Journal of radiosurgery and SBRT最新文献

Purpose: Radiosurgery for large arteriovenous malformations (AVMs) is limited by toxicity from dose spillage into normal brain, worsened by larger gradient indices in bigger targets. Proton radiosurgery theoretically reduces integral dose but has greater uncertainty due to robust planning constraints and fewer beam angles. This study evaluates whether pencil beam scanning radiosurgery (PBSR) improves normal brain dosimetry while maintaining comparable target coverage to photon radiosurgery.

Methods: The 10 largest AVMs treated with photon radiosurgery at a single institution were re-planned for PBSR in Varian Eclipse. Proton plans incorporated a 2% computed tomography (CT) density correction and 2 mm range uncertainty, with 2-4 beams per institutional practice. Plans prioritized isotoxicity to organs at risk (OARs) before matching target coverage. Dosimetric metrics were compared using a paired t-test.

Results: Median AVM size was 36.6 cc (24.3-60.1 cc). All plans prescribed 1750 cGy in one fraction. PBSR had higher gradient indices and reduced target coverage near OARs compared to photon radiosurgery. While PBSR lowered normal brain mean dose and V _5 Gy, it increased V _12 Gy, a known predictor of toxicity.

Conclusions: PBSR, as planned with current institutional constraints, leads to greater high-dose spill into normal brain and inferior target coverage near OARs. Future improvements in PBSR, such as dual-energy CT, additional beam angles, and LET-based planning, may help mitigate these limitations.

Introduction: Gamma Knife radiosurgery (GKRS) using the 4C system faces challenges with treatment cancellations due to clearance issues, frame complications, and limited treatment space. Understanding cancellation factors is crucial for optimizing patient selection and workflow, particularly with technological advancements in newer systems.

Aims and objectives: This study analyzed the factors associated with treatment feasibility and cancellation in Gamma Knife 4C (GK4C) radiosurgery and explored potential benefits of upgrading to Gamma Knife Icon (GKI) technology, incorporating evidence on clearance mechanisms and treatment improvements.

Materials and methods: A retrospective analysis was conducted on 108 consecutive patients planned for GK4C treatment between 2006 and 2020. Data on demographics, tumor characteristics, treatment parameters, and reasons for cancellation were collected. Statistical analyses examined associations between variables and treatment feasibility. Hypothetical GKI plans assessed potential improvements. A PubMed review identified 69 studies that addressed treatment cancellation and technological improvements.

Results: The main reasons for GK4C cancellation were clearance issues (41.7%), high organ-at-risk doses (35.2%), and large target volumes (23.1%). Associations were found between reason for cancellation and tumor volume, diagnosis, location, and prescribed dose. Multivariate analysis showed skull base and peripheral lesions had higher odds of clearance issues. Literature confirms that frame distortion, limited space, and inadequate collision detection are primary GK4C system limitations. GKI plans demonstrated improved target coverage and reduced organ-at-risk doses.

Conclusion: Clearance is a major limitation of GK4C radiosurgery, particularly for certain tumor locations and volumes. Literature supports that GKI technology improves treatment feasibility through frameless options, cone-beam CT guidance, enhanced collision detection, and improved stability.

Introduction: This study evaluates the relationship between key dosimetric parameters and the risk of toxicity following Gamma Knife stereotactic radiosurgery (SRS) for convexity meningiomas, with a focus on refining brain parenchyma-specific dose-volume assessment. Traditionally, V ₁₂ - the volume of brain receiving at least 12 Gy - has included the entire intracranial volume, thus potentially overestimating the safe brain exposure. We hypothesized that contouring only the brain parenchyma adjacent to the tumor, excluding non-functional spaces such as cerebrospinal fluid, sulci, and vascular structures, provides a more accurate predictor of toxicity and may improve strategies to reduce symptomatic brain edema and radiation necrosis.

Methods: In this retrospective analysis, 85 convexity meningioma lesions in 68 patients treated with SRS between 2004 and 2020 were evaluated. Detailed dosimetric parameters, including V ₁₀-V ₁₅, tumor volume, and surface area, were extracted from GammaPlan. Adjacent brain parenchyma was contoured as an organ at risk, excluding sulci and vascular structures. Statistical analyses, including receiver operating characteristic curve determination, logistic regression, and probability distribution analysis, were employed to identify dosimetric thresholds predictive of radiation-induced changes (RIC) and to compare outcomes across different prescription doses.

Results: Increased brain parenchyma V ₁₂ significantly correlated with higher RIC incidence. A parenchyma-specific V ₁₂ threshold of 2.65 cc optimally predicted both asymptomatic (sensitivity 82%, specificity 71%) and symptomatic RIC (sensitivity 85%, specificity 75%), a notably smaller volume than traditionally reported thresholds.

Conclusion: Our results support adopting brain parenchyma-specific V ₁₂ as a refined predictive dosimetric metric for assessing radiation-induced toxicity in convexity meningiomas. Implementing this refined, parenchyma-specific assessment can enhance safety in SRS, guide individualized treatment decisions, and serve as a practical reference for planning - particularly in eloquent cortical regions where minimizing high-dose brain exposure is critical.

Objective: We previously presented a genomic signature predictive of both oligometastatic disease state and oligoprogression in patients with brain metastases. We sought to validate this oligometastatic genomic signature using an independent dataset of patients without brain metastases.

Methods: Patients with non-small cell lung cancer (NSCLC) and liquid biopsy-based genomic profiling (Guardant Health) were identified in our departmental database. Those with brain metastases were excluded. Patients were assigned an oligometastatic risk score based on the previously derived genomic signature. Oligometastatic disease was defined as ≤5 metastases without diffuse single-organ involvement. For oligometastatic patients, we performed a competing risk analysis for the cumulative incidence of oligoprogression. Cox regression was used to determine association between oligometastatic risk score and oligoprogression.

Results: A total of 225 patients met inclusion criteria for this validation dataset. 158 patients (70%) had oligometastatic disease. Patients with positive and neutral/negative risk scores had a 70 vs 48% likelihood of oligometastatic disease, respectively (p = 0.03 from Fisher's exact test). Patients with positive risk scores more frequently experienced oligoprogression with a hazard ratio of 1.72 (p = 0.11). Overall survival for patients with positive and neutral/negative risk scores was 92% vs 79% at 6 months; 46% vs 60% at 12 months; 23% vs 34% at 24 months (p = 0.25).

Conclusion: In this independent dataset, our genomic signature predicted oligometastatic disease state and showed a trend towards prediction of oligoprogression. With further study, our findings may suggest a biomarker with future potential to direct local therapies in oligometastatic NSCLC patients.

Purpose: To refer our experience with stereotactic body radiotherapy (SBRT) in patients with pancreatic cancer.

Materials and methods: 45 Patients with unresectable or locally recurrent pancreatic cancer after primary surgery, were submitted to SBRT. Toxicities were graded according to CTCAE version 5. Statistical analysis was performed by the Kaplan-Meier method.

Results: The characteristics of the patients were median age 70 years (range, 46-84 years), median KPS 90% (range, 80-90%). Six patients had recurrent cancer after surgery, the other 39 patients were unresectable. Median radiation dose was 35 Gy (range, 27-40 Gy) delivered in 5 fractions. Simultaneous integrated boost with median dose of 35 Gy (range, 30-45 Gy) was given in 7 patients.After median follow-up of 10 months (range, 3-61 months) median local control was 10 months (range,5-15 months) and 49% (±8%) at 1-year. Median overall survival (OS) was 10 months (range,7-14 months), 38 % (±7%) at 1 year. Type of radiological response statistically significant influenced LC and OS, stage only LC in non-significant way. Clinical response was obtained in 12 of 36 (33%) cases. Median Numeric Rating Scale (NRS) was 7 (range, 4-8) before radiotherapy and 1 (range, 0-5) post SBRT. Acute G1-2 gastrointestinal toxicities were registered in 15% of patients, no late toxicities were found.

Conclusion: In our series we obtained a good local palliation with SBRT that is a safe and effective treatment option. Higher doses could be administered in selected patients to obtain better response to treatment that is correlated with LC and OS.

Background: Despite advances in systemic therapy, survival in metastatic colorectal cancer (mCRC) remains poor. The utility of stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS), allowing dose escalation to achieve improved local control has risen in the treatment of mCRC. However, local control (LC) and overall survival (OS) varies widely between studies, and prognostic factors are not well defined.

Methods: We retrospectively assessed LC and OS in patients with mCRC treated with SBRT/SRS between 2014 and 2022.

Results: 124 Patients were treated during the study period. Median follow up was 16.4 months (0.2-93.1 months). There were 310 lesions treated with 53% located in the brain, 22% lung, 16% liver, 4% bone, 4% nodal and 1% other. Biologically effective dose (BED10) ranged from 33.6 to 151.2 Gy.LC was 75% (95% CI 67-81%) at 1 year and 65% (95%CI 56-73%) 2 years. On multivariable analysis (MVA), older age (HR 1.04, p = 0.001) and tumour volume >2.5 cc (HR 3.13, p < 0.001) were associated with worse LC.OS from first course of SBRT/SRS was 68% at 1 year (95%CI 58-76%), and 48% at 2 years (95%CI 38-58%). On MVA, ≥2 or more lines of systemic therapy (HR 3.04, p < 0.001) and brain metastases (HR 4.24, p = 0.001) were associated with shorter OS. Living long enough to receive ≥2 courses of SBRT/SRS (HR 0.20, p = 0.004) was associated with longer OS.

Conclusion: This study demonstrates that SBRT and SRS offer effective local control, and LC is associated with tumour volume.

Introduction: Survival of patients with brain metastases (BMs) is increasing. Consequently, local disease recurrence of previously treated BMs has become more prevalent. Stereotactic radiosurgery (SRS) has been employed as a salvage therapy; however, concerns over adverse radiation events (AREs) persist. Utilization of a fractionated approach may reduce AREs in this population.

Methods: A retrospective review of locally recurrent BMs was conducted. The primary outcome was local control and AREs. Utilizing the Kaplan-Meier method, we analyzed the time to local control (LC) and overall survival (OS) for each recurrent lesion treated with SRS. Cox regression analysis was employed to examine predictors of LC and OS.

Results: Our cohort consisted of 45 patients with a median age of 62 years [interquartile range (IQR): 56.3-68.0]. The median lesion volume at the time of repeat SRS was 3.3 cm³ (IQR: 0.75-8.8). Patients were treated with a median prescription dose of 27.0 Gy (IQR: 25.0-30.0) over a median of five fractions (range: 3-5). Actuarial LC rates at 3, 6, 12, and 24 months were: 79.4%, 72.2%, 61.7%, and 54.9%, respectively. There was no ≥grade 3 treatment toxicity reported. On univariate analysis Karnofsky performance status: >70 (HR: 0.17, 95% CI: 0.06-0.5, p = 0.001) and the presence of extracranial disease at SRS (HR: 2.7, 95% CI: 1.04-6.97, p = 0.04) were significantly associated with overall survival (OS).

Conclusion: Repeat fractionated SRS is safe and efficacious for locally recurrent BMs. Performance status and systemic disease control are predictors of OS in this population.

Purpose: To investigate whether TP53 variants may be correlated with overall survival and local control following stereotactic radiosurgery (SRS) for brain metastases (BMs) from non-small cell lung cancer (NSCLC).

Methods: Patients undergoing an initial course of SRS for NSCLC brain metastases between 1/2015 and 12/2020 were retrospectively identified. Overall survival and freedom from local intracranial progression (FFLIP) were estimated via Kaplan-Meier method. Cox models assessed TP53 variant status (pathogenic variant, PV; variant not detected, ND).

Results: 255 patients underwent molecular profiling for TP53, among whom 144 (56%) had a TP53 PV. Median follow-up was 11.6 months. OS was not significantly different across TP53 status. A trend toward superior FFLIP was observed for PV (95% CI 62.9 months-NR) versus ND patients (95% CI 29.4 months-NR; p=0.06). Superior FFLIP was observed for patients with one TP53 variant versus those with TP53 ND.

Conclusion: Among NSCLC patients with BMs, the potential association between TP53 status and post-SRS FFLIP warrants further investigation in a larger prospective cohort.