS

In patients undergoing single fraction GKRS versus fractionated CKRS for NFPAs, both modalities had similar rates of tumor control, new hypopituitarism, and visual morbidity despite varying indications. This study validates the versatile use of these 2 SRS modalities for patients meeting their relative criteria, especially based on proximity to the optic apparatus and normal pituitary gland.

Postsurgical Salvage Radiosurgery for Nonfunctioning Pituitary Adenomas Touching/Compressing the Optic Chiasm: Median 13-Year Postirradiation Imaging Follow-up Results

BACKGROUND

There is little information on long-term outcomes after salvage treatment by either surgery or stereotactic radiosurgery (SRS) for patients with recurrent/residual nonfunctioning pituitary adenomas (NFPAs).

OBJECTIVE

To reappraise the efficacy and safety of SRS for patients with NFPAs touching/compressing the optic apparatus (OA).

METHODS

We studied 27 patients (14 females, 13 males; mean age: 61 [range, 19-85] yr) who underwent SRS between 1998 and 2008 for NFPAs with such condition. The median tumor volume was 4.9 (range, 1.8-50.8) cc. To avoid excess irradiation to the OA, the lower part of the tumor was covered with a 50% or a 60% isodose gradient, ie 49% to 98% (mean, 84%; median, 88%) of the entire tumor received the selected doses. Median doses at the tumor periphery/OA were 7.6/11.0 (interquartile range [IQR], 5.8-9.1/10.1-11.8) Gy.

RESULTS

Seven patients (26%) were confirmed to be deceased due to unrelated diseases at a median post-SRS period of 149 (IQR, 83-158) mo. Follow-up magnetic resonance imaging (MRI) showed tumor growth in 2 patients (7%) at the 11th and 134th post-SRS month; the former underwent surgery and the other SRS. Excluding these 2 patients, the latest follow-up MRI examinations, performed 13 to 238 (median: 168, IQR: 120-180) mo after SRS, showed no size changes in 5 (19%) and shrinkage in 20 (74%) patients. Cumulative incidences of tumor growth control were 96.3% and 91.8% at the 120th and 180th post-SRS month. None of our patients developed subjective symptoms suggesting SRS-induced optic neuropathy or endocrinological impairment.

CONCLUSION

In patients with NFPAs touching/compressing the OA, SRS achieves good long-term results.

Stereotactic radiosurgery for non-functioning pituitary adenomas: meta-analysis and International Stereotactic Radiosurgery Society practice opinion

BACKGROUND

This systematic review reports on outcomes and toxicities following stereotactic radiosurgery (SRS) for non-functioning pituitary adenomas (NFAs) and presents consensus opinions regarding appropriate patient management.

METHODS

Using the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses, a systematic review was performed from articles of ≥10 patients with NFAs published prior to May 2018 from the Medline database using the key words "radiosurgery" and "pituitary" and/or "adenoma." Weighted random effects models were used to calculate pooled outcome estimates.

RESULTS

Of the 678 abstracts reviewed, 35 full-text articles were included describing the outcomes of 2671 patients treated between 1971 and 2017 with either single fraction SRS or hypofractionated stereotactic radiotherapy (HSRT). All studies were retrospective (level IV evidence). SRS was used in 27 studies (median dose: 15 Gy, range: 5-35 Gy) and HSRT in 8 studies (median total dose: 21 Gy, range: 12-25 Gy, delivered in 3-5 fractions). The 5-year random effects local control estimate after SRS was 94% (95% CI: 93.0-96.0%) and 97.0% (95% CI: 93.0-98.0%) after HSRT. The 10-year local control random effects estimate after SRS was 83.0% (95% CI: 77.0-88.0%). Post-SRS hypopituitarism was the most common treatment-related toxicity observed, with a random effects estimate of 21.0% (95% CI: 15.0-27.0%), whereas visual dysfunction or other cranial nerve injuries were uncommon (range: 0-7%).

CONCLUSIONS

SRS is an effective and safe treatment for patients with NFAs. Encouraging short-term data support HSRT for select patients, and mature outcomes are needed before definitive recommendations can be made. Clinical practice opinions were developed on behalf of the International Stereotactic Radiosurgery Society (ISRS).

Radiation dose to neuroanatomical structures of pituitary adenomas and the effect of Gamma Knife radiosurgery on pituitary function

OBJECTIVE

Gamma Knife radiosurgery (GKRS) provides a safe and effective management option for patients with all types of pituitary adenomas. The long-term adverse effects of targeted radiation to the hypothalamic-pituitary axis in relationship to radiation dose remain unclear. In this retrospective review, the authors investigated the role of differential radiation doses in predicting long-term clinical outcomes and pituitary function after GKRS for pituitary adenomas.

METHODS

A cohort of 236 patients with pituitary tumors (41.5% nonfunctioning, 58.5% functioning adenomas) was treated with GKRS between 1998 and 2015. Point dosimetric measurements, with no minimum volume, to 14 consistent points along the hypothalamus bilaterally, pituitary stalk, and normal pituitary were made. Statistical analyses were performed to determine the impact of doses to critical structures on clinical, radiological, and endocrine outcomes.

RESULTS

With a median follow-up duration of 42.9 months, 18.6% of patients developed new loss of pituitary function. The median time to endocrinopathy was 21 months (range 2-157 months). The median dose was 2.1 Gy to the hypothalamus, 9.1 Gy to the pituitary stalk, and 15.3 Gy to the normal pituitary. Increasing age (p = 0.015, HR 0.98) and ratio of maximum dose to the pituitary stalk over the normal pituitary gland (p = 0.013, HR 0.22) were independent predictors of new or worsening hypopituitarism in the multivariate analysis. Sex, margin dose, treatment volume, nonfunctioning adenoma status, or ratio between doses to the pituitary stalk and hypothalamus were not significant predictors.

CONCLUSIONS

GKRS offers a low rate of delayed pituitary insufficiency for pituitary adenomas. Doses to the hypothalamus are low and generally do not portend endocrine deficits. Patients who are treated with a high dose to the pituitary stalk relative to the normal gland are at higher risk of post-GKRS endocrinopathy. Point dosimetry to specific neuroanatomical structures revealed that a ratio of stalk-to-gland radiation dose of 0.8 or more significantly increased the risk of endocrinopathy following GKRS. Improvement in the gradient index toward the stalk and normal gland may help preserve endocrine function.

Early versus late Gamma Knife radiosurgery following transsphenoidal surgery for nonfunctioning pituitary macroadenomas: a multicenter matched-cohort study

OBJECTIVE Gamma Knife radiosurgery (GKRS) is frequently used to treat residual or recurrent nonfunctioning pituitary macroadenomas. There is no consensus as to whether GKRS should be used early after surgery or if radiosurgery should be withheld until there is evidence of imaging-defined progression of tumor. Given the high incidence of adenoma progression after subtotal resection over time, the present study intended to evaluate the effect of timing of radiosurgery on outcome. METHODS This is a multicenter retrospective review of patients with nonfunctioning pituitary macroadenomas who underwent transsphenoidal surgery followed by GKRS from 1987 to 2015 at 9 institutions affiliated with the International Gamma Knife Research Foundation. Patients were matched by adenoma and radiosurgical parameters and stratified based on the interval between last resection and radiosurgery. Operative results, imaging data, and clinical outcomes were compared across groups following early (≤ 6 months after resection) or late (> 6 months after resection) radiosurgery. RESULTS After matching, 222 patients met the authors' study criteria (from an initial collection of 496 patients) and were grouped based on early (n = 111) or late (n = 111) GKRS following transsphenoidal surgery. There was a greater risk of tumor progression after GKRS (p = 0.013) and residual tumor (p = 0.038) in the late radiosurgical group over a median imaging follow-up period of 68.5 months. No significant difference in the occurrence of post-GKRS endocrinopathy was observed (p = 0.68). Thirty percent of patients without endocrinopathy in the early cohort developed new endocrinopathies during the follow-up period versus 27% in the late cohort (p = 0.84). Fourteen percent of the patients in the early group and 25% of the patients in the late group experienced the resolution of endocrine dysfunction after original presentation (p = 0.32). CONCLUSIONS In this study, early GKRS was associated with a lower risk of radiological progression of subtotally resected nonfunctioning pituitary macroadenomas compared with expectant management followed by late radiosurgery. Delaying radiosurgery may increase patient risk for long-term adenoma progression. The timing of radiosurgery does not appear to significantly affect the rate of delayed endocrinopathy.

Design of a modulated orthovoltage stereotactic radiosurgery system

PURPOSE

To achieve stereotactic radiosurgery (SRS) dose distributions with sharp gradients using orthovoltage energy fluence modulation with inverse planning optimization techniques.

METHODS

A pencil beam model was used to calculate dose distributions from an orthovoltage unit at 250 kVp. Kernels for the model were derived using Monte Carlo methods. A Genetic Algorithm search heuristic was used to optimize the spatial distribution of added tungsten filtration to achieve dose distributions with sharp dose gradients. Optimizations were performed for depths of 2.5, 5.0, and 7.5 cm, with cone sizes of 5, 6, 8, and 10 mm. In addition to the beam profiles, 4π isocentric irradiation geometries were modeled to examine dose at 0.07 mm depth, a representative skin depth, for the low energy beams. Profiles from 4π irradiations of a constant target volume, assuming maximally conformal coverage, were compared. Finally, dose deposition in bone compared to tissue in this energy range was examined.

RESULTS

Based on the results of the optimization, circularly symmetric tungsten filters were designed to modulate the orthovoltage beam across the apertures of SRS cone collimators. For each depth and cone size combination examined, the beam flatness and 80-20% and 90-10% penumbrae were calculated for both standard, open cone-collimated beams as well as for optimized, filtered beams. For all configurations tested, the modulated beam profiles had decreased penumbra widths and flatness statistics at depth. Profiles for the optimized, filtered orthovoltage beams also offered decreases in these metrics compared to measured linear accelerator cone-based SRS profiles. The dose at 0.07 mm depth in the 4π isocentric irradiation geometries was higher for the modulated beams compared to unmodulated beams; however, the modulated dose at 0.07 mm depth remained <0.025% of the central, maximum dose. The 4π profiles irradiating a constant target volume showed improved statistics for the modulated, filtered distribution compared to the standard, open cone-collimated distribution. Simulations of tissue and bone confirmed previously published results that a higher energy beam (≥ 200 keV) would be preferable, but the 250 kVp beam was chosen for this work because it is available for future measurements.

CONCLUSIONS

A methodology has been described that may be used to optimize the spatial distribution of added filtration material in an orthovoltage SRS beam to result in dose distributions with decreased flatness and penumbra statistics compared to standard open cones. This work provides the mathematical foundation for a novel, orthovoltage energy fluence-modulated SRS system.

Evaluation of Clinical Application and Dosimetric Comparison of Treatment Plans of Gamma Knife and CyberKnife in Treating Arteriovenous Malformations

PURPOSE

To analyze and compare the characteristics of dose distributions for Leksell Gamma Knife Perfexion (LGK-PFX) and CyberKnife (CK) in treating arteriovenous malformations (AVMs).

SUBJECTS AND METHODS

Twenty-four patients with AVMs who received CK radiosurgery at a prescribed dose (PD) of 16-25 Gy in a single fraction were selected. A LGK-PFX treatment plan with the same PD was designed for each patient. Dosimetric values for both systems were compared with respect to the conformity index (CI); selectivity index (SI); gradient index (GI) of 75, 50, and 25% of the PD; heterogeneity index; volume of the brain tissue covered by doses of 10 and 12 Gy; maximum dose delivered to the brainstem; and beam-on time.

RESULTS

The CIs of LGK-PFX and CK were 0.744 ± 0.075 and 0.759 ± 0.071 (p = 0.385), respectively. The SIs of LGK-PFX and CK were 0.764 ± 0.081 and 0.780 ± 0.076 (p = 0.424), respectively. The GI75%, GI50%, and GI25% values of LGK-PFX and CK were 1.028 ± 0.123 and 2.439 ± 0.338 (p < 0.001), 3.169 ± 0.265 and 4.972 ± 0.852 (p < 0.001), and 8.650 ± 0.914 and 14.261 ± 2.476 (p < 0.001), respectively. Volumes of the brain tissue covered by 10 Gy and 12 Gy for LGK-PFX and CK (p < 0.001) exhibited a significant difference.

CONCLUSIONS

LGK-PFX and CK exhibited similar dose conformity. LGK-PFX showed superior normal tissue sparing.

Analysis of volumetric response of pituitary adenomas receiving adjuvant CyberKnife stereotactic radiosurgery with the application of an exponential fitting model

Tumor control rates of pituitary adenomas (PAs) receiving adjuvant CyberKnife stereotactic radiosurgery (CK SRS) are high. However, there is currently no uniform way to estimate the time course of the disease. The aim of this study was to analyze the volumetric responses of PAs after CK SRS and investigate the application of an exponential decay model in calculating an accurate time course and estimation of the eventual outcome.A retrospective review of 34 patients with PAs who received adjuvant CK SRS between 2006 and 2013 was performed. Tumor volume was calculated using the planimetric method. The percent change in tumor volume and tumor volume rate of change were compared at median 4-, 10-, 20-, and 36-month intervals. Tumor responses were classified as: progression for >15% volume increase, regression for ≤15% decrease, and stabilization for ±15% of the baseline volume at the time of last follow-up. For each patient, the volumetric change versus time was fitted with an exponential model.The overall tumor control rate was 94.1% in the 36-month (range 18-87 months) follow-up period (mean volume change of -43.3%). Volume regression (mean decrease of -50.5%) was demonstrated in 27 (79%) patients, tumor stabilization (mean change of -3.7%) in 5 (15%) patients, and tumor progression (mean increase of 28.1%) in 2 (6%) patients (P = 0.001). Tumors that eventually regressed or stabilized had a temporary volume increase of 1.07% and 41.5% at 4 months after CK SRS, respectively (P = 0.017). The tumor volume estimated using the exponential fitting equation demonstrated high positive correlation with the actual volume calculated by magnetic resonance imaging (MRI) as tested by Pearson correlation coefficient (0.9).Transient progression of PAs post-CK SRS was seen in 62.5% of the patients receiving CK SRS, and it was not predictive of eventual volume regression or progression. A three-point exponential model is of potential predictive value according to relative distribution. An exponential decay model can be used to calculate the time course of tumors that are ultimately controlled.

Early versus late Gamma Knife radiosurgery following transsphenoidal resection for nonfunctioning pituitary macroadenomas: a matched cohort study

OBJECT Gamma Knife radiosurgery (GKRS) is frequently employed to treat residual or recurrent nonfunctioning pituitary macroadenomas. There is no consensus as to whether GKRS should be used early after surgery or if radiosurgery should be withheld until there is evidence of radiographic progression of tumor. METHODS This is a retrospective review of patients with nonfunctioning pituitary macroadenomas who underwent transsphenoidal surgery followed by GKRS between 1996 and 2013 at the University of Virginia Health System. Patients were stratified based on the interval between resection and radiosurgery. Operative results and imaging and clinical outcomes were compared across groups following early (≤ 6 months) or late (> 6 months) radiosurgery. RESULTS Sixty-four patients met the study criteria and were grouped based on early (n = 32) or late (n = 32) GKRS following transsphenoidal resection. There was a greater risk of tumor progression after GKRS in the late radiosurgical group (p = 0.027) over a median radiographic follow-up period of 68.5 months. Furthermore, there was a significantly higher occurrence of post-GKRS endocrinopathy in the late radiosurgical cohort (p = 0.041). Seventeen percent of patients without endocrinopathy in the early cohort developed new endocrinopathies during the follow-up period versus 64% in the late cohort (p = 0.036). This difference was primarily due to a significantly higher rate of tumor growth during the observation period of the late treatment cohort (p = 0.014). Of these patients with completely new endocrinopathies, radiation-associated pituitary insufficiency developed in 1 of 2 patients in the early group and in 3 of 7 (42.9%) patients in the late group. CONCLUSIONS Early treatment with GKRS appears to decrease the rate of radiographic and symptomatic progression of subtotally resected nonfunctioning pituitary macroadenomas compared with late GKRS treatment after a period of expectant management. Delaying radiosurgery may place the patient at increased risk for adenoma progression and endocrinopathy.

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.

Treatment of acromegaly patients with risk-adapted single or fractionated stereotactic high-precision radiotherapy: High local control and low toxicity in a pooled series

PURPOSE

The purpose of this work was to evaluate a prospectively initiated two-center protocol of risk-adapted stereotactic radiosurgery (SRS) or stereotactic radiotherapy (SRT) in patients with acromegaly.

PATIENTS AND METHODS

In total 35 patients (16 men/19 women, mean age 54 years) were prospectively included in a treatment protocol of SRS [planning target volume (PTV < 4 ccm, > 2 mm to optic pathways = low risk] or SRT (PTV ≥ 4 ccm, ≤ 2 mm to optic pathways = high risk). The mean tumor volume was 3.71 ccm (range: 0.11-22.10 ccm). Based on the protocol guidelines, 21 patients were treated with SRS and 12 patients with SRT, 2 patients received both consecutively.

RESULTS

The median follow-up (FU) reached 8 years with a 5-year overall survival (OS) of 87.3% [confidence interval (CI): 70.8-95.6%] and 5-year local control rate of 97.1% (CI: 83.4-99.8%). Almost 80% (28/35) presented tumor shrinkage during FU. Endocrinological cure was achieved in 23% and IGF-1 normalization with reduced medication was achieved in 40% of all patients. An endocrinological response was generally achieved within the first 3 years, but endocrinological cure can require more than 8 years. A new adrenocorticotropic hypopituitarism occurred in 13 patients (46.4%). A new visual field disorder and a new oculomotor palsy occurred in 1 patient, respectively. Patients with occurrence of visual/neurological impairments had a longer FU (p = 0.049).

CONCLUSION

Our SRS/SRT protocol proved to be safe and successful in terms of tumor control and protection of the visual system. The timing and rate of endocrine improvements are difficult to predict. One has to accept an unavoidable rate of additional adrenocorticotropic hypopituitarism in the long term.

Cranial stereotactic radiosurgery: current status of the initial paradigm shifter

The concept of stereotactic radiosurgery (SRS) was first described by Lars Leksell in 1951. It was proposed as a noninvasive alternative to open neurosurgical approaches to manage a variety of conditions. In the following decades, SRS emerged as a unique discipline involving a collegial partnership among neurosurgeons, radiation oncologists, and medical physicists. SRS relies on the precisely guided delivery of high-dose ionizing radiation to an intracranial target. The focused convergence of multiple beams yields a potent therapeutic effect on the target and a steep dose fall-off to surrounding structures, thereby minimizing the risk of collateral damage. SRS is typically administered in a single session but can be given in as many as five sessions or fractions. By providing an ablative effect noninvasively, SRS has altered the treatment paradigms for benign and malignant intracranial tumors, functional disorders, and vascular malformations. Literature on extensive intracranial radiosurgery has unequivocally demonstrated the favorable benefit-to-risk profile that SRS affords for appropriately selected patients. In a departure from conventional radiotherapeutic strategies, radiosurgical principles have recently been extended to extracranial indications such as lung, spine, and liver tumors. The paradigm shift resulting from radiosurgery continues to alter the landscape of related fields.

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.

Gamma knife surgery for patients with volumetric classification of nonfunctioning pituitary adenomas: a systematic review and meta-analysis

OBJECTIVE

The aim of this study was to scrutinize the literature to determine the efficacy and safety of gamma knife surgery (GKS) for the treatment of nonfunctioning pituitary adenomas (NFPAs) with volumetric classification.

METHODS

Electronic databases including MedLine, PubMed, and Cochrane Central were searched. The literature related to patients with NFPAs treated with GKS was collected. Eligible studies reported on the rate of tumor control (RTC), the rate of radiosurgery-induced optic neuropathy injury (RRIONI), the rate of radiosurgery-induced endocrinological deficits (RRIED), and other parameters.

RESULTS

A total of 17 studies met the criteria. based on the tumor volume, nfpas were divided into three groups: the RTC of group I (93 patients) with tumor volumes <2 ml was 99% (95% CI 96-100%), the RRIONI was 1% (95% CI 0-4%), and the RRIED was 1% (95% CI 0-4%). The RTC of group II (301 patients) with volumes from 2 to 4 ml was 96% (95% CI 92-99%), the RRIONI was 0 (95% CI 0-2%), and RRIED was 7% (95% CI 2-14%). The RTC of group III (531 patients) with volumes larger than 4 ml was 91% (95% CI 89-94%), the RRIONI was 2% (95% CI 0-5%), and the RRIED was 22% (95% CI 14-31%). There were significant differences in the RTC and in the RRIED among the three groups (P<0.001), indicating that there were higher RRIED and lower RTC with the increase of tumor volume.

CONCLUSIONS

NFPAs, according to tumor volume classification, need stratification for GKS treatment. GKS is the optimal choice for the treatment of group II NFPAs. Patients with residual tumor volumes of <4 ml will benefit most from GKS treatment.

Radiation-induced hypopituitarism

PURPOSE OF REVIEW

Progressive and irreversible neuro-endocrine dysfunction following radiation-induced damage to the hypothalamic-pituitary (h-p) axis is the most common complication in cancer survivors with a history of cranial radiotherapy involving the h-p axis and in patients with a history of conventional or stereotactic pituitary radiotherapy for pituitary tumours. This review examines the controversy about the site and pathophysiology of radiation damage while providing an epidemiological perspective on the frequency and pattern of radiation-induced hypopituitarism.

RECENT FINDINGS

Contrary to the previously held belief that h-p axis irradiation with doses less than 40 Gy result in a predominant hypothalamic damage with time-dependent secondary pituitary atrophy, recent evidence in survivors of nonpituitary brain tumours suggests that cranial radiation causes direct pituitary damage with compensatory increase in hypothalamic release activity. Sparing the hypothalamus from significant irradiation with sterteotactic radiotherapy for pituitary tumours does not appear to reduce the long-term risk of hypopituitarism.

SUMMARY

Radiation-induced h-p dysfunction may occur in up to 80% of patients followed long term and is often associated with an adverse impact on growth, body image, skeletal health, fertility, sexual function and physical and psychological health. A detailed understanding of pathophysiological and epidemiological aspects of radiation-induced h-p axis dysfunction is important to provide targeted and reliable long-term surveillance to those at risk so that timely diagnosis and hormone-replacement therapy can be provided.

Acromegaly: a single centre's experience of stereotactic radiosurgery and radiotherapy for growth hormone secreting pituitary tumours with the linear accelerator

Primary treatment for growth-hormone secreting pituitary adenomas usually involves surgery, with treatment options for recurrent and persistent disease including repeat surgery, medication and radiation therapy. The majority of previously published series for radiation therapy in acromegaly in the past 20 years have been based on Gamma-Knife (Elekta, Stockholm, Sweden) surgery. To our knowledge, we present the largest series of linear accelerator-based treatment for this disease, with a review of 121 patients treated at our institution; since 1990, 86 patients underwent stereotactic radiosurgery (SRS), 10 patients underwent fractionated stereotactic radiotherapy (FSRT), and for the purposes of comparison we also reviewed 25 patients who underwent conventional radiotherapy prior to 1990. Tumour volume control in all three groups was excellent and consistent with previously reported literature - only three of 86 (4%) patients undergoing SRS had a documented increase in tumour size, and none of the patients undergoing FSRT had a documented increase in size following a median follow-up of 5.5 and 5.1 years for SRS and FSRT, respectively. Target growth hormone levels of <2.5 ng/mL were met by 12 of 86 (14%) of the SRS group, and by two of 10 (20%) in the FSRT group. Target insulin-like growth factor-1 levels of age and sex matched controls were achieved in 16 of 86 patients (18.6%) post-SRS and five of 10 patients (50%) post-FSRT. New hormonal deficits requiring replacement therapy were identified in 17 of 86 (19.8%) patients post-SRS which is consistent with previously published radiosurgical series. Identified non-hormonal morbidity was low (<5%).

Stereotactic radiosurgery/radiotherapy for pituitary adenomas: a review of recent literature

The recent clinical results are reviewed of stereotactic radiosurgery/radiotherapy for the treatment of pituitary adenomas. The outcomes of pituitary adenomas treated by stereotactic radiosurgery/radiotherapy with gamma knife, CyberKnife, or linear accelerator (LINAC) radiosurgery were evaluated from articles published after 2004. Each study was evaluated for the number of patients, radiosurgical parameter (marginal dose), length of follow up, tumor growth control, rate of hormonal normalization in secretary adenomas, and adverse events. After gamma knife radiosurgery, the tumor reduction rates varied from 42.3% to 89% in non-secreting adenomas. However, the tumor control rates in non-secreting adenomas were more than 90% in most studies. In growth hormone-secreting adenomas, the rates of insulin-like growth factor-1 normalization ranged from 36.9% to 82%. In adrenocorticotropin-secreting adenomas, the rates for 24-hour urine free cortisol normalization ranged from 27.9% to 54%. In prolactin-secreting adenomas, the prolactin normalization ranged from 17.4% to 50%. New hormonal deficits ranged from 0% to 34%. New visual deficits were relatively low. The number of patients treated with CyberKnife and LINAC radiosurgery/radiotherapy was small and follow-up periods were relatively short compared to those with gamma knife treatment, but the clinical outcomes after these therapies were similar to those after gamma knife therapy. Image-guided stereotactic radiosurgery/radiotherapy with the gamma knife, CyberKnife, or LINAC system is effective and safe against pituitary adenomas. Careful long-term follow up of the patients is necessary because of long-term anti-tumor effects and delayed adverse events.

Development of a modified head and neck quality assurance phantom for use in stereotactic radiosurgery trials

An anthropomorphic head phantom, constructed from a water‐equivalent plastic shell with only a spherical target, was modified to include a nonspherical target (pituitary) and an adjacent organ at risk (OAR) (optic chiasm), within 2 mm, simulating the anatomy encountered when treating acromegaly. The target and OAR spatial proximity provided a more realistic treatment planning and dose delivery exercise. A separate dosimetry insert contained two TLD for absolute dosimetry and radiochromic film, in the sagittal and coronal planes, for relative dosimetry. The prescription was 25 Gy to 90% of the GTV, with ≤10% of the OAR volume receiving ≥8Gy for the phantom trial. The modified phantom was used to test the rigor of the treatment planning process and phantom reproducibility using a Gamma Knife, CyberKnife, and linear accelerator (linac)‐based radiosurgery system. Delivery reproducibility was tested by repeating each irradiation three times. TLD results from three irradiations on a CyberKnife and Gamma Knife agreed with the calculated target dose to within ± 4% with a maximum coefficient of variation of ±2.1%. Gamma analysis in the coronal and sagittal film planes showed an average passing rate of 99.4% and 99.5% using ±5%/3mm criteria, respectively. Results from the linac irradiation were within ±6.2% for TLD with a coefficient of variation of ±0.1%. Distance to agreement was calculated to be 1.2 mm and 1.3 mm along the inferior and superior edges of the target in the sagittal film plane, and 1.2 mm for both superior and inferior edges in the coronal film plane. A modified, anatomically realistic SRS phantom was developed that provided a realistic clinical planning and delivery challenge that can be used to credential institutions wanting to participate in NCI‐funded clinical trials.

PACS number: 87.55 ‐v

Endocrine and visual function after fractionated stereotactic radiotherapy of perioptic tumors

PURPOSE

To find out whether the use of stereotactic techniques for fractionated radiotherapy reduces toxicity to the endocrine and visual system in patients with benign perioptic tumors.

PATIENTS AND METHODS

From 1993 to 2009, 29 patients were treated with fractionated stereotactic radiotherapy. The most frequent tumor types were grade I meningioma (n = 11) and pituitary adenoma (n = 10, 7 nonfunctioning, 3 growth hormone-producing). Patients were immobilized with the GTC frame (Radionics, USA) and the planning target volume (PTV; median 24.7, 4.6-58.6 ml) was irradiated with a total dose of 52.2 Gy (range, 45.0-55.8 Gy) in 1.8-Gy fractions using a linear accelerator (6 MeV photons) equipped with a micro-multileaf collimator. Maximum doses to the optic system and pituitary gland were 53.4 Gy (range, 11.5-57.6 Gy) and 53.6 Gy (range, 12.0-57.9 Gy).

RESULTS

Median follow-up was 45 months (range, 10-105 months). Local control was achieved in all but 1 patient (actuarial rate 92% at 5 years and 10 years). In 9 of 29 patients (31%), partial remission was observed (actuarial response rate 40% at 5 years and 10 years). In 4 of 26 patients (15%) with at least partial pituitary function, new hormonal deficits developed (actuarial rate 21% at 5 years and 10 years). This rate was significantly higher in patients treated for a larger PTV (< /> 25 ml: 0% vs. 42% at 5 years and 10 years, p = 0.028). Visual function improved in 4 of 15 patients (27%) who had prior impairment. None of the patients developed treatment-related optic neuropathy, but 2 patients experienced new disease-related visual deficits.

CONCLUSION

Fractionated stereotactic radiotherapy for benign tumors of the perioptic and sellar region results in satisfactory response and local control rates and does not affect the visual system. The assumption that patients can be spared hypophyseal insufficiency only holds for small tumors.

Gamma Knife surgery for patients with nonfunctioning pituitary macroadenomas: predictors of tumor control, neurological deficits, and hypopituitarism

Object

Nonfunctioning pituitary macroadenomas often recur after microsurgery and thereby require further treatment. Gamma Knife surgery (GKS) has been used to treat recurrent adenomas. In this study, the authors evaluated outcomes following GKS of nonfunctioning pituitary macroadenomas and assessed predictors of tumor control, neurological deficits, and delayed hypopituitarism.

Methods

Between June 1989 and March 2010, 140 consecutive patients with nonfunctioning pituitary macroadenomas were treated using GKS at the University of Virginia. The median patient age was 51 years (range 21–82 years), and 56% of patients were male. Mean tumor volume was 5.6 cm3 (range 0.6–35 cm3). Thirteen patients were treated with GKS as primary therapy, and 127 had undergone at least 1 open resection prior to GKS. Ninety-three patients had a history of hormone therapy prior to GKS. The mean maximal dose of GKS was 38.6 Gy (range 10–70 Gy), the mean marginal dose was 18 Gy (range 5–25 Gy), and the mean number of isocenters was 9.8 (range 1–26). Follow-up evaluations were performed in all 140 patients, ranging from 0.5 to 17 years (mean 5 years, median 4.2 years).

Results

Tumor volume remained stable or decreased in 113 (90%) of 125 patients with available follow-up imaging. Kaplan-Meier analysis demonstrated radiographic progression free survival at 2, 5, 8, and 10 years to be 98%, 97%, 91%, and 87%, respectively. In multivariate analysis, a tumor volume greater than 5 cm3 (hazard ratio = 5.0, 95% CI 1.5–17.2; p = 0.023) was the only factor predictive of tumor growth. The median time to tumor progression was 14.5 years. Delayed hypopituitarism occurred in 30.3% of patients. No factor was predictive of post-GKS hypopituitarism. A new or worsening cranial nerve deficit occurred in 16 (13.7%) of 117 patients. Visual decline was the most common neurological deficit (12.8%), and all patients experiencing visual decline had evidence of tumor progression. In multivariate analysis, a tumor volume greater than 5 cm3 (OR = 3.7, 95% CI 1.2–11.7; p = 0.025) and pre-GKS hypopituitarism (OR = 7.5, 95% CI 1.1–60.8; p = 0.05) were predictive of a new or worsened neurological deficit.

Conclusions

In patients with nonfunctioning pituitary macroadenomas, GKS confers a high rate of tumor control and a low rate of neurological deficits. The most common complication following GKS is delayed hypopituitarism, and this occurs in a minority of patients.

Treatment of nonfunctioning pituitary adenomas: what were the contributions of the last 10 years? A critical view

OBJECTIVES

All evidence for treatment and follow-up for nonfunctioning pituitary adenomas (NFMA) is based on observational studies. The objective was to critically review the contributions of the last 10 years on treatment of NFMA.

MATERIALS AND METHODS

Systematic review.

RESULTS

Transsphenoidal surgery remains the cornerstone of treatment of NFMA. When compared to the microsurgical procedure, some, but not all, studies favor endoscopy, but endocrinological outcome is not different. Radiosurgery results in a high and durable rate of tumor control, including in those previously treated by conventional radiotherapy, but the risk of developing hypopituitarism is comparable to the risk after conventional radiotherapy. In selected patients without visual field defects, a wait-and-see approach with frequent evaluation of visual fields is possible, without the risk of irreversibly compromising visual function. Tumor progression in NFMA is difficult to predict, but the MIB-1 LI is clinically useful and is indicative of invasiveness, but does not predict recurrence. To date, the potential contribution of other proliferation markers still requires further validation, and effective medical treatment strategies are not available. New features are the role of temozolomide and rapamicin as potential therapeutical targets, combined with octreotide. Although chimeric sst-DA analogues effectively inhibit proliferation in vitro, the effects of these molecules have not yet been evaluated in clinical trials with patients with NFMA.

CONCLUSION

Surgery, followed by radiotherapy or radiosurgery in case of remnant or recurrence, remains the cornerstone of treatment of NFMA. Currently, medical treatment cannot yet be incorporated in routine clinical practice.

Comprehensive review of stereotactic radiosurgery for medically and surgically refractory pituitary adenomas

Despite advances in surgical techniques and medical therapies, a significant proportion of pituitary adenomas remain endocrinologically active, demonstrate persistent radiographic disease, or recur when followed for long periods of time. While surgical intervention remains the first-line therapy, stereotactic radiosurgery is increasingly recognized as a viable treatment option for these often challenging tumors. In this review, we comprehensively review the literature to evaluate both endocrinologic and radiographic outcomes of radiosurgical management of pituitary adenomas. The literature clearly supports the use of radiosurgery, with endocrinologic remission rates and time to remission varying by tumor type [prolactinoma: 20–30%, growth hormone secreting adenomas: ~50%, adrenocorticotrophic hormone (ACTH)-secreting adenomas: 40–65%] and radiographic control rates almost universally greater than 90% with long-term follow-up. We stratify the outcomes by tumor type, review the importance of prognostic factors (particularly, pre-treatment endocrinologic function and tumor size), and discuss the complications of treatment (with special attention to endocrinopathy and visual complications). We conclude that the literature supports the use of radiosurgery for treatment-refractory pituitary adenomas, providing the patient with a minimally invasive, safe, and effective treatment option for an otherwise resistant tumor. As such, we provide literature-based treatment considerations, including radiosurgical dose, endocrinologic, radiographic, and medical considerations for each adenoma type.

Stereotactic Irradiation of GH-Secreting Pituitary Adenomas

Radiotherapy (RT) is often employed in patients with acromegaly refractory to medical and/or surgical interventions in order to prevent tumour regrowth and normalize elevated GH and IGF-I levels. It achieves tumour control and hormone normalization up to 90% and 70% of patients at 10-15 years. Despite the excellent tumour control, conventional RT is associated with a potential risk of developing late toxicity, especially hypopituitarism, and its role in the management of patients with GH-secreting pituitary adenomas remains a matter of debate. Stereotactic techniques have been developed with the aim to deliver more localized irradiation and minimize the long-term consequences of treatment, while improving its efficacy. Stereotactic irradiation can be given in a single dose as stereotactic radiosurgery (SRS) or in multiple doses as fractionated stereotactic radiotherapy (FSRT). We have reviewed the recent published literature on stereotactic techniques for GH-secreting pituitary tumors with the aim to define the efficacy and potential adverse effects of each of these techniques.

Radiation techniques for acromegaly

Radiotherapy (RT) remains an effective treatment in patients with acromegaly refractory to medical and/or surgical interventions, with durable tumor control and biochemical remission; however, there are still concerns about delayed biochemical effect and potential late toxicity of radiation treatment, especially high rates of hypopituitarism. Stereotactic radiotherapy has been developed as a more accurate technique of irradiation with more precise tumour localization and consequently a reduction in the volume of normal tissue, particularly the brain, irradiated to high radiation doses. Radiation can be delivered in a single fraction by stereotactic radiosurgery (SRS) or as fractionated stereotactic radiotherapy (FSRT) in which smaller doses are delivered over 5-6 weeks in 25-30 treatments. A review of the recent literature suggests that pituitary irradiation is an effective treatment for acromegaly. Stereotactic techniques for GH-secreting pituitary tumors are discussed with the aim to define the efficacy and potential adverse effects of each of these techniques.

The role of radiation therapy in the management of non-functioning pituitary adenomas

Surgical removal of non-functioning pituitary adenoma (NFPA) is the first-choice therapeutic option, but radical removal of the tumor cannot be accomplished in all patients. The best strategy to prevent regrowth of NFPA is still a matter of debate. Adjuvant radiotherapy is very effective in reducing recurrence rate after incomplete removal of NFPA, but concerns still exist about long-term toxicity of radiation. Different modalities have been developed to irradiate the pituitary region. One major distinction is between radiation techniques that deliver the total dose in multiple sessions using 3 fixed radiation beams and radiosurgical equipment that delivers the total dose to the target volume in a single treatment session. Progression-free survival of patients with NFPA treated by adjuvant radiotherapy is well above 90% at 5 yr in most studies and diminishes only slightly at 10 yr. Very few studies have a more prolonged follow-up. In comparison, the 5- and 10-yr estimated recurrence rate without adjuvant radiotherapy ranged from 15% to 51% and from 44% to 78%, respectively. Complications of radiation include rare but severe side-effects, such as secondary brain neoplasm, optic neuropathy, cerebrovascular accidents, and more frequent but less severe complications, such as pituitary deficiency. Optimal management of patients with residual or recurring NFPA after surgical debulking can be achieved through the judicious use of different treatment options, necessitating close cooperation between neurosurgeons, endocrinologists, and radiation oncologists.

Recent advances in pituitary tumor management

PURPOSE OF REVIEW

Advances in the neurosurgical management of pituitary tumors have included the refinement of surgical access and significant progress in navigation technology to help further reduce morbidity and improve outcome. Similarly, stereotactic radiosurgery has evolved to become an integral part in pituitary tumors not amenable to medical or surgical treatment.

RECENT FINDINGS

The evolution of minimally invasive surgery has evolved toward endoscopic versus microscopic trans-sphenoidal approaches for pituitary tumors. Debate exists regarding each approach, with advocates for both championing their cause. Stereotactic and fractional radiosurgery have been shown to be a safe and effective means of controlling tumor growth and ensuring hormonal stabilization, with longer-term data available for GammaKnife compared with CyberKnife.

SUMMARY

The advances in trans-sphenoidal surgical approaches, navigation technological improvements and the current results of stereotactic radiosurgery are discussed.

Radiation treatment strategies for acromegaly

The high morbidity and mortality associated with acromegaly can be addressed with multiple treatment modalities, including surgery, medicines, and radiation therapy. Radiation was initially delivered through conventional fractionated radiotherapy, which targets a wide area over many treatment sessions and has been shown to induce remission in 50%&#x2013;60% of patients with acromegaly. However, conventional fractionated radiotherapy takes several years to achieve remission in patients with acromegaly and carries a risk of hypopituitarism that may limit its use. Stereotactic radiosurgery, of which there are several forms, including Gamma Knife surgery, CyberKnife therapy, and proton beam therapy, offers slightly attenuated efficacy but achieves remission in less time and provides more precise targeting of the adenoma with better control of the dose of radiation received by adjacent structures such as the pituitary stalk, pituitary gland, optic chiasm, and cranial nerves in the cavernous sinus. Of the forms of stereotactic radiosurgery, Gamma Knife surgery is the most widely used and, because of its long-term follow-up in clinical studies, is the most likely to compete with medical therapy for first-line adjuvant use after resection. In this review, the authors outline the major modes of radiation therapies in clinical use today, and they critically assess the feasibility of these modalities for acromegaly treatment. Acromegaly is a multisystem disorder that demands highly specialized treatment protocols including neurosurgical and endocrinological intervention. As more efficient forms of pituitary radiation develop, acromegaly treatment options may continue to change with radiation therapies playing a more prominent role.

The role of stereotactic radiosurgery in the multimodal management of growth hormone–secreting pituitary adenomas

Growth hormone (GH)–secreting pituitary adenomas represent a common source of GH excess in patients with acromegaly. Whereas surgical extirpation of the culprit lesion is considered first-line treatment, as many as 19% of patients develop recurrent symptoms due to regrowth of previously resected adenomatous tissue or to continued growth of the surgically inaccessible tumor. Although medical therapies that suppress GH production can be effective in the management of primary and recurrent acromegaly, these therapies are not curative, and lifelong treatment is required for hormonal control. Stereotactic radiosurgery has emerged as an effective adjunctive treatment modality, and is an appealing alternative to conventional fractionated radiation therapy. The authors reviewed the growing body of literature concerning the role of radiosurgical procedures in the treatment armamentarium of acromegaly, and identified more than 1350 patients across 45 case series. In this review, the authors report that radiosurgery offers true hormonal normalization in 17% to 82% of patients and tumor growth control in 37% to 100% of cases across all series, while minimizing adverse complications. As a result, stereotactic radiosurgery represents a safe and effective treatment option in the multimodal management of primary or recurrent acromegaly secondary to GH-secreting pituitary adenomas.

Radiation therapy and stereotactic radiosurgery for the treatment of Cushing's disease: an evidence-based review

PURPOSE OF REVIEW

The indications, efficacy, and safety of radiation therapy and stereotactic radiosurgery for Cushing's disease are evaluated.We queried PubMed using the terms, 'Cushing's disease', 'radiotherapy', and 'radiosurgery', then evaluated each study for the number of patients, method of radiation delivery, type of radiation therapy or radiosurgical device used, treatment parameters (e.g. maximal dose, tumor margin dose), length of follow-up, tumor-control rate, complications, rate of hormone normalization, newly onset loss of pituitary function, and method used to assess endocrine remission.

RECENT FINDINGS

A total of 39 peer-reviewed studies with 731 patients were included. The reported rates of tumor-volume control following radiotherapy and radiosurgery vary considerably from 66-100%. Additionally, the reported rates of endocrine remission vary substantially from 17-100%. The incidence of serious complications following radiosurgery is quite low. Although post-treatment hypopituitarism and disease recurrence were uncommon, they did occur, and this underscores the necessity for long-term follow-up in these patients.

SUMMARY

Radiosurgery and, in the modern era, less commonly, radiation therapy, offer both well tolerated and reasonably effective treatment for recurrent or residual Cushing's adenomas.

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.

HYPOFRACTIONATED CYBERKNIFE RADIOSURGERY FOR PERICHIASMATIC PITUITARY ADENOMAS

OBJECTIVE

Radiation therapy is recommended for pituitary tumors that are refractory to surgical and medical therapies. The efficacy of single-fraction radiosurgery is established for these lesions, but lesions within 3 mm of the optic pathway cannot be safely treated with doses higher than 8 to 10 Gy. We hypothesized that the optic nerve will tolerate 5 consecutive daily radiosurgery fractions of 500 cGy with effective tumor control.

METHODS

We reviewed our first 20 patients with recurrent or residual pituitary adenomas within 3 mm of the optic chiasm treated with the CyberKnife radiosurgery system (Accuray, Inc., Sunnyvale, CA). Tumors were treated with a mean coverage of 97 ± 2.2% (range, 89.8–99.7%), a mean conformity index of 1.3 ± 0.2 (range, 1.1–1.6), and a mean treatment isodose line of 74.5 ± 6.6% (range, 60–86%). The primary end point was an interim analysis of visual preservation, and secondary end points were radiographic and endocrinological tumor control.

RESULTS

The mean follow-up period for visual field testing was 26.6 ± 10.5 months (range, 10.6–41 months). The vision of all 14 patients with intact preoperative vision remained intact. Of the 5 patients with impaired vision, 2 remained stable, and 3 improved. No patient's vision deteriorated. The mean radiographic follow-up was 29.3 ± 8.6 months (range, 10.2–40.5 months). On magnetic resonance imaging, 12 tumors were stable, 8 were smaller, and none enlarged.

CONCLUSION

This preliminary study establishes that the optic nerve and chiasm tolerate CyberKnife hypofractionated radiosurgery of 5 × 500 cGy to perichiasmatic pituitary adenomas. Early data suggest that this dosing paradigm may achieve satisfactory radiographic and endocrinological tumor control for these challenging lesions, but longer follow-up is necessary to confirm these results.

Applications of radiotherapy and radiosurgery in the management of pediatric Cushing's disease: a review of the literature and our experience

Surgical extirpation of pituitary adenomas is considered the mainstay of therapy in pediatric patients with Cushing's disease. However, a small subset of patients will require adjuvant therapy either due to tumor invasiveness, or disease recurrence. Conventional radiation therapy (or radiotherapy) delivers ionizing radiation to control hormonally active cells in fractionated doses (spread out over time) in order to give normal cells time to recover, while radiosurgery involves focusing a high dose of radiation structures in a single treatment session to the adenoma while generally sparing the normal gland and surrounding of any substantial amount of radiation. This paper reviews the effectiveness of radiation in the treatment of pediatric Cushing's disease.

Radiation therapy in acromegaly

Radiation therapy is generally not a primary treatment modality for growth hormone-secreting pituitary adenomas. However, in patients with acromegaly refractory to medical and/or surgical interventions, radiation can offer durable tumor control and often biochemical remission. Technique of radiation therapy delivery and dose vary by adenoma size and extrasellar extension. Radiation can be delivered in a single sitting by stereotactic radiosurgery or in fractionated form of smaller doses delivered over typically 5-6 weeks in 25-30 treatments. A brief overview of forms of radiation modalities is reviewed followed by discussion of the role for radiation therapy, rationale of delivery method, and potential adverse effects.

Radiotherapy for nonfunctioning pituitary adenomas: from conventional to modern stereotactic radiation techniques

The initial management of nonfunctioning pituitary macroadenomas (NFAs) is usually surgery; however, a significant proportion of NFAs may require further treatment. Radiotherapy is currently used in patients with residual tumour and achieves excellent long-term control, but there are concerns about potential late toxicity. Stereotactic radiotherapy, both in the form of radiosurgery or fractionated stereotactic radiotherapy, has been developed as a more accurate technique of irradiation with more precise tumour localization and consequently a reduction in the volume of normal tissue, particularly the brain, irradiated to high radiation doses. A review of the literature suggests that new radiation techniques offer safe and effective treatment for recurrent or residual pituitary adenomas; however longer follow-up is necessary to confirm the excellent tumour control and the potential reduction of long-term radiation toxicity. Currently, radiotherapy has an important role in patients with residual or progressive disease after surgery. Patients with small or no residual tumours after surgery may generally continue on a policy of surveillance without immediate irradiation, in order to avoid the potential toxicity of treatment.

Image-guided radiosurgical ablation of intra- and extra-cranial lesions

For decades since its introduction, stereotactic radiosurgery (SRS) was used only to treat intracranial lesions because intracranial targets could be immobilized and located relative to a rigid metal frame affixed to the patient's head. Lesions outside the head were generally not treated with SRS because it is difficult to immobilize extracranial lesions and to attach stereotactic frames elsewhere on the body. Advances in computerized image guidance and robotics allowed the development of systems, such as the CyberKnife SRS System (Accuray, Inc, Sunnyvale, CA), that could target intracranial lesions without the stereotactic frame. Enhancements have resulted in a radiation delivery system that can accurately deliver high-dose, focal radiation to lesions in the spine, chest, and abdomen, even if they move during respiration. In this review we will describe the technical features of frameless SRS systems and briefly review their application to treating intracranial and extracranial lesions, focusing in particular on spinal lesions.

Efficacy and safety of CyberKnife radiosurgery for acromegaly

OBJECTIVE

Acromegaly is a disease characterized by GH hypersecretion, and is typically caused by a pituitary somatotroph adenoma. The primary mode of therapy is surgery, and radiotherapy is utilized as an adjuvant strategy to treat persistent disease. The aim of this study was to determine the efficacy and tolerability of CyberKnife stereotactic radiosurgery in acromegaly.

DESIGN

A retrospective review of biochemical and imaging data for subjects with acromegaly treated with CyberKnife stereotactic radiosurgery between 1998 and 2005 at Stanford University Hospital.

PATIENTS

Nine patients with active acromegaly were treated with radiosurgery using the CyberKnife (CK).

MEASUREMENTS

Biochemical response based on serum insulin-like growth factor-1 (IGF-1), anterior pituitary hormone function, and tumor size with MRI scans were analyzed.

RESULTS

After a mean follow up of 25.4 months (range, 6-53 months), CK radiosurgery resulted in complete biochemical remission in 4 (44.4%) subjects, and in biochemical control with the concomitant use of a somatostatin analog in an additional subject. Smaller tumor size was predictive of treatment success: baseline tumor volume was 1.28 cc (+/- 0.81, SD) vs. 3.93 cc (+/- 1.54) in subjects with a normal IGF-1 vs. those with persistent, active disease, respectively (P = 0.02). The mean biologically effective dose (BED) was higher in subjects who achieved a normal IGF-1 vs. those with persistent, active disease, 172 Gy(3) (+/-28) vs. 94 Gy(3) (+/-17), respectively (P < 0.01). At least one new anterior pituitary hormone deficiency was observed after CK in 3 (33%) patients: two developed hypogonadism, and one developed panhypopituitarism.

CONCLUSIONS

CK radiosurgery may be a valuable adjuvant therapy for the management of acromegaly.