Comparison of four techniques for spine stereotactic body radiotherapy: Dosimetric and efficiency analysis

Advanced External Beam Stereotactic Radiotherapy for Skull Base Reirradiation

BACKGROUND/OBJECTIVES

Stereotactic body radiation therapy (SBRT) for skull base reirradiation is particularly challenging, as patients have already received substantial radiation doses to the region, and nearby normal organs may have approached their tolerance limit from prior treatments. In this study, we reviewed the characteristics and capabilities of four advanced external beam radiation delivery systems and four modern treatment planning systems and evaluated the treatment plan quality of each technique using skull base reirradiation patient cases.

METHODS

SBRT plans were generated for sixteen skull base reirradiation patients using four modalities: the GK plan for the Elekta Leksell Gamma Knife Perfexion/ICON, the CyberKnife (CK) plan for the Accuray CyberKnife, the intensity-modulated proton therapy (IMPT) plan for the Hitachi ProBeat-FR proton therapy machine, and the volumetric-modulated arc therapy (VMAT) plan for the Varian TrueBeam STx. These plans were evaluated and compared using two novel gradient indices in addition to traditional dosimetry metrics for targets and organs at risk (OARs). The steepest border gradient quantified the percent prescription dose fall-off per millimeter at the boundary between the target and adjacent critical structures. This gradient index highlighted the system's ability to spare nearby critical OARs. The volume gradient assessed the extent of dose spread outside the target toward the patient's body.

RESULTS

All plans achieved comparable target coverage and conformity, while IMPT and VMAT demonstrated significantly better uniformity. The GK plans exhibited the highest border gradient, up to 20.9%/mm, followed by small-spot-size IMPT plans and CK plans. Additionally, IMPT plans showed the benefit of reduced dose spread in low-dose regions and the lowest maximum and mean doses to the brainstem and carotid artery.

CONCLUSIONS

The advanced external beam radiotherapy modalities evaluated in this study are well-suited for SBRT in skull base reirradiation, which demands precise targeting of tumors with highly conformal doses and steep dose gradients to protect nearby normal structures.

The Incidence and Influencing Factors of Sleep Disorders in Cyber Knife Patients during Treatment

OBJECTIVE

This study first analyzes the incidence and influencing factors of sleep disorders in Cyber Knife patients during treatment, in order to provide more accurate strategies for clinical prevention, early diagnosis, and treatment.

METHODS

A total of 101 patients who underwent Cyber Knife treatment at Tumor Diagnosis and Treatment Center, Huashan Hospital Affiliated to Fudan University from April 2022 to April 2023 were selected as the research objects. The Pittsburgh Sleep Quality Index (PSQI) was used for evaluation. Patients with PSQI ≥8 points were included in the occurrence group, and patients with PSQI <8 points were included in the non-occurrence group. The general sociological and disease-related characteristics of the patients, such as education, chemotherapy or targeted therapy, somatic symptoms and other features were collected. χ2 test was performed first to determine the difference between two groups, and Logistic regression analysis was used to identify the predictors of sleep disorders in Cyber Knife patients.

RESULTS

A total of 101 Cyber Knife patients were included in this study, of which 43 patients (42.58%) without sleep disorders were included in the non-occurrence group. There were 22 cases (21.78%) of mild disorder, 22 cases (21.78%) of moderate disorder, and 14 cases (13.86%) of severe disorder, all of which were included in the occurrence group. There were significant differences in education level (primary and junior high schools: 32 (55.17%) vs. 15 (34.88%) patients, p = 0.043), family monthly income (≤5000 CNY (1 USD = 6.48 CNY): 36 (62.07%) vs. 15 (34.88%) patients, p = 0.007), somatic symptoms (35 (60.34%) vs. 17 (39.53%) patients, p = 0.038), self-rating anxiety scale (SAS) (>50: 32 (55.17%) vs. 15 (34.88%) patients, p = 0.043), self-rating depression scale (SDS) (>53: 35 (60.34%) vs. 18 (41.86%) patients, p = 0.038), numerical rating scale (NRS) (>3: 30 (51.72%) vs. 13 (30.23%) patients, p = 0.031) between the group of occurrence and no occurrence group. Education level (odds ratio (OR) = 2.845, p = 0.038), somatic symptoms (OR = 2.666, p = 0.048), SAS (OR = 2.889, p = 0.042), SDS (OR = 2.928, p = 0.027) and NRS (OR = 2.981, p = 0.025) had a statistically significant effect on sleep disorders in Cyber Knife patients.

CONCLUSIONS

Cyber Knife patients are prone to sleep disorders during treatment. It is necessary to pay more attention to and take measures to reduce the occurrence of sleep disorders in clinical practice.

Efficacy of flattening filter-free beams with the acuros XB algorithm in thoracic spine stereotactic body radiation therapy

This study aimed to determine the dosimetric value of flattening filter-free (FFF) beams compared to flattening filter (FF) beams using different algorithms in the treatment planning of thoracic spine stereotactic body radiation therapy (SBRT). A total of 120 plans were created for 15 patients using the Anisotropic Analytical Algorithm (AAA) and the Acuros External Beam (AXB) algorithm with FF and FFF beams at 6 MV and 10 MV energies. Various dosimetric parameters were evaluated, including target coverage, dose spillage, and organs-at-risk sparing of the spinal cord and esophagus. Treatment delivery parameters, such as the monitor units (MUs), modulation factors (MFs), beam-on time (BOT), and dose calculation time (DCT), were also collected. Significant differences were observed in the dosimetric parameters when AXB was used for all energies (P < 0.05). 6 XFFF energy was the best option for target coverage, dose spillage, and organs-at-risk sparing. In contrast, dosimetric parameters had no significant difference when using the AAA. The AAA and AXB calculations showed that the 6 XFFF beam had the shortest DCT. The treatment delivery parameters indicated that 10 XFF beam required the fewest MUs and MFs. In addition, the 10 XFFF beam demonstrated the shortest BOT. For effective treatment of the thoracic spine using SBRT, it is recommended to use the 10 XFFF beam because of the short BOT. Moreover, the AXB algorithm should be used because of its accurate dose calculation in regions with tissue heterogeneity.

Improvement of target coverage using automated non-coplanar volumetric modulated arc therapy planning in stereotactic radiotherapy for cervical metastatic spinal tumors

This study aimed to compare dosimetric parameters for targets and organs at risk (OARs) between volumetric modulated arc therapy (VMAT) and automated VMAT (HyperArc, HA) plans in stereotactic radiotherapy for patients with cervical metastatic spine tumors. VMAT plans were generated for 11 metastases using the simultaneous integrated boost technique to deliver 35 to 40 and 20 to 25 Gy for high dose and elective dose planning target volume (PTVHD and PTVED), respectively. The HA plans were retrospectively generated using 1 coplanar and 2 noncoplanar arcs. Subsequently, the doses to the targets and OARs were compared. The HA plans provided significantly higher (p < 0.05) D_min (77.4 ± 13.1%), D_99% (89.3 ± 8.9%), and D_98% (92.5 ± 7.7%) for gross tumor volume (GTV) than those of the VMAT plans (73.4 ± 12.2%, 84.2 ± 9.6 and 87.3 ± 8.8% for D_min, D_99% and D_98%, respectively). In addition, D_99% and D_98% for PTVHD were significantly higher in the HA plans, whereas dosimetric parameters were comparable between the HA and VMAT plans for PTVED. The D_max values for the brachial plexus, esophagus, and spinal cord were comparable, and no significant difference was observed in the D_mean for the larynx, pharyngeal constrictor, thyroid, parotid grand (left and right), and Submandibular gland (left and right). The HA plans provided significantly higher target coverage of GTV and PTVHD, with a comparable dose for OARs with VMAT plans. The results of this study may contribute to the improvement of local control in clinical practice.

Stereotactic Body Radiation Therapy for Spinal Metastases: Benefits and Limitations

Progress in biological cancer characterization, targeted systemic therapies and multimodality treatment strategies have shifted the goals of radiotherapy for spinal metastases from short-term palliation to long-term symptom control and prevention of compilations. This article gives an overview of the spine stereotactic body radiotherapy (SBRT) methodology and clinical results of SBRT in cancer patients with painful vertebral metastases, metastatic spinal cord compression, oligometastatic disease and in a reirradiation situation. Outcomes after dose-intensified SBRT are compared with results of conventional radiotherapy and patient selection criteria will be discussed. Though rates of severe toxicity after spinal SBRT are low, strategies to minimize the risk of vertebral compression fracture, radiation induced myelopathy, plexopathy and myositis are summarized, to optimize the use of SBRT in multidisciplinary management of vertebral metastases.

Comparison of Ray Tracing and Monte Carlo Calculation Algorithms for Spine Lesions Treated With CyberKnife

Purpose

This study attempts to evaluate Ray Tracing (RT) and Monte Carlo (MC) algorithms for CyberKnife treatments of spine lesions and determine whether the MC algorithm is necessary for all spine treatment and compare the RT algorithm and MC algorithm at various spine lesion sites.

Methods

The CyberKnife is used for stereotactic body radiotherapy for lesions in the cervical spine (30), thoracic spine (50), lumbar spine (30), and sacral spine (15). Dose was calculated using RT and MC algorithms for patients planned with the same beam angles and monitor units. Dose-volume histograms of the target and selected critical structures are evaluated.

Results

The average target coverage of prescribed dose with MC algorithms was 94.80%, 88.47%, 92.52%, and 93.41%, respectively, in cervical, thoracic, lumbar, and sacral spine. For the thoracic spine, the RT algorithm significantly overestimates the percentage volume of the target covered by the prescribed dose, as well as overestimates doses to organs at risk in most cases, including lung, spinal cord, and esophagus. For cervical, lumbar, and sacral spine, the differences of the target coverage of prescription dose were generally less than 3% between the RT and MC algorithms. The differences of doses to organs at risk varied with lesion sites and surrounding organs.

Conclusions

In the thoracic spine lesions with beams through air cavities, RT algorithm should be limited and verified with MC algorithm, but the RT algorithm is adequate for treatment of cervical, lumbar, and sacral spine lesions without or with a small amount of beams passing through the lungs.