Single dose radiosurgical treatment of recurrent previously irradiated primary brain tumors and brain metastases: final report of RTOG protocol 90-05

Stereotactic Radiosurgery Dose Reduction for Melanoma Brain Metastases Patients on Immunotherapy or Target Therapy: A Single-Center Experience

BACKGROUND AND OBJECTIVES

Better local control but higher rates of adverse radiation events (ARE) have been reported when combining American Society for Radiation Oncology (ASTRO)-guideline-suggested dose (SD) stereotactic radiosurgery (SRS) with immunotherapy or targeted therapy for melanoma brain metastases. The objective of this study is to explore the efficacy and safety of lower prescription doses compared with ASTRO guidelines for single-fraction SRS for patients with melanoma metastases who are concurrently receiving immunotherapy or targeted therapy.

METHODS

We conducted a retrospective, single-center study on 194 patients who underwent SRS between 2009 and 2022. After propensity score matching, 71 patients with 292 metastases were included in the ASTRO-SD (20-24 Gy for <2 cm, 18 Gy for ≥2 to <3 cm) group and 33 patients with 292 metastases in the reduced dose (RD, <20 Gy for <2 cm, <18 Gy for ≥2 to <3 cm) group.

RESULTS

The median diameter (5.4 vs 5.2 mm, P = .6), prescription volume (0.2 vs 0.2 cm 3 , P = .2), and radiographic follow-up (11 vs 12 months, P = .2) were similar in the 2 groups. The cumulative incidence of progressing metastases was significantly higher in the SD compared with the RD group ( P = .018). Higher prescription volumes and ASTRO-suggested radiation doses were associated with local progression in multivariable analysis. Radiographic AREs were significantly more common in the SD compared with the RD group (8.6% vs 3.1%, P = .005). BRAF and other tyrosine kinase inhibitors' concurrent use, higher prescription volumes, and ASTRO-suggested radiation doses were associated with an increased risk of radiographic ARE.

CONCLUSION

This study provides evidence that RD SRS could offer reduced toxicity rates, while maintaining high local control as compared with the current guideline-SDs for the treatment of melanoma brain metastases.

Radiation Exposure Induced Blood-Brain Barrier Injury via Mitochondria-Mediated Sterile Inflammation

Radiation-induced brain injury (RIBI) is caused by exposure to high doses of ionizing radiation and characterized by severe cognitive dysfunction and brain necrosis. However, the pathogenesis of RIBI is not fully understood, and no effective intervention is available. This work describes a blood-brain barrier (BBB) microphysiological system (MPS), that allowed to explore the responses of BBB and distinct brain cells to radiation exposure. Following acute exposure to radiation of X-ray or γ-ray, characteristic RIBI-associated pathological responses are observed, including BBB compromise, DNA breaks, inhibited cell proliferation, cell hypertrophy, and proinflammatory cytokine release. Among the distinctive types of cells, brain endothelial cells show the highest radiosensitivity as compared to other cells in the MPS. Intriguingly, X-ray and γ-ray radiation consistently induce prominent sterile inflammation responses, especially type I interferon response, in the BBB MPS. These responses are mediated by radiation-induced mitochondrial DNA release and subsequent activation of cGAS-STING signaling pathway. Furthermore, it is found abrocitinib (JAK1 inhibitor) and idebenone (mitochondrial protectant) can attenuate radiation-induced inflammation and ameliorate injuries in the BBB MPS. These findings reveal the involvement of mitochondria-mediated sterile inflammation in RIBI pathogenesis, identifying mitochondria as a potential target for new radioprotective measures.

A feasibility trial of delayed resection for brain metastases following pre-operative stereotactic radiosurgery

PURPOSE

Pre-operative stereotactic radiosurgery (SRS) for brain metastases (BrM), an emerging alternative to post-operative SRS, is typically performed 1-2 days before resection. However, a longer period of the irradiated tumour in situ may confer anti-tumour immunological benefits. We conducted the first clinical trial to evaluate the feasibility of planned delayed resection after pre-operative SRS.

METHODS

In this single-arm trial, patients with suspected BrM suitable for pre-operative SRS and surgery were eligible. The primary endpoint was feasibility of resection 7-21 days after SRS, with a pre-defined feasibility threshold of 66% receiving this. Secondary endpoints included 6-month adverse events (AE) and local control (LC) rates. Tumour volume change was assessed from SRS- and neurosurgery-planning MRI's.

RESULT

78 patients were screened and the target accrual of 15 patients was met. Common reasons for pre-operative SRS ineligibility were lack of existing cancer diagnosis (44%) and tumour size/peri-tumoural oedema (18%). Two patients declined resection after SRS. The median SRS-to-surgery interval was 8 days (range 0-15). Nine tumours in 8 patients (56%) received delayed resection. Reasons for earlier resection were predominantly non-medical. There were no Grade > 2 AE. The 6-month BrM LC was 100%. At a median follow-up of 13.8 months, the only BrM local failure after SRS and resection occurred with a 0-day SRS-to-surgery interval. No histopathological diagnosis issues were encountered with delayed resection. An increased SRS-to-surgery interval correlated with greater tumour shrinkage.

CONCLUSIONS

The pre-defined feasibility threshold for delayed resection was not met, but more than half of patients received delayed resection without safety concerns.

TRIAL REGISTRATION NUMBER

ACTRN12622001372774 (Registered 26/10/2022).

Defining occult disease in glioblastoma using spectroscopic MRI: implications for clinical target volume delineation

BACKGROUND

Outcomes in glioblastoma are improved by surgical resection and adjuvant radiation (RT). In primary GBM (pGBM), large clinical target volume (CTV) margins typically cover occult invasion. In recurrent GBM (rGBM), RT often uses tiny CTV margins that likely omit occult invasion due to re-RT radiation necrosis concerns. Whole-brain spectroscopic MRI (sMRI) is an emerging technique with similar resolution to PET that may help define the CTV for rGBM.

METHODS

Patients with pGBM (n = 18) and rGBM (n = 19) underwent sMRI with RT simulation. T1-post contrast (T1PC) and T2/FLAIR MRI volumes were contoured. sMRI generated choline/N-acetylaspartate > 2x (Cho/NAA > 2x) volumes are known to correlate with high-risk invasion. Hausdorff distances were calculated to define the margin necessary to cover Cho/NAA > 2x in pGBM and rGBM. In rGBM, mock CTV expansions from T1PC volumes were created to determine non-selective CTV expansion sizes needed to cover Cho/NAA > 2x volumes.

RESULTS

For pGBM, the median T1PC, Cho/NAA > 2x, and T2/FLAIR volumes were 32.3 cc, 45.0 cc, and 74.8 cc respectively. For rGBM, the median T1PC, Cho/NAA > 2x, and T2/FLAIR volumes were 21.7 cc, 58.9 cc, and 118.3 cc, respectively. T2/FLAIR volumes increased more relative to T1PC volumes in rGBM than pGBM (p ≤ 0.001). Meanwhile, the median Hausdorff distance between T1PC and Cho/NAA > 2x was 22.9 mm in pGBM and 25.7 mm in rGBM, suggesting that the high-risk volume does not significantly change. In rGBM, it is common to use no CTV expansion from the T1PC volume which only included 61% of high-risk Cho/NAA > 2x volume. Conversely, T1PC expansions of 10-, 15-, and 20-mm covered 87%, 94%, and 98% of Cho/NAA > 2x volume.

CONCLUSIONS

sMRI Cho/NAA > 2x delineates high-risk occult disease in glioblastoma and extends beyond T1PC MRI borders. Typical large CTV expansions in pGBM mostly include Cho/NAA > 2x volumes. However, small CTV expansions commonly used in rGBM poorly cover Cho/NAA > 2x, suggesting that larger CTV expansions or Cho/NAA > 2x guidance may be of benefit.

T-DM1 with concurrent radiotherapy in HER2-positive breast cancer: preclinical evaluation and mechanisms, prediction, and exploration of adverse effects

Human epidermal growth factor receptor 2 (HER-2) serves as a pivotal target for breast cancer treatment and a vital prognostic marker. Anti-HER-2 therapies, which are integral to the management of HER-2-positive breast cancer, including monoclonal antibodies (e.g., trastuzumab and pertuzumab), tyrosine kinase inhibitors (e.g., lapatinib and pyrotinib), and antibody-drug conjugates (ADCs) such as trastuzumab emtansine (T-DM1). ADCs consist of a monoclonal antibody, a linker, and a cytotoxic payload, engineered to deliver chemotherapy selectively to tumor cells, thereby reducing the systemic toxicity associated with traditional chemotherapy. T-DM1, a HER-2-targeting ADC, combines the humanized anti-HER-2 IgG1 trastuzumab with DM1, a cytotoxic agent that inhibits microtubule formation. T-DM1 has significantly enhanced the prognosis of HER-2-positive breast cancer patients who fail to achieve a pathological complete response or develop distant metastases after neoadjuvant trastuzumab and pertuzumab therapy. While the combination therapy of T-DM1 with radiotherapy demonstrates an acceptable safety profile overall, clinicians should remain vigilant regarding potential severe treatment-related toxicities that have been observed in specific clinical scenarios. Nevertheless, limited research exists regarding the adverse effects and mechanisms of T-DM1 in combination with radiotherapy. This review investigates preclinical studies on the interactions between T-DM1 and radiotherapy, investigates associated adverse effects and their underlying mechanisms, identifies predictive factors and prognostic implications, and explores potential therapeutic strategies involving the concurrent T-DM1 with radiotherapy.

Development of a recursive partitioning analysis for prediction of radiation necrosis following single-fraction stereotactic radiosurgery for intact brain metastases

PURPOSE/OBJECTIVE

Radiation necrosis (RN) is a potential complication after stereotactic radiosurgery (SRS) for brain metastases. This study develops a recursive partitioning analysis (RPA) to identify patients at risk for RN following SRS.

METHODS

Patients who underwent single-fraction SRS for intact brain metastases at a single institution from 2017 to 2021 were identified. Cox regression identified factors associated with RN, and variables with p < 0.1 were included in the RPA. Patients with staged SRS, incomplete records, or less than 3 months of follow-up were excluded.

RESULTS

The study included 170 patients with 919 lesions, with median follow-up of 9 months. Primary disease sites were non-small cell lung cancer (NSCLC, 49%), breast cancer (12%), melanoma (11%), renal cancer (6%), and others (22%). Median prescription dose was 24 Gy, and median maximum lesion dimension (MLD) was 0.7 cm. RN occurred in 110 (12.2%) lesions, of which 32 (3.5%) were symptomatic, at median of 4.9 months after SRS. Variables for RPA included primary disease site, tumor location, MLD, prior SRS, number of SRS targets, dosimetry, prior hemorrhage, and concurrent systemic therapy. RPA identified four groups: Group 1 (MLD ≤ 0.8 cm, non-breast/NSCLC/renal), Group 2 (MLD ≤ 0.8 cm, breast/NSCLC/renal), Group 3 (MLD > 0.8 cm, no post-SRS hemorrhage), and Group 4 (MLD > 0.8 cm, post-SRS hemorrhage). Two-year RN free survival was 99% (Group 1), 89% (Group 2), 70% (Group 3), and 52% (Group 4).

CONCLUSION

This is the first RPA model for RN after single-fraction SRS, which may aid in risk assessment and distinguishing RN from tumor progression.

Stereotactic radiosurgery for patients with brain metastases: current principles, expanding indications and opportunities for multidisciplinary care

The management of brain metastases is challenging and should ideally be coordinated through a multidisciplinary approach. Stereotactic radiosurgery (SRS) has been the cornerstone of management for most patients with oligometastatic central nervous system involvement (one to four brain metastases), and several technological and therapeutic advances over the past decade have broadened the indications for SRS to include polymetastatic central nervous system involvement (>4 brain metastases), preoperative application and fractionated SRS, as well as combinatorial approaches with targeted therapy and immune-checkpoint inhibitors. For example, improved imaging and frameless head-immobilization technologies have facilitated fractionated SRS for large brain metastases or postsurgical cavities, or lesions in proximity to organs at risk. However, these opportunities come with new challenges and questions, including the implications of tumour histology as well as the role and sequencing of concurrent systemic treatments. In this Review, we discuss these advances and associated challenges in the context of ongoing clinical trials, with insights from a global group of experts, including recommendations for current clinical practice and future investigations. The updates provided herein are meaningful for all practitioners in clinical oncology.

Analysis of the impact of rotation error on PTV margins in multiple brain metastases fractionated stereotactic radiotherapy based on single-isocenter multi-target technique

Background

Rotational error cannot be overlooked in single-isocenter multi-target (SIMT) stereotactic radiotherapy. This retrospective study aimed to evaluate the treatment accuracy of linear accelerator-based fractionated stereotactic radiotherapy (FSRT) using SIMT non-coplanar volumetric modulated arc therapy (VMAT) in patients with multiple brain metastases. We explored the impact of rotational error on planning target volume (PTV) margins, providing clinical evidence for the selection of appropriate PTV margin values.

Methods

A total of 161 patients with multiple brain metastases (733 treatments; actual clinical PTV margins ranged from 1~2 mm) were included. Theoretical PTV margins were calculated based on the Van Herk and Jenghwa Chang formulas. We analyzed the influence of the distance from each target to the treatment isocenter, rotational errors, and PTV margin on treatment outcomes. Additionally, individualized PTV margins for each patient were calculated using the Jenghwa Chang formula and patients were divided into subgroups according to a 2-mm threshold for further analysis.

Results

The mean residual translational setup errors ranged from -0.04~0.01 mm, and rotational setup errors ranged from 0.15°~0.49°, both within acceptable limits. According to the Van Herk formula, required margins in posterior-anterior, superior-inferior, and right-left directions were 1.44 mm, 1.68 mm, and 1.78 mm, respectively. By incorporating both translational and rotational errors using the Jenghwa Chang formula, the comprehensive margin ranged from 1.69~1.79 mm (calculated based on the 95% confidence interval of distances from targets to isocenter). Additionally, when the mean distance from all targets to their respective treatment isocenters was 30.62 mm, the required margin calculated solely for translational errors using the Jenghwa Chang formula was 1.23 mm; if rotational errors were neglected, target coverage probability would decrease from 95% to 73%. Further subgroup analysis showed that 25 patients whose individualized theoretical margins exceeded 2 mm tended to experience worse outcomes compared to others, including intracranial local failure (ILF, defined as lesion progression within the previously irradiated intracranial region during follow-up; 32.00% vs. 22.29%, P = 0.32), one-year local control (64.00% vs. 65.44%, P = 0.89), and one-year intracranial progression-free survival (iPFS, 44.00% vs. 51.45%, P = 0.85). However, these differences did not reach statistical significance.

Conclusion

This study confirms that the SIMT non-coplanar VMAT technique ensures treatment accuracy for FSRT in multiple brain metastases. Rotational errors reduce dose coverage, and a minimum safety margin of 1.79 mm is recommended to ensure tumor coverage and reduce local failure, providing a basis for future treatment optimization.

Post-operative hypofractionated stereotactic radiotherapy for brain metastases from lung and breast cancer in patients without prior WBRT: a retrospective dose escalation study

This study investigated hypofractionated stereotactic radiotherapy (HSRT) for resected brain metastases and how the dose-fractionation affects local control (LC) and radionecrosis (RN). We retrospectively evaluated patients with brain metastases who were treated between 2010 and 2023. Post-operative HSRT was delivered in three or five fractions. The primary objective was to determine the effect of dose escalation and fractionation on LC. Secondary objectives included identifying factors associated with RN. Statistical analyses were conducted using Chi-square or Fisher's exact tests for categorical data and Mann-Whitney U tests for continuous variables (significance level: p < 0.05). After a median follow-up of 19 months, 34 patients out of 212 (16%) had local recurrence. A biologically effective dose (BED10) > 28.8 Gy was associated with better LC (p = 0.002), but no benefit was found for a BED10 > 48 Gy. RN developed in 34 patients (16%). A prescription BED10 > 48 Gy was associated with an increased incidence of symptomatic RN (p = 0.002). For HSRT in three fractions, a CTV D99% ≥ 29 Gy significantly improved the LC (p = 0.04), and V30Gy, V23.1 Gy, and V18Gy were significantly associated with an increased risk of RN. The fractionation was not found to affect the LC or RN. This large, retrospective cohort study on post-operative HSRT indicates that a BED10 of 40.9-48 Gy (3 × 7,7 Gy or 5 × 6 Gy) to the planning target volume results in excellent LC while limiting the risk of RN. No difference in LC or RN was found for different fractionations.

Immune Modulation Through Stereotactic Radiotherapy: The Role of TBX21, GATA-3, FoxP3, and RORɣt

Background and Objectives: Stereotactic radiotherapy enhances local tumor control by delivering high doses directly to the tumor. It is thought to activate the immune system via T-cells, possibly creating a systemic response. This study aims to evaluate stereotactic body radiotherapy's (SBRT) impact on the immune system by measuring T-cell transcription factors, such as TBX21, GATA-3, FoxP3, and RORɣt. Materials and Methods: Peripheral blood samples were collected from 103 patients before SBRT and from 66 patients two months post-treatment. We measured transcription factors TBX21, GATA-3, FOXP3, and RORγt using ELISA, and performed a complete blood count and C-reactive protein analysis to rule out infections. Statistical analyses included paired t-tests and correlation analyses to assess changes before and after treatment. Results: Post-treatment, significant reductions were observed in TBX21 (Th1), GATA-3 (Th2), and FOXP3 (Treg), while RORɣt (Th17) remained stable but trended higher in lung cancer patients. No correlations were found with demographic factors. However, TBX21 levels were significantly related to the planning target volume (PTV) and biologically effective dose (BED10) in the lung region. Larger PTVs (≥16.5 cc) and higher BED10 doses (≥100 Gy) were linked to smaller reductions in TBX21 (p = 0.008, p = 0.04) and increased RORɣt levels (p = 0.01). Conclusions: Stereotactic radiotherapy reduces immunosuppressive markers like FOXP3 and GATA-3, indicating its potential to boost immune activation by suppressing Treg and Th2 cells. Larger target volumes and higher BED10 values may enhance Th1 responses through TBX21. These findings suggest that SBRT activates the immune system, and its combination with immunotherapy could be promising.

Phase 1/2 Dose Escalation Trial of 3-Fraction Stereotactic Radiosurgery for Resection Cavities from Large Brain Metastases

PURPOSE

We performed a dose escalation trial of hypofractionated stereotactic radiosurgery (SRS) to determine the maximum tolerated dose (MTD) of 3-fraction SRS for brain metastases resection cavities.

METHODS AND MATERIALS

Following surgical resection of a brain metastasis, patients were enrolled by SRS treatment volume onto 2 arms: arm 1 = 4.2-14.1 cm3, approximating a 2 to 3 cm diameter sphere, and arm 2 = 14.2-33.5 cm3 or a 3 to 4 cm sphere equivalent. Dose escalation levels were 24, 27, 30, and 33 Gy in 3 consecutive-day fractions, with 6 patients at each dose level in a 6 + 6 trial design. Dose-limiting toxicity was defined as either acute (within 30 days of SRS) grade 3 to 5 central nervous system toxicity and/or late grade 3 to 5 radiation necrosis occurring at any subsequent timepoint. The MTD was defined as the highest dose where 0 to 1 out of 6 or 0 to 3 out of 12 had a dose-limiting toxicity.

RESULTS

From 2009 to 2014, 48 evaluable patients were enrolled. One (2%) patient had acute G3 toxicity; dose escalation proceeded to 33 Gy. No MTD was reached. Overall, 14 (29%) of 48 patients had G1-4 late radiation necrosis; G1 in 4 (8%), G2 in 6 (13%), G3 in 2 (4%), and G4 in 2 (4%). At the 33 Gy dose level, any grade necrosis was 58% in all 12 patients, 83% in the 6 patients on the larger volume arm 2; no G3-4 necrosis occurred in smaller arm 1 targets. With a median overall survival of 24 months (95% CI, 18-35), the 1-year cumulative incidence rates were: 10% (95% CI, 3.8-21) for local progression, 48% (95% CI, 33-61) for distant intracranial progression, and 13% (95% CI, 5-24) for radiation necrosis. Nodular meningeal disease occurred in 15% (7 of 48) of patients.

CONCLUSIONS

Grade 3 to 4 toxicity was 8% and no MTD was reached with dose escalation to 33 Gy in 3 fractions. However, with a 58% incidence of G1-4 radiation necrosis at the 33 Gy level and 33% G3-4 necrosis at 30 Gy on arm 2, a 3-fraction dose of 27-30 Gy for targets 2 to 3 cm and 27 Gy for targets 3 to 4 cm may provide the optimal balance between toxicity and tumor control. A dose of 33 Gy is reserved for cavities <3 cm where tumor control may benefit from higher doses.

Multidisciplinary management strategies for recurrent brain metastasis after prior radiotherapy: An overview

As cancer patients with intracranial metastatic disease experience increasingly prolonged survival, the diagnosis and management of recurrent brain metastasis pose significant challenges in clinical practice. Prior to deciding upon a management strategy, it is necessary to ascertain whether patients have recurrent/progressive disease vs adverse radiation effect, classify the recurrence as local or distant in the brain, evaluate the extent of intracranial disease (size, number and location of lesions, and brain metastasis velocity), the status of extracranial disease, and enumerate the interval from the last intracranially directed intervention to disease recurrence. A spectrum of salvage local treatment options includes surgery (resection and laser interstitial thermal therapy [LITT]) with or without adjuvant radiotherapy in the forms of external beam radiotherapy, intraoperative radiotherapy, or brachytherapy. Nonoperative salvage local treatments also range from single fraction and fractionated stereotactic radiosurgery (SRS/FSRS) to whole brain radiation therapy (WBRT). Optimal integration of systemic therapies, preferably with central nervous system (CNS) activity, may also require reinterrogation of brain metastasis tissue to identify actionable molecular alterations specific to intracranial progressive disease. Ultimately, the selection of the appropriate management approach necessitates a sophisticated understanding of patient, tumor, and prior treatment-related factors and is often multimodal; hence, interdisciplinary evaluation for such patients is indispensable.

Precision radiotherapy with molecular-profiling of CNS tumours

Diagnoses of CNS malignancies in the primary and metastatic setting have significantly advanced in the last decade with the advent of molecular pathology. Using a combination of immunohistochemistry, next-generation sequencing, and methylation profiling integrated with traditional histopathology, patient prognosis and disease characteristics can be understood to a much greater extent. This has recently manifested in predicting response to targeted drug therapies that are redefining management practices of CNS tumours. Radiotherapy, along with surgery, still remains an integral part of treating the majority of CNS tumours. However, the rapid advances in CNS molecular diagnostics have not yet been effectively translated into improving CNS radiotherapy. We explore several promising strategies under development to integrate molecular oncology into radiotherapy, and explore future directions that can serve to use molecular diagnostics to personalize radiotherapy. Evolving the management of CNS tumours with molecular profiling will be integral to supporting the future of precision radiotherapy.

Single- versus multi-fraction spine stereotactic radiosurgery (ALL-STAR) for patients with spinal metastases: a randomized phase III trial protocol

BACKGROUND

For patients with spine metastases, stereotactic radiosurgery (SRS) provides excellent local control and pain response. Despite increasing use of this treatment modality, there is no consensus on the optimal dose and fractionation of spine SRS for efficacy and toxicity. We have initiated a single-center phase III randomized trial that compares two dose regimens with similar biological equivalent dose (BED) to determine the isolated effect of SRS fractionation on local control.

METHODS

Patients with one to three cervical, thoracic, or lumbar spine metastases spanning no more than two contiguous vertebral levels in need of radiation will be eligible for enrollment. Patients will be assigned 1:1 to receive either 22 Gy in 1 fraction or 28 Gy in 2 fractions. Biased coin randomization will be used to randomly assign patients while balancing the following stratifying variables between the two treatment arms at baseline: gastrointestinal histology (yes/no), paraspinal tissue extension (yes/no), epidural compression (low-/high-grade), and number of sites treated (one to three). The primary endpoint is one-year local control, defined per Spine Response Assessment in Neuro-Oncology (SPINO) criteria. The secondary endpoints include patient-reported health-related quality of life (HRQOL), pain associated with the treated site, vertebral compression fracture (VCF), and two-year local control. Patients will be followed for these outcomes at one to two weeks, one month, three months, and six months after treatment, and every six months thereafter until 24 months after treatment. While on the study, patients will receive routine co-interventions as clinically indicated.

DISCUSSION

The studies published thus far comparing the single- and multi-fraction SRS are lacking long-term local control outcomes and are limited by selection bias as well as single-fraction arms with higher BED, which is correlated with improved local control. Our study will isolate the effect of fractionation by comparing one-year local control in patients treated with single- and multi-fraction SRS with equivalent BED. We anticipate that the results of this, as well as secondary endpoints such as pain response, adverse effects, and quality of life will provide much-needed guidance regarding optimal dose and fractionation for both maximizing local control and minimizing toxicity.

CLINICAL TRIAL INFORMATION

NCT#06173401. Approved by Stanford Scientific Review Committee (study ID: BRN0060) on 9/12/2023 and Stanford Institutional Review Board (study ID: IRB-72248) on 11/14/2023.

Brain metastases from lung cancer: recent advances and novel therapeutic opportunities

Metastatic intracranial progression drastically impacts prognosis, therapeutic considerations and quality of life. The increasing incidence of lung cancer patients developing brain metastases (BM) parallels the incorporation of more effective systemic agents and improved surveillance. Our evolving knowledge of BM pathophysiology, along with advancements in surgical, radiotherapy and systemic therapy options, is rapidly changing prognostication and treatment paradigms. Optimal management of BM in the modern era is patient-specific, dependent on performance status, comorbidities, intracranial and extracranial disease burden, leptomeningeal disease, and the presence of targetable mutations. The purpose of this review is to provide a detailed overview of the detection, prognostication, and multidisciplinary, management of BM arising from non-small cell lung cancer and small cell lung cancer. We discuss contemporary evidence and active clinical trials supporting a wide array of treatment options, including surgery, radiosurgery, memory-avoidance whole brain radiation, craniospinal irradiation, chemotherapy, targeted agents and immunotherapy. Multidisciplinary paradigms will continue to evolve as currently accruing randomized trials evaluating these promising treatments options mature.

Outcomes of Patients With Five or More Brain Metastases Treated With Stereotactic Radiosurgery From 2014 to 2019: A UK Series

AIMS

Treatment with stereotactic radiosurgery/radiotherapy (SRS/SRT) is standard practice in selected patients with small numbers of brain metastases (BMs). It is less accepted in those with ≥5 BMs, due to the lack of a prospective evidence base. While randomised trials are ongoing, we present the experience of a single UK cancer centre in using SRS/SRT for patients with 5 or more BMs without whole brain radiotherapy (WBRT).

MATERIALS AND METHODS

Patients undergoing treatment at a single centre between 2014 and 2019 were prospectively identified. All follow-up imaging was reviewed to identify any evidence of local failure or distant brain progression, which was analysed using a death-censored approach.

RESULTS

A total of N = 88 patients were included, with a median of seven BMs (range: 5-37). Post-SRS/SRT toxicity events occurred in 42%, most commonly reliance on steroids for ≥4 weeks (36% of the cohort). Median survival was 10 months, with median freedom from local failure and distant brain progression of 12 and 8 months, respectively; none of these outcomes differed significantly by the number of BMs. Brain-directed salvage treatment was required after a median of 21 months, and was not significantly associated with the number of BMs.

CONCLUSION

SRS/SRT alone may have a role in the management of selected patients with multiple BMs. Since the number of BMs were not significantly associated with overall survival or disease control, the National Health Service (NHS) commissioning criteria should continue to be based on tumour volume.

Feasibility Study of Detecting and Segmenting Small Brain Tumors in a Small MRI Dataset with Self-Supervised Learning

Objectives: This paper studies the segmentation and detection of small metastatic brain tumors. This study aims to evaluate the feasibility of training a deep neural network for the segmentation and detection of metastatic brain tumors in MRI using a very small dataset of 33 cases, by leveraging large public datasets of primary tumors; Methods: This study explores various methods, including supervised learning, two transfer learning approaches, and self-supervised learning, utilizing U-net and Swin UNETR models; Results: The self-supervised learning approach utilizing the Swin UNETR model yielded the best performance. The Dice score for small brain tumors was approximately 0.19. Sensitivity reached 100%, while specificity was 54.5%. When excluding subjects with hyperintensities, the specificity improved to 80.0%; Conclusions: It is feasible to train a model using self-supervised learning and a small dataset for the segmentation and detection of small brain tumors.

Stereotactic aspiration alone or Ommaya placement and aspiration followed by stereotactic radiosurgery for cystic brain metastasis: A systematic review and meta-analysis

Introduction

Cystic brain metastases (BMs) are often more challenging to treat than solid BMs. Stereotactic cyst aspiration for volume reduction followed by stereotactic radiosurgery (SRS) is an alternative treatment modality that may benefit patients with large cystic BMs not favorable for SRS alone nor microsurgical resection.

Research question

Here, we perform a systematic review and meta-analysis of stereotactic aspiration alone or reservoir (Ommaya) placement plus aspiration followed by SRS for cystic BMs.

Material and methods

Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we reviewed articles published between 1968 and December 31-th, 2022. We retained 10 studies reporting 280 patients.

Results

Overall rate of tumor control for combined treatment of Ommaya placement plus aspiration plus SRS was 81.2% (62.5-99.9%, p < 0.001) and for stereotactic aspiration plus SRS was 64.7% (46.1-83.3%, p < 0.001). Overall rate of further intervention for combined treatment of Ommaya placement plus aspiration plus SRS was 15.8% (p = 0.08) and for stereotactic aspiration plus SRS was 14.8% (5.3-24.4%, p = 0.002). Overall complication rate for combined treatment of Ommaya placement plus aspiration plus SRS was 12.8% (2.3-23.3%, p = 0.01) and for stereotactic aspiration plus SRS was 1.5% (p = 0.12).

Discussion and conclusion

Combined treatment of Ommaya placement plus cyst aspiration plus SRS in cystic BMs yields better local control as compared to stereotactic aspiration plus SRS, with similar rate of further intervention between procedures. Aspiration of the cyst plus SRS should be considered for patients with cystic metastases not able to undergo open surgery or upfront SRS.

Preoperative versus postoperative stereotactic radiosurgery for brain metastases: a systematic review and meta-analysis of comparative studies

Resection is often the primary treatment for large brain tumors but is less practical for multiple brain metastases (BM). Current guidelines recommend stereotactic radiosurgery (SRS) for untreated BMs or following the surgical removal of a solitary BM to reduce the risk of local tumor recurrence. Preoperative SRS (pre-SRS) shows promise with fewer complications and more precise targeting, but it lacks tissue diagnosis and may hinder wound healing. This study aims to compare the safety and efficacy of pre-SRS and postoperative SRS (post-SRS) for BM treatment. A comprehensive literature search was conducted in PubMed, Embase, Scopus, and Cochrane Library. Studies were selected based on PICO criteria, including patients with metastatic intracranial lesions undergoing preoperative or postoperative radiosurgery. Data related to outcomes and complications were extracted. Meta-analysis was performed, employing the fixed effect model due to study design similarities and limited patient numbers. Four studies encompassing 616 BM patients (221 preoperative, 405 postoperative) were included. Patient characteristics, including age, gender, cancer source, and lesion location, were similar between groups. Radiosurgery modalities included LINAC and Gamma Knife, with hypofractionated treatments more common postoperatively. Outcomes showed comparable overall survival (p = 0.07), local failure (p = 0.26), and distant failure rates (p = 0.84) between groups. The preoperative group had lower risks of radiation necrosis (p = 0.02) and leptomeningeal disease (p = 0.03) in 1-year follow-up, with significantly better composite outcomes (p = 0.04). No significant difference in wound issues was observed (p = 0.98). This review reveals pre- and post-SRS for BM have similar outcomes for LF, DF, and OS. Pre-SRS potentially lowers RN and LMD risks, with better tumor targeting and less radiation to healthy tissue, while post-SRS targets residual disease but with higher complication risks. Future research should optimize SRS protocols.

Treatment Outcome of Brain Metastases from Breast Cancer Following Gamma Knife Radiosurgery: A Retrospective Study in Vietnam

BackgroundGamma Knife radiosurgery has proven to be highly effective for small brain lesions and those with a limited number of metastases. This study aimed to evaluate the treatment outcome of Gamma Knife radiosurgery in Vietnamese breast cancer patients with brain metastasis.MethodsThis retrospective descriptive study included 75 patients treated between January 2019 and December 2023. Eligible patients had 1 to 5 brain lesions ≤ 3 cm, a Karnofsky Performance Status (KPS) score of ≥ 60, and no prior whole-brain radiotherapy or brain tumor resection. Clinical characteristics were documented, and imaging responses were evaluated using RECIST criteria. Overall survival (OS), brain-specific progression-free survival (BSPFS), and overall response rates were analyzed using Kaplan-Meier survival curves and Cox regression.ResultsSeventy-five patients were included in the study, with a median follow-up time of 15.9 months. The median age was 53.0 years (range: 29-73 years), and 39 patients (52%) were HER2-positive. The median total tumor volume per patient was 3.78 cm3. A total of 152 brain tumors were identified, of which 131 (86.2%) were <2 cm in diameter, 36 patients (48.0%) had a single lesion. The intracranial tumor control rates were 96% at 3 months and 92.5% at 6 months. The median overall survival (OS) was 17.2 months (range: 13.7-20.7 months). Multivariate analysis revealed that the total volume of metastatic lesions ≤7.0 cm3, hormone receptor negativity, ≤ 3 lines of systemic treatment before brain metastasis and controlled extracranial metastases were correlated with both BSPFS and OS.ConclusionGamma Knife radiosurgery is an effective treatment for limited brain metastases, demonstrating a high rate of local control over brain lesions, which contributed to the promising survival outcome in Vietnamese breast cancer patients.

Association between tumor location and toxicity outcomes after stereotactic radiosurgery for brain metastases

PURPOSE

Toxicities associated with stereotactic radiosurgery (SRS) are important when considering treatment and supportive management for patients with brain metastases. We herein assessed the association between brain metastasis location and risk of toxicity after SRS.

METHODS

We conducted a retrospective institutional review of patients treated with SRS for brain metastases between 2008 and 2023. Outcomes included radiation necrosis, seizure, local failure, and overall survival (OS).

RESULTS

We reviewed 215 patients treated to 605 metastases (median diameter 10 mm, IQR 5-17 mm), in the frontal (34%), cerebellar (19%), parietal (16%), temporal (13%), and occipital (13%) regions. Median follow-up was 16 months (IQR 7-36). New-onset seizures developed in 11% (19/174) of patients without prior seizure and was higher in patients with motor or sensory cortex lesions (12/48, 25%) on multivariate analysis (MVA, P = 0.02). SRS-related grade ≥ 2 symptomatic radionecrosis occurred in 6% (33/605) of lesions and correlated with larger metastasis volume (P < 0.001) and renal cell carcinoma histology (P < 0.05), while supratentorial location was nearly significant (MVA, P = 0.06). Median OS across all patients was 16 months (95% CI 12-20). Patients with symptomatic radiation necrosis had a longer median survival compared to those who did not (43 vs. 14 months, P = 0.002), which remained significant alongside Karnofsky performance status and extracranial disease on MVA.

CONCLUSION

Brain metastasis location in the motor or sensory cortex is associated with increased risk of new-onset seizure following SRS and may warrant consideration of steroid and/or anti-epileptic prophylaxis. Symptomatic radiation necrosis is uncommon in the cerebellum and may be increasing with improvements in survival.

Clinical Outcomes and Relevance of Composite V12 Gy in Patients With Four or More Brain Metastases Treated With Single Fraction Stereotactic Radiosurgery

AIMS

Tissue V12Gy (total brain volume receiving 12Gy including target) can predict for late toxicity in single target benign disease treated with stereotactic radiosurgery (SRS). The value of this metric remains uncertain for multiple brain metastases. This retrospective cohort study reports the outcomes and evaluates the predictors of toxicity in patients with four or more brain metastases treated with single-fraction SRS.

MATERIALS AND METHODS

Two hundred twenty-six patients with 2160 metastases treated from 2014-21 were retrospectively studied. Symptomatic late toxicity (new/progressive neurological symptoms ≥3 months post SRS) with magnetic resonance imaging (MRI) changes suggestive of treatment effect were analysed. Kaplan-Meier and competing risk analysis was used to assess survival and toxicity respectively.

RESULTS

median number of metastases/patient was 6 (range: 4-41) and median composite tissue V12Gy (inclusive of planning target volume (PTV)) was 11.3 cc (IQR: 6.1 cc-17.1 cc). Sixteen out of the 226 patients developed symptomatic late radiation adverse event (R-AE), and the cumulative incidence was 4.9% at 1 year and 6.9% at 2 years. The total target volume was significantly predictive of the risk of late R-AE. Volume of the largest lesion, V12Gy and V15Gy did not predict for late R-AE, but plotted graphs showed suggestions of linear relationships between dosimetric parameters and late R-AE.

CONCLUSION

Within the limitations of this study, the cumulative incidence of symptomatic toxicity remains acceptable despite routinely accepting a composite tissue V12Gy in excess of 10 cc to treat multiple brain metastases.

ADVANCES IN KNOWLEDGE

V12Gy has limitations as a plan quality metric in multiple brain metastases treated with SRS. There is insufficient evidence to have a defined target limit as <10 cc.

Evaluation of Anti-Angiogenic Therapy Combined with Immunotherapy and Chemotherapy as a Strategy to Treat Locally Advanced and Metastatic Non-Small-Cell Lung Cancer

Immunotherapy has made recent improvements in disease-free survival (DFS) and/or overall survival (OS) in all stages of non-small-cell lung cancer (NSCLC). Here, we review the tumor microenvironment and its immunosuppressive effects and discuss how anti-angiogenic therapies may potentiate the anti-carcinogenic effects of immunotherapy. We also review all the past literature and discuss strategies of combining anti-angiogenic therapy and immunotherapy +/- chemotherapy and hypothesize how we can use this strategy for non-small-cell lung cancer in metastatic previously untreated/previously treated settings in previously treated EGFR-mutated NSCLC for the upfront treatment of brain metastases prior to radiation therapy and for the incorporation of this strategy into stage III unresectable disease. We assert the use of anti-angiogenic therapy and immunotherapy when combined appropriately with chemotherapy and radiotherapy has the potential to increase the long-term survivals in both the stage III and metastatic setting so that we can now consider more patients to experience curative treatment.

How safe and effective is irradiating radiation-induced meningiomas? Single-center experience in primary and salvage Gamma-Knife Radiosurgery, systematic review, and metanalysis of current evidence on the topic

This is a single-center experience and metanalysis of the safety and efficacy measures of Gamma-knife stereotactic radiosurgery (SRS-GK) for radiation-induced meningiomas (RIMs). This study comprised a single-center analysis of SRS-GK for RIMs at IRCCS San Raffaele Hospital, Milan, Italy, and a systematic literature review and meta-analysis to address the actuarial local control (LC), distant control (DC), progression-free survival (PFS), and toxicity. The original series comprised 13 patients harboring 30 RIMs. Partial response was observed in 26 %, stability in 52 %, and progression in 22 %. The 5-year LC and DC rates were 71 % and 67 %. One patient developed radionecrosis, and an additional 2 presented edema. Metanalysis comprised 4 papers and data from the original series, comprising 146 patients and 308 RIMs. The 5-year LC was 84 %, the DC 67 %, and radionecrosis in 1.4 %. SRS-GK has an efficacy profile falling between that observed for radiologically suspected sporadic meningiomas and confirmed higher-grade lesions.

Multi-institutional report of trastuzumab deruxtecan and stereotactic radiosurgery for HER2 positive and HER2-low breast cancer brain metastases

Trastuzumab-deruxtecan (T-DXd) has demonstrated intracranial efficacy; however, safety and efficacy data remains limited with stereotactic radiosurgery (SRS). A multi-institutional review was performed with HER2+ or HER2-low metastatic breast cancer treated with T-DXd and SRS for active brain metastases. We identified 215 lesions treated over 48 SRS courses in 34 patients. Median follow up from T-DXd initiation was 13.9 months. The cumulative incidence of symptomatic radiation necrosis at 24 months per lesion was 2.1% and per patient 11%. The 12-month LC was 97%. HER2-low was associated with worse distant intracranial control (DIC) (adjusted HR 2.5, 95% CI 1.1-5.6, p = 0.03) and worse systemic progression free survival (PFS) (HR 4.1, 95% CI 1.6-10.7, p = 0.004). Concurrent SRS and T-DXd has excellent local control, without an increased risk of radiation necrosis. HER2-low disease is associated with worse systemic PFS and DIC with T-DXd compared to HER2+.

Analysis of linear accelerator-based fractionated stereotactic radiotherapy in brain metastases: efficacy, safety, and dose tolerances

Objective

To assess the efficacy and safety of linear accelerator-based fractionated stereotactic radiotherapy (LINAC-FSRT) in patients with brain metastases (BM).

Methods

We retrospectively analyzed 214 patients treated with LINAC-FSRT, categorized based on biologically effective dose (BED10, α/β = 10) into two groups (≤55 Gy, >55 Gy). Stratified analyses were conducted based on targeted therapy to compare survival outcomes. To examine brain tissue dose-tolerance volume, patients were divided into two groups: the standard Hypofractionated Treatment Effects in the Clinic (HyTEC) protocol group and an adjusted HyTEC protocol group where dose-volume restrictions exclude the planning target volume (PTV).

Results

Results as of December 2023 showed median intracranial progression-free survival (iPFS) at 12.4 months, with median overall survival (OS) not reached and a one-year local control (LC) rate of 68.7%. Mild to moderate toxicity affected 17.3% of patients, while severe toxicity occurred in 2.8%. Multivariate Cox analysis indicated that uncontrolled extracranial disease significantly reduced iPFS (HR = 2.692, 95%CI:1.880-3.853, P < 0.001) and OS (HR = 3.063, 95%CI:1.987-4.722, P < 0.001). BED10 >55 Gy (HR = 0.656, 95%CI:0.431-0.998, P = 0.049) improved OS, showing statistical significance (P = 0.037) without affecting iPFS or CNS toxicity (P = 0.127, P = 0.091). Stratified analysis highlighted nearly significant OS improvements with high-dose FSRT and targeted therapy (P = 0.054), while concurrent therapy markedly enhanced iPFS (P = 0.027). No significant differences were observed in intracranial local failure (ILF-which represents progression in previously treated areas during follow-up), one-year LC rates, iPFS, or OS between dose-volume groups. Adjusting HyTEC volume restrictions did not significantly increase CNS adverse reactions (P = 0.889).

Conclusions

LINAC-FSRT is safe and effective in BM. BED10>55 Gy notably enhances OS post-LINAC-FSRT and may benefit LC. High BED10 FSRT with targeted therapy likely boosts synergy, and concurrent targeted therapy significantly improves iPFS. Diminishing dose volume constraints at different fractions based on the HyTEC guidelines is feasible.

The safety and efficacy of stereotactic radiosurgery in patients with gastrointestinal cancer brain metastasis: a systematic review and meta-analysis

Central nervous system Tumors, including metastasis, are a considerable source of morbidity and mortality. Currently, treatment options such as surgery, radiotherapy, and chemotherapy have been introduced to prevent the progression of the disease, but still, these patients do not have a good prognosis. Stereotactic radiosurgery (SRS) reduces the damage to the surroundings by focusing the radiation on the tumor tissue. In this paper, we aim to investigate the outcomes of SRS on patients with gastrointestinal-originated brain metastases. A systematic review and meta-analysis used the PRISMA guideline from inception until 27th March 2024, utilizing the relevant key terms. Records were screened and included based on pre-defined inclusion and exclusion criteria. Demanding data was extracted and analyzed using STATA v. 17. This meta-analysis of 29 studies examining SRS for brain metastases from gastrointestinal cancers revealed several significant findings. The pooled distant intracranial disease rate was 33% (95% CI: 0.21-0.45). Local tumor control rates were high, with an overall pooled rate of 88% (95% CI: 0.83-0.92). Survival outcomes showed a 6-month overall survival (OS) rate of 47% (95% CI: 0.42-0.52), decreasing to 32% at one year and 11% at two years. The 5-year OS rate was 2% (95% CI: 0.01-0.03). Subgroup analyses revealed variations in outcomes based on primary tumor site, with gastric cancer patients showing better short-term survival (73% at six months) compared to hepatic primaries (31% at six months). The 6-month progression-free survival (PFS) rate was 67% (95% CI: 0.12-1.22). Tumor control outcomes showed complete regression in 11% of cases, partial regression in 44%, stable disease in 30%, and progression in 20%. The overall mortality rate was 84% (95% CI: 0.75-0.93). This meta-analysis supports the efficacy of SRS in managing brain metastases from gastrointestinal cancers. SRS offers effective local control and may improve quality of life despite poor long-term outcomes. The high rates of distant intracranial progression underscore the need for comprehensive management strategies addressing both local and systemic disease. Future research should optimize patient selection, combine SRS with novel systemic therapies, and identify predictive biomarkers to improve outcomes in this challenging patient population.

Immunotherapy benefits for large brain metastases in non-small cell lung cancer

INTRODUCTION

Non-small cell lung cancer (NSCLC) patients with large brain metastases (BrM) defined as >2 cm in diameter historically face grim prognoses. With immunotherapy emerging as a promising avenue for BrM management and being commonly used in NSCLC, its application in addressing large BrM remains underexplored.

METHODS

This retrospective study conducted across the MedStar Georgetown Cancer Network aimed to assess the efficacy of immunotherapy in non-biomarker driven NSCLC patients with large BrM following initial treatment.

RESULTS

Thirty-six patients were included, all of whom underwent neurosurgery and/or radiation before commencing immunotherapy. The median intracranial progression-free survival (PFS) was 9.2 months and the median overall survival (OS) reached 31 months. Utilizing multivariable Cox penalized regression, the intracranial PFS hazard ratio (HR) was 0.07 (95% confidence interval (CI), 0.02-0.26) for patients who received at least 90 days of immunotherapy compared to those who did not. Each additional 30 days of immunotherapy was associated with an OS HR 0.77 (95% CI, 0.67-0.90).

CONCLUSION

This real-world data highlights the potential of immunotherapy in large BrM NSCLC patients, a population often excluded from clinical trials. This study contributes insights that can inform future treatment approaches, emphasizing the need for further exploration of immunotherapy's role in enhancing outcomes for this challenging patient population.

Advances in the Management of Lung Cancer Brain Metastases

Lung cancer, both non-small cell and small cell, harbors a high propensity for spreading to the central nervous system. Radiation therapy remains the backbone of the management of brain metastases. Recent advances in stereotactic radiosurgery have expanded its indications and ongoing studies seek to elucidate optimal fractionation and coordination with systemic therapies, especially targeted inhibitors with intracranial efficacy. Efforts in whole-brain radiotherapy aim to preserve neurocognition and to investigate the need for prophylactic cranial irradiation. As novel combinatorial strategies are tested and prognostic/predictive biomarkers are identified and tested, the management of brain metastases in lung cancer will become increasingly personalized to optimally balance intracranial efficacy with preserving neurocognitive function and patient values.

Limitations of outcome prediction based on interfractional volume changes of large (≥ 10cm3) brain metastases during fractionated gamma knife radiosurgery

PURPOSE

This study investigated the interfractional volume changes of large (≥ 10 cm3) brain metastases (BMs) during fractionated gamma knife radiosurgery (FGKRS) to assess its predictive value for tumor control outcomes.

METHODS

The patients who underwent FGKRS for large BMs between January 2017 and December 2022 in our center were reviewed. The interfractional volume change was defined as the disparity in tumor volume (TV) measured between the magnetic resonance images acquired on the first treatment day and those obtained after 2 or 3 fractions during the course of FGKRS.

RESULTS

A total of 73 lesions in 70 patients with various primary pathologies were included. Over a median follow-up period of 11 months (range 1-77), the tumor control rate was 63%. Initial TV (cm3) was associated with progression free survival (PFS) and overall survival (OS) in both univariate and multivariate analyses (p = 0.01). Interfractional TV changes revealed an increase in 13 (17.8%) lesions, no change in 14 (19.2%) lesions, and a decrease in 46 (63.0%) lesions, with a mean volume reduction of 5% ± 0.12. Three cut-offs (5%, 10% and 15% volume decrement) were established and patients were divided into two groups based on each reference point. However, there were no significant differences in PFS and OS between the two groups, irrespective of the chosen cut-off value used.

CONCLUSION

Interfractional volume changes of large BMs were not found to be associated with tumor control outcomes. Neither significant interfractional volume reduction nor significant volume increase necessarily predicts the tumor control, making early close monitoring essential after FGKRS.

ACROPath Oligometastases: The American College of Radiation Oncology Clinical Pathway

Radiation oncology is among the most data-driven specialties in medicine. Recently, a wealth of peer-reviewed data has been published supporting the treatment of oligometastatic malignancies, demonstrating improved survival with metastasis-directed therapy, such as stereotactic body radiation therapy (SBRT), when combined with appropriate patient selection and treatment. However, there are currently few, if any, established guidelines that synthesize the abundance of data specific to radiotherapy into a single, easily accessed resource for clinicians. ACROPath® is a major initiative of the American College of Radiation Oncology (ACRO) that aims to present aggregated clinical pathway data in a highly usable format that is readily accessible to clinicians at the point of care in real time. The oligometastases pathway is the first published algorithm in this collection, with additional pathways anticipated in future publications. Clinical radiation oncologists with expertise in the treatment and management of oligometastatic disease were recruited from across ACRO's diverse membership, including both academic and private practice physicians, to ensure a broad-based experience and insight. Individual participants were assigned subsections of the pathway for guideline development, and then, each subsection was presented to the full group for evaluation and consensus development based on published data. Rather than presenting an unstructured set of treatment options, as is common in other treatment guidelines, this initiative aimed to categorize appropriate treatments based on published clinical evidence in a hierarchy further ranked by efficacy, toxicity, and cost. Based on these strata, treatment recommendations were collated and grouped into three rank categories (gold, silver, or bronze) to denote the degree of applicability. The team assembled an interactive document that will eventually be available online, and it is summarized in detail here. Recommendations are grouped both by the anatomic site of metastasis and by the primary tumor type, recognizing that original histology might impact the treatment differently in different anatomic locations. After a review of available published clinical evidence, the committee reached a consensus on all recommendations presented, categorizing each option as gold, silver, or bronze to guide clinicians appropriately. This first iteration of ACROPath® Oligometastases represents one of the few comprehensive clinical decision support tools available for managing patients with limited metastatic disease. It presents available data in a highly accessible, easily used reference, which will be formally reviewed and updated by the committee as frequently as emerging data requires, likely at six- to 12-month intervals.

Effective Personalization of Stereotactic Radiosurgery for Brain Metastases in the Modern Era: Opportunities for Innovation

ABSTRACT

As survival rates improve for patients with metastatic disease, more patients are requiring complex treatment for brain metastases. Stereotactic radiosurgery (SRS) is a conformal radiotherapy technique that allows high ablative dose to be delivered to a specific target and is a standard effective local therapy for the treatment of patients with limited brain metastases. This review highlights the current landscape of SRS treatment in the context of modern therapeutic advances and identifies new research frontiers to personalize SRS and maximize the therapeutic ratio.

Very early symptomatic metastasis pseudoprogression after stereotactic brain radiosurgery in a melanoma patient treated with BRAF/MEK inhibitors: a case report and review of the literature

Introduction

Significant therapeutic changes have recently occurred in the management of melanoma brain metastases (BMs), both in the field of local treatments, with the rise of stereotactic radiotherapy (RT), as well as in systemic ones, with the advent of immunotherapy and targeted therapies (TT). These advances have brought about new challenges, particularly regarding the potential interactions between new TT (notably BRAF/MEK inhibitors) and irradiation. Through a clinical case, we will discuss a side effect not previously described in the literature: ultra-early pseudoprogression (PP) following brain stereotactic radiosurgery (SRS), in a patient treated with dabrafenib-trametinib.

Case presentation

A 61-year-old patient with BRAFV600E-mutated melanoma, receiving second-line dabrafenib-trametinib therapy, was referred for SRS on three progressing meningeal implants, without evidence of systemic progression. Four days after the first RT session (1x6 Gy on a fronto-orbital lesion prescribed 5x6 Gy, and 1x20 Gy single fraction on the other lesions), the patient presented with an epileptic seizure. An MRI, compared to the planning MRI ten days earlier, revealed significant progression of the irradiated lesions. The patient's condition improved with dexamethasone and levetiracetam, and RT was halted out of caution. A follow-up MRI at one month demonstrated a size reduction of all treated lesions. Subsequent imaging at five months revealed further shrinking of the two lesions treated with an ablative dose of 20 Gy, while the under-treated fronto-orbital lesion progressed. These dynamics suggest an initial PP in the three irradiated lesions, followed by good response in the ablatively treated lesions and progression in the partially treated lesion.

Conclusion

To our knowledge, this represents the first documented case of ultra-early PP following brain SRS in a patient receiving concomitant dabrafenib-trametinib. It highlights the need for particular vigilance when using tyrosine kinase inhibitors (TKIs) with SRS, and warrants further research into potential treatment interactions between RT and novel systemic agents, as well as the optimal treatment sequence of melanoma BMs.

Risk of radionecrosis in HER2-positive breast cancer with brain metastasis receiving trastuzumab emtansine (T-DM1) and brain stereotactic radiosurgery

OBJECTIVES

To investigate the potential relationship between trastuzumab emtansine (T-DM1) treatment and radionecrosis induced by brain stereotactic radiosurgery (SRS) in patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer.

MATERIALS AND METHODS

Patients with HER2-positive breast cancer who were diagnosed with brain metastasis and received both SRS and HER2-targeted agents between 2012 and 2022 were retrospectively analyzed. Patients who received T-DM1 within 1 year (either before or after) of SRS were considered as 'T-DM1 exposure (+)'. T-DM1 exposure (-) group had other HER2-targeted agents or received T-DM1 more than 1 year before or after SRS. Symptomatic radionecrosis was defined as Common Terminology Criteria for Adverse Events grade 2 or greater.

RESULTS

A total of 103 patients with 535 treatment sessions were included from seven tertiary medical centers in Korea and Italy. The median follow-up duration was 15.5 months (range 1.1-101.9). By per-patient analysis, T-DM1 exposure (+) group had an increased risk of overall radionecrosis after multivariate analysis (HR 2.71, p = 0.020). Additionally, T-DM1 exposure (+) group was associated with a higher risk of symptomatic radionecrosis compared to T-DM1 exposure (-) patients (HR 4.34, p = 0.030). In per-treatment analysis, T-DM1 exposure (+) was linked to higher incidences of overall (HR 3.13, p = 0.036) and symptomatic radionecrosis (HR 10.4, p = 0.013) after multivariate analysis. A higher prevalence of radionecrosis was observed with T-DM1 exposure (+) and a previous history of whole brain radiotherapy.

CONCLUSION

An increased risk of radionecrosis was observed in patients receiving T-DM1 with brain SRS. Further research is needed to better understand the optimal sequence and interval for administering T-DM1 and SRS.

Preoperative stereotactic radiosurgery for patients with 1-4 brain metastases: A single-arm phase 2 trial outcome analysis (NCT03398694)

Background

Stereotactic radiosurgery (SRS) following surgical resection is the standard of care for patients with symptomatic oligo brain metastasis (BM), however, it is associated with 10-15% local failure. Targeting a resection cavity is imprecise, thus preoperative radiosurgery where the target is well-defined may be superior, however, the efficacy of preoperative SRS has not yet been tested in a clinical trial.

Methods

We conducted a phase 2, single-arm trial of preoperative SRS followed by surgical resection in patients with 1-4 symptomatic oligo BMs (NCT03398694) with the primary objective of measuring 6-month local control (LC). SRS was delivered to all patients utilizing a gamma knife or linear accelerator as per RTOG-9005 dosing criteria [Shaw E, Scott C, Souhami L, et al. Single dose radiosurgical treatment of recurrent previously irradiated primary brain tumors and brain metastases: final report of RTOG protocol 90-05. Int J Radiat Oncol Biol Phys. 2000;47(2):291-298] based on tumor diameter with the exception that the largest lesion diameter treated was 5 cm with 15 Gy with all SRS treatment given in single fraction dosing.

Results

The trial screened 50 patients, 48 patients were treated under the protocol and 32 patients completed the entire follow-up period. Of all the patients who completed the follow-up period, the primary endpoint of 6-month LC was 100% (95% CI: 0.891-1.000; P = .005). Secondary endpoints, presented as medians, were overall survival (17.6 months), progression-free survival (5.3 months), distant in-brain failure (40.8% at 1 year), leptomeningeal failure (4.8% at 1 year), and radiation necrosis (7.7% at 1 year).

Conclusions

Our data confirms superior local control in patients who received preoperative SRS when compared to historical controls. Further study with a larger randomized cohort of patients is warranted to fully understand the benefits of preoperative SRS.

Multifraction stereotactic radiotherapy utilizing inhomogeneous dose distribution for brainstem metastases: a single-center retrospective analysis

Brainstem metastases are challenging to manage owing to the critical neurological structures involved. Although stereotactic radiotherapy (SRT) offers targeted high doses while minimizing damage to adjacent normal tissues, the optimal dose fractionation remains undefined. This study evaluated the efficacy and safety of multifraction SRT with an inhomogeneous dose distribution. This retrospective study included 31 patients who underwent 33 treatments for 35 brainstem lesions using linear accelerator-based multifraction SRT (30 Gy in five fractions, 35 Gy in five fractions or 42 Gy in 10 fractions) with an inhomogeneous dose distribution (median isodose, 51.9%). The outcomes of interest were local failure, toxicity and symptomatic failure. The median follow-up time after brainstem SRT for a lesion was 18.6 months (interquartile range, 10.0-24.3 months; range, 1.8-39.0 months). Grade 2 toxicities were observed in two lesions, and local failure occurred in three lesions. No grade 3 or higher toxicities were observed. The 1-year local and symptomatic failure rates were 8.8 and 16.7%, respectively. Toxicity was observed in two of seven treatments with a gross tumor volume (GTV) greater than 1 cc, whereas no toxicity was observed in treatments with a GTV less than 1 cc. No clear association was observed between the biologically effective dose of the maximum brainstem dose and the occurrence of toxicity. Our findings indicate that multifraction SRT with an inhomogeneous dose distribution offers a favorable balance between local control and toxicity in brainstem metastases. Larger multicenter studies are needed to validate these results and determine the optimal dose fractionation.

Dosimetric and Clinical Prognostic Factors in Single-Isocenter Linac-Based Stereotactic Radiotherapy for Brain Metastases

Background/Objectives: To report on predictive factors in Linac-based SRT for single and multiple BM. Methods: Consecutive patients receiving either one or three fractions of single-isocenter coplanar VMAT SRT were retrospectively included. The GTV-PTV margin was 1-2 mm. The delivered target dose was estimated by recalculating the original plans on roto-translated CT according to errors recorded by post-treatment CBCT. The Kaplan-Meier method estimated local progression-free survival (LPFS), intracranial progression-free survival (IPFS), and overall survival (OS). Log-rank and Wilcoxon-Mann-Whitney tests evaluated inter-group differences, whereas Cox regression analysis assessed prognostic factors. Results: Fifty females and fifty males, with a median age of 69 years, received 107 SRTs. A total of 213 BM (range, 1-10 per treatment) with a median volume of 0.22 cc were irradiated with a median minimum BED of 59.5 Gy. The median delivered GTV D95 reduction was -0.3%. The median follow-up was 11 months. Nineteen LP events and a 1-year LC rate of 90.1% were observed. The GTV coverage did not correlate with LC, while the GTV volume was a risk factor for LP, with the 1-year rate dropping to 73% for volumes ≥ 0.88 cc. The median LPFS, IPFS, and OS were 6, 5, and 7 months, respectively. Multivariate analysis showed that patients with melanoma histology and those receiving a second or subsequent systemic therapy line had the worst outcomes, whereas patients with adenocarcinoma histology and mutations showed better results. Conclusions: The accuracy and efficacy of the Linac-based SRT approach for BM were confirmed, but the dose distribution alone failed to predict the treatment response, suggesting that other factors must be considered to maximize SRT outcomes.

Phase I trial of dose escalation for preoperative stereotactic radiosurgery for patients with large brain metastases

BACKGROUND

Single-session stereotactic radiosurgery (SRS) or surgical resection alone for brain metastases larger than 2 cm results in unsatisfactory local control. We conducted a phase I trial for brain metastases(>2 cm) to determine the safety of preoperative SRS at escalating doses.

METHODS

Radiosurgery dose was escalated at 3 Gy increments for 3 cohorts based on maximum tumor dimension starting at: 18 Gy for >2-3 cm, 15 Gy for >3-4 cm, and 12 Gy for >4-6 cm. Dose-limiting toxicity was defined as grade III or greater acute toxicity.

RESULTS

A total of 35 patients/36 lesions were enrolled. For tumor size >2-3 cm, patients were enrolled up to the second dose level (21 Gy); for >3-4 cm and >4-6 cm cohorts the third dose level (21 and 18 Gy, respectively) was reached. There were 2 DLTs in the >3-4 cm arm at 21 Gy. The maximum tolerated dose of SRS for >2-3 cm was not reached; and was 18 Gy for both >3-4 cm arm and >4-6 cm arm. With a median follow-up of 64.0 months, the 6- and 12-month local control rates were 85.9% and 76.6%, respectively. One patient developed grade 3 radiation necrosis at 5 months. The 2-year rate of leptomeningeal disease (LMD) was 0%.

CONCLUSIONS

Preoperative SRS with dose escalation followed by surgical resection for brain metastases greater than 2 cm in size demonstrates acceptable acute toxicity. The phase II portion of the trial will be conducted at the maximum tolerated SRS doses.

Stereotactic radiosurgery and radiotherapy for brainstem metastases: An international multicenter analysis

Brainstem metastases (BSM) present a significant neuro-oncological challenge, resulting in profound neurological deficits and poor survival outcomes. Stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (FSRT) offer promising therapeutic avenues for BSM despite their precarious location. This international multicenter study investigates the efficacy and safety of SRS and FSRT in 136 patients with 144 BSM treated at nine institutions from 2005 to 2022. The median radiographic and clinical follow-up periods were 6.8 and 9.4 months, respectively. Predominantly, patients with BSM were managed with SRS (69.4%). The median prescription dose and isodose line for SRS were 18 Gy and 65%, respectively, while for FSRT, the median prescription dose was 21 Gy with a median isodose line of 70%. The 12-, 24-, and 36-month local control (LC) rates were 82.9%, 71.4%, and 61.2%, respectively. Corresponding overall survival rates at these time points were 61.1%, 34.7%, and 19.3%. In the multivariable Cox regression analysis for LC, only the minimum biologically effective dose was significantly associated with LC, favoring higher doses for improved control (in Gy, hazard ratio [HR]: 0.86, p < .01). Regarding overall survival, good performance status (Karnofsky performance status, ≥90%; HR: 0.43, p < .01) and prior whole brain radiotherapy (HR: 2.52, p < .01) emerged as associated factors. In 14 BSM (9.7%), treatment-related adverse events were noted, with a total of five (3.4%) radiation necrosis. SRS and FSRT for BSM exhibit efficacy and safety, making them suitable treatment options for affected patients.

Dose conformity and falloff in single-lesion intracranial SRS with DCA and VMAT methods

BACKGROUND

Intracranial stereotactic radiosurgery (SRS) aims at achieving highly conformal dose distribution and, at the same time, attaining rapid dose falloff outside the treatment target. SRS is performed using different techniques including dynamic conformal arcs (DCA) and volumetric modulated arc therapy (VMAT).

PURPOSE

In this study, we compare dose conformity and falloff in DCA and VMAT plans for SRS with a single target.

METHODS

To compare dose conformity in SRS plans, we employ a novel conformity indexC I d e x p $C{I}_{{d}_{exp}}$ , RTOG conformity index (C I R T O G $C{I}_{RTOG}$ ), and Riet-Paddick conformity index (C I R P $C{I}_{RP}$ ). In addition, we use indicesR 50 % $R50\% $ ,V 10 G y ${V}_{10Gy}$ , andV 12 G y ${V}_{12Gy}$ to evaluate dose falloff. For each of the considered 118 cases of SRS, two plans were created using DCA and VMAT. A two-tailed Student's t-test was used to evaluate the difference between the employed indices for the DCA and VMAT plans.

RESULTS

The studied VMAT plans were characterized by higher dose conformity than the DCA plans. The differences between the conformity indices for the DCA plans and VMAT plans were statistically significant. The DCA plans had a smaller number of monitor units (MUs) and smaller indices R50%, V10 Gy, and V12 Gy than the VMAT plans. However, the differences between R50%, V10 Gy, and V12 Gy for the DCA and VMAT plans were not statistically significant.

CONCLUSIONS

Although the studied VMAT plans had higher dose conformity, they also had larger MUs than the DCA plans. In terms of dose falloff characterized by parameters R50%, V10 Gy, and V12 Gy, DCA serves as a reasonable alternative to VMAT in the case of a single brain metastasis.

Cognitive Dysfunction in Non-CNS Metastatic Cancer: Comparing Brain Metastasis, Non-CNS Metastasis, and Healthy Controls

Limited research has compared cognition of people with non-central nervous system metastatic cancer (NCM) vs. metastatic brain cancer (BM). This prospective cross-sectional study was comprised 37 healthy controls (HC), 40 NCM, and 61 BM completing 10 neuropsychological tests. The NCM performed below HCs on processing speed and executive functioning tasks, while the BM group demonstrated lower performance across tests. Tasks of processing speed, verbal fluency, and verbal memory differentiated the clinical groups (BM < NCM). Nearly 20% of the NCM group was impaired on at least three neuropsychological tests whereas approximately 40% of the BM group demonstrated the same level of impairment.

Two-Day Fraction Gamma Knife Radiosurgery for Large Brain Metastasis

OBJECTIVE

We investigated how treating large brain metastasis (LBM) using 2-day fraction Gamma Knife radiosurgery (GKRS) affects tumor control and patient survival. A prescription dose of 10.3 Gy was applied for 2 consecutive days, with a biologically effective dose equivalent to a tumor single-fraction dose of 16.05 Gy and a brain single-fraction dose of 15.12 Gy.

METHODS

Between November 2017 and December 2021, 42 patients (mean age, 68.3 years; range, 50-84 years; male, 29 [69.1%]; female, 13 [30.9%]) with 44 tumors underwent 2-day fraction GKRS to treat large volume brain metastasis. The main cancer types were non-small cell lung cancer (n=16), small cell lung cancer (n=7), colorectal cancer (n=7), breast cancer (n=3), gastric cancer (n=2), and other cancers (n=7). Twenty-one patients (50.0%) had a single LBM, 19 (46.3%) had a single LBM and other metastases, and two had two (4.7%) large brain metastases. At the time of the 2-day fraction GKRS, the tumors had a mean volume of 23.1 mL (range, 12.5-67.4). On each day, radiation was administered at a dose of 10.3 Gy, mainly using a 50% isodose-line.

RESULTS

We obtained clinical and magnetic resonance imaging follow-up data for 34 patients (81%) with 35 tumors, who had undergone 2-day fraction GKRS. These patients did not experience acute or late radiation-induced complications during follow-up. The median and mean progression-free survival (PFS) periods were 188 and 194 days, respectively. The local control rates at 6, 9, and 12 months were 77%, 40%, and 34%, respectively. The prognostic factors related to PFS were prior radiotherapy (p=0.019) and lung cancer origin (p=0.041). Other factors such as tumor volumes, each isodose volumes, and peri-GKRS systemic treatment were not significantly related to PFS. The overall survival period of the 44 patients following repeat stereotactic radiosurgery (SRS) ranged from 15-878 days (median, 263±38 days; mean, 174±43 days) after the 2-day fraction GKRS. Eight patients (18.2%) were still alive.

CONCLUSION

Considering the unsatisfactory tumor control, a higher prescription dose should be needed in this procedure as a salvage management. Moreover, in the treatment for LBM with fractionated SRS, using different isodoses and prescription doses at the treatment planning for LBMs should be important. However, this report might be a basic reference with the same fraction number and prescription dose in the treatment for LBMs with frame-based SRS.

Single versus multiple fraction stereotactic radiosurgery for medium-sized brain metastases (4-14 cc in volume): reducing or fractionating the radiosurgery dose?

Background and purpose

Stereotactic radiosurgery (SRS) of brain metastases (BM) and resection cavities is a widely used and effective treatment modality. Based on target lesion size and anatomical location, single fraction SRS (SF-SRS) or multiple fraction SRS (MF-SRS) are applied. Current clinical recommendations conditionally recommend either reduced dose SF-SRS or MF-SRS for medium-sized BM (2-2.9 cm in diameter). Despite excellent local control rates, SRS carries the risk of radionecrosis (RN). The purpose of this study was to assess the 12-months local control (LC) rate and 12-months RN rate of this specific patient population.

Materials and methods

This single-center retrospective study included 54 patients with medium-sized intact BM (n=28) or resection cavities (n=30) treated with either SF-SRS or MF-SRS. Follow-up MRI was used to determine LC and RN using a modification of the "Brain Tumor Reporting and Data System" (BT-RADS) scoring system.

Results

The 12-month LC rate following treatment of intact BM was 66.7% for SF-SRS and 60.0% for MF-SRS (p=1.000). For resection cavities, the 12-month LC rate was 92.9%% after SF-SRS and 46.2% after MF-SRS (p=0.013). For intact BM, RN rate was 17.6% for SF-SRS and 20.0% for MF-SRS (p=1.000). For resection cavities, RN rate was 28.6% for SF-SRS and 20.0% for MF-SRS (p=1.000).

Conclusion

Patients with intact BM showed no statistically significant differences in 12-months LC and RN rate following SF-SRS or MF-SRS. In patients with resection cavities the 12-months LC rate was significantly better following SF-SRS, with no increase in the RNFS.

Comparative evaluation of outcomes amongst different radiosurgery management paradigms for patients with large brain metastasis

INTRODUCTION

This study compares four management paradigms for large brain metastasis (LMB): fractionated SRS (FSRS), staged SRS (SSRS), resection and postoperative-FSRS (postop-FSRS) or preoperative-SRS (preop-SRS).

METHODS

Patients with LBM (≥ 2 cm) between July 2017 and January 2022 at a single tertiary institution were evaluated. Primary endpoints were local failure (LF), radiation necrosis (RN), leptomeningeal disease (LMD), a composite of these variables, and distant intracranial failure (DIF). Gray's test compared cumulative incidence, treating death as a competing risk with a random survival forests (RSF) machine-learning model also used to evaluate the data.

RESULTS

183 patients were treated to 234 LBMs: 31.6% for postop-FSRS, 28.2% for SSRS, 20.1% for FSRS, and 20.1% for preop-SRS. The overall 1-year composite endpoint rates were comparable (21 vs 20%) between nonoperative and operative strategies, but 1-year RN rate was 8 vs 4% (p = 0.012), 1-year overall survival (OS) was 48 vs. 69% (p = 0.001), and 1-year LMD rate was 5 vs 10% (p = 0.052). There were differences in the 1-year RN rates (7% FSRS, 3% postop-FSRS, 5% preop-SRS, 10% SSRS, p = 0.037). With RSF analysis, the out-of-bag error rate for the composite endpoint was 47%, with identified top-risk factors including widespread extracranial disease, > 5 total lesions, and breast cancer histology.

CONCLUSION

This is the first study to conduct a head-to-head retrospective comparison of four SRS methods, addressing the lack of randomized data in LBM literature amongst treatment paradigms. Despite patient characteristic trends, no significant differences were found in LF, composite endpoint, and DIF rates between non-operative and operative approaches.

New Frontiers in the Treatment of Patients with HER2+ Cancer and Brain Metastases: Is Radiotherapy Always Useful?

Brain metastases (BM) pose a significant challenge in the management of HER2+ breast cancer since almost 50% of patients with HER2+ breast cancer develop brain tumors. The complex process of brain metastases involves genetic mutations, adaptations and mechanisms to overcome the blood-brain barrier. While radiotherapy is still fundamental in local therapy, its use is associated with cognitive adverse effects and limited long-term control, necessitating the exploration of alternative treatments. Targeted therapies, including tyrosine kinase inhibitors, monoclonal antibodies, and antibody-drug conjugates, offer promising options for HER2+ breast cancer patients with BM. Clinical trials have demonstrated the efficacy of these agents in controlling tumor growth and improving patient outcomes, posing the question of whether radiotherapy is always the unique choice in treating this cancer. Ongoing research into novel anti-HER2 antibodies and innovative combination therapies holds promise for advancing treatment outcomes and enhancing patient care in this clinical scenario. This narrative review provides a comprehensive overview of traditional medical treatments, molecularly targeted therapy and investigational agents in the management of HER2+ breast cancer with BM, highlighting the evolving landscape and potential future directions in treatment strategies to improve patient survival and quality of life.

Evaluation of Normal Tissue Objective Function for Treatment Planning of Solitary Brain Metastasis Using Intensity-modulated Radiosurgery Techniques

Purpose

The purpose of this study was to systematically examine the normal tissue objective (NTO) function by comparing its variations for planning solitary brain metastasis with intensity-modulated and volumetric-modulated arc radiosurgery techniques.

Materials and Methods

Twenty-two cases were retrospectively planned with two NTO parameter sets named A and B using intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) techniques. The Type A set used slope, k = 0.4 mm-1 plus end dose, De = 20%, whereas the Type B set used k = 1.0 mm-1 plus De = 10%. The resulting four plan types were assessed using mean dose to 5 mm exterior ring, normal brain receiving 12 Gy (V12), 5 Gy total brain dose volume (V5), gradient index (R50%), focal index (FI), Paddick conformity index (PCI), prescription isodose surface (PIDS), and MU/Gy.

Results

Brain doses were significantly lower for VMAT than for IMRT. R50% was more favorable for VMAT than for IMRT for each planning target volume (PTV). The mean FI was comparable between the corresponding IMRT and VMAT plan types. PCI was better for the IMRT_A plan type. PIDS was significantly lower for Type B plans than Type A for both techniques. For PTVs <3 cm3, IMRT plans showed poor dosimetry and required NTO settings stricter than Type B.

Conclusions

The application of NTO variations demonstrated varied dosimetry for IMRT and VMAT techniques. The NTO parameter variations produced field size and/or beamlet size/shape variations. The strict NTO parameter set generated more conformal beam apertures to reduce the brain dose. VMAT plan types showed significantly lower brain doses and better dosimetry for all target sizes.

Prediction of radiologic outcome-optimized dose plans and post-treatment magnetic resonance images: A proof-of-concept study in breast cancer brain metastases treated with stereotactic radiosurgery

Background and purpose

Information in multiparametric Magnetic Resonance (mpMR) images is relatable to voxel-level tumor response to Radiation Treatment (RT). We have investigated a deep learning framework to predict (i) post-treatment mpMR images from pre-treatment mpMR images and the dose map ("forward models"), and, (ii) the RT dose map that will produce prescribed changes within the Gross Tumor Volume (GTV) on post-treatment mpMR images ("inverse model"), in Breast Cancer Metastases to the Brain (BCMB) treated with Stereotactic Radiosurgery (SRS).

Materials and methods

Local outcomes, planning computed tomography (CT) images, dose maps, and pre-treatment and post-treatment Apparent Diffusion Coefficient of water (ADC) maps, T1-weighted unenhanced (T1w) and contrast-enhanced (T1wCE), T2-weighted (T2w) and Fluid-Attenuated Inversion Recovery (FLAIR) mpMR images were curated from 39 BCMB patients. mpMR images were co-registered to the planning CT and intensity-calibrated. A 2D pix2pix architecture was used to train 5 forward models (ADC, T2w, FLAIR, T1w, T1wCE) and 1 inverse model on 1940 slices from 18 BCMB patients, and tested on 437 slices from another 9 BCMB patients.

Results

Root Mean Square Percent Error (RMSPE) within the GTV between predicted and ground-truth post-RT images for the 5 forward models, in 136 test slices containing GTV, were (mean ± SD) 0.12 ± 0.044 (ADC), 0.14 ± 0.066 (T2w), 0.08 ± 0.038 (T1w), 0.13 ± 0.058 (T1wCE), and 0.09 ± 0.056 (FLAIR). RMSPE within the GTV on the same 136 test slices, between the predicted and ground-truth dose maps, was 0.37 ± 0.20 for the inverse model.

Conclusions

A deep learning-based approach for radiologic outcome-optimized dose planning in SRS of BCMB has been demonstrated.

Preoperative radiosurgery for brain metastases (PREOP-1): A feasibility trial

Purpose

Preoperative radiosurgery (SRS) of brain metastases (BM) aims to achieve cavity local control with a reduction in leptomeningeal relapse (LMD) and without additional radionecrosis compared to postoperative SRS. We present the final results of a prospective feasibility trial of linac-based stereotactic radiosurgery (SRS) prior to neurosurgical resection of a brain metastasis (PREOP-1).

Methods

Eligibility criteria included a BM up to 4 cm in diameter for elective resection. The primary endpoint was the feasibility of delivering linac-based preoperative SRS in all patients prior to anticipated gross tumour resection. Secondary endpoints included rates of LMD, local control and overall survival. Exploratory endpoints were the level of expression of immunological and proliferative markers.

Results

Thirteen patients of median age 65 years (range 41-77) were recruited. Twelve patients (92 %) received preoperative radiosurgery and metastasectomy and one patient went directly to surgery and received postoperative SRS, thus the primary endpoint was not met. The median time between referral and preoperative SRS was 6.5 working days (1-10) and from SRS to neurosurgery was 1 day (0-5). The median prescribed dose was 16 Gy (14-19) to a median planning target volume of 12.7 cm3 (5.9-26.1). Five patients completed 12-month follow-up after preoperative SRS without local recurrence or leptomeningeal disease. The patient who received postoperative FSRT developed LMD after six months. There was one transient toxicity (grade 2 alopecia) and nine patients have died from extracranial causes. Patients reported significant improvement in motor weakness at 6 months (P = 0.04). No pattern in changes of marker expression was observed.

Conclusion

In patients with large brain metastasis without raised intracranial pressure, linac-based preoperative SRS was feasible in 12/13 patients and safe in 12/12 patients without any surgical delay or intracranial complications.