Hippocampal-sparing whole-brain radiotherapy: a "how-to" technique using helical tomotherapy and linear accelerator-based intensity-modulated radiotherapy

Separating or combining immune checkpoint inhibitors (ICIs) and radiotherapy in the treatment of NSCLC brain metastases

With the advancement of imaging technology, systemic disease control rate and survival rate, the morbidity of brain metastases (BMs) from non-small cell lung cancer (NSCLC) has been riding on a steady upward trend (40%), but management of BMs from NSCLC remains obscure. Systemic therapy is anticipated to offer novel therapeutic avenues in the management of NSCLC BMs, and radiotherapy (RT) and immunotherapy have their own advantages. Recently, it was confirmed that immune checkpoint inhibitors (ICIs) and RT could mutually promote the efficacy in the treatment of BMs from NSCLC. In this paper, we provide a review on current understandings and practices of separating or combining ICIs and RT, which could provide a reference for the coming laboratory and clinical studies and contribute to the development of new approaches in NSCLC BMs.

Stereotactic Radiosurgery to More Than 10 Brain Metastases: Evidence to Support the Role of Radiosurgery for Ideal Hippocampal Sparing in the Treatment of Multiple Brain Metastases

BACKGROUND

Brain metastases are a common occurrence, with literature supporting the treatment of a limited number of brain metastases with stereotactic radiosurgery (SRS), as opposed to whole brain radiotherapy (WBRT). Less well understood is the role of SRS in patients with ≥10 brain metastases.

METHODS

Patients treated with SRS to ≥10 brain metastases without concurrent WBRT between March 1999 and December 2016 were reviewed. Analysis was performed for overall survival, treated lesion freedom from progression (FFP), freedom from new metastases (FFNMs), and adverse radiation effect. Hippocampal volumes were retrospectively generated in patients treated with up-front SRS for evaluation of dose volume metrics.

RESULTS

A total of 143 patients were identified with 75 patients having up-front SRS and 68 patients being treated as salvage therapy after prior WBRT. The median number of lesions per patient was 13 (interquartile range [IQR], 11-17). Median total volume of treatment was 4.1 cm³ (IQR, 2.0-9.9 cm³). The median 12-month FFP for up-front and salvage treatment was 96.8% (95% confidence interval [CI], 95.5-98.1) and 83.6% (95% CI, 79.9-87.5), respectively (P < 0.001). Twelve-month FFNMs for up-front and salvage SRS was 18.8% (95% CI, 10.9-32.3) versus 19.2% (95% CI, 9.7-37.8), respectively (P = 0.90). The mean hippocampal dose was 150 cGy (IQR, 100-202 cGy).

CONCLUSIONS

Excellent rates of local control can be achieved when treating patients with >10 intracranial metastases either in the up-front or salvage setting. Hippocampal sparing is readily achievable with expected high rates of new metastatic lesions in treated patients.

The Risk of Radiogenic Second Cancer Based on Differential DVH: Central Nervous System Malignant Tumor in Children

OBJECTIVES

To quantify the risk of radiogenic second cancer in pediatric patients receiving hippocampal-sparing craniospinal irradiation either with intensity-modulated radiation therapy or tomotherapy due to the development of a solid second cancer after radiotherapy using the concept of excess absolute risk.

METHODS

Computed tomography images of 15 pediatric patients who received craniospinal irradiation treatment were selected for this study. For each case, intensity-modulated radiation therapy and tomotherapy plans were computed. Then, the dosimetry parameters were analyzed. Differential dose-volume histograms were generated, and the excess absolute risks were calculated for each plan of each patient.

RESULTS

The tomotherapy group was superior to the intensity-modulated radiation therapy group in target area homogeneity index (P < .001). Tomotherapy offered greater hippocampal sparing than intensity-modulated radiation therapy in terms of D _2% (15.66 vs 23.05 Gy, P < .001) and D_mean (9.79 vs 20.29 Gy, P < .001). Tomotherapy craniospinal irradiation induced a much higher risk than intensity-modulated radiation therapy craniospinal irradiation to the thyroid and lungs (excess absolute risk: thyroid 28.7 vs 26.9 per 10 000 PY, P = .010; lung 20.5 vs 18.9 per 10 000 PY, P = .003). Both techniques conferred a higher risk to the stomach, but there was little difference. In addition, the 2 plans induced less carcinogenic risk to the liver (excess absolute risk 4.2 vs 4.0 per 10 000 PY, P = .020).

CONCLUSIONS

The tomotherapy plan has obvious advantages in the protection of the hippocampus for children undergoing craniospinal irradiation treatment. Tomotherapy increased the risk of radiogenic second cancer in organ at risk, and therefore, it is imperative to take the risk factor into consideration in the formulation of treatment protocols.

Patterns of brain metastasis immediately before prophylactic cranial irradiation (PCI): implications for PCI optimization in limited-stage small cell lung cancer

Background

Prophylactic cranial irradiation (PCI) is indicated for limited-stage small cell lung cancer (LS-SCLC) with good response to chemoradiotherapy (CRT). However, brain metastasis (BM) developed in LS-SCLC before PCI is not rare. In this study, we comprehensively investigated the features of pre-PCI BMs, aiming to explore the potential of PCI optimization for LS-SCLC.

Methods

One-hundred-ten LS-SCLC patients achieving clinical complete remission after definitive CRT with contrast-enhanced cranial magnetic resonance imaging (MRI) at baseline and immediately before PCI were included. The time trend and risk factors for pre-PCI BM were evaluated. Several radiological features, including numbers, sizes, and locations of pre-PCI BMs, were investigated to explore the technical feasibility of stereotactic radiotherapy and hippocampal-avoidance (HA) PCI.

Results

Twenty-four (21.8%) of the LS-SCLC patients harbored pre-PCI BM, all except one were asymptomatic. CRT duration (CRT-D) was the only independent risk factor for pre-PCI BM. The pre-PCI BM rate gradually increased in line with a growing time interval between treatment initiation and pre-PCI MRI. Pre-PCI BM and prolonged CRT-D were both correlated with worse overall survival. Of 129 pre-PCI intracranial lesions, 2 (1.5%) were in the HA region. Eight of the 24 (33.3%) pre-PCI BM patients were ineligible for stereotactic radiotherapy.

Conclusion

Our findings suggest that PCI is still of importance in LS-SCLC, and MRI evaluation before PCI is indispensable. Investigations are warranted to explore the possibility of moving PCI up to before CRT completion in LS-SCLC patients with prolonged CRT-D. HA-PCI could be considered to reduce neurotoxicity.

Electronic supplementary material

The online version of this article (10.1186/s13014-019-1371-4) contains supplementary material, which is available to authorized users.

Management of CNS disease in ALK-positive non-small cell lung cancer: Is whole brain radiotherapy still needed?

Anaplastic lymphoma kinase (ALK)-positive non-small cell lung cancer (3 to 5% of all non-small cell lung cancers) carries a particularly high risk of central nervous system dissemination (60% to 90%). As the use of ALK inhibitors improves treatment outcomes over chemotherapy, the determent of central nervous system metastases has become an increasingly relevant therapeutic dilemma considering young age and possible extended overall survival. The goal of brain metastases management is to optimize both overall survival and quality of life, with the high priority of neurocognitive function preservation. Unfortunately in the first year on crizotinib, the pioneering ALK inhibitors, approximately one third of these patients fail in the central nervous system, which is explained by an inadequate central nervous system drug penetration through the blood-brain barrier. Central nervous system-directed radiotherapy represents the most important strategy to control intracranial disease burden and extend the survival benefit with crizotinib. The role of whole brain irradiation in the treatment of brain metastases diminishes, as this technique is associated with the risk of neurocognitive decline. Stereotactic radiotherapy represents an alternative technique that delivers ablative doses of ionizing radiation to the limited volume of oligometastatic brain disease, offering sparing of the adjacent brain parenchyma and reduced neurotoxicity. The next generation ALK inhibitors were designed to cross the blood-brain barrier more efficiently than crizotinib and achieve higher concentration in the cerebrospinal fluid, offering prominent ability to control central nervous system spread. In the phase III ALEX trial the intracranial control was significantly better with alectinib as compared to crizotinib and it translated into survival benefit. Other next generation ALK inhibitors (i.e. ceritinib, brigatinib, lorlatinib) also demonstrated promising activity in the central nervous system.

Redefining Ventricular Target Volume in Germinoma: Is Inclusion of Temporal Horns Necessary?

PURPOSE

We reviewed the outcomes of a retrospective germinoma cohort and analyzed radiation therapy plans to determine dosimetric differences for critical structures.

METHODS AND MATERIALS

Data from pediatric patients treated with photon radiation for intracranial germinoma were analyzed for clinical outcomes and dosimetry to critical structures, with particular interest in the temporal ventricular horns (TVHs). A consensus contour was generated for TVH-sparing ventricular clinical target volumes (CTVs) via deformable image registration.

RESULTS

Twelve and 10 patients had their TVHs included or excluded in their ventricular CTVs, respectively. All patients were living at the time of analysis. One patient relapsed in the fourth ventricle, which had been omitted from the radiation therapy field. Mean dose was significantly lower to the hippocampi (Δ = -578 cGy, P = .0016) and temporal lobes (Δ = -599 cGy, P = .0007) in the TVH-excluded cohort compared with those with TVHs included in the treatment field.

CONCLUSIONS

Exclusion of the TVHs from the CTV results in significant dose sparing to the hippocampi and temporal lobes. Clinical outcomes remain excellent with no deaths and no TVH failures. Exclusion of TVHs from the ventricular CTV in germinoma requires prospective study.

Single-Fraction Stereotactic Radiosurgery Versus Hippocampal-Avoidance Whole Brain Radiation Therapy for Patients With 10 to 30 Brain Metastases: A Dosimetric Analysis

PURPOSE

To compare normal tissue dosimetry between hippocampal-avoidance whole brain radiation therapy (HA-WBRT) and stereotactic radiosurgery (SRS) in patients with 10 to 30 brain metastases, and to describe a novel SRS strategy we term Spatially Partitioned Adaptive RadiosurgEry (SPARE).

METHODS AND MATERIALS

A retrospective review identified SRS treatment plans with >10 brain metastases located >5 mm from the hippocampi. Our Gamma Knife Icon (GKI) SPARE (GKI-Spr) technique treats multiple metastases with single-fraction SRS partitioned over consecutive days while limiting the total treatment time to ≤60 minutes per day. Hippocampal and normal brain dosimetry were compared among GKI-Spr, single-fraction single-day GKI (GKI-Sfr), and 30 Gy in 10 fractions HA-WBRT. Dose metrics were converted to equivalent dose in 2 Gy fractions.

RESULTS

Ten cases were analyzed. Compared with HA-WBRT, GKI-Spr significantly reduced the median equivalent dose in 2 Gy fractions hippocampal maximum point dose, mean dose, and dose to 40% of the hippocampi (D40%) by 86%, 93%, and 93%, respectively, and similarly for GKI-Sfr by 81%, 92%, and 91%, respectively. The normal brain median mean dose was reduced by 95% with GKI-Spr and 94% with GKI-Sfr. Compared with GKI-Sfr, GKI-Spr further reduced all normal brain and hippocampal dose metrics (P ≤ .014).

CONCLUSIONS

GKI yields superior hippocampal and normal brain dosimetry compared with HA-WBRT, and GKI-Spr results in further dosimetric advantages.

Dummy Run of Quality Assurance Program before Prospective Study of Hippocampus-Sparing Whole-Brain Radiotherapy and Simultaneous Integrated Boost for Multiple Brain Metastases from Non-small Cell Lung Cancer: Korean Radiation Oncology Group (KROG) 17-06 Study

PURPOSE

Lung Cancer Subcommittee of Korean Radiation Oncology Group (KROG) has recently launched a prospective clinical trial (KROG 17-06) of hippocampus-sparing whole brain radiotherapy (HS-WBRT) with simultaneous integrated boost (SIB) in treating multiple brain metastases from non-small cell lung cancer. In order to improve trial quality, dummy run studies among the participating institutions were designed. This work reported the results of two-step dummy run procedures of the KROG 17-06 study.

MATERIALS AND METHODS

Two steps tested hippocampus contouring variability and radiation therapy planning compliance. In the first step, the variation of the hippocampus delineation was investigated for two representative cases using the Dice similarity coefficients. In the second step, the participating institutions were requested to generate a HS-WBRT with SIB treatment plan for another representative case. The compliance of the treatment plans to the planning protocol was evaluated.

RESULTS

In the first step, the median Dice similarity coefficients of the hippocampus contours for two other dummy run cases changed from 0.669 (range, 0.073 to 0.712) to 0.690 (range, 0.522 to 0.750) and from 0.291 (range, 0.219 to 0.522) to 0.412 (range, 0.264 to 0.598) after providing the hippocampus contouring feedback. In the second step, with providing additional plan priority and extended dose constraints to the target volumes and normal structures, we observed the improved compliance of the treatment plans to the planning protocol.

CONCLUSION

The dummy run studies demonstrated the notable inter-institutional variability in delineating the hippocampus and treatment plan generation, which could be decreased through feedback from the trial center.

Whole-brain helical tomotherapy with integrated boost for brain metastases in patients with malignant melanoma - final results of the BRAIN-RT trial

Background: Patients with multiple brain metastases (BMs) from malignant melanoma have a poor prognosis. Recent developments in radiation techniques allow simultaneous integrated boost (SIB) concepts while sparing organs at risk. Data on conventional versus dose-escalated radiation approaches in multiple BMs from malignant melanoma are warranted.

Methods: In this prospective, single-center, randomized two-armed study (trial ID: DRKS00005127), patients with multiple BMs from malignant melanoma were treated with either conventional whole-brain radiotherapy (WBRT) applying 30 Gy in 10 fractions (standard arm) or helical tomotherapy applying 30 Gy to the whole brain with an integrated boost to metastases of 50 Gy in 10 fractions and sparing of the hippocampus (HA-WBRT, experimental arm). The primary endpoint was treatment-related toxicity, while secondary endpoints were imaging response, intracerebral progression-free survival (PFS), overall survival (OS) and quality of life.

Results: The study was stopped early due to slow patient recruitment. A total number of 7 patients were enrolled (standard arm n=3, experimental arm n=4), and were followed-up for a median time of 5 months between August 2013 and July 2017. All patients were treated according to protocol. The median OS, intracerebral PFS and follow-up time were 5 months, 2 months and 5 months, respectively. The local control in every individual BM was significantly longer in the experimental versus the standard arm. No patient developed radiation-related high-grade toxicities.

Conclusion: HA-WBRT with SIB results in improved local control in the individual melanoma BMs without radiation-associated high-grade toxicities. Survival times were comparable to published data.

The Effects of Brain Tumours upon Medical Decision-Making Capacity

Purpose of Review

Informed consent is the integral part of good medical practice in patients with brain tumours. Capacity to consent may be affected by the brain disorder or its treatment. We intend to draw upon the current neuro-oncology literature to discuss the influence intracranial tumours have upon patients’ capacity to consent to treatment and research.

Recent Findings

We performed a systematic review of studies of capacity to consent for treatment or research in patients with intracranial tumours. The search retrieved 1597 papers of which 8 were considered eligible for review.

Summary

Although there are obvious inherent limitations to solely assessing cognition, most research consistently demonstrated increased risk of incapacity in brain tumour patients with cognitive impairment. Specific items in cognitive screening batteries, for example Semantic Verbal Fluency Test (SVFT), Hopkins Verbal Learning Test (HVLT-Recall), and Trail Making Test A/B (TMT), are simple, easily applied tests that may act as significant red flags to identify patients at increased risk of incapacity and who subsequently will require additional cognitive/psychiatric evaluation or more formal tests for capacity to consent for treatment or research.

Effect of Postoperative Radiotherapy for Brain Metastases: An Analysis

INTRODUCTION

Brain metastases (BM) have a very poor prognosis, creating a demand for effective local therapies, such as radiotherapy (RT) and neurosurgery, the combination of which is debatable. The aim of the present study was to investigate prognostic factors and to develop treatment recommendations for patients with BM.

MATERIAL AND METHODS

A total of 84 patients treated between May 2011 and July 2016 were analyzed in a single-institution retrospective study.

RESULTS

Overall survival (OS) was 10.3 months. Poor OS was defined by a Karnofsky performance index of ≤70% (2.9 vs. 15.8 months; p = 0.009), male gender (6.5 vs. 18.3 months; p = 0.044), and incomplete neurosurgical resection (2.5 vs. 15.8 months; p = 0.017). These factors were also shown to be significant in univariate analysis, while only radical resection remained significant in multivariate testing (p = 0.023). A direct comparison between whole-brain RT (with or without boost) and local RT illustrated a superior OS for local therapy (22.7 vs. 9.5 months; p = 0.022), especially in case of up to 3 metastases (p = 0.041). Intracranial control was 81% with a median duration of 31.6 months.

CONCLUSION

Combined modality treatment of RT and neurosurgery is effective and feasible. A complete removal of all metastases is the cardinal prognostic factor.

Improving dosimetric outcome for hippocampus and cochlea sparing whole brain radiotherapy using spot-scanning proton arc therapy

This feasibility study shows that Spot-scanning Proton Arc therapy (SPArc) is able to significantly reduce the dose to the hippocampus and cochlea compared to both Volumetric Modulated Arc Photon Therapy (VMAT) and the robust optimized Intensity Modulated Proton Therapy (ro-IMPT) plans in whole brain radiotherapy. Furthermore, SPArc not only improves plan robustness but could potentially deliver a treatment as efficient as ro-IMPT when proton system's energy layer switch time is less than 1 s.

Changes in cortical thickness and volume after cranial radiation treatment: A systematic review

Cognitive decline has a clear impact on quality of life in patients who have received cranial radiation treatment. The pathophysiological process is most likely multifactorial, with a possible role for decreased cortical thickness and volume. As radiotherapy treatment systems are becoming more sophisticated, precise sparing of vulnerable regions and tissue is possible. This allows radiation oncologists to make treatment more patient-tailored. A systematic search was performed to collect and review all available evidence regarding the effect of cranial radiation treatment on cortical thickness and volume. We searched the Pubmed, Embase and Cochrane databases, with an additional reference check in the Scopus database. Studies that examined cortical changes on MRI within patients as well as between treated and non-treated patients were included. The quality of the studies was assessed with a checklist specially designed for this review. No meta-analysis was performed due to the lack of randomised trials. Out of 1915 publications twenty-one papers were selected, of which fifteen observed cortical changes after radiation therapy. Two papers reported radiation-dependent decrease in cortical thickness within patients one year after radiation treatment, suggesting a clear relation between the two. However, study quality was considered mostly suboptimal, and there was great inhomogeneity between the included studies. This means that, although there has been increasing interest in the effects of radiation treatment on cortex morphology, no reliable conclusion can be drawn based on the currently available evidence. This calls for more research, preferably with a sufficiently large patient population, and adequate methodology.

Whole brain radiotherapy using four-field box technique with tilting baseplate for parotid gland sparing

PURPOSE

The aim of this study is to evaluate the efficacy and feasibility of four-field box whole brain radiotherapy (FB-WBRT) with tilting baseplate by comparing bilateral WBRT (B-WBRT).

METHODS AND MATERIALS

Between March 2016 and September 2018, 20 patients with brain metastases underwent WBRT using the four-field box technique. WBRT is performed with a dose of 30 Gy in 10 fractions daily. Two computed tomography simulations per person were performed. One was in the traditional supine position for B-WBRT and the other by applying the tilting acrylic supine baseplate to elevate the head by 40° for FB-WBRT. The B-WBRT used the field-in-field technique, which is the most commonly used method in our institution. The FB-WBRT comprised anterior, posterior, and bilateral beams. A wedge was applied in anterior and posterior fields to compensate for skull convexity.

RESULTS

The average of Dmean of both parotid glands was 10.2 Gy (range, 3.8 to 17.8 Gy) in B-WBRT and 5.4 Gy (range, 2.0 to 11.7 Gy) in FB-WBRT (p < 0.05). Compared to B-WBRT, FB-WBRT reduced the mean dose of the right and left parotid glands from 10.1 Gy to 4.9 Gy and from 10.4 Gy to 5.8 Gy, respectively (p < 0.05). Further, V5, V10, V15, V20, and V25 for the parotid gland decreased significantly in FB-WBRT (p < 0.05). The Dmax and Dmean of lens decreased according to the dose-volume histogram.

CONCLUSION

Compared to B-WBRT, FB-WBRT with a tilting baseplate is a simple and effective method that takes feature of noncoplanar beam to protect the parotid gland.

Distribution of metastasis in the brain in relation to the hippocampus: a retrospective single-center analysis of 565 metastases in 116 patients

OBJECTIVE

To examine the distribution of brain metastases (BM) in relation to the hippocampus, so as to determine the risk of metastasis in the hippocampus, and thus provide experimental evidence for the hippocampal avoidance (HA) in patients with BM during radiotherapy.

METHODS

(1) For the retrospective analysis of 116 patients diagnosed with malignancies, confirmed as BM, from December 2014 to December 2016 at the First Affiliated Hospital of Bengbu Medical College. We obtained the T1-weighted, postcontrast axial, sagittal, and coronal Magnetic Resonance imaging (MRI) images f the patients, in supine position, using the head restraints and head thermoplastic masks to adjust the positioning, with computed tomography (CT) positioning scan ranging from the head to the mandible (layer thickness: 3 mm). CT and MRI images were fused on a Philips Pinnacle v9.8 treatment planning system;(2) Every metastasis of the 565 metastases was contoured;(3) hippocampus were contoured, and hippocampus with 5 mm expansion envelopes were analyzed;(4) Using the SPSS 16.0 software, we analyzed the relation between the distribution and age, sex, Karnofsky performance status (KPS), primary site, aggregate volume of intracranial metastases and the whole brain. The data were analyzed using a binary logistic regression analysis method, with two-sided P < 0.05 for statistical significance.

RESULTS

In this study, we recruited 116 patients with 565 metastases. Among them, 1.7% (n = 2) had metastases in the hippocampus, and 11.2% (n = 13) had metastases within 5 mm of the hippocampus, of which more than half were patients with non-small cell lung cancer (n = 7). Using a binary logistic regression to analyze the relation between the metastases located within 5 mm of the hippocampus and age (P = 0.395), sex (P = 0.139), KPS (P = 0.724), primary site (P = 0.894), aggregate volume of intracranial metastases (p = 0.093) and the whole brain (p = 0.998), and none of them showed statistically significant difference between them and the metastases location (P>0.05).

CONCLUSION

This study showed a low risk for the perihippocampal metastases (PHM) and no significant correlation between PHM and age, sex, KPS, primary site, aggregate volume of intracranial metastases and the whole brain. Accordingly, it is may be acceptable to avoid the perihippocampal region during whole brain radiotherapy.

FAst Segmentation Through SURface Fairing (FASTSURF): A novel semi-automatic hippocampus segmentation method

Objective

The objective is to present a proof-of-concept of a semi-automatic method to reduce hippocampus segmentation time on magnetic resonance images (MRI).

Materials and methods

FAst Segmentation Through SURface Fairing (FASTSURF) is based on a surface fairing technique which reconstructs the hippocampus from sparse delineations. To validate FASTSURF, simulations were performed in which sparse delineations extracted from full manual segmentations served as input. On three different datasets with different diagnostic groups, FASTSURF hippocampi were compared to the original segmentations using Jaccard overlap indices and percentage volume differences (PVD). In one data set for which back-to-back scans were available, unbiased estimates of overlap and PVD were obtained. Using longitudinal scans, we compared hippocampal atrophy rates measured by manual, FASTSURF and two automatic segmentations (FreeSurfer and FSL-FIRST).

Results

With only seven input contours, FASTSURF yielded mean Jaccard indices ranging from 72(±4.3)% to 83(±2.6)% and PVDs ranging from 0.02(±2.40)% to 3.2(±3.40)% across the three datasets. Slightly poorer results were obtained for the unbiased analysis, but the performance was still considerably better than both tested automatic methods with only five contours.

Conclusions

FASTSURF segmentations have high accuracy and require only a fraction of the delineation effort of fully manual segmentation. Atrophy rate quantification based on completely manual segmentation is well reproduced by FASTSURF. Therefore, FASTSURF is a promising tool to be implemented in clinical workflow, provided a future prospective validation confirms our findings.

Non-coplanar whole brain radiotherapy is an effective modality for parotid sparing

Background

The purpose of this study was to evaluate the efficacy and feasibility of non–coplanar whole brain radiotherapy (NC–WBRT) for parotid sparing.

Methods

Fifteen cases, previously treated with WBRT were selected. NC–WBRT plans were generated. The beam arrangement for the non–coplanar plans consisted of superior anterior, right, and left beams. After generation of the non–coplanar plans a field–in–field technique was applied to the bilateral parallel opposed beams in order to reduce maximum dose and increase dose homogeneity. The NC–WBRT plans were subsequently compared with the previously generated bilateral WBRT (B–WBRT) plans. A field–in–field technique was also used with the B–WBRT plans according to our departmental protocol. As per our institutional practice a total dose of 30 Gy in 10 fractions of WBRT was administered 5 days a week.

Results

The mean dose to the parotid gland for the two different plans were 16.2 Gy with B–WBRT and 13.7 Gy with NC–WBRT (p<0.05). In the NC–WBRT plan, the V_5Gy, V_10Gy, V_15Gy, V_20Gy, and V_25Gy of the parotid were significantly lower (p<0.05) than those of the B–WBRT plan. The D_max of the lens was also lower by 10% with NC–WBRT.

Conclusion

The use of NC–WBRT plans could be a simple and effective method to reduce irradiated volumes and improve the dose–volume parameters of the parotid gland.

Dosimetric Comparison of Four Volumetric-Modulated Arc Therapy Beam Arrangements Utilized for Hippocampal-Sparing Whole-Brain Radiation Therapy

PURPOSE

In the present study, the performance of four VMAT beam arrangements used for hippocampal-sparing whole-brain radiation therapy is addressed.

MATERIAL AND METHODS

Data corresponding to 20 patients were utilized so as to generate plans for every beam configuration. A preliminary study was conducted to assess the optimal distance between optimization structures (PTVx) and hippocampi. V25, V30, D50%, D2%, D98%, homogeneity index (HI) and Paddick conformity factor (CF) were evaluated for PTV. D100% and Dmax were considered for hippocampi. All plans were required to perform at least as recommended in RTOG 0933 trial regarding organs at risk (OAR) sparing and PTV objectives.

RESULTS

Considerable hippocampi sparing alongside with a reasonably low decrease in PTV coverage was achieved using a 7 mm distance between hippocampi and PTV optimization structure. Beam setup 3 (comprised of two full arcs with 0° couch angle and two half arcs with 90° couch angle) achieved the best PTV coverage, HI and CF, while it performed the second-best sparing in hippocampi and lenses. Moreover, beam setup 3 was the second-fastest treatment, although it resulted in the highest number of delivered MU among all beam setups. Beam setup 1 (comprised of two full arcs with no couch angles) was the fastest and it delivered a significantly less amount of monitor units compared with the other beam setups evaluated. Furthermore, a higher robustness was obtained by using no couch angles. Although beam setup 1 was the least optimal considering OAR sparing, it still performed better than required in the RTOG 0933 trial.

CONCLUSIONS

Overall, beam setup 3 was considered to be the best. It is worth mentioning that, apart from our results, the election of one of these beam arrangements might be dependent on the amount of patient workload at a specific institution.

Incidence of Hippocampal Metastases: Laterality and Implications for Unilateral Hippocampal Avoiding Whole Brain Radiotherapy

Introduction

Hippocampi sparing whole brain radiotherapy (WBRT) is an evolving approach in the treatment of patients with multiple brain metastases, pursuing mitigation of verbal memory decline as a consequence of hippocampal radiation injury. Accumulating data are showing different postradiotherapy changes in the left and right hippocampus with a theoretical proposal of only unilateral (dominant, left) hippocampal sparing during WBRT.

Method

The aim of this retrospective study is to describe spatial distribution of brain metastases on MRI in a cohort of 260 patients (2595 metastases) and to evaluate distribution separately in the left and right hippocampus and in respective hippocampal avoiding zones (HAZ, region with subtherapeutic radiation dose), including evaluation of location of metastatic mass centre.

Results

The median number of brain metastases was three, with lung cancer being the most common type of primary tumour; 36% had single metastasis. Almost 8% of patients had metastasis within hippocampus (1.1% of all metastases) and 18.1% of patients within HAZ (3.3% of all metastases). No statistically significant difference was observed in the laterality of hippocampal involvement, also when the location of centre of metastases was analyzed. There were more patients presenting the centre of metastasis within left (15) versus right (6) HAZ approaching the borderline of statistical significance.

Conclusion

No significant difference in the laterality of BM seeding within hippocampal structures was observed. The hypothesized unilateral sparing WBRT would have theoretical advantage in about 50% reduction in the risk of subsequent recurrence within spared regions.

Advantages of intensity modulated proton therapy during hippocampal avoidance whole brain radiation therapy

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Whole-brain intensity modulated proton therapy capably spares hippocampal volumes.

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Hippocampal avoidance whole-brain radiotherapy may benefit pediatric populations.

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Intensity modulated proton therapy provides superior target-dose homogeneity relative to modulated x-rays.

Background and purpose

Intensity modulated proton therapy (IMPT) allows for modulation parameterized for individual beamlets by position, intensity, and depth. This modulation capability is ideally suited for sparing organs at risk intermediate of the radiation target, such as hippocampal volumes within the whole brain. This work compared IMPT relative to volumetric modulated arc therapy (VMAT) during hippocampal avoidance whole brain radiation therapy (HA WBRT).

Materials and methods

Ten adult and ten pediatric patients previously treated for central nervous system malignancies were identified. IMPT and VMAT treatment plans employing HA WBRT were generated for each patient, delivering 30 GyE (Gray Equivalent) in 10 fractions for adults and 36 GyE in 20 fractions for pediatrics. Dose indices, including dose volume histogram metrics and homogeneity index HI = [D5% − D95%]/[D_mean] × 100, were used to assess plan quality and describe target coverage and normal-tissue sparing.

Results

IMPT offered significant benefits relative to VMAT for hippocampal sparing. Hippocampal mean dose was reduced from 13.7 ± 0.8 Gy with VMAT to 5.4 ± 0.3 GyE using IMPT for pediatrics, and was reduced from 11.7 ± 0.9 Gy with VMAT to 4.4 ± 0.2 GyE using IMPT for adults. IMPT similarly lowered left hippocampal mean dose. Dose to 95% of the clinical target volume was statistically equivalent for both groups; however IMPT reduced the homogeneity index by roughly half.

Conclusion

This manuscript demonstrates that HA IMPT can match or exceed dosimetric benefits offered with modulated X-rays. Inclusion of IMPT in future prospective studies is warranted.

Subventricular Zone Radiation Dose and Outcome for Glioblastoma Treated Between 2006 and 2012

Objective Stem cells residing in the subventricular zone (SVZ) may be related to recurrence, potentially affecting outcome in glioblastoma (GBM). This study investigated the relationship of SVZ radiation dose and survival in a large cohort treated with surgery and chemoradiotherapy (CRT). Methods Patients with GBM treated between 2006 and 2012 (n = 370) were identified. SVZs were contoured from planning computed tomography (CT) with magnetic resonance imaging (MRI) registration where available. Dose was extracted from dose volume histograms. Kaplan-Meier (KM) progression-free survival (PFS) and overall survival (OS) estimates were compared with log-rank tests for SVZ doses. Multivariate analysis (MVA) identified clinical and treatment-related factors significantly associated with outcome. Results Median follow-up was 16.4 months, 48.1% underwent gross total resection (GTR), 37.5% subtotal resection, and 14.4% biopsy without resection. Median PFS was 8.9 months (95% CI: 8.3-9.8 months), and OS was 16.5 months (95% CI: 15.2-17.6 months). PFS was significantly lower for older age (>50 years, P = 0.045), poor Karnofsky performance status (KPS, P = 0.049), multifocality (P < 0.001), and incomplete adjuvant chemotherapy (P < 0.001). Worse OS was associated with poor KPS (P = 0.001), biopsy only (P = 0.003), multifocality (P = 0.009), and failure to complete adjuvant chemotherapy (P < 0.001). SVZ dose was not associated with outcome for any of the dose levels assessed. On MVA, multifocality was associated with worse PFS (P < 0.01). Poor performance status and biopsy only were associated with worse OS (both P < 0.01). Conclusion In this analysis of a large cohort of GBM treated with surgery and CRT, increased SVZ dose was not associated with improved survival.

The Feasibility of Integrating Resting-State fMRI Networks into Radiotherapy Treatment Planning

BACKGROUND

Functional magnetic resonance imaging (fMRI) presents the ability to selectively protect functionally significant regions of the brain when primary brain tumors are treated with radiation therapy. Previous research has focused on task-based fMRI of language and sensory networks; however, there has been limited investigation on the inclusion of resting-state fMRI into the design of radiation treatment plans.

METHODS AND MATERIALS

In this pilot study of 9 patients with primary brain tumors, functional data from the default mode network (DMN), a network supporting cognitive functioning, was obtained from resting-state fMRI and retrospectively incorporated into the design of radiation treatment plans. We compared the dosimetry of these fMRI DMN avoidance treatment plans with standard of care treatment plans to demonstrate feasibility. In addition, we used normal tissue complication probability models to estimate the relative benefit of fMRI DMN avoidance treatment plans over standard of care treatment plans in potentially reducing memory loss, a surrogate for cognitive function.

RESULTS

On average, we achieved 20% (P = 0.002) and 12% (P = 0.002) reductions in the mean and maximum doses, respectively, to the DMN without compromising the dose coverage to the planning tumor volume or the dose-volume constraints to organs at risk. Normal tissue complication probability models revealed that when the fMRI DMN was considered during radiation treatment planning, the probability of developing memory loss was lowered by more than 20%.

CONCLUSION

In this pilot study, we demonstrated the feasibility of including rs-MRI data into the design of radiation treatment plans to spare cognitively relevant brain regions during radiation therapy. These results lay the groundwork for future clinical trials that incorporate such treatment planning methods to investigate the long-term behavioral impact of this reduction in dose to the cognitive areas and their neural networks that support cognitive performance.

Intensity-modulated radiation therapy combined with concomitant temozolomide for brain metastases from lung adenocarcinoma

Short-term efficacy, adverse effects and the impact on quality of life (QoL) of a concomitant treatment with intensity-modulated radiation therapy (IMRT) and temozolomide (TMZ) in patients with brain metastases (BMs) from lung adenocarcinoma were evaluated. This study sought to confirm the benefit of adding TMZ to IMRT in patients with BMs from lung adenocarcinoma. Nine patients were enrolled and received a dose of 30 Gy in 10 daily fractions to clinical tumor volume (CTV) according to IMRT, then additional dose of 9 Gy in 3 fractions of IMRT was delivered to gross tumor volume (GTV) only with concomitant TMZ (75 mg/m²/day) orally during RT for 3 weeks. One patient achieved complete response (CR) (11.1%), 6 patients obtained partial response (PR) (66.7%), and there were no patients in progression. Therefore, objective response (OR) reached 77.8%. The main adverse effects included neutropenia, anemia, vomiting, fatigue and dizziness. Grade ≥3 of hematologic toxicities did not occur. However, the other 9 patients who received only intensity-modulated radiation had much worse results. The CR was 0, PR rate was 44.4%, OR rate was 44.4%. The results indicated that the benefit of adding TMZ to IMRT was confirmed in patients with BMs from lung adenocarcinoma. The treatment was active, a significant OR was observed, and achieved an improvement in QoL demonstrated by QoL grade (p<0.05).

Clinical outcomes in patients with brain metastases from breast cancer treated with single-session radiosurgery or whole brain radiotherapy

OBJECTIVE Gamma Knife radiosurgery (GKRS) is used to treat brain metastases from breast cancer (BMB) as the sole treatment or in conjunction with tumor resection and/or whole brain radiotherapy (WBRT). This study evaluates outcomes in BMB based on treatment techniques and tumor biological features. METHODS The authors reviewed all patients treated with BMB between 2004 and 2014. Patients were identified from a prospectively collected radiosurgery database and institutional tumor registry; 214 patients were identified. Data were collected from aforementioned sources and supplemented with chart review where needed. Independent radiological review was performed for all available brain imaging in those treated with GKRS. Survival analyses are reported using Kaplan-Meier estimates. RESULTS During the 10-year study period, 214 patients with BMB were treated; 23% underwent GKRS alone, 46% underwent a combination of GKRS and WBRT, and 31% underwent WBRT alone. Median survival after diagnosis of BMB in those treated with GKRS alone was 21 months, and in those who received WBRT alone it was 3 months. In those treated with GKRS plus WBRT, no significant difference in median survival was observed between those receiving WBRT upfront or in a salvage setting following GKRS (19 months vs 14 months, p = 0.63). The median survival of patients with total metastatic tumor volume of ≤ 7 cm³ versus > 7 cm³ was 20 months vs 7 months (p < 0.001). Human epidermal growth factor receptor-2 (Her-2) positively impacted survival after diagnosis of BMB (19 months vs 12 months, p = 0.03). Estrogen receptor status did not influence survival after diagnosis of BMB. No difference was observed in survival after diagnosis of BMB based on receptor status in those who received WBRT alone. CONCLUSIONS In this single-institution series of BMB, the addition of WBRT to GKRS did not significantly influence survival, nor did the number of lesions treated with GKRS. Survival after the diagnosis of BMB was most strongly affected by Her-2 positivity and total metastatic tumor volume.

Cognitive impairment and morphological changes after radiation therapy in brain tumors: A review

Life expectancy of patients treated for brain tumors has lengthened due to the therapeutic improvements. Cognitive impairment has been described following brain radiotherapy, but the mechanisms leading to this adverse event remain mostly unknown. Technical evolutions aim at enhancing the therapeutic ratio. Sparing of the healthy tissues has been improved using various approaches; however, few dose constraints have been established regarding brain structures associated with cognitive functions. The aims of this literature review are to report the main brain areas involved in cognitive adverse effects induced by radiotherapy as described in literature, to better understand brain radiosensitivity and to describe potential future improvements.

Inter-observer variation of hippocampus delineation in hippocampal avoidance prophylactic cranial irradiation

BACKGROUND

Hippocampal avoidance prophylactic cranial irradiation (HA-PCI) techniques have been developed to reduce radiation damage to the hippocampus. An inter-observer hippocampus delineation analysis was performed and the influence of the delineation variability on dose to the hippocampus was studied.

MATERIALS AND METHODS

For five patients, seven observers delineated both hippocampi on brain MRI. The intra-class correlation (ICC) with absolute agreement and the generalized conformity index (CI_gen) were computed. Median surfaces over all observers' delineations were created for each patient and regional outlining differences were analysed. HA-PCI dose plans were made from the median surfaces and we investigated whether dose constraints in the hippocampus could be met for all delineations.

RESULTS

The ICC for the left and right hippocampus was 0.56 and 0.69, respectively, while the CI_gen ranged from 0.55 to 0.70. The posterior and anterior-medial hippocampal regions had most variation with SDs ranging from approximately 1 to 2.5 mm. The mean dose (D_mean) constraint was met for all delineations, but for the dose received by 1% of the hippocampal volume (D_1%) violations were observed.

CONCLUSION

The relatively low ICC and CI_gen indicate that delineation variability among observers for both left and right hippocampus was large. The posterior and anterior-medial border have the largest delineation inaccuracy. The hippocampus D_mean constraint was not violated.

Simultaneously avoiding the hippocampus and hypothalamic-pituitary axis during whole brain radiotherapy: A planning study

Whole brain radiotherapy (WBRT) is the preferred treatment for multiple brain metastases, and patients with limited-stage small cell lung cancer undergo prophylactic cranial irradiation after complete remission. However, neurotoxicity remains a complication. In addition to protecting the hippocampus from irradiation to preserve cognitive function, it is also critical to avoid irradiating the hypothalamic-pituitary axis to preserve endocrine and immune function. This study aimed to evaluate the feasibility of delivering WBRT while protecting the hippocampus and hypothalamic-pituitary axis. Thirteen patients with limited-stage small cell lung cancer were enrolled in this study. The hippocampus, hypothalamus, and pituitary gland were contoured based on T1-weighted magnetic resonance imaging. The prescribed dose to the whole brain planning target volume was 25 Gy in 10 fractions. Two treatment plans using equispaced coplanar intensity-modulated radiotherapy (IMRT) were generated: WBRT with hippocampus avoidance (H-A) and WBRT with hippocampus, hypothalamus, and pituitary gland avoidance (H-HP-A). Both "H-A" and "H-HP-A" plans successfully protected the hippocampus, which received mean doses of 9.1 and 9.6 Gy, respectively (p = 0.0002), whereas the "H-HP-A" plan decreased the doses to both the hypothalamus (mean dose 11.06 Gy) and the pituitary gland (mean dose 10.66 Gy). Both "H-A" and "H-HP-A" plans showed similar target coverage of 95.1%. The homogeneity index of the "H-A" plan was slightly better than that of the "H-HP-A" plan (0.20 vs 0.23, p= 0.0012). In conclusion, the use of equispaced coplanar IMRT was found to simultaneously protect the hippocampus and hypothalamic-pituitary axis while delivering WBRT with acceptable target coverage and homogeneity.

A novel voxel based homogeneity index: Rationale and clinical implications for whole-brain radiation therapy

PURPOSE OR OBJECTIVE

A homogeneity index (HI) measures the uniformity of a dose distribution within a given target volume. Traditional HIs only use a limited number of dose-volume histogram data-points for calculation. A voxel-based homogeneity index (VHI) is proposed which utilizes the entire information of the three-dimensional dose distribution. We compared the VHI with existing HIs and analyzed if VHI results were associated with treatment outcomes in patients who underwent therapeutic WBRT.

MATERIAL AND METHODS

The VHI analyzes deviations from the prescribed dose in each voxel of the target volume. We retrospectively analyzed WBRT treatment plans. Overall survival (OS), CNS progression-free-survival (CNS PFS) and hazard rates were compared for tertile-split levels of the VHI using the Kaplan-Meier methods and multivariable Cox-regression analysis.

RESULTS

WBRT treatment plans (n = 770) were used for HIs comparison. OS and CNS PFS were assessed for 430 patients. The VHI showed a higher sensitivity for dose inhomogeneities. Lower OS and CNS PFS were observed for higher levels of VHI_Underdosage, particularly in patients with good performance status (KPS >70%) (OS: Log-rank P = .007, HR = 1.37 95%CI [1.09, 1.72]).

CONCLUSION

Higher sensitivity and feasibility to assess treatment plan quality using the VHI were demonstrated. First clinical implications were found in terms of compromised OS/CNS PFS for WBRT with radiation underdosage.

Hippocampal sparing in stereotactic radiotherapy for brain metastases: To contour or not contour the hippocampus?

PURPOSE

The aim of our study was to evaluate hippocampal irradiation in patients treated with fractionated stereotactic brain radiotherapy.

PATIENTS AND METHODS

Retrospective hippocampal dosimetric analysis performed on 22 patients with one to four brain metastases treated with fractionated stereotactic radiotherapy using volumetric intensity-modulated arc therapy. Original plans did not include hippocampus as avoidance structure in optimization criteria; hippocampus was retrospectively delineated on magnetic resonance coregistered with planning CT and using as reference the RTOG 0933 atlas. Hippocampus was defined both as a single and as pair organ. Constraints analysed were: Dmax<16Gy, D40%<7.3Gy, D100%=Dmin<9Gy. Assuming a α/β ratio of 2Gy, biologically equivalent dose in 2Gy fractions was calculated. Hippocampal-sparing plans were developed in cases where hippocampal constraints were not respected in the original plan.

RESULTS

Among constraints analysed Dmax and D40% have been exceeded in ten out of 22 cases. The constraints were not respected in patients with more than one metastatic lesion and in three patients with only one lesion. Considering all exceeded constraints values in non-hippocampal sparing plans, the 50% of them was respected after replanning. No significant differences were found among conformity and homogeneity index between non-hippocampal sparing and hippocampal sparing plans.

CONCLUSION

Volumetric intensity-modulated arc therapy hippocampal sparing plans significantly decreases dose to hippocampus assuring an equal target coverage and organs at risk avoiding.

The EPTN consensus-based atlas for CT- and MR-based contouring in neuro-oncology

PURPOSE

To create a digital, online atlas for organs at risk (OAR) delineation in neuro-oncology based on high-quality computed tomography (CT) and magnetic resonance (MR) imaging.

METHODS

CT and 3 Tesla (3T) MR images (slice thickness 1 mm with intravenous contrast agent) were obtained from the same patient and subsequently fused. In addition, a 7T MR without intravenous contrast agent was obtained from a healthy volunteer. Based on discussion between experienced radiation oncologists, the clinically relevant organs at risk (OARs) to be included in the atlas for neuro-oncology were determined, excluding typical head and neck OARs previously published. The draft atlas was delineated by a senior radiation oncologist, 2 residents in radiation oncology, and a senior neuro-radiologist incorporating relevant available literature. The proposed atlas was then critically reviewed and discussed by European radiation oncologists until consensus was reached.

RESULTS

The online atlas includes one CT-scan at two different window settings and one MR scan (3T) showing the OARs in axial, coronal and sagittal view. This manuscript presents the three-dimensional descriptions of the fifteen consensus OARs for neuro-oncology. Among these is a new OAR relevant for neuro-cognition, the posterior cerebellum (illustrated on 7T MR images).

CONCLUSION

In order to decrease inter- and intra-observer variability in delineating OARs relevant for neuro-oncology and thus derive consistent dosimetric data, we propose this atlas to be used in photon and particle therapy. The atlas is available online at www.cancerdata.org and will be updated whenever required.

Hippocampus-sparing radiotherapy using volumetric modulated arc therapy (VMAT) to the primary brain tumor: the result of dosimetric study and neurocognitive function assessment

Background

We hypothesized that hippocampal-sparing radiotherapy via volumetric modulated arc therapy (VMAT) could preserve the neurocognitive function (NCF) of patients with primary brain tumors treated with radiotherapy.

Methods

We reviewed data from patients with primary brain tumors who underwent hippocampal-sparing brain radiotherapy via VMAT between February 2014 and December 2015. The optimization criteria for the contralateral hippocampus was a maximum dose (D_max) of less than 17 Gy. For NCF evaluations, the Seoul Verbal Learning Test for total recall, delayed recall, and recognition (SVLT-TR, DR, and Recognition) was performed at baseline and at seven months after radiotherapy.

Results

A total of 26 patients underwent NCF testing seven months after radiotherapy. Their median age was 49.5 years (range 26–77 years), and 14 (53.8%) had grade III/IV tumors. The median D_max to the contralateral hippocampus was 16.4 Gy (range 3.5-63.4). The median mean dose to the contralateral hippocampus, expressed as equivalent to a 2-Gy dose (EQD_2/2), was 7.4 Gy₂ (0.7–13.1). The mean relative changes in SVLT-TR, SVLT-DR, and SVLT-Recognition at seven months compared to the baseline were − 7.7% (95% confidence interval [CI], − 19.6% to 4.2%), − 9.2% (95% CI, − 25.4% to 7.0%), and − 3.4% (− 12.7% to 5.8%), respectively. Two patients (7.7%) showed deteriorated NCF in the SVLT-TR and SVLT-DR, and three (11.5%) in the SVLT-Recognition. The mean dose of the left hippocampus and bilateral hippocampi were significantly higher in patients showing deterioration of the SVLT-TR and SVLT-Recognition than in those without deterioration.

Conclusions

The contralateral hippocampus could be effectively spared in patients with primary brain tumor via VMAT to preserve the verbal memory function. Further investigation is needed to identify those patients who will most benefit from hippocampal-sparing radiotherapy of the primary brain tumor.

Electronic supplementary material

The online version of this article (10.1186/s13014-018-0975-4) contains supplementary material, which is available to authorized users.

Assessment of multi-criteria optimization (MCO) for volumetric modulated arc therapy (VMAT) in hippocampal avoidance whole brain radiation therapy (HA-WBRT)

This study compared the dosimetric performance of (a) volumetric modulated arc therapy (VMAT) with standard optimization (STD) and (b) multi‐criteria optimization (MCO) to (c) intensity modulated radiation therapy (IMRT) with MCO for hippocampal avoidance whole brain radiation therapy (HA‐WBRT) in RayStation treatment planning system (TPS). Ten HA‐WBRT patients previously treated with MCO‐IMRT or MCO‐VMAT on an Elekta Infinity accelerator with Agility multileaf collimators (5‐mm leaves) were re‐planned for the other two modalities. All patients received 30 Gy in 15 fractions to the planning target volume (PTV), namely, PTV30 expanded with a 2‐mm margin from the whole brain excluding hippocampus with margin. The patients all had metastatic lesions (up to 12) of variable sizes and proximity to the hippocampus, treated with an additional 7.5 Gy from a simultaneous integrated boost (SIB) to PTV37.5. The IMRT plans used eight to eleven non‐coplanar fields, whereas the VMAT plans used two coplanar full arcs and a vertex half arc. The averaged target coverage, dose to organs‐at‐risk (OARs) and monitor unit provided by the three modalities were compared, and a Wilcoxon signed‐rank test was performed. MCO‐VMAT provided statistically significant reduction of D100 of hippocampus compared to STD‐VMAT, and Dmax of cochleas compared to MCO‐IMRT. With statistical significance, MCO‐VMAT improved V30 of PTV30 by 14.2% and 4.8%, respectively, compared to MCO‐IMRT and STD‐VMAT. It also raised D95 of PTV37.5 by 0.4 Gy compared to both MCO‐IMRT and STD‐VMAT. Improved plan quality parameters such as a decrease in overall plan Dmax and total monitor units (MU) were also observed for MCO‐VMAT. MCO‐VMAT is found to be the optimal modality for HA‐WBRT in terms of PTV coverage, OAR sparing and delivery efficiency, compared to MCO‐IMRT or STD‐VMAT.

The Interdisciplinary Management of Brain Metastases

BACKGROUND

20-40% of patients with malignant tumors have one or more brain metastases in the course of their illness. Brain metastases are the first manifestation of cancer in 5-10%. Manifestations such as intracranial hypertension or focal neurologic deficits are seen in over 80% of patients with brain metastases. Uncertainty surrounds the treatment of patients with intracranial metastases, as the existing data are derived from trials with low levels of evidence.

METHODS

This article is based on a selective literature review and on the authors' own experience of 100 consecutive patients who underwent surgery at the Department of Neurosurgery at Ruhr University Bochum (RUB), Germany.

RESULTS

Multimodal treatment enables successful surgery for an increasing number of patients with brain metastases. The modalities and goals of treatment are established for each patient individually by an interdisciplinary tumor board. Drug therapy is usually indicated. Surgical resection followed by stereotactic radiotherapy prolongs mean survival by 3-6 months and lowers the risk of recurrence from 40% to 12.5%. In the authors' own experience, even seriously ill patients can benefit from the resection of brain metastases. The 30-day morbidity was 29%, accounted for mainly by medical complications such as pulmonary embolism, renal failure, and sepsis.

CONCLUSION

Through the close interdisciplinary collaboration of neurosurgeons, radiation oncologists, and medical oncologists, the symptomatic state and the prognosis of patients with brain metastases can be improved. Longer overall survival implies that further studies will have to pay special attention to the toxicity of treatment.

Neurocognitive aspects of brain metastasis

Brain metastases are common, occurring in approximately 20% of cancer patients. One of the biggest concerns for these patients and their families is neurocognitive decline. Neurocognitive issues in this patient population are complex and many patients have neurocognitive impairment due to systemic therapies even before they develop brain metastases. The development of brain metastases as well as the treatment of these tumors can cause decline in neurocognitive function. Diffuse treatments such as whole-brain radiotherapy are more frequently associated with neurocognitive decline than focal interventions such as radiosurgery, surgical resection, and implantable chemotherapy wafers. For patients with brain metastases treatment decisions require a multidisciplinary approach, balancing many factors including the neurocognitive impact of treatment and the disease process itself. Finally, to continue to advance the field there needs to be continued utilization, both off and on clinical trial, of performance-based clinical outcome assessments (i.e., neurocognitive tests) to objectively assess and measure the neurocognitive outcomes of these patients.

[Neurocognition: Impact of radiotherapy]

The cognitive evaluation is essential to arrest the impact of brain tumours on brain functions. Radiation therapy on the brain has side effects, which can impact on the cognitive functioning. The cognitive disorders constitute a predictive factor of the quality of life of the patients impacting on their autonomy, as well as on their social and professional life. This problem thus takes a more and more important place in the reflection on the cancer care. A better detection of these cognitive disorders requires a better cognitive evaluation from the diagnosis. What would allow the implementation of preventive actions upstream. This prospect of improvement of the coverage of the cognitive consequences of the irradiation should allow a better social reinstatement after the treatment, as well as a facilitation for the preservation of autonomy and functional independence. However, a complete cognitive evaluation is expensive in time and asks for a qualified personnel, which often slows down the exploration and the follow-up of the disorders.

Real-Time Whole-Brain Radiation Therapy: A Single-Institution Experience

PURPOSE

To demonstrate the feasibility of a real-time whole-brain radiation therapy (WBRT) workflow, taking advantage of contemporary radiation therapy capabilities and seeking to optimize clinical workflow for WBRT.

METHODS AND MATERIALS

We developed a method incorporating the linear accelerator's on-board imaging system for patient simulation, used cone-beam computed tomography (CBCT) data for treatment planning, and delivered the first fraction of prescribed therapy, all during the patient's initial appointment. Simulation was performed in the linear accelerator vault. An acquired CBCT data set was used for scripted treatment planning protocol, providing inversely planned, automated treatment plan generation. The osseous boundaries of the brain were auto-contoured to create a target volume. Two parallel-opposed beams using field-in-field intensity modulate radiation therapy covered this target to the user-defined inferior level (C1 or C2). The method was commissioned using an anthropomorphic head phantom and verified using 100 clinically treated patients.

RESULTS

Whole-brain target heterogeneity was within 95%-107% of the prescription dose, and target coverage compared favorably to standard, manually created 3-dimensional plans. For the commissioning CBCT datasets, the secondary monitor unit verification and independent 3-dimensional dose distribution comparison for computed and delivered doses were within 2% agreement relative to the scripted auto-plans. On average, time needed to complete the entire process was 35.1 ± 10.3 minutes from CBCT start to last beam delivered.

CONCLUSIONS

The real-time WBRT workflow using integrated on-site imaging, planning, quality assurance, and delivery was tested and deemed clinically feasible. The design necessitates a synchronized team consisting of physician, physicist, dosimetrist, and therapists. This work serves as a proof of concept of real-time planning and delivery for other treatment sites.

Is Hippocampal Avoidance During Whole-Brain Radiotherapy Risky for Patients With Small-Cell Lung Cancer? Hippocampal Metastasis Rate and Associated Risk Factors

Objectives:

Hippocampal avoidance during whole-brain radiotherapy is performed to prevent neural stem cell injury causing neurocognitive dysfunction. Nevertheless, the estimated risk of metastases in hippocampal avoidance area in small-cell lung cancer is unknown. The current study aimed to characterize the metastatic distribution within the brain relative to the hippocampus, estimate the incidence of hippocampal metastasis in patients with small-cell lung cancer, and identify clinical and radiographic variables that may be associated with the risk of hippocampal avoidance area metastasis.

Materials and Methods:

Patients with small-cell lung cancer treated with therapeutic whole-brain radiotherapy between January 2010 and December 2015 were reviewed. T1-weighted, postcontrast axial magnetic resonance images obtained just before therapeutic cranial irradiation were retrieved and reviewed for each patient. The hippocampal avoidance area was defined as hippocampus and 5-mm ring area adjacent to the hippocampus to account for necessary dose falloff between the hippocampus and the whole-brain planning target volume. Metastatic lesions within hippocampal avoidance area were defined as hippocampal metastasis. Hippocampal metastasis rate and characteristics of patients with hippocampal metastasis were analyzed and compared to patients without hippocampal metastasis.

Results:

Fifty-four patients evaluated with cranial magnetic resonance imaging were enrolled. Hippocampal metastasis rate was 32% (17 patients). A total of 4.4% of all metastases involved the hippocampal avoidance area. The most common location was frontal lobe. Being younger than 65 years of age was found to be an independent risk factor for HM (odds ratio: 4.8, 95% confidence interval: 1-23.2, P = .049). The number of brain metastases was significantly higher in patients with hippocampal metastasis (P = .027), and hippocampal metastasis rate was also higher in patients having larger hippocampus (P = .026) and larger brain volumes (P = .02).

Conclusion:

Hippocampal metastasis might be more common in small-cell lung cancer. Reducing the dose to the hippocampus by hippocampal avoiding whole-brain radiotherapy plan in small-cell lung cancer may be risky for the development of HM compared with other malignant solid tumors.

Hippocampal sparing approach in fractionated stereotactic brain VMAT radio therapy: A retrospective feasibility analysis

Volumetric Modulated Arc Therapy (VMAT) techniques for fractioned stereotactic brain radiotherapy (FSBRT) can achieve highly conformal dose distribution to intracranial lesions. However, they can potentially increase the dose to hippocampus (H) causing neurocognitive toxicity during the first four months after irradiation. The purpose of this study was to assess the feasibility of hippocampal‐sparing (HS) treatment plans in 22 patients with brain metastasis treated with VMAT technique. Firstly, we retrospectively analyzed hippocampal doses in all 22 VMAT original (not hippocampal‐sparing, NHS) plans. Plans with hippocampal dose exceeding constraints (9 out of 22) were re‐planned considering dose constraints on the hippocampus (H) and on hippocampal avoidance zone (HAZ) generated using 5 mm isotropic margin to the hippocampus. Conformity (CI) and homogeneity indexes (HI) on the target and MUs, were maintained as close as possible to the original plans. Mean CI_NHS and CI_HS obtained were: 0.79 ± 0.11 and 0.81 ± 0.10, respectively (P = 0.75); mean HI_NHS and HI_HS were 1.05 ± 0.02 and 1.04 ± 0.01 respectively (P = 0.72). In both sets of plans, the mean MU values were similar: 1033 ± 275 and 1022 ± 234 for NHS and HS respectively. In HS plans, the mean hippocampal dose was decreased by an average of 35%. After replanning, the D_max (21.3 Gy) for HAZ and H was met by 45% (4/9) and 78% (7/9) of the NHS plans, respectively. The worst results were obtained for cases with target volumes extention closer than 12 mm to H, because of the difficulty to spare hippocampus without compromising target coverage. After replanning D_40% constraint value (7.3 Gy) was met by all the 9 NHS plans. In conclusion, this study suggests that an hippocampal‐sparing approach to FSBRT is feasible resulting in a decrease in the dose to the hippocampus without any loss in conformity or increase in treatment time.

Improved plan quality with automated radiotherapy planning for whole brain with hippocampus sparing: a comparison to the RTOG 0933 trial

BACKGROUND

Whole-brain radiation therapy (WBRT) with hippocampus sparing (HS) has been investigated by the radiation oncology working group (RTOG) 0933 trial for patients with multiple brain metastases. They showed a decrease of adverse neurocognitive effects with HS WBRT compared to WBRT alone. With the development of automated treatment planning system (aTPS) in the last years, a standardization of the plan quality at a high level was achieved. The goal of this study was to evaluate the feasibility of using an aTPS for the treatment of HS WBRT and see if the RTOG 0933 dose constraints could be achieved and improved.

METHODS

Ten consecutive patients treated with HS WBRT were enrolled in this study. 10 × 3 Gy was prescribed according to the RTOG 0933 protocol to 92% of the target volume (whole-brain excluding the hippocampus expanded by 5 mm in 3-dimensions). In contrast to RTOG 0933, the maximum allowed point dose to normal brain was significantly lowered and restricted to 36.5 Gy. All patients were planned with volumetric modulated arc therapy (VMAT) technique using four arcs. Plans were optimized using Auto-Planning (AP) (Philips Radiation Oncology Systems) with one single AP template and optimization.

RESULTS

All the constraints from the RTOG 0933 trial were achieved. A significant improvement for the maximal dose to 2% of the brain with a reduction of 4 Gy was achieved (33.5 Gy vs. RTOG 37.5 Gy) and the minimum hippocampus dose was reduced by 10% (8.1 Gy vs. RTOG 9 Gy). A steep dose gradient around the hippocampus was achieved with a mean dose of 27.3 Gy at a distance between 0.5 cm and 1 cm from the hippocampus. The effective working time to optimize a plan was kept below 6'.

CONCLUSION

Automated treatment planning for HS WBRT was able to fulfil all the recommendations from the RTOG 0933 study while significantly improving dose homogeneity and decreasing unnecessary hot spot in the normal brain. With this approach, a standardization of plan quality was achieved and the effective time required for plan optimization was minimized.

Prophylactic Cranial Irradiation Following Surgical Resection of Early-Stage Small-Cell Lung Cancer: A Review of the Literature

With increasing use of low-dose screening CT scans, the diagnosis of early-stage small-cell lung cancer (SCLC) without evidence of mediastinal nodal or distant metastasis is likely to become more common, but the role of adjuvant therapies such as prophylactic cranial irradiation (PCI) are not well understood in this population. We performed a review of the literature pertaining to the impact of PCI in patients who underwent surgical resection of early-stage SCLC. Four studies were identified that were pertinent including three single-institution retrospective analyses and a National Cancer Database analysis. Based upon these studies, we estimate the rate of brain metastases to be 10-15% for Stage I and 15-25% for Stage II disease without PCI. However, the impact of PCI on the development of brain metastases and its ultimate impact on overall survival were not consistent across these studies. In summary, there is sparse evidence to guide recommendations for PCI following resection of early-stage SCLC. While it may be reasonable to offer PCI to maximize likelihood of cure, alternative strategies such as observation with close imaging follow-up can also be considered for the appropriate patient given the known neurocognitive side effects of PCI.

Radiological distribution of brain metastases and its implication for the hippocampus avoidance in whole brain radiotherapy approach

OBJECTIVE

Hippocampus avoidance in whole brain radiotherapy (HA-WBRT) offers the feasibility of less-impaired cognitive function than conventional WBRT. The study aims to assess the radiological distribution of brain metastases (BMs) with relation to the hippocampus and peri-hippocampus region as defined by the RTOG 0933 for better understanding of margin definition in HA-WBRT treatment planning.

METHODS

Consecutive patients with diagnosis of BM from enhanced MRI between March 2011 and July 2016 were analysed. The pre-treatment T₁ weighted, T₂ weighted, T₂ flair, three-dimensional spoiled gradient axial and contrast-enhanced axial cranial MR images of 226 patients are examined. The closest distances between the edge of hippocampus and the margin of tumours on different planes were measured.

RESULTS

A total of 226 patients with 1080 visible metastatic sites were reviewed. The origin of the primary tumors was in 72.6% lung (n = 164), in 45 cases (19.9%) breast cancer and in 7.5% other malignancies (n = 17). There were 758 (70.2%) lesions situated beyond the tentorium. The median size of single lesion was 13.9 ± 14.7 mm. Impossible, it seems that more of the patients are with only one lesion, to verify. The hippocampus involvement was found in 3.1% (n = 7, 95% CI 0.01-0.05) within 5 mm, 5.7% (n = 13, 95% CI 0.03-0.09) within 10mm and 8.4% (n = 19, 95% CI 0.05-0.12) within 20 mm. In multivariate analysis, the number 6 BM or higher was found to be an independent risk factor for hippocampal involvement (HI) (OR: 5.2, 5.38 and 3.84 in 5, 10 and 20 mm).

CONCLUSION

This radiological study found that the incidence of hippocampus involvement is low in patients with BM. HA-WBRT can be delivered under the context of complete radiological diagnosis after careful delineation, proper margin definition and individual planning optimization. Advances in knowledge: The incidence of HI in patients with initial diagnosis of BM from solid tumours impacts the radiotherapeutic decision. Our radiological data analysed the incidence of HI not only to the conventional 5 mm margin definition, but also expanded to wider margins as 10 and 20 mm from hippocampus, which will help the treatment planning optimization with different technique.

Volumetric-modulated arc therapy (VMAT) for whole brain radiotherapy: not only for hippocampal sparing, but also for reduction of dose to organs at risk

A prospective clinical trial, Radiation Therapy Oncology Group (RTOG) 0933, has demonstrated that whole brain radiotherapy (WBRT) using conformal radiation delivery technique with hippocampal avoidance is associated with less memory complications. Further sparing of other organs at risk (OARs) including the scalp, ear canals, cochleae, and parotid glands could be associated with reductions in additional toxicities for patients treated with WBRT. We investigated the feasibility of WBRT using volumetric-modulated arc therapy (VMAT) to spare the hippocampi and the aforementioned OARs. Ten patients previously treated with nonconformal WBRT (NC-WBRT) using opposed lateral beams were retrospectively re-planned using VMAT with hippocampal sparing according to the RTOG 0933 protocol. The OARs (scalp, auditory canals, cochleae, and parotid glands) were considered as dose-constrained structures. VMAT plans were generated for a prescription dose of 30 Gy in 10 fractions. Comparison of the dosimetric parameters achieved by VMAT and NC-WBRT plans was performed using paired t-tests using upper bound p-value of < 0.001. Average beam on time and monitor units (MUs) delivered to the patients on VMAT were compared with those obtained with NC-WBRT. All VMAT plans met RTOG 0933 dosimetric criteria including the dose to hippocampi of 100% of the volume (D_100%) of 8.4 ± 0.3 Gy and maximum dose of 15.6 ± 0.4 Gy, respectively. A statistically significant dose reduction (p < 0.001) to all OARs was achieved. The mean and maximum scalp doses were reduced by an average of 9 Gy (32%) and 2 Gy (6%), respectively. The mean and maximum doses to the auditory canals were reduced from 29.5 ± 0.5 Gy and 31.0 ± 0.4 Gy with NC-WBRT, to 21.8 ± 1.6 Gy (26%) and 27.4 ± 1.4 Gy (12%) with VMAT. VMAT also reduced mean and maximum doses to the cochlea by an average of 4 Gy (13%) and 2 Gy (6%), respectively. The parotid glands mean and maximum doses with VMAT were 4.4 ± 1.9 Gy and 15.7 ± 5.0 Gy, compared to 12.8 ± 4.9 Gy and 30.6 ± 0.5 Gy with NC-WBRT, respectively. The average dose reduction of mean and maximum of parotid glands from VMAT were 65% and 50%, respectively. The average beam on time and MUs were 2.3minutes and 719 on VMAT, and 0.7 minutes and 350 on NC-WBRT. This study demonstrated the feasibility of WBRT using VMAT to not only spare the hippocampi, but also significantly reduce dose to OARs. These advantages of VMAT could potentially decrease the toxicities associated with NC-WBRT and improve patients' quality of life, especially for patients with favorable prognosis receiving WBRT or patients receiving prophylactic cranial irradiation (PCI).

Risk of dry eye syndrome in patients treated with whole-brain radiotherapy

With improvements in systemic therapy, patients with cancer treated with whole-brain radiotherapy (WBRT) are living long enough to develop late toxicities, including dry eye syndrome. In general practice, dose to the lacrimal gland (LG) is not constrained (maximum constraint <40 Gy) in WBRT. The purpose of this study was to measure dose to the LG in WBRT and determine methods for reducing radiation exposure. We conducted a retrospective review of 70 3-dimensional (3D) conformal plans; thirty-six plans with a radiation prescription of 30 Gy in 10 fractions and 34 plans with a prescription of 37.5 Gy in 15 fractions. LGs were contoured in accordance with Freedman and Sidani (2015). Biological effective dose (BED)3 maximum constraints were calculated from 40 Gy and 20 Gy to be 32.17 Gy (30 Gy) and 36.70 Gy (37.5 Gy). Both regimens demonstrated supraorbital blocking by 3 methods: T1, bordering the supraorbital ridge; T2, no contact with supraorbital ridge; and T3, coverage of the supraorbital ridge. Mean dose for the plans with a 30-Gy prescription and the plans with a 37.5-Gy prescription was 27.5 Gy and 35.2 Gy, respectively (p ≤ 0.0001). BED3 maximum constraint (D_max) was violated 16 of 26 (61.5%) in T1 (average D_max: 32.2 Gy), 13 of 28 (46.4%) in T2 (average D_max: 32.1 Gy), and 5 of 18 (27.8%) in T3 (average D_max: 31.8 Gy) for the 30-Gy prescription. D_max was violated in 32 of 32 (100%) in T1 (average D_max: 40.1 Gy), 22 of 22 (100%) in T2 (average D_max: 40.3 Gy), and 14 of 14 (100%) in T3 (average D_max: 39.4) for the 37.5 Gy prescription. Average D_max for the 37.5-Gy prescription was highly significant in favor of T3 (p = 0.0098). Patients who receive WBRT may develop dry eye syndrome as a late toxicity. Constraints are commonly violated with a prescription of 37.5 Gy. Methods to reduce dose include T3 supraorbital blocking, an easily implementable change that may dramatically improve patient quality of life.