Linac-based radiosurgery or fractionated stereotactic radiotherapy with flattening filter-free volumetric modulated arc therapy in elderly patients : A mono-institutional experience on 110 brain metastases

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

OBJECTIVE

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.

METHODS

Between January 2011 and November 2021, 101 consecutive EPs 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.

RESULTS

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 Status was 80 (range, 40-100). The median follow-up time was 10 months (range, 0-76), as was the median survival. The 6-month, 1-year, and 2-year survival in the EP group was 58.3%, 43.2%, and 28.5%, respectively. Freedom from local failure at 6 months and 1 and 2 years was 97%, 95%, and 91.5%, respectively. Freedom from distant failure at 6 months and 1 and 2 years in EPs was 70.6%, 59.4%, and 54.2%, respectively. A high neutrophil/lymphocyte ratio >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 in the Cox proportional hazards model were being female and a good pretreatment Karnofsky Performance Status.

CONCLUSIONS

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. Neutrophil/lymphocyte ratio can be an important factor in treatment decisions for EPs with BMs.

Robotic stereotactic radiosurgery for intracranial meningiomas in elderly patients: assessment of treatment efficacy and safety

Purpose

Stereotactic radiosurgery (SRS) has been increasingly used to treat intracranial pathologies in elderly patients. The treatment efficiency of SRS has been demonstrated in meningiomas, with excellent local control. We aimed to analyze the safety of robotic SRS in elderly patients with meningiomas.

Methods

We searched for patients with suspected WHO °I meningioma ≥ 60 years old, who underwent CyberKnife (CK) SRS from January 2011 to December 2021. Tumor localization was categorized using the "CLASS" algorithmic scale. Tumor response was evaluated using the Response Assessment in Neuro-Oncology (RANO) criteria for meningiomas. Adverse effects were graded using the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 and a cox regression was performed to investigate possible predictors.

Results

We identified 82 patients with 102 CK-treated lesions that matched the criteria for the first SRS. The median age was 70 [IQR 64-75] years, and 24.3% of the patients were aged > 75 years. Multiple lesions (up to six) were treated in 14.1% of the SRS-sessions. A previous surgery was performed in 57.3% of lesions, with a median time interval of 41 [IQR 10 - 58] months between the initial surgical procedure and the SRS treatment. In 47.9% of cases, CLASS 3 meningiomas at high-risk locations were irradiated. Single fraction radiosurgery was applied to 62.5% of the lesions, while in the remaining cases multi-session SRS with three to five fractions was used. During the median follow-up period of 15.9 months, lesion size progression was observed in 3 cases. Karnofsky Performance Status (KPS) declined by ≥ 20 points in four patients. Adverse effects occurred in 13 patients, while only four patients had CTCAE ≥2 toxicities. Hereby only one of these toxicities was persistent. The occurrence of complications was independent of age, planned target volume (PTV), high-risk localization, and surgery before SRS.

Conclusion

The data indicates that SRS is a safe, efficient, and convenient treatment modality for elderly patients with meningioma, even at high-risk locations.

CyberKnife-based stereotactic radiosurgery or fractionated stereotactic radiotherapy in older patients with brain metastases from non-small cell lung cancer

PURPOSE

We analyzed clinical results of CyberKnife (CK)-based stereotactic radiosurgery (SRS) or fractionated stereotactic radiotherapy (FSRT) in older patients (age ≥65 years) affected by brain metastases (BM) from non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

Forty-three older patients with 92 BM were treated with CK-based SRS/FSRT at our institution between 2009 and 2019. The end-point was overall survival (OS). Univariate and multivariate analyses were performed to identify the prognostic factors influencing OS. The in-field local control (IFLC) within the SRS/FSRT field was also assessed.

RESULTS

During a median follow-up period of 18 months, the median OS was 32 months. NSCLC-specific graded prognostic assessment (GPA) (p = 0.027) was an independent significant factor affecting OS in the multivariate analysis. The median IFLC period was 31 months, and the total BM volume (p = 0.025) appeared to be a significant feature of IFLC. No adverse events >grade 2 were reported after SRS/FSRT.

CONCLUSION

CK-based SRS/FSRT is a safe and efficient option for older patients with BM arising from NSCLC, showing good OS without severe side effects. GPA, which was consisted in age, performance status, extra-cerebral metastasis, and number of BM, seemed to be predictive factors for OS.

Brain Linac-Based Radiation Therapy: "Test Drive" of New Immobilization Solution and Surface Guided Radiation Therapy

AIM

To test inter-fraction reproducibility, intrafraction stability, technician aspects, and patient/physician's comfort of a dedicated immobilization solution for Brain Linac-based radiation therapy (RT).

METHODS

A pitch-enabled head positioner with an open-face mask were used and, to evaluate inter- and intrafraction variations, 1-3 Cone-Beam Computed Tomography (CBCT) were performed. Surface Guided Radiation Therapy (SGRT) was used to evaluate intrafraction variations at 3 time points: initial (i), final (f), and monitoring (m) (before, end, and during RT). Data regarding technician mask aspect were collected.

RESULTS

Between October 2019 and April 2020, 69 patients with brain disease were treated: 45 received stereotactic RT and 24 conventional RT; 556 treatment sessions and 863 CBCT's were performed. Inter-fraction CBCT mean values were longitudinally 0.9 mm, laterally 0.8 mm, vertically 1.1 mm, roll 0.58°, pitch 0.59°, yaw 0.67°. Intrafraction CBCT mean values were longitudinally 0.3 mm, laterally 0.3 mm, vertically 0.4 mm, roll 0.22°, pitch 0.33°, yaw 0.24°. SGRT intrafraction mean values were: i_, m_, f_ longitudinally 0.09 mm, 0.45 mm, 0.31 mm; i_, m_, f_ laterally 0.07 mm, 0.36 mm, 0.20 mm; i_, m_, f_ vertically 0.06 mm, 0.31 mm, 0.22 mm; i_, m_, f_ roll 0.025°, 0.208°, 0.118°; i_, m_, f_ pitch 0.036°, 0.307°, 0.194°; i_, m_, f_ yaw 0.039°, 0.274°, 0.189°.

CONCLUSIONS

This immobilization solution is reproducible and stable. Combining CBCT and SGRT data confirm that 1 mm CTV-PTV margin for Linac-based SRT was adequate. Using open-face mask and SGRT, for conventional RT, radiological imaging could be omitted.

Reduction of inter-observer differences in the delineation of the target in spinal metastases SBRT using an automatic contouring dedicated system

BACKGROUND

Approximately one third of cancer patients will develop spinal metastases, that can be associated with back pain, neurological symptoms and deterioration in performance status. Stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT) have been offered in clinical practice mainly for the management of oligometastatic and oligoprogressive patients, allowing the prescription of high total dose delivered in one or few sessions to small target volumes, minimizing the dose exposure of normal tissues. Due to the high delivered doses and the proximity of critical organs at risk (OAR) such as the spinal cord, the correct definition of the treatment volume becomes even more important in SBRT treatment, thus making it necessary to standardize the method of target definition and contouring, through the adoption of specific guidelines and specific automatic contouring tools. An automatic target contouring system for spine SBRT is useful to reduce inter-observer differences in target definition. In this study, an automatic contouring tool was evaluated.

METHODS

Simulation CT scans and MRI data of 20 patients with spinal metastases were evaluated. To evaluate the advantage of the automatic target contouring tool (Elements SmartBrush Spine), which uses the identification of different densities within the target vertebra, we evaluated the agreement of the contours of 20 spinal target (2 cervical, 9 dorsal and 9 lumbar column), outlined by three independent observers using the automatic tool compared to the contours obtained manually, and measured by DICE similarity coefficient.

RESULTS

The agreement of GTV contours outlined by independent operators was superior with the use of the automatic contour tool compared to manually outlined contours (mean DICE coefficient 0.75 vs 0.57, p = 0.048).

CONCLUSIONS

The dedicated contouring tool allows greater precision and reduction of inter-observer differences in the delineation of the target in SBRT spines. Thus, the evaluated system could be useful in the setting of spinal SBRT to reduce uncertainties of contouring increasing the level of precision on target delivered doses.

SBRT for elderly oligometastatic patients as a feasible, safe and effective treatment opportunity

The constantly increasing life expectancy is raising the issue of treating oncological older patients, who were traditionally candidates to best supportive care or palliative treatments. Several literature data support SBRT in the treatment of the oligometastatic patient as a potentially curable therapeutic option. However, data on older patients are lacking. This study presents the outcomes of a cohort of 61 oligometastatic patients over the age of 80 years who received SBRT, that was proposed to all patients with a minimum Karnofsky Performance Status ≥ 70 and a life expectancy of at least 6 months, with up to five oligometastatic lesions. Radiotherapy was delivered in 3-10 fractions with VMAT-IGRT technique. Toxicity was retrospectively collected according to CTCAE v4.0. Data were retrospectively collected and analyzed. Univariate and multivariate analysis were performed for assessing any potential predictive factor for clinical outcomes. A total of 90 oligometastases were treated in 61 patients with median age 82 years (range, 80-90). The most frequent histology was colorectal cancer (27% of cases). Median follow-up was 20 months (range, 2-63). Local control rates at 1- and 2-years were 98.8% and 88.2%, with colorectal histology being associated with worse LC rates (p = 0.014) at univariate analysis. Progression-free survival rates at 1- and 2-years were 48.6% and 30.5%. Oligorecurrent lesions and single oligometastases were associated with better PFS rates (respectively, p = 0.04 and p = 0.011). Overall survival rates were 75% and 60.5%, polymetastatic spread being predictive of worse survival outcomes at multivariate analysis (p = 0.012). No G2 or higher adverse events were recorded. Our study supports the role of SBRT for the treatment of elderly oligometastatic patients, highlighting the possibility to further explore this therapeutic option in the management of older oncological patients.

Linac-based STereotactic Arrhythmia Radioablation (STAR) for ventricular tachycardia: a treatment planning study

OBJECT

To analyze geometrical approaches, prescription modalities, and delivery efficiency for linear accelerator (Linac)-based STereotactic Arrhythmia Radioablation (STAR) for ventricular tachycardia.

METHODS

The anatomy and planning target volume (PTV) of the first Italian STAR patient were used. To assess geometrical approaches, 3 plans prescribed to 75% isodose-line, differing for number, length of arcs, and couch rotations, were generated and compared (Plans#1-3). Volumetric-arc with 6-MV flattening-filter-free (FFF) was employed. To evaluate prescription modality and delivery, the best geometrical plan was compared with other plans prescribed on 70%, 65%, and 60% isodose-line and with another one using 10MV-FFF beams (Plans#4-7).

RESULTS

For Plans#1-3, PTV coverage, mean cardiac dose, monitor units (MUs), and beam-delivery-time (BDT) were 96-98.5%, 4.9-5.2 Gy, 7047-7790, and 5-6 min, respectively. Plans#4-7 were similar in terms of mean cardiac dose, MUs and BDT to Plans#1-3, except in maximum dose and lower time for 10MV-FFF plan.

CONCLUSION

Linac-based STAR is safe and efficient in terms of BDT and MUs. To ensure high dose to PTV, different dose prescription modalities should be evaluated. The 10FFF approach was the faster but not suitable in patient with cardiac implantable electronic devices.

Single isocenter SRS using CAVMAT offers improved robustness to commissioning and treatment delivery uncertainty compared to VMAT

Purpose

In this study, we evaluate and compare single isocenter multiple target VMAT (SIMT) and Conformal Arc Informed VMAT (CAVMAT) radiosurgery's sensitivity to uncertainties in dosimetric leaf gap (DLG) and treatment delivery. CAVMAT is a novel planning technique that uses multiple target conformal arcs as the starting point for limited inverse VMAT optimization.

Methods

All VMAT and CAVMAT plans were recalculated with DLG values of 0.4, 0.8, and 1.2 mm. DLG effect on V_6Gy[cc], V_12Gy[cc], and V_16Gy[cc], and target dose was evaluated. Plans were delivered to a Delta⁴ (ScandiDos, Madison, WI) phantom and gamma analysis performed with varying criteria. Log file analysis was performed to evaluate MLC positional error. Sixteen targets were delivered to a SRS MapCHECK (Sun Nuclear Corp., Melbourne, FL) to evaluate VMAT and CAVMAT's dose difference (DD) as a function of DLG.

Results

VMAT's average maximum and minimum target dose sensitivity to DLG was 9.08 ±3.50%/mm and 9.50 ± 3.30%/mm, compared to 3.20 ± 1.60%/mm and 4.72 ± 1.60%/mm for CAVMAT. For VMAT, V_6Gy[cc], V_12Gy[cc], and V_16Gy[cc] sensitivity was 35.83 ± 9.50%/mm, 34.12 ± 6.60%/mm, and 39.23 ± 8.40%/mm. In comparison, CAVMAT's sensitivity was 23.19 ± 4.50%/mm, 22.45 ± 4.40%/mm, and 24.88 ± 4.90%/mm, respectively. Upon delivery to the Delta⁴, CAVMAT offered superior dose agreement compared to VMAT. For a 1%/1 mm gamma analysis, VMAT and CAVMAT had a passing rate of 94.53 ± 4.40% and 99.28 ± 1.70%, respectively. CAVMAT was more robust to DLG variation, with the SRS MapCHECK plans yielding an absolute average DD sensitivity of 2.99 ± 1.30%/mm compared to 5.07 ± 1.10%/mm for VMAT. Log files demonstrated minimal differences in MLC positional error for both techniques.

Conclusions

CAVMAT remains robust to delivery uncertainties while offering a target dose sensitivity to DLG less than half that of VMAT, and 65% of that of VMAT for V_6Gy[cc], V_12Gy[cc], and V_16Gy[cc]. The superior dose agreement and reduced sensitivity of CAVMAT to DLG uncertainties indicate promise as a robust alternative to VMAT for SIMT SRS.

Progress and prospects of flattening filter free beam technology in radiosurgery and stereotactic body radiotherapy

The aim of this work is to summarize and evaluate the current status of knowledge on flattening filter free (FFF) beams and their applications in stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT). A PubMed search was undertaken in order to identify relevant publications using FFF and stereotactic radiotherapy as keywords. On a clinical aspect, lung tumors treated with FFF SBRT show promising results in terms of local control and overall survival with acute toxicities consistent with those that occur with standard radiotherapy. Beside lung, SBRT is suitable for different anatomical sites such as liver, prostate, cervix, etc. offering similar results: reduced treatment time, good tumor control and mild acute toxicities. Regarding brain tumors, the employment of SRS with FFF beams significantly reduces treatment time and provides notable normal tissue sparing due to the sharp dose fall-off outside the tumor.

Management of brain metastases in elderly patients with lung cancer

The incidence of brain metastases (BM) is continuing to grow in the elderly population with lung cancer, but these patients are seriously under-represented in clinical trials. Thus, their treatment is not based on the evidence from randomized prospective studies. Age is a well recognized poor prognostic factor for survival in patients with BM from lung cancer, which is reflected in prognostic scales, but its impact on the patients' prognosis reflected by its value in gradually updated grading indices seems to decrease. The reason for poorer outcomes in the elderly is unknown—it may result from the influence of the age per se, simplified staging work-up and suboptimal treatment in this patient subgroup or the excess toxicity of the aggressive anticancer treatment secondary to the impaired physiological regulation mechanisms and comorbidities. The main goal of treatment of BM is to ameliorate neurological symptoms and delay neurological progression, with the focus on the improvement and maintenance of the patients’ quality of life. The possible treatment options for BM from lung cancer are whole-brain radiotherapy, stereotactic radiosurgery, surgery, chemotherapy, targeted therapies and best supportive care. The aim of this review is to summarize the problems related to the management of BM in elderly patients with lung cancer, to analyze the value of the above mentioned treatment options, and to provide an insight into the influence of age-related clinical factors on the patients’ outcomes.

Hybrid volumetric modulated arc therapy for hypofractionated radiotherapy of breast cancer: a treatment planning study

Purpose

This study aims to evaluate the best possible practice using hybrid volumetric modulated arc therapy (H-VMAT) for hypofractionated radiation therapy of breast cancer. Different combinations of H‑VMAT—a combination of three-dimensional radiotherapy (3D-CRT) and VMAT—were analyzed regarding planning target volume (PTV), dose coverage, and exposure to organs at risk (OAR).

Methods

Planning computed tomography scans were acquired in deep-inspiration breath-hold. A total of 520 treatment plans were calculated and evaluated for 40 patients, comprising six different H‑VMAT plans and a 3D-CRT plan as reference. H‑VMAT plans consisted of two treatment plans including 3D-CRT and VMAT. During H‑VMAT planning, the use of hard wedge filters (HWF) and beam energies were varied. The reference plans were planned with mixed beam energies and the inclusion/omission of HWF.

Results

Compared to the reference treatment plans, all H‑VMAT plans showed consistently better PTV dose coverage, conformity, and homogeneity. Additionally, OAR protection was significantly improved with several H‑VMAT combinations (p < 0.05). The comparison of different H‑VMAT combinations showed that inclusion of HWF in the base plan had a negative impact on PTV dose coverage, conformity, and OAR exposure. It also increased the planned monitor units and beam-on time. Advantages of using lower beam energies (6-MV photons) in both the base plan and in the VMAT supplementary dose were observed.

Conclusion

The H‑VMAT technique is an effective possibility for generating homogenous and conformal dose distributions. With the right choice of H‑VMAT combination, superior OAR protection is achieved compared to 3D-CRT.

Efficacy and safety of CyberKnife radiosurgery in elderly patients with brain metastases: a retrospective clinical evaluation

Background

Stereotactic radiosurgery (SRS) has been increasingly applied for up to 10 brain metastases instead of whole brain radiation therapy (WBRT) to achieve local tumor control while reducing neurotoxicity. Furthermore, brain-metastasis incidence is rising due to the increasing survival of patients with cancer. Our aim was to analyze the efficacy and safety of CyberKnife (CK) radiosurgery for elderly patients.

Methods

We retrospectively identified all patients with brain metastases ≥ 65 years old treated with CK-SRS at our institution since 2011 and analyzed data of primary diseases, multimodality treatments, and local therapy effect based on imaging follow-up and treatment safety. Kaplan–Meier analysis for local progression-free interval and overall survival were performed.

Results

We identified 97 patients (233 lesions) fulfilling the criteria at the first CK-SRS. The mean age was 73.2 ± 5.8 (range: 65.0–87.0) years. Overall, 13.4% of the patients were > 80 years old. The three most frequent primary cancers were lung (40.2%), kidney (22.7%), and malignant melanoma (15.5%). In 38.5% (47/122 treatments) multiple brain metastases were treated with the CK-SRS, with up to eight lesions in one session. The median planning target volume (PTV) was 1.05 (range: 0.01–19.80) cm³. A single fraction was applied in 92.3% of the lesions with a median prescription dose of 19 (range: 12–21) Gy. The estimated overall survivals at 3-, 6-, and 12 months after SRS were 79, 55, and 23%, respectively. The estimated local tumor progression-free intervals at 6-, 12-, 24-, 36-, and 72 months after SRS were 99.2, 89.0, 67.2, 64.6, and 64.6%, respectively. Older age and female sex were predictive factors of local progression. The Karnofsky performance score remained stable in 97.9% of the patients; only one patient developed a neurological deficit after SRS of a cerebellar lesion (ataxia, CTCAE Grade 2).

Conclusions

SRS is a safe and efficient option for the treatment of elderly patients with brain metastases with good local control rates without the side effects of WBRT. Older age and female sex seem to be predictive factors of local progression. Prospective studies are warranted to clarify the role of SRS treatment for elderly patients.

Radiosurgery treatment planning using conformal arc informed volumetric modulated arc therapy

Linac based radiosurgery to multiple metastases is commonly planned with volumetric modulated arc therapy (VMAT) as it effectively achieves high conformality to complex target arrangements. However, as the number of targets increases, VMAT can struggle to block between targets, which can lead to highly modulated and/or nonconformal multi-leaf collimator (MLC) trajectories that unnecessarily irradiation of healthy tissue. In this study we introduce, describe, and evaluate a treatment planning technique called Conformal Arc Informed VMAT (CAVMAT), which aims to reduce the dose to healthy tissue while generating highly conformal treatment plans. CAVMAT is a hybrid technique which combines the conformal MLC trajectories of dynamic conformal arcs with the MLC modulation and versatility of inverse optimization. CAVMAT has 3 main steps. First, targets are assigned to subgroups to maximize MLC blocking between targets. Second, arc weights are optimized to achieve the desired target dose, while minimizing MU variation between arcs. Third, the optimized conformal arc plan serves as the starting point for limited inverse optimization to improve dose conformity to each target. Twenty multifocal VMAT cases were replanned with CAVMAT with 20Gy applied to each target. The total volume receiving 2.5_Gy[cm³], 6_Gy[cm³], 12_Gy[cm³], and 16_Gy[cm³], conformity index, treatment delivery time, and the total MU were used to compare the VMAT and CAVMAT plans. In addition, CAVMAT was compared to a broad range of planning strategies from various institutions (108 linear accelerator based plans, 14 plans using other modalities) for a 5-target case utilized in a recent plan challenge. For the linear accelerator-based plans, a plan complexity metric based on aperture opening area and perimeter, total monitor units (MU), and MU for a given aperture opening was utilized in the plan challenge scoring algorithm to compare the submitted plans to CAVMAT. After re-planning the 20 VMAT cases, CAVMAT reduced the average V_2.5Gy[cm³] by 25.25 ± 19.23%, V_6Gy[cm³] by 13.68 ± 18.97%, V_12Gy[cm³] by 11.40 ± 19.44%, and V_16Gy[cm³] by 6.38 ± 19.11%. CAVMAT improved conformity by 3.81 ± 7.57%, while maintaining comparable target dose. MU for the CAVMAT plans increased by 24.35 ± 24.66%, leading to an increased treatment time of 2 minutes. For the plan challenge case, CAVMAT was 1 of 12 linac based plans that met all plan challenge scoring criteria. Compared to the average submitted VMAT plan, CAVMAT increased the V_10%Gy[%] of healthy tissue (Brain-PTV) by roughly 3.42%, but in doing so was able to reduce the V_25%Gy[%] by roughly 3.73%, while also reducing V_50%Gy[%]_, V_75%Gy[%], and V_100%Gy[%]_. The CAVMAT technique successfully eliminated insufficient MLC blocking between targets prior to the inverse optimization, leading to less complex treatment plans and improved tissue sparing. Tissue sparing, improved conformity, and decreased plan complexity at the cost of slight increase in treatment delivery time indicates CAVMAT to be a promising method to treat brain metastases.

Sparing the hippocampus and the hypothalamic- pituitary region during whole brain radiotherapy: a volumetric modulated arc therapy planning study

BACKGROUND

Feasibility testing of a simultaneous sparing approach of hippocampus, hypothalamus and pituitary gland in patients undergoing whole-brain radiotherapy (WBRT) with and without a concomitant boost to metastatic sites.

INTRODUCTION

Cognitive impairment and hormonal dysfunction are common side effects of cranial radiotherapy. A reduced dose application to the patho-physiologically involved functional brain areas, i.e. hippocampus, hypothalamus and pituitary gland, could reduce these common side effects. While hippocampal sparing is already a common practice to improve cognitive outcome, technical experience of additional combined sparing of the hypothalamus/pituitary gland (HT-P) is insufficient.

METHODS

Twenty patients were included in the planning study. In 11 patients, a total dose of 36 Gy of WBRT (2 Gy per fraction) plus a simultaneous integrated boost (SIB) of 9 Gy (0.5 Gy per fraction, total dose: 45 Gy) to the brain metastases was applied. In 9 patients, prophylactic cranial irradiation (PCI) was simulated with a total dose of 30 Gy (2 Gy per fraction). In both patient cohorts, a sparing approach of the hippocampus and the HT-P area was simulated during WBRT. For all treatment plans, volumetric modulated arc therapy (VMAT) was used. Quality assurance included assessment of homogeneity, conformality and target coverage.

RESULTS

The mean dose to the hippocampus and HT-P region was limited to less than 50% of the prescribed dose to the planning target volume (PTV) in all treatment plans. Dose homogeneity (HI) of the target volume was satisfying (median HI = 0.16 for WBRT+SIB and 0.1 for PCI) and target coverage (conformation number, CN) was not compromised (median CN = 0.82 for SIB and 0.86 for PCI).

CONCLUSION

Simultaneous dose reduction to the hippocampus and the HT-P area did not compromise the PTV coverage in patients undergoing WBRT+SIB or PCI using VMAT. While the feasibility of the presented approach is promising, prospective neurologic, endocrine outcome and safety studies are required.

Single-Isocenter Volumetric Modulated Arc Therapy vs. CyberKnife M6 for the Stereotactic Radiosurgery of Multiple Brain Metastases

Introduction: Stereotactic radiosurgery (SRS) is becoming more frequently used for patients with multiple brain metastases (BMs). Single-isocenter volumetric modulated arc therapy (SI-VMAT) is an emerging alternative to dedicated systems such as CyberKnife (CK). We present a dosimetric comparison between CyberKnife M6 and SI-VMAT, planned at RayStation V8B, for the simultaneous SRS of five or more BM.

Patients and Methods: Twenty treatment plans of CK-based single-session SRS to ≥5 brain metastases were replanned using SI-VMAT for delivery at an Elekta VersaHD linear accelerator. Prescription dose was 20 or 18 Gy, conformally enclosing at least 98% of the total planning target volume (PTV), with PTV margin-width adapted to the respective SRS technique. Comparatively analyzed quality metrics included dose distribution to the healthy brain (HB), including different isodose volumes, conformity, and gradient indices. Estimated treatment time was also compared.

Results: Median HB isodose volumes for 3, 5, 8, 10, and 12 Gy were consistently smaller for CK-SRS compared to SI-VMAT (p < 0.001). Dose falloff outside the target volume, as expressed by the gradient indices GI_high and GI_low, was consistently steeper for CK-SRS compared to SI-VMAT (p < 0.001). CK-SRS achieved a median GI_high of 3.1 [interquartile range (IQR), 2.9–1.3] vs. 5.0 (IQR 4.3–5.5) for SI-VMAT (p < 0.001). For GI_low, the results were 3.0 (IQR, 2.9–3.1) for CK-SRS vs. 5.6 (IQR, 4.3–5.5) for SI-VMAT (p < 0.001). The median conformity index (CI) was 1.2 (IQR, 1.1–1.2) for CK-SRS vs. 1.5 (IQR, 1.4–1.7) for SI-VMAT (p < 0.001). Estimated treatment time was shorter for SI-VMAT, yielding a median of 13.7 min (IQR, 13.5–14.0) compared to 130 min (IQR, 114.5–154.5) for CK-SRS (p < 0.001).

Conclusion: SI-VMAT offers enhanced treatment efficiency in cases with multiple BM, as compared to CyberKnife, but requires compromise regarding conformity and integral dose to the healthy brain. Additionally, delivery at a conventional linear accelerator (linac) may require a larger PTV margin to account for delivery and setup errors. Further evaluations are warranted to determine whether the detected dosimetric differences are clinically relevant. SI-VMAT could be a reasonable alternative to a dedicated radiosurgery system for selected patients with multiple BM.

Impact of adjuvant radiotherapy on the survival of women with optimally resected stage III endometrial cancer in the era of modern radiotherapy: a retrospective study

Background

The optimal adjuvant treatment for stage III endometrial cancer in the era of modern radiotherapy remains undefined. We investigated the benefit of adjuvant radiotherapy for women who underwent optimal resection for stage III endometrial cancer in the era of modern radiotherapy.

Methods

We retrospectively reviewed patients with endometrial cancer who were treated between 2010 and 2018. Adjuvant treatment included radiotherapy by modern radiotherapy techniques (intensity-modulated or volumetric modulated arc radiotherapy), chemotherapy, or both. Recurrence-free survival (RFS) and overall survival (OS) were calculated using the Kaplan-Meier method and analyzed via multivariate Cox proportional hazards models.

Results

One hundred sixty-one patients were initially included (52, 9, and 100 with stages IIIA, IIIB, and IIIC cancer, respectively); 154 patients (96%) received adjuvant therapy. Such adjuvant treatment was associated with improved RFS (p = 0.014) and OS (p = 0.044) over surgery alone. Adjuvant radiotherapy by modern radiotherapy techniques led to low incidence of acute (25%) and chronic (7%) grade ≥ 2 gastrointestinal toxicity. On univariate analysis, non-endometrioid histology and grade 3 status were associated with higher risks of tumor recurrence and death, whereas adjuvant radiotherapy alone or in combination chemotherapy reduced their risks. On multivariate analysis, non-endometrioid histology was associated with increased recurrence (hazard ratio [HR], 2.95; p = 0.009), whereas adjuvant radiotherapy alone or with chemotherapy was associated with lower recurrence (HR, 0.62; p = 0.042). Patients > 60 years of age (p = 0.038) as well as those with endometrioid histology (p = 0.045), lymphovascular space invasion (p = 0.031), and ≥ 2 positive lymph nodes (p = 0.044) benefited most from adjuvant radiotherapy.

Conclusions

Modern adjuvant radiotherapy (intensity-modulated or volumetric modulated arc radiotherapy) alone or with chemotherapy should be considered for women with optimally resected stage III endometrial cancer.

Trial registration

ClinicalTrials.gov, NCT04251676. Registered 24 January 2020. Retrospectively registered.

Noncoplanar VMAT for Brain Metastases: A Plan Quality and Delivery Efficiency Comparison With Coplanar VMAT, IMRT, and CyberKnife

Purpose:

To compare plan quality and delivery efficiency of noncoplanar volumetric modulated arc therapy with coplanar volumetric modulated arc therapy, intensity-modulated radiation therapy, and CyberKnife for multiple brain metastases.

Methods:

For 15 patients with multiple brain metastases, noncoplanar volumetric modulated arc therapy, coplanar volumetric modulated arc therapy, intensity-modulated radiation therapy, and CyberKnife plans with a prescription dose of 30 Gy in 3 fractions were generated. Noncoplanar volumetric modulated arc therapy and coplanar volumetric modulated arc therapy plans consisted of 4 noncoplanar arcs and 2 full coplanar arcs, respectively. Intensity-modulated radiation therapy plans consisted of 7 coplanar fields. CyberKnife plans used skull tracking to ensure accurate position. All plans were generated to cover 95% target volume with prescription dose. Gradient index, conformity index, normal brain tissue volume (V_3Gy − V_24Gy), monitor units, and beam on time were evaluated.

Results:

Gradient index was the lowest for CyberKnife (3.49 ± 0.65), followed by noncoplanar volumetric modulated arc therapy (4.21 ± 1.38), coplanar volumetric modulated arc therapy (4.87 ± 1.35), and intensity-modulated radiation therapy (5.36 ± 1.98). Conformity index was the largest for noncoplanar volumetric modulated arc therapy (0.87 ± 0.03), followed by coplanar volumetric modulated arc therapy (0.86 ± 0.04), CyberKnife (0.86 ± 0.07), and intensity-modulated radiation therapy (0.85 ± 0.05). Normal brain tissue volume at high-to-moderate dose spreads (V_24Gy − V_9Gy) was significantly reduced in noncoplanar volumetric modulated arc therapy over that of intensity-modulated radiation therapy and coplanar volumetric modulated arc therapy. Normal brain tissue volume for noncoplanar volumetric modulated arc therapy was comparable with noncoplanar volumetric modulated arc therapy at high-dose level (V_24Gy − V_15Gy) and larger than CyberKnife at moderate-to-low dose level (V_12Gy − V_3Gy). Monitor units was highest for CyberKnife (28 733.59 ± 7197.85), followed by intensity-modulated radiation therapy (4128.40 ± 1185.38), noncoplanar volumetric modulated arc therapy (3105.20 ± 371.23), and coplanar volumetric modulated arc therapy (2997.27 ± 446.84). Beam on time was longest for CyberKnife (30.25 ± 7.32 minutes), followed by intensity-modulated radiation therapy (2.95 ± 0.85 minutes), noncoplanar volumetric modulated arc therapy (2.61 ± 0.07 minutes), and coplanar volumetric modulated arc therapy (2.30 ± 0.23 minutes).

Conclusion:

For brain metastases far away from organs-at-risk, noncoplanar volumetric modulated arc therapy generated more rapid dose falloff and higher conformity compared to intensity-modulated radiation therapy and coplanar volumetric modulated arc therapy. Noncoplanar volumetric modulated arc therapy provided a comparable dose falloff with CyberKnife at high-dose level and a slower dose falloff than CyberKnife at moderate-to-low dose level. Noncoplanar volumetric modulated arc therapy plans had less monitor units and shorter beam on time than CyberKnife plans.

Feasibility and preliminary clinical results of linac-based Stereotactic Body Radiotherapy for spinal metastases using a dedicated contouring and planning system

Background

Stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT) are well established local treatment approaches in several cancer settings. Although SBRT is still under investigation for spinal metastases, promising results in terms of a high effectiveness and optimal tolerability have been recently published on this topic. For spinal SBRT, one of the most relevant issues is represented by the inter-observer variability in target definition. Recently, several technological innovations, including specific tools such as multimodality-imaging (computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET-CT), automated volumes contouring and planning, could allow clinicians to minimize the uncertainties related to spinal SBRT workflow. Aim of this study is to report the feasibility of the clinical application of a dedicated software (Element®, Brainlab™ Germany) for spinal metastases SBRT.

Material and method

The patient selection criteria for SBRT in spinal metastases were the following: age > 18 years, diagnosis of spinal metastases (n ≤ 3), life expectancy > 3 months, controlled primary tumor or synchronous diagnosis and Spinal Instability Neoplastic Score (SINS) ≤ 12 points. All radiation target volumes were defined and planned with the support of the dedicated software Elements® (Brainlab™ Germany). Different dose prescription have been used: 12 Gy in single fraction, 12 Gy, 18 Gy, 21 Gy and 24 Gy in 3 fractions. Toxicity was assessed according to the Common Terminology Criteria for Adverse Events (CTCAE) v4.0. SPSS version 20 was used for statistical analysis.

Results

From April 2018 to April 2019, 54 spinal metastases in 32 recruited patients were treated with Linac-based SBRT. With a median follow-up of 6 months (range 3–12), local control rates at 6 months and 9 months were 86 and 86%, respectively. No adverse events ≥3 grade were observed.

Conclusions

This preliminary experience shows that with respect to acute toxicity and early clinical response, linac-based using Elements® Spine SRS is a feasible and effective approach.

LINAC based stereotactic radiosurgery for multiple brain metastases: guidance for clinical implementation

Introduction: Stereotactic radiosurgery (SRS) is a promising treatment option for patients with multiple brain metastases (BM). Recent technical advances have made LINAC based SRS a patient friendly technique, allowing for accurate patient positioning and a short treatment time. Since SRS is increasingly being used for patients with multiple BM, it remains essential that SRS be performed with the highest achievable quality in order to prevent unnecessary complications such as radionecrosis. The purpose of this article is to provide guidance for high-quality LINAC based SRS for patients with BM, with a focus on single isocenter non-coplanar volumetric modulated arc therapy (VMAT). Methods: The article is based on a consensus statement by the study coordinators and medical physicists of four trials which investigated whether patients with multiple BM are better palliated with SRS instead of whole brain radiotherapy (WBRT): A European trial (NCT02353000), two American trials and a Canadian CCTG lead intergroup trial (CE.7). This manuscript summarizes the quality assurance measures concerning imaging, planning and delivery. Results: To optimize the treatment, the interval between the planning-MRI (gadolinium contrast-enhanced, maximum slice thickness of 1.5 mm) and treatment should be kept as short as possible (< two weeks). The BM are contoured based on the planning-MRI, fused with the planning-CT. GTV-PTV margins are minimized or even avoided when possible. To maximize efficiency, the preferable technique is single isocenter (non-)coplanar VMAT, which delivers high doses to the target with maximal sparing of the organs at risk. The use of flattening filter free photon beams ensures a lower peripheral dose and shortens the treatment time. To bench mark SRS treatment plan quality, it is advisable to compare treatment plans between hospitals. Conclusion: This paper provides guidance for quality assurance and optimization of treatment delivery for LINAC-based radiosurgery for patients with multiple BM.

Stereotactic radiosurgery in elderly patients with brain metastases: comparison with non-elderly patients using database of a multi-institutional prospective observational study (JLGK0901-Elderly)

PURPOSE

Stereotactic radiosurgery (SRS) has been increasingly used for elderly patients with brain metastases (BMs). However, no studies based on a large sample size have been reported. To compare SRS treatment results between elderly and non-elderly patients, we performed a subset study of elderly patients using our prospectively-accumulated multi-institution study database (JLGK0901 Study, Lancet Oncol 15:387-395, 2014).

METHODS

During the 2009-2011 period, 1194 eligible patients undergoing gamma knife SRS alone for newly diagnosed BMs were enrolled in this study from 23 gamma knife facilities in Japan. Observation was discontinued at the end of 2013. The 1194 patients were divided into the two age groups, 693 elderly ( ≥ 65 years) and 501 non-elderly ( < 65 years) patients. Our study protocol neither set an upper age limit nor required dose de-escalation.

RESULTS

Median post-SRS survival time was significantly shorter in the elderly than in the non-elderly patient group (10.3 vs 14.3 months, HR 1.380, 95% CI 1.218-1.563, p < 0.0001). However, regarding all secondary endpoints including neurological death, neurological deterioration, SRS-related complications, leukoencephalopathy, local recurrence, newly-developed tumors, meningeal dissemination, salvage SRS, whole brain radiotherapy and surgery and decreased mini-mental state examination scores, the elderly patient group was not inferior to the non-elderly patient group. In the 693 elderly patients, there was no post-SRS median survival time difference between those with 5-10 versus 2-4 tumors (10.8 vs 8.9 months, HR 0.936, 95% CI 0.744-1.167, p = 0.5601).

CONCLUSIONS

We conclude that elderly BM patients are not unfavorable candidates for SRS alone treatment.

Role of Radiosurgery/Stereotactic Radiotherapy in Oligometastatic Disease: Brain Oligometastases

During the natural history of oncologic diseases, approximately 20-40% of patients affected by cancer will develop brain metastases. Non-small lung cancer, breast cancer, and melanoma are the primaries that are most likely to metastasize into the brain. To date, the role of Radiosurgery/Stereotactic Radiotherapy (SRS/SRT) without Whole brain irradiation (WBRT) is a well-recognized treatment option for patients with limited intracranial disease (1-4 BMs) and a life-expectancy of more than 3-6 months. In the current review, we focused on randomized studies that evaluate the potential benefit of radiosurgery/stereotactic radiotherapy for brain oligometastases. To date, no difference in overall survival has been observed between SRS/SRT alone compared to WBRT plus SRS. Notably, SRS alone achieved higher local control rates compared to WBRT. A possible strength of SRS adoption is the potential decreased neurocognitive impairment.