Efficacy of Gamma Knife radiosurgery in the management of pituitary prolactinoma

Background:

Gamma Knife radiosurgery (GKR) has been widely used in the management of a variety of intracranial tumors, including pituitary adenomas. Pituitary prolactinoma (Prs) is one of the most common types of these adenomas.

Methods:

This prospective study included 50 patients with pituitary Prs over a period from June 2017 to June 2018 at the Neurosciences Hospital, Baghdad/Iraq. The GKR procedure was performed using the Leksell Gamma Knife^® Perfexion™, 192 beams of Cobalt 60 radiation were delivered through the intact skull to the pituitary Prs.

Results:

There is a significant female predominance 32 (72%). The results after 6 months of GKR showed significant improvement regarding the size of adenoma, prolactin hormone level, contrast enhancement on MRI, and medical treatment.

Conclusion:

The study showed that the GKR is a safe and effective modality of treatment in the management of pituitary Prs.

Use of predictive spatial modeling to reveal that primary cancers have distinct central nervous system topography patterns of brain metastasis

OBJECTIVE

Brain metastasis is the most common intracranial neoplasm. Although anatomical spatial distributions of brain metastasis may vary according to primary cancer subtype, these patterns are not understood and may have major implications for treatment.

METHODS

To test the hypothesis that the spatial distribution of brain metastasis varies according to cancer origin in nonrandom patterns, the authors leveraged spatial 3D coordinate data derived from stereotactic Gamma Knife radiosurgery procedures performed to treat 2106 brain metastases arising from 5 common cancer types (melanoma, lung, breast, renal, and colorectal). Two predictive topographic models (regional brain metastasis echelon model [RBMEM] and brain region susceptibility model [BRSM]) were developed and independently validated.

RESULTS

RBMEM assessed the hierarchical distribution of brain metastasis to specific brain regions relative to other primary cancers and showed that distinct regions were relatively susceptible to metastasis, as follows: bilateral temporal/parietal and left frontal lobes were susceptible to lung cancer; right frontal and occipital lobes to melanoma; cerebellum to breast cancer; and brainstem to renal cell carcinoma. BRSM provided probability estimates for each cancer subtype, independent of other subtypes, to metastasize to brain regions, as follows: lung cancer had a propensity to metastasize to bilateral temporal lobes; breast cancer to right cerebellar hemisphere; melanoma to left temporal lobe; renal cell carcinoma to brainstem; and colon cancer to right cerebellar hemisphere. Patient topographic data further revealed that brain metastasis demonstrated distinct spatial patterns when stratified by patient age and tumor volume.

CONCLUSIONS

These data support the hypothesis that there is a nonuniform spatial distribution of brain metastasis to preferential brain regions that varies according to cancer subtype in patients treated with Gamma Knife radiosurgery. These topographic patterns may be indicative of the abilities of various cancers to adapt to regional neural microenvironments, facilitate colonization, and establish metastasis. Although the brain microenvironment likely modulates selective seeding of metastasis, it remains unknown how the anatomical spatial distribution of brain metastasis varies according to primary cancer subtype and contributes to diagnosis. For the first time, the authors have presented two predictive models to show that brain metastasis, depending on its origin, in fact demonstrates distinct geographic spread within the central nervous system. These findings could be used as a predictive diagnostic tool and could also potentially result in future translational and therapeutic work to disrupt growth of brain metastasis on the basis of anatomical region.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

8+ Year Performance of the Gamma Knife Perfexion/Icon Patient Positioning System and Possibilities for Preemptive Fault Detection Using Statistical Process Control

BACKGROUND

The large fractional doses, steep dose gradients, and small targets found in intracranial radiosurgery require extremely low beam delivery uncertainty. In the case of Gamma Knife radiosurgery (GKRS), this includes minimizing patient positioning system (PPS) positioning uncertainty. Existing QA techniques are recipe based, and feature point in time pass/fail tolerances. However, modern treatment machines, including the Gamma Knife Perfexion/Icon systems, record extensive internal data in treatment logs. These data can be analyzed through statistical process control (SPC) methods which are designed to detect changes in process behavior. The purpose of this study was to characterize the long-term (8+ year) performance of a Perfexion/Icon unit and use SPC methods to determine if performance changes could be detected at levels lower than existing QA and internal manufacturer performance tolerances.

METHODS

In-house software was developed to parse Perfexion/Icon log-files and store relevant information on shot delivery in a relational database. A last-in, first-out (LIFO) queuing algorithm was created to heuristically match messages associated with a given delivered shot. Filtering criteria were developed to filter QA and uncompleted shots. The resulting matched shots were extracted. Achieved versus planned PPS position was determined for each PPS motor as well as for the vector magnitude difference in PPS position. Exponentially weighted moving average (EWMA) control charts were plotted to determine when process behavior changed over time.

RESULTS

53833 shots were delivered over an 8+ year span in the study. The mean vector magnitude PPS difference was 32.7 µm, with 97.5% of all shots within 70.1 µm. Several changes in PPS positioning behavior were observed over time, corresponding with control system faults on several occasions requiring PPS recalibration. EWMA control charts clearly demonstrate that these faults could be identified and possibly predicted as many as 3 years before there were faults beyond control system tolerance.

CONCLUSION

The PPS of Gamma Knife Perfexion/Icon systems has extremely low positioning uncertainties. EWMA control chart method can be utilized to track PPS performance over time and can potentially detect changes in performance that may indicate a component requiring maintenance. This would allow planned service visits to mitigate problems and prevent unplanned downtime.

Hippocampal sparing in patients receiving radiosurgery for ≥25 brain metastases

PURPOSE/OBJECTIVES

To report our dosimetric analysis of the hippocampi (HC) and the incidence of perihippocampal tumor location in patients with ≥25 brain metastases who received stereotactic radiosurgery (SRS) in single or multiple sessions.

MATERIALS/METHODS

Analysis of our prospective registry identified 89 patients treated with SRS for ≥25 brain metastases. HC avoidance regions (HA-region) were created on treatment planning MRIs by 5 mm expansion of HC. Doses from each session were summed to calculate HC dose. The distribution of metastases relative to the HA-region and the HC was analyzed.

RESULTS

Median number of tumors irradiated per patient was 33 (range 25-116) in a median of 3 (range1-12) sessions. Median bilateral HC D_min (D₁₀₀), D₄₀, D₅₀, D_max, and D_mean (Gy) was 1.88, 3.94, 3.62, 16.6, and 3.97 for all patients, and 1.43, 2.99, 2.88, 5.64, and 3.07 for patients with tumors outside the HA-region. Multivariate linear regression showed that the median HC D₄₀, D₅₀, and D_min were significantly correlated with the tumor number and tumor volume (p < 0.001). Of the total 3059 treated tumors, 83 (2.7%) were located in the HA-region in 57% evaluable patients; 38 tumors (1.2%) abutted or involved the HC itself.

CONCLUSIONS

Hippocampal dose is higher in patients with tumors in the HA-region; however, even for patients with a high burden of intracranial disease and tumors located in the HA-regions, SRS affords hippocampal sparing. This is particularly relevant in light of our finding of eventual perihippocampal metastases in more than half of our patients.

Medial thalamotomy using stereotactic radiosurgery for intractable pain: a systematic review

Medial thalamotomy using stereotactic radiosurgery (SRS) is a potential treatment for intractable pain. However, the ideal treatment parameters and expected outcomes from this procedure remain unclear. The aim of this systematic review is to provide further insights on medial thalamotomy using SRS, specifically for intractable pain. A systematic review was performed to identify all clinical articles discussing medial thalamotomy using SRS for intractable pain. Only studies in which SRS was used to target the medial thalamus for pain were included. For centers with multiple publications, care was taken to avoid recounting individual patients. The literature review revealed six studies describing outcomes of medial thalamotomy using SRS for a total of 125 patients (118 included in the outcome analysis). Fifty-two patients were treated for cancer pain across three studies, whereas five studies included 73 patients who were treated for nonmalignant pain. The individual studies demonstrated initial meaningful pain reduction in 43.3-100% of patients, with an aggregate initial meaningful pain reduction in 65 patients (55%) following SRS medial thalamotomy. This effect persisted in 45 patients (38%) at the last follow-up. Adverse events were observed in six patients (5%), which were related to radiation in five patients (4%). Medial thalamotomy using SRS is effective for select patients with treatment-resistant pain and is remarkably safe when modern radiation delivery platforms are used. More posteriorly placed lesions within the medial thalamus were associated with better pain relief. More studies are warranted to shed light on differences in patient responses.

Stereotactic Radiosurgery for Choroid Plexus Tumors: A Report of the International Radiosurgery Research Foundation

BACKGROUND

Choroid plexus tumors (CPT) are rare epithelial tumors of the choroid plexus. Gross total resection (GTR) may be curative, but it is not always possible.

OBJECTIVE

To evaluate the role of Gamma Knife stereotactic radiosurgery (GKSRS) as either a primary or adjuvant management option for WHO grade I-III CPT through a multicenter project.

METHODS

A total of 32 patients (20 females) with a total of 43 treated tumors were included in the analysis. A total of 25 patients (78%) had undergone initial surgical resection. The median total tumor volume was 2.2 cc, and the median margin and maximum doses were 13 and 25.5 Gy, respectively.

RESULTS

Local tumor control was achieved in 69% of cases. Local tumor progression-free survival (PFS) rate for low-grade tumors at 1, 3, and 5 yr was 90%, 77%, 58%, respectively. The actuarial local tumor PFS rate for high-grade tumors at 1, 3, and 5 yr was 77%, 62%, and 62%, respectively. There was no significant difference in local tumor control rates between low- and high-grade CPT (P = .3). Gender, age, and degree of resection were not associated with treated tumor PFS. Distant intracranial spread developed in 6 patients at a median of 22 mo after initial SRS. Actuarial distant brain tumor PFS rate at 1, 2, 5, and 10 yr was 93%, 88%, 78%, and 65%, respectively. Three patients (9%) developed persistent symptomatic adverse radiation effects at a median of 11 mo after the procedure.

CONCLUSION

GKSRS represents a minimally invasive alternative management strategy for imaging defined or surgically recurrent low- and high-grade CPT.

Stereotactic Radiosurgery for Perioptic Meningiomas: An International, Multicenter Study

BACKGROUND

Stereotactic radiosurgery (SRS) is increasingly used for management of perioptic meningiomas.

OBJECTIVE

To study the safety and effectiveness of SRS for perioptic meningiomas.

METHODS

From 12 institutions participating in the International Radiosurgery Research Foundation (IRRF), we retrospectively assessed treatment parameters and outcomes following SRS for meningiomas located within 3 mm of the optic apparatus.

RESULTS

A total of 438 patients (median age 51 yr) underwent SRS for histologically confirmed (29%) or radiologically suspected (71%) perioptic meningiomas. Median treatment volume was 8.01 cm3. Median prescription dose was 12 Gy, and median dose to the optic apparatus was 8.50 Gy. A total of 405 patients (93%) underwent single-fraction SRS and 33 patients (7%) underwent hypofractionated SRS. During median imaging follow-up of 55.6 mo (range: 3.15-239 mo), 33 (8%) patients experienced tumor progression. Actuarial 5-yr and 10-yr progression-free survival was 96% and 89%, respectively. Prescription dose of ≥12 Gy (HR: 0.310; 95% CI [0.141-0.679], P = .003) and single-fraction SRS (HR: 0.078; 95% CI [0.016-0.395], P = .002) were associated with improved tumor control. A total of 31 (10%) patients experienced visual decline, with actuarial 5-yr and 10-yr post-SRS visual decline rates of 9% and 21%, respectively. Maximum dose to the optic apparatus ≥10 Gy (HR = 2.370; 95% CI [1.086-5.172], P = .03) and tumor progression (HR = 4.340; 95% CI [2.070-9.097], P < .001) were independent predictors of post-SRS visual decline.

CONCLUSION

SRS provides durable tumor control and quite acceptable rates of vision preservation in perioptic meningiomas. Margin dose of ≥12 Gy is associated with improved tumor control, while a dose to the optic apparatus of ≥10 Gy and tumor progression are associated with post-SRS visual decline.

A radiomics-based model for predicting local control of resected brain metastases receiving adjuvant SRS

•

SRS has emerged as an alternative to WBRT for surgically resected brain metastases.

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Pre-therapy radiomic features are predictive of local control after cavity SRS.

•

Radiomic features were superior to clinical features for predicting local control.

Purpose

Adjuvant radiosurgery to the cavities of surgically resected brain metastases provides excellent local tumor control while reducing the risk of deleterious cognitive decline associated with whole brain radiotherapy. A subset of these patients, however, will develop disease recurrence following radiosurgery. In this study, we sought to assess the predictive capability of radiomic-based models, as compared with standard clinical features, in predicting local tumor control.

Methods

We performed a retrospective chart review of patients treated with adjuvant radiosurgery for resected brain metastases at the “Institution” from 2009 to 2019. Shape, intensity and texture based radiomics features of the cavities were extracted from the pre-radiosurgery treatment planning MRI scans and trained using a gradient boosting technique with K-fold cross validation.

Results

In total, 71 cavities from 67 treated patients were included for analysis. The 6 and 12 month local control estimates were 86% and 76%, respectively. The 6 and 12 month overall survival was 78% and 55%, respectively. Thirty-six patients developed intracranial failures outside of the surgical cavity. The predictive model for local control trained on imaging features from the whole cavity achieved an area-under-the-curve (AUC) of 0.73 on the validation set versus an AUC of 0.40 for the clinical features.

Conclusions

Here we report a single institutional experience using radiomic-based predictive modeling of local tumor control following adjuvant Gamma Knife radiosurgery for resected brain metastases. We found the radiomics features to provide more robust predictive models of local control rates versus clinical features alone. Such techniques could potentially prove useful in the clinical setting and warrant further investigation.

Repeat stereotactic radiosurgery for progressive vestibular schwannomas after previous radiosurgery: a systematic review and meta-analysis

Vestibular schwannomas (VS) are slow-growing intracranial extraaxial benign tumors, developing from the vestibular part of the eight cranial nerves. Stereotactic radiosurgery (SRS) has now a long-term scientific track record as first intention treatment for small- to medium-sized VS. Though its success rate is very high, SRS for VS might fail to control tumor growth in some cases. However, the literature on repeat SRS after previously failed SRS remains scarce and reported in a low number of series with a limited number of cases. Here, we aimed at performing a systematic review and meta-analysis of the literature on repeat SRS for VS. Using PRISMA guidelines, we reviewed manuscripts published between January 1990 and October 2020 and referenced in PubMed. Tumor control and cranial nerve outcomes were evaluated with separate meta-analyses. Eight studies comprising 194 patients were included. The overall rate of patients treated in repeat SRS series as per overall series with first SRS was 2.2% (range 1.2–3.2%, p < 0.001). The mean time between first and second SRS was 50.7 months (median 51, range 44–64). The median marginal dose prescribed at first SRS was 12 Gy (range 8–24) and at second SRS was 12 Gy (range 9.8–19). After repeat SRS, tumor stability was reported in 61/194 patients, i.e., a rate of 29.6% (range 20.2–39%, I² = 49.1%, p < 0.001). Tumor decrease was reported in 83/194 patients, i.e., a rate of 54.4% (range 33.7–75.1%, I² = 89.1%, p < 0.001). Tumor progression was reported in 50/188 patients, i.e., a rate of 16.1% (range 2.5–29.7%, I² = 87.1%, p = 0.02), rarely managed surgically. New trigeminal numbness was reported in 27/170 patients, i.e., a rate of 9.9% (range 1.4–18.3%, p < 0.02). New facial nerve palsy of worsened of previous was reported in 8/183 patients, i.e., a rate of 4.3% (range 1.4–7.2%, p = 0.004). Hearing loss was reported in 12/22 patients, i.e., a rate of 54.3% (range 24.8–83.8%, I² = 70.7%, p < 0.001). Repeat SRS after previously failed SRS for VS is associated with high tumor control rates. Cranial nerve outcomes remain favorable, particularly for facial nerve. The rate of hearing loss appears similar to the one related to first SRS.

Biologically effective dose correlates with linear tumor volume changes after upfront single-fraction stereotactic radiosurgery for vestibular schwannomas

Vestibular schwannomas (VSs) are benign, slow-growing tumors. Management options include observation, surgery, and radiation. In this retrospective trial, we aimed at evaluating whether biologically effective dose (BED) plays a role in tumor volume changes after single-fraction first intention stereotactic radiosurgery (SRS) for VS. We compiled a single-institution experience (n = 159, Lausanne University Hospital, Switzerland). The indication for SRS was decided after multidisciplinary discussion. Only cases with minimum 3 years follow-up were included. The Koos grading, a reliable method for tumor classification was used. Radiosurgery was performed using Gamma Knife (GK) and a uniform marginal prescription dose of 12 Gy. Mean BED was 66.3 Gy (standard deviation 3.8, range 54.1-73.9). The mean follow-up period was 5.1 years (standard deviation 1.7, range 3-9.2). The primary outcome was changes in 3D volumes after SRS as function of BED and of integral dose received by the VS. Random-effect linear regression model showed that tumor volume significantly and linearly decreased over time with higher BED (p < 0.0001). Changes in tumor volume were also significantly associated with age, sex, number of isocenters, gradient index, and Koos grade. However, the effect of BED on tumor volume change was moderated by time after SRS and Koos grade. Lower integral doses received by the VSs were inversely correlated with BED in relationship with tumor volume changes (p < 0.0001). Six (3.4%) patients needed further intervention. For patients having uniformly received the same marginal dose prescription, higher BED linearly and significantly correlated with tumor volume changes after SRS for VSs. BED could represent a potential new treatment paradigm for patients with benign tumors, such as VSs, for attaining a desired radiobiological effect. This could further increase the efficacy and decrease the toxicity of SRS not only in benign tumors but also in other SRS indications.

Pretreatment ADC predicts tumor control after Gamma Knife radiosurgery in solid vestibular schwannomas

BACKGROUND

Radiosurgery is a well-established treatment for vestibular schwannomas (VSs), but it is often difficult to identify which tumors will respond to treatment. We sought to determine whether pretreatment or posttreatment tumor apparent diffusion coefficient (ADC) values could predict tumor control in patients undergoing Gamma Knife radiosurgery (GKRS) and whether these values could differentiate between cases of pseudoprogression and cases of true progression in the early posttreatment period.

METHODS

We retrospectively identified patients who underwent GKRS for solid VSs between June 2008 and November 2016 and who had a minimum follow-up of 36 months. Pretreatment and posttreatment minimum, mean, and maximum ADC values were measured for the whole tumor volume and were compared between patients with tumor control and those with tumor progression. In patients with early posttreatment tumor enlargement, ADC values were compared between patients with pseudoprogression and those with true progression.

RESULTS

Of the 44 study patients, 34 (77.3%) demonstrated tumor control at final follow-up. Patients with tumor control had higher pretreatment minimum (1.35 vs 1.09; p = 0.008), mean (1.80 vs 1.45; p = 0.004), and maximum (2.41 vs 1.91; p = 0.011) ADC values than patients with tumor progression. ADC values did not differ between patients with pseudoprogression and those with true progression at early posttreatment follow-up.

CONCLUSIONS

ADC values may be helpful in predicting response to GKRS in patients with solid VSs but cannot predict which tumors will undergo pseudoprogression. Patients with higher pretreatment ADC values may be more likely to demonstrate posttreatment tumor control.

Safety and efficacy of upfront stereotactic radiosurgery for brain metastases with high cumulative intracranial tumor volume (> 7 ml): analysis of 233 consecutive patients

BACKGROUND

The cumulative intracranial tumor volume (CITV) has recently been suggested to be a more relevant predictive factor for patients with brain metastases (BM) treated with stereotactic radiosurgery (SRS). We aimed to investigate the feasibility of upfront SRS for patients with BM having a high CITV, i.e., exceeding 7 ml.

METHODS

Two hundred thirty-three consecutive patients with BM having a CITV > 7 ml who underwent SRS as first-line treatment from 2011 to 2019 were retrospectively identified. The overall survival (OS) and intracranial disease control rates were analyzed. Multivariate proportional hazards models were used to identify prognostic factors associated with treatment outcome. Toxicity and salvage therapy were also investigated.

RESULTS

The median OS was 8.7 months (95% confidence interval: 7.1-10.4), and 6-month and 1-year OS rates were 60 and 40%, respectively. Systemic anticancer therapy (hazard ratio (HR): 0.45, p < 0.001), female sex (HR: 0.61, p = 0.001), synchronous SRS (HR: 0.57, p = 0.003), number of BM (HR: 1.04, p = 0.008), controlled extracranial disease (HR: 0.56, p = 0.009), Karnofsky performance status (HR: 0.87, p = 0.015), and staged SRS (HR: 0.71, p = 0.037) were found to be factors independently associated with OS. Post-SRS toxicities of CTCAE grades 3, 4, and 5 were observed in 14, 5, and 1 patient, respectively. As salvage management, repeat SRS, whole brain radiotherapy, and surgical resection were required for 84, 16, and 10 patients, respectively, CONCLUSIONS: With vigilant surveillance and appropriate salvage management, upfront SRS alone can be considered as a relatively safe and effective treatment strategy even for BM with CITV > 7 ml.

Extracranial dose and the risk of radiation-induced malignancy after intracranial stereotactic radiosurgery: is it time to establish a therapeutic reference level?

BACKGROUND

To measure extracranial doses from Gamma Knife Perfexion (GKP) intracranial stereotactic radiosurgery (SRS) and model the risk of malignancy after SRS for different treatment platforms.

METHODS

Doses were measured for 20 patients undergoing SRS on a GKP at distances of 18, 43 and 75 cm from the target, corresponding to the approximate positions of the thyroid, breast and gonads respectively. A literature review was conducted to collect comparative data from other radiosurgery platforms. All data was used to calculate the dose to body organs. The National Cancer Institute (NCI) RadRAT calculator was used to estimate excess lifetime cancer risk from this exposure. Five different age groups covering childhood and younger adults were modelled for both sexes.

RESULTS

Extracranial doses delivered during SRS with the GKP were a median 0.04%, 0.008% and 0.002% of prescription dose at 18 cm, 43 cm and 70 cm from the isocentre respectively. Comparison with the literature revealed that the extracranial dose was lowest from GKP, then linacs equipped with micro-multileaf collimators (mMLC), then linacs equipped with circular collimators (cones), and highest from Cyberknife (CK). Estimated lifetime risks of radiation-induced malignancy in the body for patients treated with SRS aged 5-45 years were 0.03-0.88%, 0.36-11%, 0.61-18% and 2.2-39% for GKP, mMLC, cones and CK respectively.

CONCLUSIONS

We have compared typical extracranial doses from different platforms and quantified the lifetime risk of radiation-induced malignancy. The risk varies with platform. This should be taken into account when treating children and young adults with SRS. The concept of a therapeutic reference level (TRL), similar to the diagnostic reference level (DRL) established in radiology, is proposed.

Gamma Knife Stereotactic Radiosurgery for the treatment of chordomas and chondrosarcomas

INTRODUCTION

Primary chordomas and chondrosarcomas of the skull base are difficult tumours to treat successfully. Despite advances in surgical techniques, a gross total resection is often impossible to achieve. In addition, some patients may be deemed unsuitable or not wish to undergo extensive surgery for these conditions. This study examines the role of Gamma Knife Stereotactic Radiosurgery (GKRS) in the treatment of these difficult cases.

METHODS

All patients harbouring either a chordoma or chondrosarcoma treated at the National Centre for Stereotactic Radiosurgery, Royal Hallamshire Hospital, Sheffield, UK, between 1985 and 2018, were reviewed with regard to their clinical presentations, pre- and post-treatment imaging, GKRS prescriptions and outcomes.

RESULTS

In total, 24 patients with a mean tumour volume of 13 cm³ in the chordoma group (n=15) and 12 cm³ in the chondrosarcoma group (n=9) underwent GKRS. The 5- and 10-year overall survival rates for the chordoma group were 67% and 53% respectively, while for the chondrosarcoma group, they were 78% at both time points. The tumour control rates at 5 and 10 years in the chordoma group were 67% and 49% and for the chondrosarcoma group 78% at both time points. Patients with tumour volumes of less than 7 cm³ before GKRS treatment demonstrated a statistically significant longer overall survival rate (p=0.03).

CONCLUSIONS

GKRS offers a comparable option to proton beam therapy for the treatment of these tumours. Early intervention for tumour volumes of less than 7 cm³ gives the best long-term survival rates.

Brain Arteriovenous Malformations: The Role of Imaging in Treatment Planning and Monitoring Response

Brain arteriovenous malformations (AVMs) are characterized by shunting between pial arteries and cortical or deep veins, with the presence of an intervening nidus of tortuous blood vessels. These lesions present a therapeutic challenge, because their natural history entails a risk of intracranial hemorrhage, but treatment may cause significant morbidity. In this article, imaging features of AVMs on MR imaging and catheter angiography are reviewed to stratify the risk of hemorrhage and guide appropriate management. The angioarchitecture of AVMs may evolve over time, spontaneously or in response to treatment, necessitating ongoing imaging surveillance.

68Ga-DOTATOC PET/CT Follow Up after Single or Hypofractionated Gamma Knife ICON Radiosurgery for Meningioma Patients

⁶⁸Ga-DOTATOC represents a useful tool in tumor contouring for radiosurgery planning. We present a case series of patients affected by meningiomas on who we performed ⁶⁸Ga-DOTATOC positron emission tomography (PET)/CT pre-operatively, a subgroup of which also underwent a post-operative ⁶⁸Ga-DOTATOC PET/CT to evaluate the standardized uptake value (SUV) modification after Gamma Knife ICON treatment in single or hypofractionated fractions. Twenty patients were enrolled/included in this study: ten females and ten males. The median age was 52 years (range 33-80). The median tumor diameter was 3.68 cm (range 0.12-22.26 cm), and the median pre-radiotherapy maximum SUV value was 11 (range 2.3-92). The average of the relative percentage changes between SUVs at baseline and follow up was -6%, ranging from -41% to 56%. The SUV was reduced in seven out of 12 patients (58%), stable in two out of 12 (17%), and increased in three out of 12 (25%), suggesting a biological response of the tumor to the Gamma Knife treatment in most of the cases. ⁶⁸Ga-DOTATOC-PET represents a valuable tool in assessing the meningioma diagnosis for primary radiosurgery; it is also promising for follow-up assessment.

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.

Genomic alterations predictive of response to radiosurgery in recurrent IDH-WT glioblastoma

INTRODUCTION

Despite aggressive treatment, glioblastoma invariably recurs. The optimal treatment for recurrent glioblastoma (rGBM) is not well defined. Stereotactic radiosurgery (SRS) for rGBM has demonstrated favorable outcomes for selected patients; however, its efficacy in molecular GBM subtypes is unknown. We sought to identify genetic alterations that predict response/outcomes from SRS in rGBM-IDH-wild-type (IDH-WT).

METHODS

rGBM-IDH-WT patients undergoing SRS at first recurrence and tested by next-generation sequencing (NGS) were reviewed (2009-2018). Demographic, clinical, and molecular characteristics were evaluated. NGS interrogating 205-genes was performed. Primary outcome was survival from GK-SRS assessed by Kaplan-Meier method and multivariable Cox proportional-hazards.

RESULTS

Sixty-three lesions (43-patients) were treated at 1st recurrence. Median age was 61-years. All patients were treated with resection and chemoradiotherapy. Median time from diagnosis to 1st recurrence was 8.7-months. Median cumulative volume was 2.895 cm3 and SRS median marginal dose was 18 Gy (median isodose-54%). Bevacizumab was administered in 81.4% patients. PFS from SRS was 12.9-months. Survival from SRS was 18.2-months. PTEN-mutant patients had a longer PFS (p = 0.049) and survival from SRS (p = 0.013) in multivariable analysis. Although no statistically significant PTEN-mutants patients had higher frequency of radiation necrosis (21.4% vs. 3.4%) and lower in-field recurrence (28.6% vs. 37.9%) compared to PTEN-WT patients.

CONCLUSIONS

SRS is a safe and effective treatment option for selected rGBM-IDH-WT patients following first recurrence. rGBM-IDH-WT harboring PTEN-mutation have improved survival with salvage SRS compared to PTEN-WT patients. PTEN may be used as a molecular biomarker to identify a subset of rGBM patients who may benefit the most from SRS.

Gamma Knife radiosurgery as the initial treatment for elderly patients with nonfunctioning pituitary adenomas

PURPOSE

The aim of this study was to investigate the efficacy and safety of initial Gamma Knife radiosurgery (GKRS) for elderly patients with nonfunctioning pituitary adenomas (NFPAs).

METHODS

We retrospectively reviewed 45 elderly patients underwent GKRS as the initial treatment for NFPAs at our institution between December 2007 and December 2017. Patients' radiographic and clinical data were collected.

RESULTS

The median age of patients at the time of GKRS was 71 years (range 65-82 years). The median tumor volume was 2.6 cm³ (range 0.3-21.8 cm³). The median marginal dose was 13 Gy (range 6-23 Gy). The median maximum dose to the optic apparatus was 6.5 Gy (range 2.3-10.3 Gy). Thirty-five patients (77.8%) achieved tumor regression, 6 patients (13.3%) had tumor stable and 4 patients (8.9%) occurred tumor progression during a median radiological follow-up time of 51.4 months (range 11.1-158.7 months). The crude tumor control rate was 91.1%. The actuarial tumor control rates were 100%, 95.0%, 87.6%, and 87.6%, at 1, 3, 5, and 10 years after initial GKRS, respectively. New-onset hypopituitarism occurred in 6 patients. Two patients with pre-GKRS visual dysfunction developed further deterioration of visual function. No other radiation-induced complications were noted.

CONCLUSION

Initial GKRS can provide a high tumor control rate as well as low risk of postradiosurgical complications for elderly patients with NFPAs. Attention should be paid to avoid radiation-related adverse effects including hypopituitarism, optic neuropathy and cranial neuropathy in elderly patients.

Stereotactic radiosurgery as the primary management for patients with Koos grade IV vestibular schwannomas

OBJECTIVE

While extensive long-term outcome studies support the role of stereotactic radiosurgery (SRS) for smaller-volume vestibular schwannomas (VSs), its role in the management for larger-volume tumors remains controversial.

METHODS

Between 1987 and 2017, the authors performed single-session SRS on 170 patients with previously untreated Koos grade IV VSs (volumes ranged from 5 to 20 cm3). The median tumor volume was 7.4 cm3. The median maximum extracanalicular tumor diameter was 27.5 mm. All tumors compressed the middle cerebellar peduncle and distorted the fourth ventricle. Ninety-three patients were male, 77 were female, and the median age was 61 years. Sixty-two patients had serviceable hearing (Gardner-Robertson [GR] grades I and II). The median margin dose was 12.5 Gy.

RESULTS

At a median follow-up of 5.1 years, the progression-free survival rates of VSs treated with a margin dose ≥ 12.0 Gy were 98.4% at 3 years, 95.3% at 5 years, and 90.7% at 10 years. In contrast, the tumor control rate after delivery of a margin dose < 12.0 Gy was 76.9% at 3, 5, and 10 years. The hearing preservation rates in patients with serviceable hearing at the time of SRS were 58.1% at 3 years, 50.3% at 5 years, and 35.9% at 7 years. Younger age (< 60 years, p = 0.036) and initial GR grade I (p = 0.006) were associated with improved serviceable hearing preservation rate. Seven patients (4%) developed facial neuropathy during the follow-up interval. A smaller tumor volume (< 10 cm3, p = 0.002) and a lower margin dose (≤ 13.0 Gy, p < 0.001) were associated with preservation of facial nerve function. The probability of delayed facial neuropathy when the margin dose was ≤ 13.0 Gy was 1.1% at 10 years. Nine patients (5%) required a ventriculoperitoneal shunt because of delayed symptomatic hydrocephalus. Fifteen patients (9%) developed detectable trigeminal neuropathy. Delayed resection was performed in 4% of patients.

CONCLUSIONS

Even for larger-volume VSs, single-session SRS prevented the need for delayed resection in almost 90% at 10 years. For patients with minimal symptoms of tumor mass effect, SRS should be considered an effective alternative to surgery in most patients, especially those with advanced age or medical comorbidities.

Follow-up Brain Imaging Within 30 Days of Gamma-Knife Surgery for New Symptoms: Retrospective Analysis

OBJECTIVE

Gamma Knife surgery is a complementary procedure to open microsurgery for several indications. However, posttreatment symptomatic complaints are common and often result in short-term follow-up imaging. Here we evaluate the efficacy of repeat brain imaging within 30 days of a Gamma Knife procedure by analyzing the frequency with which that imaging reveals addressable pathology.

METHODS

All patients who underwent Gamma Knife treatments at our institution between January 2013 and August 2019 were retrospectively analyzed, and any patient who received imaging of the brain within 30 days for a symptomatic complaint was evaluated.

RESULTS

Of the 956 Gamma Knife cases performed, 78 (8.2%) scans were performed within a 30-day time frame for symptomatic complaints. Of these, the most common complaint was headache (25%). Most images demonstrated no changes when compared with the treatment scan (68%) and there were no hemorrhages and only 1 stroke (<1%). Univariate analysis revealed that sex (P = 0.046), treatment volume (P < 0.001), and treatments for metastasis (P < 0.001) or glioma (P < 0.001) were associated with symptomatic complaints leading to imaging, but no factors were associated with higher rates of abnormal imaging.

CONCLUSIONS

Gamma Knife therapy remains a safe treatment for multiple indications, but it is not risk free and acute symptomatic complaints are common. However, our data suggest that the need for reimaging within 30 days for symptomatic complaints is likely overestimated as obtained imaging does not usually show any change and the rate of significant complication is exceedingly low.

Role of Gamma Knife Radiosurgery in Small Cell Lung Cancer: A Multi-Institutional Retrospective Study of the International Radiosurgery Research Foundation (IRRF)

BACKGROUND

Despite a high incidence of brain metastases in patients with small-cell lung cancer (SCLC), limited data exist on the use of stereotactic radiosurgery (SRS), specifically Gamma Knife™ radiosurgery (Elekta AB), for SCLC brain metastases.

OBJECTIVE

To provide a detailed analysis of SCLC patients treated with SRS, focusing on local failure, distant brain failure, and overall survival (OS).

METHODS

A multi-institutional retrospective review was performed on 293 patients undergoing SRS for SCLC brain metastases at 10 medical centers from 1991 to 2017. Data collection was performed according to individual institutional review boards, and analyses were performed using binary logistic regression, Cox-proportional hazard models, Kaplan-Meier survival analysis, and competing risks analysis.

RESULTS

Two hundred thirty-two (79%) patients received SRS as salvage following prior whole-brain irradiation (WBRT) or prophylactic cranial irradiation, with a median marginal dose of 18 Gy. At median follow-up after SRS of 6.4 and 18.0 mo for surviving patients, the 1-yr local failure, distant brain failure, and OS were 31%, 49%, and 28%. The interval between WBRT and SRS was predictive of improved OS for patients receiving SRS more than 1 yr after initial treatment (21%, <1 yr vs 36%, >1 yr, P = .01). On multivariate analysis, older age was the only significant predictor for OS (hazard ratio 1.63, 95% CI 1.16-2.29, P = .005).

CONCLUSION

SRS plays an important role in the management of brain metastases from SCLC, especially in salvage therapy following WBRT. Ongoing prospective trials will better assess the value of radiosurgery in the primary management of SCLC brain metastases and potentially challenge the standard application of WBRT in SCLC patients.

Outcomes after stereotactic radiosurgery for schwannomas of the oculomotor, trochlear, and abducens nerves

OBJECTIVE

Cranial nerve (CN) schwannomas are intracranial tumors that are commonly managed by stereotactic radiosurgery (SRS). There is a large body of literature supporting the use of SRS for vestibular schwannomas. Schwannomas of the oculomotor nerves (CNs III, IV, and VI) are rare skull base tumors, occurring close to the brainstem and often involving the cavernous sinus. Resection can cause significant morbidity, including loss of nerve function. As for other schwannomas, SRS can be used to manage these tumors, but only a handful of cases have been published so far, often among reports of other uncommon schwannoma locations.

METHODS

The goal of this study was to collect retrospective multicenter data on tumor control, clinical evolution, and morbidity after SRS. This study was performed through the International Radiosurgery Research Foundation. Patients managed with single-session SRS for an oculomotor cranial nerve schwannoma (CN III, IV, or VI) were included. The diagnosis was based on diplopia or ptosis as the main presenting symptom and anatomical location on the trajectory of the presumed cranial nerve of origin, or prior resection confirming diagnosis. Demographic, SRS dose planning, clinical, and imaging data were collected from chart review of the treated patients. Chi-square and Kaplan-Meier analyses were performed.

RESULTS

Seven institutions submitted data for a total of 25 patients. The median follow-up time was 41 months. The median age at the time of treatment was 52 years. There were 11 CN III schwannomas, 11 CN IV schwannomas, and 3 CN VI schwannomas. The median target volume was 0.74 cm3, and the median marginal dose delivered was 12.5 Gy. After SRS, only 2 patients (including the only patient with neurofibromatosis type 2) had continued tumor growth. Crude local control was 92% (23/25), and the 10-year actuarial control was 86%. Diplopia improved in the majority of patients (11/21), and only 3 had worsening following SRS, 2 of whom also had worsened ptosis, both in the context of tumor progression.

CONCLUSIONS

SRS for schwannomas of the oculomotor, trochlear, and abducens nerves is effective and provides tumor control rates similar to those for other cranial nerve schwannomas. SRS allows improvement of diplopia in the majority of patients. SRS should therefore be considered as a first-line treatment option for oculomotor nerve schwannomas.

Dose homogeneity analysis of adjuvant radiation treatment in surgically resected brain metastases: Comparison of IORT, SRS, and IMRT indices

PURPOSE

Although surgery remains a treatment option for symptomatic brain metastases, the need for adjuvant radiation after surgery is widely accepted as standard. Despite a multitude of randomized trials aimed at identifying the ideal radiation treatment plan for surgically resected metastases, the development of new delivery regiments necessitates a periodic re-evaluation of dosimetric performance/outcome. Here, we compare the homogeneity index (HI) across three platforms: single-session stereotactic radiosurgery (SRS), multisession stereotactic radiotherapy, and intraoperative radiotherapy (IORT).

METHODS AND MATERIALS

Patients treated with IORT after surgical resection of brain metastases were identified and dosimetric parameters collected from the dose-volume histograms based on the development of conformal plans for adjuvant radiation using Gamma Knife-SRS (GK-SRS), linear accelerator based intensity-modulated radiation therapy, and IORT. HIs were calculated using four established methods and compared across platforms within the patient cohort. Statistical analyses were performed using analysis of variance.

RESULTS

The mean maximal doses for the GK-SRS and IMRT plans were 30 Gy and 29 Gy with margin prescription doses of 16 Gy and 24 Gy, respectively. The IORT dose was 30 Gy to the applicator surface. HIs varied based on calculation methods, but maintained consistency when comparing across platforms with IORT having the lower mean HI value (0.56; 95% confidence interval (CI) 0.55-0.60) in single-fraction treatment, compared with GK-SRS (0.77; 95% CI 0.76-0.80). The mean multisession IMRT HI was lower than both single-fraction treatment modalities at 0.41 (95% CI 0.40-0.42).

CONCLUSIONS

When using the HI as the primary dosimetric parameter for adjuvant radiation plans after surgical resection of brain metastases IORT offers improved dose homogeneity compared with GK-SRS in single-fraction treatment, whereas fractionated LINAC-based IMRT was superior with respect to the HI in comparison among all three methods.