Results of gamma knife radiosurgery in acromegaly

Efficacy and safety of radiosurgery in acromegaly

Stereotactic radiosurgery (SRS) more and more frequently plays a crucial role in the treatment of acromegaly. We provide a systematic review of the literature and meta-analysis, according to PRISMA, on SRS for the management of growth hormone (GH)-secreting pituitary adenomas, including several radiosurgical techniques, with the aim of describing efficacy and safety of this treatment. A weighted random effects model was used to calculate pooled outcome estimates. From 346 abstract reviews, 27 retrospective studies were included. Despite the variability in hormonal remission criteria and the heterogeneity between treatment guidelines among included studies, most of them reported an endocrine remission rate between 40% and 60%. Random effects meta-analysis for overall endocrine remission and 5-year probability of remission estimate after SRS were 46% (95% CI: 39-53%) and of 48% (95% CI: 38-57%), respectively. Random effects meta-analysis for new hypopituitarism estimate after SRS was 23% (95% CI: 17-29%). Furthermore, incidence of radiation induced optic neuropathy after SRS ranged between 0% and 6% This meta-analysis confirms and quantifies safety and effectiveness of SRS to achieve endocrine remission after surgical management in acromegaly.

Prospective intraoperative and histologic evaluation of cavernous sinus medial wall invasion by pituitary adenomas and its implications for acromegaly remission outcomes

Recurrence and biochemical remission rates vary widely among different histological subtypes of pituitary adenoma. In this prospective study, we evaluated 107 consecutive primary pituitary adenomas operated on by a single neurosurgeon including 28 corticotroph, 27 gonadotroph, 24 somatotroph, 17 lactotroph, 5 null-cell and 6 plurihormonal. In each case, we performed direct endoscopic intraoperative inspection of the medial wall of the cavernous sinus, which was surgically removed when invasion was visualized. This was performed irrespective of tumor functional status. Medial wall resection was performed in 47% of pituitary adenomas, and 39/50 walls confirmed pathologic evidence of invasion, rendering a positive predictive value of intraoperative evaluation of medial wall invasion of 78%. We show for the first-time dramatic disparities in the frequency of medial wall invasion among pathological subtypes. Somatotroph tumors invaded the medial wall much more often than other adenoma subtypes, 81% intraoperatively and 69% histologically, followed by plurihormonal tumors (40%) and gonadotroph cell tumors (33%), both with intraoperative positive predictive value of 100%. The least likely to invade were corticotroph adenomas, at a rate of 32% intraoperatively and 21% histologically, and null-cell adenomas at 0%. Removal of the cavernous sinus medial wall was not associated with permanent cranial nerve morbidity nor carotid artery injury, although 4 patients (all Knosp 3-4) experienced transient diplopia. Medial wall resection in acromegaly resulted in the highest potential for biochemical remission ever reported, with an average postoperative day 1 GH levels of 0.96 ug/L and surgical remission rates of 92% based on normalization of IGF-1 levels after surgery (mean = 15.56 months; range 3-30 months). Our findings suggest that tumor invasion of the medial wall of the cavernous sinus may explain the relatively low biochemical remission rates currently seen for acromegaly and illustrate the relevance of advanced intradural surgical approaches for successful and durable outcomes in endonasal pituitary surgery for functional adenomas.

Dosimetric parameters associated with the long-term oncological outcomes of Gamma Knife surgery for sellar and parasellar tumors in pediatric patients

OBJECTIVE

The authors aimed to investigate the dosimetric parameter and the minimally required dose associated with long-term control of sellar and parasellar tumors after Gamma Knife surgery (GKS) in children.

METHODS

A retrospective analysis was performed on pediatric patients younger than 19 years of age who were diagnosed with sellar and parasellar tumors and received GKS at the authors' institution from 1998 to 2019. Cox proportional hazards regression analyses were used to investigate the dosimetric parameters associated with treatment outcome. The Kaplan-Meier method was used to analyze tumor control rates after GKS.

RESULTS

Overall, 37 patients with 40 sellar and parasellar tumors, including 22 craniopharyngiomas and 12 pituitary adenomas, had a mean follow-up of 85.8 months. The gross target volume was 0.05 cm3 to 15.28 cm3, and the mean marginal dose was 15.8 Gy (range 9.6-30.0 Gy). Ten patients experienced treatment failure at a mean of 28.0 ± 26.7 months. The actuarial 5- and 10-year tumor control rates were 79.0% and 69.8%, respectively. D98% was an independent predictive factor of tumor control (HR 0.846 [95% CI 0.749-0.956], p = 0.007), with a cutoff value of 11.5 Gy for the entire cohort and 10 Gy for the craniopharyngioma group. Visual deterioration occurred in 2 patients with the maximum point dose of 10.1 Gy and 10.6 Gy to the optic apparatus.

CONCLUSIONS

In pediatric patients, D98% was a reliable index of the minimum required dose for long-term control of sellar and parasellar tumors after GKS. The optimal D98% value for each tumor diagnosis needs to be elucidated in the future.

Pituitary adenomas

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

Gamma Knife Radiosurgery for Pituitary Tumors: A Systematic Review and Meta-Analysis

Simple Summary

Pituitary tumors represent approximately 10–15% of all brain neoplasms. Gamma Knife, the most commonly used stereotactic radiosurgery technique worldwide, plays an important role in the treatment of several pituitary neoplasm. It is currently used in cases of residual or recurrent tumors after surgery or as primary treatment when surgery is contraindicated. Its goals are long-term tumor control, preservation of visual function, and, for secreting pituitary adenomas, endocrine remission. Several retrospective case-series (level of evidence IV) on Gamma Knife for pituitary tumors have been published describing encouraging outcomes; only one systematic review and meta-analysis on non-functioning pituitary adenoma has been recently reported. We provide a systematic review of the literature and meta-analysis from the last two decades on Gamma Knife radiosurgery for several pituitary tumors with the aim of describing and confirming safety and effectiveness of this technique.

Abstract

To describe and evaluate outcomes of Gamma Knife radiosurgery (GK) for the treatment of pituitary tumors over the past twenty years, a systematic review and meta-analysis according to PRISMA statement was performed. Articles counting more than 30 patients were included. A weighted random effects models was used to calculate pooled outcome estimates. From 459 abstract reviews, 52 retrospective studies were included. Among them, 18 reported on non-functioning pituitary adenomas (NFPA), 13 on growth hormone (GH)-secreting adenomas, six on adrenocorticotropic hormone (ACTH)-secreting adenomas, four on prolactin hormone (PRL)-secreting adenomas, and 11 on craniopharyngiomas. Overall tumor control and five-year progression free survival (PFS) estimate after one GK procedure for NFPA was 93% (95% CI 89–97%) and 95% (95% CI 91–99%), respectively. In case of secreting pituitary adenomas, overall remission (cure without need for medication) estimates were 45% (95% CI 35–54%) for GH-secreting adenomas, 64% (95% CI 0.52–0.75%) for ACTH-secreting adenomas and 34% (95% CI: 19–48%) for PRL-secreting adenomas. The pooled analysis for overall tumor control and five-year PFS estimate after GK for craniopharyngioma was 74% (95% CI 67–81%) and 70% (95% CI: 64–76%), respectively. This meta-analysis confirms and quantifies safety and effectiveness of GK for pituitary tumors.

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.

Mortality in Acromegalic Patients: Etiology, Trends, and Risk Factors

Although acromegaly has been associated with increased mortality rates, evidence shows that the application of the recent treatment modalities has reduced the risk of death in these patients, being comparable with the general population. As a result of the changing trends regarding mortality, the aim is to review the current literature to create enough evidence about the recent trends of mortality in patients with acromegaly. Moreover, this review aims to identify the possible etiology and the related risk factors. Old studies have reported that cardiovascular complications were the major etiology for death among acromegalic patients. However, recent studies showed that malignancies-induced complications might be the leading factor, while other studies reported that cardiovascular complications are still the main culprit. Nonetheless, the recently estimated risk is similar to that in the general population. Studies reported a decrease in mortality rates among patients with acromegaly within the last decades, which is probably attributable to the recent changes in the management updates, the less frequent exposure to radiotherapy and focus on the common cardiovascular disorders associated with the disease. This review also found that exposure to radiotherapy, old age, hypopituitarism, active acromegaly, and high growth hormone (GH) levels are significant predictors of mortality in acromegalic patients. In conclusion, more effort should be made to decrease GH to favorable levels based on the recent guidelines.

Gamma Knife radiosurgery for acromegaly: Evaluating the role of the biological effective dose associated with endocrine remission in a series of 42 consecutive cases

INTRODUCTION

Stereotactic radiosurgery (SRS) is a valuable treatment option for persistent and/or recurrent acromegaly secondary to growth hormone (GH) secreting pituitary adenoma (PA). Here, we assess the role of biological effective dose (BED) received by PA treated with SRS in relation with endocrine remission.

METHODS

Forty-two patients (minimum 6 months follow-up) were included. Mean marginal dose was 27.7 (median 28, 20-35), and mean BED received by tumour was 193.1 Gy_2.47 (median 199.7, 64.1-237.1). Based on the median values, we divided the patients in high tumour BED group (H-BEDtm, 199.7-237.1 Gy_2.47, n = 12) and low BED one (L- BEDtm, 64.1-199.7 Gy_2.47 , n = 10). The two groups did not differ by pretherapeutic IGF-1 levels (p = .1) or by the prescribed dose (p = .6).

RESULTS

Mean follow-up period was 62.5 months (median 60.5, 9-127). Probability of IGF-1 normalization was 65% at 3 years and 72.4% at 4 years, remaining stable until last follow-up. Twenty-two (52.4%) patients had complete endocrine remission in absence of any Somatostatin analogues. Actuarial rates were 33% at 3 years and 57.4% at 7 years, further remaining stable during follow-up course. In univariate analysis, only statistically significant parameter was pretherapeutic serum IGF-1 and IGF-1 index (p = .01). Five patients (5/26, 19.3%) without previous hypopituitarism developed new pituitary insufficiency. H-BEDtm was associated with higher rates of endocrine remission compared with L-BEDtm, with actuarial probability of 70.2% versus 48.2% at 9 years, although this did not reach statistical significance (p > .05).

CONCLUSION

Our study confirms that SRS by Gamma Knife is safe and effective for GH-secreting PA. Pretherapeutic serum levels of IGF-1 were only statistically significant parameter for endocrine remission.

Comparing primary gamma knife radiosurgery and postoperative gamma knife radiosurgery for acromegaly: A monocenter retrospective study

OBJECTIVE

To compare the efficacy and safety between primary GKS and postoperative GKS for acromegaly, and to elucidate predictors associated with endocrine remission, we performed a monocenter, retrospective study.

METHOD

Seventy-five patients with acromegaly who had received GKS in West China Hospital between March 2010 and December 2018 were included in this study. Endocrine remission was defined as age-sex matched IGF-I normalization and either nadir level of GH <1 ng/mL after OGTT or the random GH < 2.0 ng/mL.

RESULTS

We didn't find significant differences in endocrine remission, biochemical recurrence, imaging regression, imaging progression, radiation-induced complications between the primary GKS group and the postoperative GKS group(P > 0.05). Actuarial rates of durable endocrine remission at 3, 5, 8 year were 10.60 %, 33.80 % and 70.60 % in the primary GKS group and 6.70 %, 43.40 % and 78.80 % in the postoperative GKS group(P = 0.800). Only base nadir GH after OGTT (HR = 0.637,95 % CI:0.416-0.977; P = 0.039) was found to be a predictor of duration endocrine remission.

CONCLUSION

We find comparable efficacy and safety between primary GKS and postoperative GKS. Lower base nadir GH after OGTT was a positive predictor associated with endocrine remission. GKS should be considered for residual or recurrent tumor after surgery. For those who couldn't sustain surgery, GKS is an alternative treatment. Further studies are required to elucidate the efficacy and safety of GKS in acromegaly.

The Impact of Insulin-Like Growth Factor Index and Biologically Effective Dose on Outcomes After Stereotactic Radiosurgery for Acromegaly: Cohort Study

BACKGROUND

Stereotactic radiosurgery (SRS) is a safe and effective treatment for acromegaly.

OBJECTIVE

To improve understanding of clinical and dosimetric factors predicting biochemical remission.

METHODS

A single-institution cohort study of nonsyndromic, radiation-naïve patients with growth hormone-producing pituitary adenomas (GHA) having single-fraction SRS between 1990 and 2017. Exclusions were treatment with pituitary suppressive medications at the time of SRS, or <24 mo of follow-up. The primary outcome was biochemical remission-defined as normalization of insulin-like growth factor-1 index (IGF-1i) off suppression. Biochemical remission was assessed using Cox proportional hazards. Prior studies reporting IGF-1i were assessed via systematic literature review and meta-analysis using random-effect modeling.

RESULTS

A total of 102 patients met study criteria. Of these, 46 patients (45%) were female. The median age was 49 yr (interquartile range [IQR] = 37-59), and the median follow-up was 63 mo (IQR = 29-100). The median pre-SRS IGF-1i was 1.66 (IQR = 1.37-3.22). The median margin dose was 25 Gy (IQR = 21-25); the median estimated biologically effective dose (BED) was 169.49 Gy (IQR = 124.95-196.00). Biochemical remission was achieved in 58 patients (57%), whereas 22 patients (22%) had medication-controlled disease. Pre-SRS IGF-1i ≥ 2.25 was the strongest predictor of treatment failure, with an unadjusted hazard ratio (HR) of 0.51 (95% CI = 0.26-0.91, P = .02). Number of isocenters, margin dose, and BED predicted remission on univariate analysis, but after adjusting for sex and baseline IGF-1i, only BED remained significant-and was independently associated with outcome in continuous (HR = 1.01, 95% CI = 1.00-1.01, P = .02) and binary models (HR = 2.27, 95% CI = 1.39-5.22, P = .002). A total of 24 patients (29%) developed new post-SRS hypopituitarism. Pooled HR for biochemical remission given subthreshold IGF-1i was 2.25 (95% CI = 1.33-3.16, P < .0001).

CONCLUSION

IGF-1i is a reliable predictor of biochemical remission after SRS. BED appears to predict biochemical outcome more reliably than radiation dose, but confirmatory study is needed.

Effect of Stereotactic Radiosurgery on Residual or Relapsed Pituitary Adenoma: A Systematic Review and Meta-Analysis

BACKGROUND

In pituitary tumors, the presence of residual tumor after transsphenoidal surgery and recurrence of the tumor after resection are frequent, and the best treatment is not well established. The effects and complications of stereotactic radiosurgery have not been extensively studied.

OBJECTIVE

We aimed to reveal the effect of stereotactic radiosurgery on residual and recurrent adenomas.

METHODS

A systematic review of the literature in the MEDLINE/PubMed, Cochrane Central Database, and Google Scholar was conducted using the criteria of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. The search was structured according to the PICOT (i.e., Participants, types of Interventions, Comparator between the treatments, types of Outcome measures, and Follow-up [Time of duration]) strategy. The methodologic quality assessment (risk of bias) was performed according to the Methodological Index for Non-Randomized Studies scale. The studies were grouped and analyzed after data extraction using the software "R".

RESULTS

Twenty-six articles including 2315 patients were analyzed, with an average follow-up duration of 57.8 months and mean radiation marginal dose of 19.6 Gy. The overall tumor control rate was 95%, tumor reduction rate was 46%, and hormonal control rate was 67%. The side effects were evaluated.

CONCLUSIONS

Stereotactic radiosurgery was efficient in residual or recurrence tumor control, with few side effects, and is recommended for treating residual or recurrent tumors, both secreting and nonsecreting tumors. A limitation of this study is that there were no randomized trials included in the synthesis.

Stereotactic Radiosurgery for Acromegaly: An International Multicenter Retrospective Cohort Study

BACKGROUND

Stereotactic radiosurgery (SRS) is a treatment option for persistent or recurrent acromegaly secondary to a growth hormone secreting pituitary adenoma, but its efficacy is inadequately defined.

OBJECTIVE

To assess, in a multicenter, retrospective cohort study, the outcomes of SRS for acromegaly and determine predictors.

METHODS

We pooled and analyzed data from 10 participating institutions of the International Gamma Knife Research Foundation for patients with acromegaly who underwent SRS with endocrine follow-up of ≥6 mo.

RESULTS

The study cohort comprised 371 patients with a mean endocrine follow-up of 79 mo. IGF-1 lowering medications were held in 56% of patients who were on pre-SRS medical therapy. The mean SRS treatment volume and margin dose were 3.0 cm3 and 24.2 Gy, respectively. The actuarial rates of initial and durable endocrine remission at 10 yr were 69% and 59%, respectively. The mean time to durable remission after SRS was 38 mo. Biochemical relapse after initial remission occurred in 9%, with a mean time to recurrence of 17 mo. Cessation of IGF-1 lowering medication prior to SRS was the only independent predictor of durable remission (P = .01). Adverse radiation effects included the development of ≥1 new endocrinopathy in 26% and ≥1 cranial neuropathy in 4%.

CONCLUSION

SRS is a definitive treatment option for patients with persistent or recurrent acromegaly after surgical resection. There appears to be a statistical association between the cessation of IGF-1 lowering medications prior to SRS and durable remission.

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.

Radiosurgery as primary management for acromegaly

OBJECTIVE

Transsphenoidal surgery (TSS) remains the recommended primary treatment for acromegaly. Long-term outcome data are not available for patients treated with gamma knife radiosurgery (STRS) as a primary treatment.

DESIGN

Retrospective cohort study.

DATA COLLECTION

notes review, laboratory results, general physician notes, patient questionnaire and death certification.

PATIENTS

Twenty acromegaly patients underwent primary STRS at the National Centre for Radiosurgery, Sheffield, UK, between 1985 and 2015.

MEASUREMENTS

Biochemical control (GH/IGF1), hypopituitarism, morbidity and mortality were all recorded.

RESULTS

At 20 years of follow-up, control was seen in all on acromegaly-specific medication (n = 12) and 75% of those off medication (3/4). Time for 50% to achieve control on medication was 3 years, and 7.4 years off medication. Median marginal radiation dose was 27.5 Gy, and median follow-up was 166.5 months. 53% of patients developed new hypopituitarism at a median follow-up of 146 months, and the development of first onset of hypopituitarism occurred as late as 20 years after treatment. With MRI planning, no other complications were noted. Three patients underwent subsequent TSS due to poor biochemical control. During follow-up, 7 patients died at a median age of 65 years. There were no STRS-related deaths.

CONCLUSION

This is the longest follow-up of patients who have undergone primary STRS for acromegaly. It shows low morbidity, but significant latency to biochemical control and new-onset hypopituitarism. This mandates very long-term follow-up for these patients. STRS has shown good long-term efficacy providing initial control can be afforded by optimal medical management. While TSS remains best practice, STRS offers an alternative for those in whom surgery is not an option.

Factors affecting early versus late remission in acromegaly following stereotactic radiosurgery

Stereotactic radiosurgery (SRS) is a well-established treatment modality for patients with acromegaly. Our previously published study demonstrated a median time to remission of 29 months. This study aims to identify factors affecting the timing of remission and also to quantify the rate of late remission. This is a retrospective analysis of acromegaly patients who underwent SRS between 1988 and 2016. Early and late remissions were defined based on our prior median remission time of 29 months. The median imaging and endocrine follow-ups are 66 and 104.8 months, respectively. Multivariate analysis was conducted to analyze factors leading to late remission. A total number of 157 patients, of those 102 (64.9%) patients achieved remission. of those 102 patients, 62 patients (60.7%) had remission in less than 29 months (early remission) whereas 40 patients (39.3%) achieved remission later than (late remission) 29 months. The two groups differed significantly in the time interval between the last resection and the first SRS (p = 0.040) whole sella radiosurgery (p = 0.025) or radiosurgery to the cavernous sinus (p = 0.041). Competing risk analysis showed the interval between resection and SRS was significantly longer in the late remission group (HR 1.013, 95% CI 1.004-1.02; p = 0.007). Fifty-one of 157 patients (32.5%) developed a new endocrine deficiency following SRS. Those with shorter time between resection and SRS were more likely to achieve early remission. While most patients achieve remission in less than 4 years, the latency of effect with SRS yields a small percentage of patients achieving remission beyond that time point.

Radiation therapy for older patients with brain tumors

The incidence of brain tumors in the elderly population has increased over the last few decades. Current treatment includes surgery, radiotherapy and chemotherapy, but the optimal management of older patients with brain tumors remains a matter of debate, since aggressive radiation treatments in this population may be associated with high risks of neurological toxicity and deterioration of quality of life. For such patients, a careful clinical status assessment is mandatory both for clinical decision making and for designing randomized trials to adequately evaluate the optimal combination of radiotherapy and chemotherapy.

Several randomized studies have demonstrated the efficacy and safety of chemotherapy for patients with glioblastoma or lymphoma; however, the use of radiotherapy given in association with chemotherapy or as salvage therapy remains an effective treatment option associated with survival benefit. Stereotactic techniques are increasingly used for the treatment of patients with brain metastases and benign tumors, including pituitary adenomas, meningiomas and acoustic neuromas. Although no randomized trials have proven the superiority of SRS over other radiation techniques in older patients with brain metastases or benign brain tumors, data extracted from recent randomized studies and large retrospective series suggest that SRS is an effective approach in such patients associated with survival advantages and toxicity profile similar to those observed in young adults. Future trials need to investigate the optimal radiation techniques and dose/fractionation schedules in older patients with brain tumors with regard to clinical outcomes, neurocognitive function, and quality of life.

Updates in outcomes of stereotactic radiation therapy in acromegaly

Purpose Treatment of acromegaly has undergone important progress in the last 20 years mainly due to the development of new medical options and advances in surgical techniques. Pituitary surgery is usually first-line therapy, and medical treatment is indicated for persistent disease, while radiation (RT) is often used as third-line therapy. The benefits of RT (tumor volume control and decreased hormonal secretion) are hampered by the long latency of the effect and the high risk of adverse effects. Stereotactic RT methods have been developed with the aim to provide more precise targeting of the tumor with better control of the radiation dose received by the adjacent brain structures. The purpose of this review is to present the updates in the efficacy and safety of pituitary RT in acromegalic patients, with an emphasis on the new stereotactic radiation techniques. Methods A systematic review was performed using PubMed and articles/abstracts and reviews detailing RT in acromegaly from 2000 to 2016 were included. Results Stereotactic radiosurgery and fractionated stereotactic RT (FSRT) for patients with persistent active acromegaly after surgery and/or during medical therapy provide comparable high rates of tumor control, i.e. stable or decrease in size of the tumor in 93-100% of patients at 5-10 years and endocrinological remission in 40-60% of patients at 5 years. Hypofractionated RT is an optimal option for tumors located near the optic structures, due to its lower toxicity for the optic nerves compared to single-dose radiosurgery. The rate of new hypopituitarism varies from 10 to 50% at 5 years and increases with the duration of follow-up. The risk for other radiation-induced complications is usually low (0-5% for new visual deficits, cranial nerves damage or brain radionecrosis and 0-1% for secondary brain tumors) and risk of stroke may be higher in FSRT. Conclusion Although the use of radiotherapy in patients with acromegaly has decreased with advances in medical treatments, it remains an effective treatment option after unsuccessful surgery and/or resistance or unavailability of medical therapy. Long-term studies evaluating secondary morbidity and mortality rate after the new stereotactic techniques are needed, in order to evaluate their potential brain-sparing effect.

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.

Advances in Gamma Knife radiosurgery for pituitary tumors

PURPOSE OF REVIEW

For the residual/recurrent pituitary adenomas, stereotactic radiosurgery (SRS) plays an important role in long-term tumor control and, for secretory adenomas, endocrine remission. The purpose of this review is to address the advances in SRS technique and detail the latest treatment strategies for various types of pituitary adenomas with a focus on recently published literature.

RECENT FINDINGS

From recent publications, SRS may be considered as an upfront treatment in patients with an adenoma that resides largely in the cavernous sinus and for whom resection is unlikely to produce substantial reduction in the overall tumor volume. Early treatment (<6 months after prior resection) with SRS appears to decrease the rate of tumor progression of subtotally resected nonfunctioning pituitary macroadenomas. Some types of adenomas may appear more aggressive with a high recurrence rate, for example, silent corticotroph pituitary adenomas, or sparsely granulated somatotroph-cell adenomas, may be indicated for a high-radiation dose. Finally, whole-sellar radiation and fractionated SRS are the alternative strategies, and may be indicated for challenging cases.

SUMMARY

The role of SRS for the pituitary adenoma is well established, and the treatment strategy is increasingly individualized based upon tumor histology, location, and volume. Hypopituitarism is the most complicated and can occur even years after SRS.

Effective time window in reducing pituitary adenoma size by gamma knife radiosurgery

OBJECTIVES

Although the effectiveness of gamma knife radiosurgery (GKRS) in controlling the size of pituitary adenomas has been well demonstrated in many studies, the time period in which significant changes in tumor size occurs has been investigated in a limited fashion. It is important to determine the therapeutic window of GKRS in treating pituitary adenomas, i.e., the effective timeframe during which significant size reduction of these tumors occurs, so that alternative treatments such as further GKRS or microsurgery might be prescribed in a timely manner if clinically indicated.

METHODS

This was a nested sample of an ongoing local cohort study on GKRS for pituitary adenomas at the University of Virginia. Magnetic resonance imaging (MRI) using dedicated sequences was employed. Only patients with a baseline MRI (TP0) and at least 1 follow-up study performed in the University Hospital after GKRS were included. The follow-up scans were performed at five time-points (TP1-TP5) which were 6, 12, 24, 36 and 48 months after GKRS. The dimensional indices of the tumors were measured in three orthogonal planes, i.e., transverse (TR), antero-posterior (AP) and cranio-caudal (CC). The volumes of the tumors were estimated by using the following formula: [Formula: see text]. Tumor volume decrease by more than 25% from baseline was considered as 'shrinkage', <25% tumor size increase or decrease was considered 'static', and more than 25% increase as 'increment'. Our cohort consisted of 21 patients, with functioning adenomas in 13 subjects i.e. six adrenocorticotrophic hormone (ACTH)-secreting and seven growth hormone (GH)-secreting, and non-functioning (NF) adenomas in eight subjects.

RESULTS

In 26 adenomas (8 ACTH, 9 GH and 9 NF), tumor control (tumor shrinkage or static) were achieved in 21 tumors (80.8%); 89, 75, and 78% for GH-secreting, ACTH-secreting and NF adenomas respectively, at the end of the 4-year follow-up period. Analysis of variance showed significant differences of GKRS margin dose among different types of tumors (p = 0.013), but not of baseline tumor volumes (p = 0.240). Logistic regression analysis showed no significant association of margin dose, baseline volume or tumor type with the tumor control outcome. Comparison of tumor change using dimensional indices relative to the base time point (TP0) showed that in the sample there was an average reduction of 1.290 mm at TP1 (6 months) with p values 0.155 (parametric t test) and 0.098 (non-parametric Wilcoxon signed-ranked test) respectively, showing a moderate reduction in tumor dimensional indices. The change in dimensional indices at later time points (TP2-TP5) showed an average reduction ranging from 1.930 to 2.471 mm. Significant reduction in the mean dimensional indices was firstly observed at TP2 (1 year) with p values 0.013 (t test) and 0.018 (Wilcoxon signed-rank test). Such scale of reduction in the dimensional indices appeared to be maintained along the time axis (from TP2 to TP5).

CONCLUSIONS

Significant decrease in tumor dimensional indices tended to occur at 1 year post-GKRS. Although to a lesser extent, such decrease in dimensional indices continued up to the end of our follow-up period.

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.

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.