Hypofractionated stereotactic radiotherapy for large brain metastases: Optimizing the dosimetric parameters

Synergizing Success: The Role of Anlotinib Combinations in Advanced Non-Small Cell Lung Cancer Treatment

Anlotinib, a novel receptor tyrosine kinase inhibitor that is taken orally, targets several RTKs and is authorized as a third-line treatment for patients with advanced non-small cell lung cancer (NSCLC). Anlotinib is also used in combination with immunotherapy or chemotherapy for advanced NSCLC. We aimed to explore the efficacy and safety of anlotinib-based regimens in NSCLC treatment, focusing on combination therapies. We also addressed challenges that hinder oncologists from using it, such as toxicity and resistance mechanisms. A systematic approach involves searching the National Institute of Health PubMed, Scopus, MedLine, and Web of Science databases up to April 2024. Relevant studies were identified and analyzed for their methodologies, outcomes, and patient characteristics. Findings revealed that numerous effective combination regimens, such as anlotinib with platinum-based chemotherapy and anlotinib combined with PD-1 blockades, have shown positive results in terms of progression-free survival (PFS), overall survival (OS), and objective response rate (ORR). On the other hand, NSCLC treatment faces hurdles due to drug resistance and its toxicity profile. These challenges underscore the need for continued research and optimization of treatment strategies.

Comparative study of dynamic conformal arc therapy and volumetric modulated arc therapy for treating single brain metastases: A retrospective analysis of dosimetric and clinical outcomes

Background and purpose

Stereotactic radiation therapy (SRT) is commonly used to treat brain metastases (BMs). This retrospective study compared two SRT techniques, dynamic conformal arc therapy (DCAT) and volumetric modulated arc therapy (VMAT), for single BM treatments.

Material and methods

Data of patients treated between January 2010 and June 2020 were considered. Patients with multiple BMs, resected BMs, reirradiation, whole-brain radiation therapy and brainstem metastases were excluded. We focused our analysis on 97 patients who received 23.1 Gy in three fractions. Acute toxicities and follow-up outcomes were recorded. Dosimetric data were analyzed in two subgroups (PTV ≤ 10 cc and PTV > 10 cc).

Results

DCAT and VMAT were used in 70 (72.2 %) and 27 (27.8 %) patients, respectively. Acute toxicities were not significantly different between groups (p = 0.259), and no difference was detected in the incidence rate of radionecrosis, local recurrence and cerebral recurrence (p > 0.999, p > 0.999 and p = 0.682, respectively). PTV coverage was better with DCAT for small volumes (PTV ≤ 10 cc). Mean conformity index (CI) was significantly higher with VMAT and mean gradient index (GI) was significantly lower with DCAT whatever volume subgroups (p < 0.001). DCAT had more heterogeneous plans and VMAT required more monitor units. DCAT resulted in reduced low and intermediate doses, whereas VMAT led to decreased high doses.

Conclusion

DCAT and VMAT are two effective and safe SRT techniques for BMs treatment. In the era of re-irradiation, it is important to reduce the doses delivered to healthy tissues. Further prospective studies are needed to validate these findings.

Stereotactic Radiation Therapy of Single Brain Metastases: A Literature Review of Dosimetric Studies

Stereotactic radiotherapy (SRT) plays a major role in treating brain metastases (BMs) and can be delivered using various equipment and techniques. This review aims to identify the dosimetric factors of each technique to determine whether one should be preferred over another for single BMs treatment. A systematic literature review on articles published between January 2015 and January 2022 was conducted using the MEDLINE and ScienceDirect databases, following the PRISMA methodology, using the keywords "dosimetric comparison" and "brain metastases". The included articles compared two or more SRT techniques for treating single BM and considered at least two parameters among: conformity (CI), homogeneity (HI) and gradient (GI) indexes, delivery treatment time, and dose-volume of normal brain tissue. Eleven studies were analyzed. The heterogeneous lesions along with the different definitions of dosimetric indexes rendered the studied comparison almost unattainable. Gamma Knife (GK) and volumetric modulated arc therapy (VMAT) provide better CI and GI and ensure the sparing of healthy tissue. To conclude, it is crucial to optimize dosimetric indexes to minimize radiation exposure to healthy tissue, particularly in cases of reirradiation. Consequently, there is a need for future well-designed studies to establish guidelines for selecting the appropriate SRT technique based on the treated BMs' characteristics.

Feasibility of a simultaneously integrated boost concept for hypofractionated stereotactic radiotherapy of unresected brain metastases

BACKGROUND

In stereotactic radiotherapy, dose is prescribed to an isodose surrounding the planning target volume (PTV). However, the desired dose inhomogeneity inside the PTV leaves the specific dose distribution to the gross tumor volume (GTV) unspecified. A simultaneously integrated boost (SIB) to the GTV could solve this shortcoming. In a retrospective planning study with 20 unresected brain metastases, a SIB approach was tested against the classical prescription.

METHODS

For all metastases, the GTV was isotropically enlarged by 3 mm to a PTV. Two plans were generated, one according to the classical 80% concept with 5 times 7 Gy prescribed (on D_2%) to the 80% PTV surrounding isodose (with D_98%(PTV) ≥ 35 Gy), and the other one following a SIB concept with 5 times 8.5 Gy average GTV dose and with D_98%(PTV) ≥ 35 Gy as additional requirement. Plan pairs were compared in terms of homogeneity inside GTV, high dose in PTV rim around GTV, and dose conformity and gradients around PTV using Wilcoxon matched pairs signed rank test.

RESULTS

The SIB concept was superior to the classical 80% concept concerning dose homogeneity inside GTV: Heterogeneity index of GTV was in the SIB concept (median 0.0513, range 0.0397-0.0757) significantly (p = 0.001) lower than in the 80% concept (median 0.0894, range 0.0447-0.1872). Dose gradients around PTV were not inferior. The other examined measures were comparable.

CONCLUSION

Our stereotactic SIB concept better defines the dose distribution inside PTV and can be considered for clinical use.

Dosimetric Effects of Dynamic Jaw Tracking and Collimator Angle Optimization in Non-Coplanar Cranial Arc Radiotherapy

The stereotactic treatment of single cranial targets using noncoplanar volumetric modulated arc therapy (VMAT) allows for effective dose delivery to the target, while sparing normal brain tissue. In this study, the dosimetric effect of adding dynamic jaw tracking and automatic collimator angle selection in the optimization of single target cranial VMAT plans was investigated. Twenty-two cranial targets, previously treated with VMAT without dynamic jaw tracking and automatic collimator angle optimization (CAO) were chosen for replanning. Target volumes ranged from 0.441cc to 25.863cc with doses between 18Gy and 30Gy delivered in 1 to 5 fractions. Original plans were reoptimized with automatic CAO, keeping all other objectives the same (CAO plans). Next, original plans were reoptimized with both dynamic jaw tracking and CAO (DJT plans). Original, CAO, and DJT target doses were compared using the Paddick gradient index (GI) and the Paddick inverse conformity index (ICI), while normal tissue dose was compared using the volume of the normal brain receiving 5Gy, 10Gy, and 12Gy. The normal tissue volume was normalized to target size to allow cross comparison between plans. A one-sided t-test was performed to determine whether the changes in the plan metrics were statistically significant. CAO plans had improved GIs compared to the originals (p = 0.03) with insignificant changes in other plan metrics (p > 0.20). The addition of dynamic jaw tracking in DJT plans greatly improved ICIs and normal brain metrics (p < 0.01) compared to the CAO plans with minor improvement in ICIs (p = 0.07). The combined effect of adding dynamic jaw tracking and collimator optimization led to improvements in all metrics of the DJT plans when compared to the original (p < 0.02). The addition of dynamic jaw tracking and CAO led to improvements in both target and normal tissue dose metrics for single-target noncoplanar cranial VMAT plans.

CT-MR Image Fusion for Post-Implant Dosimetry Analysis in Brain Tumor Seed Implantation- a Preliminary Study

Purpose

To calculate and evaluate postimplant dosimetry (PID) with CT-MR fusion technique after brain tumor brachytherapy and compare the result with CT-based PID.

Methods and Materials

16 brain tumor patients received MR-guided intervention with Iodine-125 (¹²⁵I) seed implantation entered this preliminary study for PID evaluation. Registration and fusion of CT and MR images of the same patients were performed one day after operation. Seeds identification and targets delineation were carried out on CT, MR, and CT-MR fusion images, each. The number and location of seeds on MR or CT- MR fusion images were compared with those of actually implanted seeds. Clinical target volume (CTV) and dosimetric parameters such as %D90, %V100 and external V100 were measured and calculated. In addition, the correlation of the fusion to CT CTV ratio and other factors were analyzed.

Results

The numbers of fusion seeds were not significantly different compared with reference seeds (t =1.76, p >0.05). The difference between reference seeds numbers and truly extracted MR seeds numbers was statistically significant (t =3.91, p <0.05). All dosimetric parameters showed significant differences between the two techniques (p <0.05). The mean CTV delineated on fusion images was 34.3 ± 33.6, smaller than that on CT images. The mean values of external V100, %V100 and %D90 on fusion images were larger than those on CT images. Correlation analysis showed that the fusion-CT V100 ratio was positively and significantly correlated with the fusion-CT volume ratio.

Conclusions

This preliminary study indicated that CT-MR fusion-based PID exhibited good accuracy for ¹²⁵I brain tumor brachytherapy dosimetry when compared to CT-based PID and merits further research to establish best-outcome protocols.

Anlotinib Combined with Cranial Radiotherapy for Non-Small Cell Lung Cancer Patients with Brain Metastasis: A Retrospectively, Control Study

Introduction

Cranial radiotherapy (CRT) is the main treatment for non-small cell lung cancer (NSCLC) with brain metastasis (BM) and non-EGFR/ALK/ROS1-TKIs indication, and anlotinib can improve overall prognosis. However, the clinical effects of CRT combined with anlotinib for the treatment of NSCLC with BM remain unclear.

Methods

We retrospectively analyzed the clinical effects of anlotinib + CRT versus CRT alone in NSCLC patients with BM and non-EGFR/ALK/ROS1-TKIs indication from September 2016 to June 2020. The progression-free survival (PFS) and overall survival (OS) of anlotinib + CRT versus CRT alone were analyzed. After evaluation of the clinical characteristics to generate a baseline, the independent prognostic factors for intracranial PFS (iPFS) and OS were subjected to univariate and multivariate analysis. Finally, subgroup analysis for iPFS and OS was performed to assess treatment effects using randomized stratification factors and stratified Cox proportional hazards models.

Results

This study included data for 73 patients with BM at baseline. Of the 73 patients, 45 patients received CRT alone, and 28 patients received CRT + anlotinib. There was no significant difference in clinical features between the two groups (P > 0.05). Compared with the CRT group, the combined group had longer iPFS (median iPFS [miPFS]: 3.0 months vs 11.0 months, P = 0.048). However, there were no significant differences in OS, extracranial PFS, and systemic PFS. For clinical features, univariate and multivariate analysis showed that the plus anlotinib treatment was an independent advantage predictor of iPFS (hazard ratio [HR] 0.51; 95% confidence interval [CI] 0.27–0.95; P = 0.04), and age ≥57 years (HR 1.04, 95% CI 1.01–1.08, P = 0.014) and KPS score ≤80 (HR 1.04, 95% CI 1.01–1.08, P = 0.014) were independent disadvantage predictors of OS (P < 0.05). In addition, although this difference was not statistically significant (p > 0.05), the patients with the anlotinib + local CRT (LCRT) treatment had the longest iPFS (miPFS: 27.0 months) and OS (median OS [mOS]: 36 months). The miPFS and mOS values for the LCRT group were 11 months and 18 months, respectively, with shorter values for whole-brain RT (WBRT) + anlotinib group, WBRT + LCRT + anlotinib group, WBRT, and WBRT + LCRT.

Conclusion

Anlotinib can improve the intracranial lesion control and survival prognosis of NSCLC patients with CRT.