Stereotactic Radiotherapy For Brain Metastases Research Articles

The dosimetric parameters impact on local recurrence in stereotactic radiotherapy for brain metastases.

Stereotactic radiotherapy (SRT) for brain metastases (BM) allows very good local control (LC). However, approximately 20%-30% of these lesions will recur. The objective of this retrospective study was to evaluate the impact of dosimetric parameters on LC in cerebral SRT. Patients treated with SRT for 1-3 BM between January 2015 and December 2018 were retrospectively included. A total of 349 patients with 538 lesions were included. The median gross tumour volume (GTV) was 2 cm3 (IQR, 0-7). The median biological effective dose with α/β = 10 (BED10) was 60 Gy (IQR, 32-82). The median prescription isodose was 71% (IQR, 70-80). Correlations with LC were examined using the Cox regression model. The median follow-up period was 55 months (min-max, 7-85). Median overall survival was 17.8 months (IQR, 15.2-21.9). There were 95 recurrences and LC at 1 and 2 years was 87.1% (95% CI, 84-90) and 78.1% (95% CI, 73.9-82.4), respectively. Univariate analysis showed that systemic treatment, dose to 2% and 50% of the planning target volume (PTV), BED10 > 50 Gy, and low PTV and GTV volume were significantly correlated with better LC. In the multivariate analysis, GTV volume, isodose, and BED10 were significantly associated with LC. These results show the importance of a BED10 > 50 Gy associated with a prescription isodose <80% to optimize LC during SRT for BM. Isodose, BED, and GTV volume were significantly associated with LC. A low isodose improves LC without increasing the risk of radionecrosis.

Robust and optimal dose distribution for brain metastases with robotic radiosurgery system: recipe for an inflection point.

Purpose.This study aims to establish a robust dose prescription methodology in stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) for brain metastases, considering geometrical uncertainty and minimising dose exposure to the surrounding normal brain tissue.Methods and Materials.Treatment plans employing 40%-90% isodose lines (IDL) at 10% IDL intervals were created for variously sized brain metastases. The plans were constructed to deliver 21 Gy in SRS. Robustness of each plan was analysed using parameters such as the near minimum dose to the tumour, the near maximum dose to the normal brain, and the volume of normal brain irradiated above 14 Gy.Results.Plans prescribed at 60% IDL demonstrated the least variation in the near minimum dose to the tumour and the near maximum dose to the normal brain under conditions of minimal geometrical uncertainty relative to tumour radius. When the IDL-percentage prescription was below 60%, geometrical uncertainties led to increases in these doses. Conversely, they decreased with IDL-percentage prescriptions above 60%. The volume of normal brain irradiated above 14 Gy was lowest at 60% IDL, regardless of geometrical uncertainty.Conclusions.To enhance robustness against geometrical uncertainty and to better spare healthy brain tissue, a 60% IDL prescription is recommended in SRS and SRT for brain metastases using a robotic radiosurgery system.

Clinical Results and Hematologic Predictors of Linear Accelerator–Based Stereotactic Radiosurgery or Fractionated Stereotactic Radiotherapy for Brain Metastasis in Patients Aged 75 Years or Older: A Retrospective Study

This study aimed to evaluate prognostic factors including pre-radiosurgical blood count in elderly patients (EPs) with brain metastasis (BM) who were treated using linear accelerator (linac)-based, stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (fSRT) with a micro-multileaf collimator. Between January 2011 and November 2021, 101 consecutive elderly patients with BM were treated by linac-based SRS or fSRT using linac with a micro-multileaf collimator. EPs were defined as patients aged ≥75 years. The tumors originated from the lungs (n = 90, 89.1%), colon (n = 2, 2.0%), and others (n = 9, 8.8%) in these EPs. The median pretreatment Karnofsky Performance Scale (KPS) score was 80 (range: 40–100). The median follow-up time was 10 (range: 0–76) months, as was the median survival time. The 6-month and 1 and 2-year survival rates in the EP group were 58.3%, 43.2%, 28.5%, respectively. Freedom from local failure at 6 months and 1 and 2 years were 97%, 95%, and 91.5%, respectively. Freedom from distant failure at 6 months and 1 and 2 years in EPs were 70.6%, 59.4%, and 54.2%, respectively. A high neutrophil/lymphocyte ratio (NLR) >5.33 was an unfavorable predictor of prognosis for EPs with BMs treated with SRS and fSRT (p<0.001). In the EPs, the prognostic factors associated with prolonged survival time in the Cox proportional hazards model were being female and a good pretreatment KPS score. The findings of our study highlight the efficacy of linac-based SRS and fSRT with a micro-multileaf collimator in the treatment of EPs with BMs. NLR can be an important factor in treatment decisions for EPs with BMs.

Stereotactic radiotherapy for brain metastases in patients with non-small cell lung cancer: CyberKnife-M6 experience

Stereotactic radiotherapy for brain metastases in patients with non-small cell lung cancer: CyberKnife-M6 experience

Predictors of local control after robotic stereotactic radiotherapy for brain metastases: 10-years-experience after Cyberknife installation.

To evaluate the factors influencing brain metastases (BM) local control (LC) after stereotactic radiotherapy (SRT). Between 2010 and 2020, a cohort of 145 patients (246 BM) treated consecutively with robotic radiosurgery was analysed. Median age was 61 years (range, 29-90 years). Median radiological follow-up of the lesions was 21.7 months (range, 3-115 months). The mean overall survival and LC were 33.0 and 82.7 months, respectively. On univariate analysis, sex, primary cancer site, histological type, use of systemic steroids, maximum diameter, volume, early MRI response, isodose line, number of fractions, BED10 value, and BED10 value proportional to volume and maximum diameter were significant factors for LC. On multivariate analysis, female sex (hazard ratio [HR]: 2.10 P: 0.035), adenocarcinoma histology (HR: 6.54 P: 0.001), no steroid use (HR: 3.60 P: 0.001), maximum diameter (≤1 cm) (HR: 2.64 P: 0.018), complete response of lesion at first follow-up MRI compared to stable or progressive disease (HR: 4.20, P = 0.024; HR: 19.15, P < 0.001), isodose line (≥90%) (HR: 2.00 P: 0.036), and tumour volume (PTV ≤2 cc) (HR: 5.19 P: 0.001) were independent factors improving LC. SRT is an effective treatment for patients with a limited number of BM with a high LC rate. There are many factors related to the patient, tumour, and radiotherapy plan that have an impact on LC after SRT in brain metastases. These results warrant further investigation in a prospective setting.

P2.03-01 Effectiveness and Safety of Combining Bevacizumab and Fractionated Stereotactic Radiotherapy for Brain Metastases in NSCLC Patients

P2.03-01 Effectiveness and Safety of Combining Bevacizumab and Fractionated Stereotactic Radiotherapy for Brain Metastases in NSCLC Patients

Dose-effect relationship of linear accelerator based stereotactic radiotherapy for brain metastases

ObjectiveThe purpose of this study is to reveal the dose-effect relationship of linear accelerator (LINAC)-based stereotactic radiotherapy (SRT) in patients with brain metastases (BM).Materials and methodsThe PubMed, Cochrane, and Web of Science databases were used to identify studies that reported local tumour control after LINAC-based SRT in patients with BMs. Studies of other approaches that could affect local tumour control, such as whole brain radiotherapy, targeted therapy, and immunotherapy, were excluded from the dose-effect relationship analysis. Data extracted included patient and treatment characteristics and tumour local control. Probit model in XLSTAT 2016 was used for regression analysis, and P < 0.05 was set as the statistically significant level.ResultsAfter literature screening, 19 eligible studies involving 1523 patients were included in the probit model regression analysis. There was no significant dose-effect relationship between nominal BED10 and peripheral BED10 versus 12-month local control probability. There were significant dose effect relationships between the centre BED10 and the average BED10 versus the 12-month local control probability, with P values of 0.015 and 0.011, respectively. According to the model, the central BED10 and the average BED10 corresponding to probabilities of 90% 12-month local control were 109.2 GyBED10 (95% confidence interval (CI): 88.7–245.9 GyBED10) and 87.8 GyBED10 (95% CI: 74.3–161.5 GyBED10), respectively. A 12-month local control rate of 86.9% (95% CI: 81.7–89.7%) and 85.5% (95% CI: 81.2–89.2%) can be expected at a centre BED10 of 80 Gy and an average BED10 of 60 Gy, respectively.ConclusionFor patients with BM treated with LINAC-based SRT, more attention should be given to the central and average doses of PTV. A clear definition of the dose prescription should be established to ensure the effectiveness and comparability of treatment.

Symptomatic Necrosis With Antibody-Drug Conjugates and Concurrent Stereotactic Radiotherapy for Brain Metastases

This cohort study investigates whether brain metastases that manifest after stereotactic radiotherapy with concurrent antibody-drug conjugates are associated with an increased risk of symptomatic radiation necrosis.

Frameless Fractionated Linear Accelerator-Based Stereotactic Radiotherapy for Brain Metastases: Results of a Single-Arm Phase II Multi-Institutional Clinical Trial

Stereotactic radiotherapy (SRT) yields high rates of local control for brain metastases while minimizing neurocognitive side effects. While advanced SRT platforms are widely available in urban centers, rural/suburban patients face geographic and socioeconomic barriers to access SRS. For this reason, we conducted a multi-institutional Phase 2 clinical trial to test the safety and efficacy of 3-5 fraction frameless fractionated stereotactic radiotherapy (FFSRT) for brain metastases in an integrated academic satellite network MATERIALS/METHODS: This IRB-approved Phase 2 trial was conducted for patients ≥18-years-old with 1-4 brain metastases. Brain metastases involving the optic pathway or brainstem were excluded. Gross tumor volume (GTV) was delineated with a volumetric brain MRI and planning target volume (PTV) was GTV + 2 mm margin. Radiation dose was based on GTV size: < 3.0 cm, 27 Gy in 3 fractions, and 3.0-3.9 cm, 30 Gy in 5 fractions. Toxicity was evaluated using the Common Terminology Criteria for Adverse Events (CTCAE) version 4. Of 76 evaluable patients, the median age was 67 years, 56.6% were female, 82.9% were white/Caucasian and 89.6% had an Eastern Cooperative Oncology Group performance status ≤ 2. Most brain metastases were from lung cancer (51.3%) and breast cancer (15.7%). With median follow-up of 10 months, local control was 93%, median survival was 1.8 years (95% confidence interval (CI): 1.5-2.4 years), 1-year OS was 73.8% (95% CI: 0.59-0.84), and 2-year OS was 31% (95% CI: 0.12-0.52). There were no CTCAE Grade ≥ 3 protocol-related adverse events. Outcomes of this trial compare favorably with contemporary SRT trials for brain metastases. FFSRT may provide opportunities to expand SRS access for underserved populations across the MDACC enterprise and in future clinical trials for brain metastases.

External validation of three prognostic scores for brain metastasis velocity in patients treated with intracranial stereotactic radiotherapy

Background and introductionBrain metastasis velocity (BMV) has been proposed as a prognostic factor for overall survival (OS) in patients with brain metastases (BMs). In this study, we conducted an external validation and comparative assessment of the performance of all three BMV scores. Materials and methodsPatients treated with intracranial stereotactic radiotherapy (SRT) for BM at a single center between 2014 and 2018 were identified. Where possible, all three BMV scores were calculated. Log-rank tests and linear, logistic and Cox regression analysis were used for validation and predictor identification of OS. ResultsFor 333 of 384 brain metastasis patients, at least one BMV score could be calculated. In a sub-group of 187 patients, “classic” BMV was validated as categorical (p < 0.0001) and continuous variable (HR 1.02; 95% CI 1.02–1.03; p < 0.0001). In a sub-group of 284 patients, “initial” BMV was validated as categorical variable (high-risk vs. low-risk; p < 0.01), but not as continuous variable (HR 1.02; 95% CI 0.99–1.04; p = 0.224). “Volume-based” BMV could not be validated in a sub-group of 104 patients. On multivariable Cox regression analysis, iBMV (HR 1.85; 95% CI 1.01–3.38; p < 0.05) and cBMV (HR 2.32; 95% CI 1.15 4.68; p < 0.05) were predictors for OS for intermediate-risk patients after first SRT and first DBFs, respectively. cBMV proved to be the dominant predictor for OS for high-risk patients (HR 2.99; 95% CI 1.30–6.91; p < 0.05). ConclusionThis study externally validated cBMV and iBMV as prognostic scores for OS in patients treated with SRT for BMs whereas validation of vBMV was not achieved.

Modern Stereotactic Radiotherapy for Brain Metastases from Lung Cancer: Current Trends and Future Perspectives Based on Integrated Translational Approaches.

Brain metastases (BMs) represent the most frequent metastatic event in the course of lung cancer patients, occurring in approximately 50% of patients with non-small-cell lung cancer (NSCLC) and in up to 70% in patients with small-cell lung cancer (SCLC). Thus far, many advances have been made in the diagnostic and therapeutic procedures, allowing improvements in the prognosis of these patients. The modern approach relies on the integration of several factors, such as accurate histological and molecular profiling, comprehensive assessment of clinical parameters and precise definition of the extent of intracranial and extracranial disease involvement. The combination of these factors is pivotal to guide the multidisciplinary discussion and to offer the most appropriate treatment to these patients based on a personalized approach. Focal radiotherapy (RT), in all its modalities (radiosurgery (SRS), fractionated stereotactic radiotherapy (SRT), adjuvant stereotactic radiotherapy (aSRT)), is the cornerstone of BM management, either alone or in combination with surgery and systemic therapies. We review the modern therapeutic strategies available to treat lung cancer patients with brain involvement. This includes an accurate review of the different technical solutions which can be exploited to provide a "state-of-art" focal RT and also a detailed description of the systemic agents available as effective alternatives to SRS/SRT when a targetable molecular driver is present. In addition to the validated treatment options, we also discuss the future perspective for focal RT, based on emerging clinical reports (e.g., SRS for patients with many BMs from NSCLC or SRS for BMs from SCLC), together with a presentation of innovative and promising findings in translational research and the combination of novel targeted agents with SRS/SRT.

Intraoperative or postoperative stereotactic radiotherapy for brain metastases: time to systemic treatment onset and other patient-relevant outcomes

PurposeIntraoperative radiotherapy (IORT) has become a viable treatment option for resectable brain metastases (BMs). As data on local control and radiation necrosis rates are maturing, we focus on meaningful secondary endpoints such as time to next treatment (TTNT), duration of postoperative corticosteroid treatment, and in-hospital time.MethodsPatients prospectively recruited within an IORT study registry between November 2020 and June 2023 were compared with consecutive patients receiving adjuvant stereotactic radiotherapy (SRT) of the resection cavity within the same time frame. TTNT was defined as the number of days between BM resection and start of the next extracranial oncological therapy (systemic treatment, surgery, or radiotherapy) for each of the groups.ResultsOf 95 BM patients screened, IORT was feasible in 84 cases (88%) and ultimately performed in 64 (67%). The control collective consisted of 53 SRT patients. There were no relevant differences in clinical baseline features. Mean TTNT (range) was 36 (9 − 94) days for IORT patients versus 52 (11 − 126) days for SRT patients (p = 0.01). Mean duration of postoperative corticosteroid treatment was similar (8 days; p = 0.83), as was mean postoperative in-hospital time (11 versus 12 days; p = 0.97). Mean total in-hospital time for BM treatment (in- and out-patient days) was 11 days for IORT versus 19 days for SRT patients (p < 0.001).ConclusionIORT for BMs results in faster completion of interdisciplinary treatment when compared to adjuvant SRT, without increasing corticosteroid intake or prolonging in-hospital times. A randomised phase III trial will determine the clinical effects of shorter TTNT.

Effect and safety of combining bevacizumab and fractionated stereotactic radiotherapy for brain metastases in patients with non-small cell lung cancer: A phase II trial.

e21132 Background: W e aimed to assess the efficacy and safety of c ombining b evacizumab and fractionated stereotactic radiotherapy ( FSRT ) for brain metastases (BMs) in non-small cell lung cancer ( NSCLC ) patients with stable extracranial disease status in this study. Methods: NSCLC patients with BMs were recruited between J anuary 20 20 and J anuary 202 2 . P atients were assigned to receive FSRT of 40Gy in 10 fractions (BED 56eGy) or 30Gy in 5 fractions (BED 48eGy). Meanwhile, bevacizumab was administered before FSRT (d1) and after FSRT (d21) with a dosage of 7.5mg/Kg. The primary endpoint of the study is intra-cranial progression-free survival (IPFS) . The secondary endpoints contained overall survival (OS), progression-free survival (PFS) , quality of life (QOL) score and toxicities. All time-to-event endpoints (IPFS, OS and PFS) were measured from the end of radiotherapy. Results: From J anuary 2020 and J anuary 202 2, 108 patients were recruited with a median follow-up duration was 15.2 months . The 1-year IPFS and OS rate were 82.9% ( 95% confidence interval (CI), 79.6%-86.2% ) and 80.4% ( 95% CI, 76.8%-84.0% ), respectively . The median PFS was 15.0 months ( 95% CI, 9.50-20.50 months ). The median IPFS and OS had not been reached at the time of the last follow-up. The treatment-related toxicities were mild with low incidence. Reversible mild hypertension and cerebral radio-necrosis were observed in 2 and 1 patients, respectively. No signs of ex tra-lesional haemorrhage and progression of peri-lesional oedema was found during the assessment period of treatment response. More importantly, significant improvent of QOL was observed in symptomatic patients. Conclusions: The combination of FSRT with bevacizumab in patients with NSCLC was well tolerated and achieved promising intracranial disease control. Patients maintained satisfactory QOL after receiving the combined regimen with low incidence of cerebral radio-necrosis. Clinical trial information: NCT04345146 .

Fractionated stereotactic radiotherapy of brain metastases: results of a retrospective study

BackgroundLasting local control of brain metastases following stereotactic radiotherapy is becoming increasingly relevant since systemic treatment constantly improves the prognosis of patients with extracranial metastases.Methods73 patients with 103 brain metastases received hypofractionated stereotactic radiotherapy (FSRT) in 6 fractions of 5 Gy between January 2017 and December 2021 at the University Hospital Regensburg, Germany. The study retrospectively evaluated local progression free survival (LPFS), overall survival (OS) and distant brain progression free survival (DPFS) of patients without prior radiotherapy of the brain. Response rate and brain radiation necrosis were reported. Cox proportional hazard models evaluated prognostic factors of OS and LPFS.ResultsThe median patient age was 61.0 years (Interquartile range, IQR 51.0, 67.5). The most common tumor types were malignant melanoma (34.2%) and non-small cell lung adenocarcinoma (26.0%). The median gross tumor volume (GTV) was 0.9 cm³ (IQR 0.4, 3.6). The median follow-up time of all patients was 36.3 months (95%CI 29.1, 43.4). The median OS was 17.4 months (95%CI 9.9, 24.9). Overall survival rates at 6-, 12-, 18-, 24-, and 30 months were 81.9%, 59.1%, 49.0%, 41.3%, and 37.2%, retrospectively. The mean LPFS was 38.1 months (95%CI 31.4, 44.9), while the median LPFS has not been reached. LPFS rates at 6-, 12-, 18-, 24- and 30 months were 78.9%, 68.7%, 64.3%, 61.6% and 58.7%, retrospectively. Median DPFS of all patients was 7.7 months (95%CI 6.1, 9.3). Six, 12-, 18-, 24- and 30 months DPFS rates were 62.1%, 36.3%, 31.1%, 24.8% and 21.7%. Five brain metastases (4.8%) developed brain radiation necrosis. In multivariate analysis, the number of brain metastases negatively affected LPFS. Non-melanoma and non-renal cell cancer was associated with a higher chance of LPFS in comparison to other cancer. A GTV > 1.5 cm³ translated into a higher risk of death compared to a GTV ≤ 1.5 cm³ and Karnofsky performance score was predictive of OS.ConclusionsFSRT in 6 fractions of 5 Gy seems to be an effective treatment with an acceptable local control for patients with brain metastases although melanoma and renal cell cancer seem to have a worse local control in comparison to other cancer.Trial registrationThis study is retrospectively registered.

Linear accelerator-based stereotactic radiotherapy for brain metastases, including multiple and large lesions, carries a low incidence of acute toxicities: a retrospective analysis

BackgroundData on acute toxicities after stereotactic radiotherapy (SRT) for brain metastases, including multiple and large lesions, are lacking. We aimed to evaluate the incidence and nature of toxicities immediately after SRT using a linear accelerator.MethodsThis retrospective study reviewed the medical records of 315 patients with brain metastases treated with SRT at our institution between May 2019 and February 2022. In total, 439 SRT sessions were performed for 2161 brain metastases. The outcome of interest was immediate side effects (ISEs), defined as new or worsening symptoms occurring during SRT or within 14 days after the end of SRT.ResultsGrade ≥ 2 and ≥ 3 ISEs occurred in 16 (3.6%) and 7 (1.6%) cases, respectively. Among 63 treatments for 10 or more lesions (range: 10–40), 1 (1.6%) ISE occurred. Among 22 treatments for lesions with a maximum tumor volume of > 10 cc, 2 (9.1%) ISEs occurred. Grade ≥ 3 ISEs included 1, 4, 1, and 1 cases of grade 3 nausea, grade 3 new-onset partial and generalized seizures, grade 3 obstructive hydrocephalus, and grade 5 intracranial hemorrhage, respectively. ISEs were more common in patients with a larger maximum tumor volume, primary sites other than lung and breast cancer, and pre-treatment neurological symptoms.ConclusionSRT using a linear accelerator for brain metastases, including multiple and large lesions, is safe, with a low incidence of ISEs. Serious complications immediately after SRT are rare but possible; therefore, careful follow-up is necessary after treatment initiation.

PO-1136 Reirradiation by stereotactic radiotherapy of brain metastases in case of local recurrence

PO-1136 Reirradiation by stereotactic radiotherapy of brain metastases in case of local recurrence

PO-1994 Stereotactic Radiotherapy For Brain Metastases: a dosimetric analysis between two techniques

PO-1994 Stereotactic Radiotherapy For Brain Metastases: a dosimetric analysis between two techniques

Re-Irradiation by Stereotactic Radiotherapy of Brain Metastases in the Case of Local Recurrence.

To evaluate the efficacy and safety of a second course of stereotactic radiotherapy (SRT2) treatment for a local recurrence of brain metastases previously treated with SRT (SRT1), using the Hypofractionated Treatment Effects in the Clinic (HyTEC) reporting standards and the European Society for Radiotherapy and Oncology guidelines. From December 2014 to May 2021, 32 patients with 34 brain metastases received salvage SRT2 after failed SRT1. A total dose of 21 to 27 Gy in 3 fractions or 30 Gy in 5 fractions was prescribed to the periphery of the PTV (99% of the prescribed dose covering 99% of the PTV). After SRT2, multiparametric MRI, sometimes combined with 18F-DOPA PET-CT, was performed every 3 months to determine local control (LC) and radionecrosis (RN). After a median follow-up of 12 months (range: 1-37 months), the crude LC and RN rates were 68% and 12%, respectively, and the median overall survival was 25 months. In a multivariate analysis, the performance of surgery was predictive of a significantly better LC (p = 0.002) and survival benefit (p = 0.04). The volume of a normal brain receiving 5 Gy during SRT2 (p = 0.04), a dose delivered to the PTV in SRT1 (p = 0.003), and concomitant systemic therapy (p = 0.04) were associated with an increased risk of RN. SRT2 is an effective approach for the local recurrence of BM after initial SRT treatment and is a potential salvage therapy option for well-selected people with a good performance status. Surgery was associated with a higher LC.

Dosimetric Parameters in Hypofractionated Stereotactic Radiotherapy for Brain Metastases: Do Flattening Filter-Free Beams Bring Benefits? A Preliminary Study.

This study aimed to compare the dosimetric results of flattening filter-free (FFF) vs. flattened (FF) treatment plans for fractionated stereotactic radiotherapy (fSRT), with the goal to highlight potential advantages of FFF beams. A group of 18 patients with brain metastases treated with fSRT (30 Gy delivered in 5 fractions) were included. The dosimetric parameters evaluated were: (1) physical dosimetric parameters (number of monitor units (MUs), conformity index (CI), dose gradient index (DGI), beam on time (BOT)); (2) clinical dosimetric parameters pertaining to target volume (PTV) and organs at risk (OARs). Two treatment plans were performed for all patients: one used 6 MV FFF beams and the other used 6 MV flattened beams. A slight increase in MUs was observed for the FFF mode (+23.3 MUs). The CI showed a difference of -2.7% for the FF plans (p = 0.28), correlated with a poorer coverage of the PTV. DGI values reported in terms of PTV are in line with international recommendations and showed a +1.9% difference for FFF plans. An average BOT of 90.3 s was reported for FFF plans, which was 2.3 times shorter than that required for FF plans delivery (p ≤ 0.001). A slight decrease of PTV coverage (-1.26%, p = 0.036) for FF plans can be considered relevant, but no other significant differences were observed between the two optimizations. No statistically significant benefit of using FFF beams to reduce V20 for normal brain could be demonstrated. These dosimetric results encourage the implementation of fSRT with standard flattened beams in centers where FFF linacs are not available.

Dose Reduction to Motor Structures in Adjuvant Fractionated Stereotactic Radiotherapy of Brain Metastases: nTMS-Derived DTI-Based Motor Fiber Tracking in Treatment Planning.

Background: Resection of brain metastases (BM) close to motor structures is challenging for treatment. Navigated transcranial magnetic stimulation (nTMS) motor mapping, combined with diffusion tensor imaging (DTI)-based fiber tracking (DTI-FTmot.TMS), is a valuable tool in neurosurgery to preserve motor function. This study aimed to assess the practicability of DTI-FTmot.TMS for local adjuvant radiotherapy (RT) planning of BM. Methods: Presurgically generated DTI-FTmot.TMS-based corticospinal tract (CST) reconstructions (FTmot.TMS) of 24 patients with 25 BM resected during later surgery were incorporated into the RT planning system. Completed fractionated stereotactic intensity-modulated RT (IMRT) plans were retrospectively analyzed and adapted to preserve FTmot.TMS. Results: In regular plans, mean dose (Dmean) of complete FTmot.TMS was 5.2 ± 2.4 Gy. Regarding planning risk volume (PRV-FTTMS) portions outside of the planning target volume (PTV) within the 17.5 Gy (50%) isodose line, the DTI-FTmot.TMS Dmean was significantly reduced by 33.0% (range, 5.9−57.6%) from 23.4 ± 3.3 Gy to 15.9 ± 4.7 Gy (p < 0.001). There was no significant decline in the effective treatment dose, with PTV Dmean 35.6 ± 0.9 Gy vs. 36.0 ± 1.2 Gy (p = 0.063) after adaption. Conclusions: The DTI-FTmot.TMS-based CST reconstructions could be implemented in adjuvant IMRT planning of BM. A significant dose reduction regarding motor structures within critical dose levels seems possible.