Ablative Radiotherapy Research Articles

Simulation of DIII-D disruption with argon pellet injection and runaway electron beam

Abstract The next generation of large tokamaks, including ITER, will be equipped with a disruption mitigation system (DMS) that can be activated if a disruption is deemed to be imminent. Introducing impurities by pellet (large or shattered) or massive gas injection has been shown to be an effective mitigation mechanism on many tokamaks. The goal of the mitigation is to lessen the thermal and electromagnetic loads from the disruption without generating enough high-energy (runaway) electrons to damage the device. Variations of this mitigation process with impurity injection are presently being tested on many experiments. We have modeled one such impurity injection experiment on DIII-D using the M3D-C1 nonlinear 3D extended MHD code (Jardin et al 2012 Comput. Sci. Discovery 6 014002), The model includes an argon large pellet injection and ablation model, impurity ionization, recombination, and radiation, and runaway electron formation and subsequent evolution, including both Dreicer and avalanche sources. We obtain reasonable agreement with the experimental results for the timescale of the thermal and current quench and for the magnitude of the runaway electron plateau formed during the mitigation. This is the first 3D full MHD simulation with pellets and REs to simulate the disruption process and it also provides a partial validation of the M3D-C1 DMS model.

Radio-opaque contrast agents for liver cancer targeting with KIM during radiation therapy (ROCK-RT): an observational feasibility study.

This observational study aims to establish the feasibility of using x-ray images of radio-opaque chemoembolisation deposits in patients as a method for real-time image-guided radiation therapy of hepatocellular carcinoma. This study will recruit 50 hepatocellular carcinoma patients who have had or will have stereotactic ablative radiation therapy and have had transarterial chemoembolisation with a radio-opaque agent. X-ray and computed tomography images of the patients will be analysed retrospectively. Additionally, a deep learning method for real-time motion tracking will be developed. We hypothesise that: (i) deep learning software can be developed that will successfully track the contrast agent mass on two thirds of cone beam computed tomography (CBCT) projection and intra-treatment images (ii), the mean and standard deviation (mm) difference in the location of the mass between ground truth and deep learning detection are ≤ 2mm and ≤ 3mm respectively and (iii) statistical modelling of study data will predict tracking success in 85% of trial participants. Developing a real-time tracking method will enable increased targeting accuracy, without the need for additional invasive procedures to implant fiducial markers. Registered to ClinicalTrials.gov (NCT05169177) 12th October 2021.

EP.07B.05 Comparison of Image-Guided Thermal Ablation or Stereotactic Body Radiation Therapy for Primary Non-Small Cell Lung Cancer

EP.07B.05 Comparison of Image-Guided Thermal Ablation or Stereotactic Body Radiation Therapy for Primary Non-Small Cell Lung Cancer

297 - Personalised motion management for Stereotactic Ablative Radiation Therapy to the Lung

297 - Personalised motion management for Stereotactic Ablative Radiation Therapy to the Lung

Optimizing target and diaphragmatic configuration, and dosimetric benefits using continuous positive airway pressure in stereotactic ablative radiotherapy for lung tumors.

This study aimed to evaluate the impact of facilitating target delineation of continuous positive airway pressure (CPAP) in patients undergoing stereotactic ablative radiation therapy (SABR) for lung tumors by lung expansion and respiratory motion management. We performed a prospective single-institutional trial of patients who were diagnosed with either primary lung cancer or lung metastases and received SABR with a dose of 40 to 60 Gy in 4 fractions. Four-dimensional computed tomography simulations were conducted for each patient: once without CPAP and again with CPAP. Thirty-two patients with 39 tumors were analyzed, after the withdrawal of five patients due to discomfort. For 26 tumors separated from the diaphragm, CPAP significantly increased the superoinferior distance between the tumor and the diaphragm (5.96 cm vs. 8.06 cm; p < 0.001). For 13 tumors located adjacent to the diaphragm, CPAP decreased the overlap of planning target volume (PTV) with the diaphragm significantly (6.32 cm3 vs. 4.09 cm3; p = 0.002). PTV showed a significant reduction with CPAP (25.06 cm3 vs. 22.52 cm3, p = 0.017). In dosimetric analyses, CPAP expanded lung volume by 58.4% with a significant reduction in mean dose and V5 to V40. No more than grade 2 adverse events were reported. This trial demonstrated significant improvement of CPAP in target delineation uncertainties for lung SABR, with dosimetric benefits, a favorable safety profile and tolerability. Further investigation is warranted to explore the role of CPAP as a novel strategy for respiratory motion management.

Is an all-phase ITV (internal target volume) a gold standard in the target definition of hepatocellular carcinoma?

Stereotactic ablative body radiation (SABR) is a well-recognized treatment option for hepatocellular carcinoma (HCC). Due to the inherent motion of liver tumors, effective motion management is crucial for successful SABR. In the motion-encompassing motion management technique, all 10 respiratory phase image datasets are delineated and designated as the internal target volume (ITV). Some treatment centers use single or combination image sets to delineate the target volume. This study determines which specialty image set most closely matches an all-phase ITV contour on a synchronized contrast-enhanced 4DCT. Synchronized 4DCT contrast and delayed scans were acquired for 10 patients in the study. The maximum intensity projection (MiP), average intensity projection (AvgIP), and minimum intensity projection (MinIP) images were generated. The ITV delineation was done in all 10 phases (ITV_all_phase). The ITV_2phase combines the peak inhale and exhale phase, ITV_2M combines MiP and MinIP, and ITV_3M combines MiP, MinIP, and AvgIP. All ITVs were compared to ITV_all_phase with Dice similarity index (DSI) and volumes. Using ITV_all_phase as the reference, the DSI and the mean ITV volumes for the different ITVs were as follows: ITV_all_phase (1 and 116.69 cc), ITV_2phase (0.87 and 105.27 cc), MiP (0.76 and 98.24 cc), AvgIP (0.72 and 94.54 cc), ITV_MinIP (0.67 and 81.08 cc), ITV_2M (0.84 and 106.26 cc), and ITV_3M (0.86 and 112.51 cc). The study demonstrates that in the motion-encompassing technique of motion management, the target volume generated by delineating all phases of 4DCT provides the most accurate representation for patients with HCC. Specialty image sets and their combinations, while sometimes close, tend to result in less accurate targeting. Hence, the all-phase 4DCT method should be preferred to avoid geographical misses and ensure optimal treatment outcomes. However, our conclusion may be limited by the technique we employed.

Abstract A022: Neoadjuvant ablative radiation downstages high-risk features and alters immune response in pancreatic cancer

Abstract Purpose: Increasing evidence shows neoadjuvant (NA) therapy benefits surgical selection and survival in localized pancreatic cancer. However, the optimal NA therapy for resectable, borderline resectable (BRPC), and locally advanced pancreatic cancer (LAPC) remains unclear. We hypothesize that NA stereotactic ablative radiotherapy (SAbR) benefits patients with BRPC and LAPC who do not progress on chemotherapy (CTH), especially with arterial involvement. To evaluate this, we retrospectively reviewed outcomes and molecular features of patients treated with NA CTH and NA CTH followed by SAbR to understand the contribution of radiation. Methods: We retrospectively reviewed clinical data for 133 patients treated with NA CTH and 48 with NA CTH + SAbR. Bulk RNA sequencing was performed on fresh surgical tissue from 29 CTH-treated and 14 CTH + SABR-treated patients. We conducted gene set enrichment analysis (GSEA), CIBERSORTx cellular deconvolution, and Single-Cell Identification of Subpopulations with Bulk Sample Phenotype Correlation (Scissor) analysis to correlate clinical outcomes with transcriptomic features. Results: Molecular subtyping of PDAC transcriptomic signatures from post-treatment tissues revealed similar subtype proportions after both treatments. However, at baseline and before surgery, patients receiving SABR had more advanced clinical T staging, NCCN resectability, and arterial involvement. Despite this, the NA CTH + SAbR cohort showed similar overall survival, local-regional progression-free survival (LRPFS), and distant metastasis progression-free survival (DPFS) compared to NA CTH only. NA CTH + SABR-treated patients had significantly improved post-treatment T and N staging, tumor size, and treatment effect. These improvements correlated with better survival, LRPFS, and DPFS. RNAseq analysis indicated that patients with nodal involvement had significantly increased GSEA of MYC targets and worse DPFS. Tumor-arterial involvement at diagnosis significantly reduced local-regional control for NA CTH only. In contrast, patients with arterial involvement receiving NA CTH + SAbR had significantly improved local control. CIBERSORTx cell fraction deconvolution revealed no significant differences in tumor and immune cell subsets between treatments, but GSEA indicated substantial changes in immune-related gene sets, particularly those related to myeloid and T cell activation, suggesting functional changes correlating with treatment response and local control. Scissor identified gene signatures from activated CD8 T cells correlating with improved local control, while signatures from Treg and naïve T cells negatively impacted LRPFS. Conclusions: Molecular analysis and clinical features showed that patients treated with NA CTH + SAbR experienced downstaging and had similar outcomes, with indications of a differential immune response. Given these findings, the role of SAbR in the NA setting should be further evaluated, especially in the context of improved chemotherapy and novel combination therapies that leverage biological responses. Citation Format: Peter Q. Leung, Eslam A. Elghonaimy, Ahmed M. Elamir, Megan Wachsmann, Song Zhang, Neha Barrows, Rachel von Ebers, Cassandra Hamilton, Grace Josephson, Salwan Al Mutar, Patricio M. Polanco, Nina N. Sanford, Syed M. Ali Kazmi, Matthew R. Porembka, David Hsieh, Adam C. Yopp, Muhammad S. Beg, Herbert J. Zeh, Todd A. Aguilera. Neoadjuvant ablative radiation downstages high-risk features and alters immune response in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr A022.

Adrenal Insufficiency following Stereotactic Ablative Radiotherapy (SAbR) of Adrenal Gland Metastases.

Adrenal metastases are often treated with stereotactic ablative radiation (SAbR). We aimed to assess the incidence, timing, and factors associated with the development of primary adrenal insufficiency (PAI) following SAbR. A retrospective cohort study comprised 66 consecutive patients (73% men, median age 61 years) who underwent SAbR for adrenal metastasis. The series encompassed metastases from renal cell carcinoma (41%), lung tumors (38%), colorectal adenocarcinoma (9%), melanoma (5%), and others (7%). Median follow-up was 17 months from SAbR. Nine (14%) patients developed PAI at a median of 4.3 months (range, 0.7-20.2). The incidence of PAI was 44% in patients with prior adrenalectomy receiving unilateral SAbR, 44% with bilateral SAbR, 2% with unaffected contralateral gland, and 0% with bilateral metastases treated with unilateral SAbR. PAI was associated with prior adrenalectomy (odds ratio [OR] 32) and bilateral SAbR (OR 8.2), but not age, sex, metastasis size, or biological effective dose. Post-SAbR 6-month and 1-year local control rates were 82% and 75%, respectively. Patients undergoing SAbR for adrenal metastasis are at high risk of developing PAI. PAI is associated with bilateral SAbR and contralateral adrenalectomy. PAI is unlikely with a remaining unaffected adrenal gland or in the setting of bilateral adrenal metastases with unilateral SAbR.

Focal therapy for oligometastatic and oligoprogressive renal cell carcinoma: a narrative review.

Metastatic renal cell carcinoma (RCC) can present with oligometastatic disease and/or develop oligoprogression following systemic therapy. Cytoreductive and focal metastasis-directed therapy options include resection, stereotactic ablative radiation and thermal ablation. Aggressive focal therapy may allow delay in initiation of or modification to systemic therapy and improve clinical outcomes. In this narrative review we synthesize current practice guidelines and prospective data on focal therapy management options and highlight future research. Patient selection and the choice of focal treatment techniques are controversial due to limited and heterogeneous data and patients may benefit from multidisciplinary evaluation. Prospective comparative trials with clearly defined inclusion criteria and relevant end points are needed to clarify the risks and benefits of different approaches.

Durable local control with hypofractionated radiation therapy for unresectable or metastatic melanoma

Background and purposeAs patients with advanced melanoma live longer in the context of systemic therapy advancements, better strategies for durable control of bulky tumors are needed. In this study, we evaluated if dose-escalated hypofractionated radiation therapy (HFRT) can provide durable local control and improve tumor-associated symptoms in patients with unresectable or bulky metastatic melanoma for whom stereotactic ablative radiotherapy (RT) approaches are not feasible due to tumor size or location. Materials and methodsWe retrospectively reviewed 49 patients with unresectable or bulky metastatic melanoma who were treated to a total of 53 tumor targets with 12–17 fractions HFRT at our institution between 2015–2022. Clinical scenarios included: unresectable, locoregional only disease (26 %); oligometastatic disease (<3 total sites, 17 %); oligoprogressive disease (<3 sites progressing, 17 %); and aggressive palliation (>5 known sites of disease or with at least 3 sites progressing, 40 %). ResultsOf the 53 HFRT targets, 91 % (n = 48) had radiographic evidence of response as defined by either stabilization (6 %, n = 3), decreased size (74 %, n = 39), or decreased FDG avidity (11 %, n = 6). Of the 43 symptomatic patients, 98 % (n = 42) had symptomatic improvement. One −year local control was 79 %, with 2-year progression-free and overall survival of 33 % and 39 % respectively. The most common acute toxicities were radiation dermatitis (16 %, n = 8) or a pain flare (14 %, n = 7). Late toxicities were uncommon and typically grade 1. ConclusionHFRT provides favorable local control and symptomatic relief with limited toxicity in tumors not amenable to surgical resection or stereotactic ablative RT.

Off-Protocol Radiation Therapy in Phase 3 Metastatic Solid Tumor Trials.

Increasing data suggest that radiation therapy, particularly ablative radiation therapy, alters the natural history of metastatic disease. For patients with metastatic disease enrolled in prospective trials testing systemic therapy, the use of off-protocol radiation therapy to improve clinical symptoms or extend the duration of study systemic therapy may influence study endpoints. We sought to evaluate how often off-protocol radiation therapy was permitted among systemic therapy phase 3 trials, how often off-protocol radiation therapy is used, and whether off-protocol radiation therapy correlated with study outcomes. Two-arm, superiority-design, phase 3 randomized trials testing systemic therapy were screened from ClinicalTrials.gov. Protocol availability was required to assess the trial approach to off-protocol radiation therapy if not described in the manuscript. Adjusted odds ratios with 95% CI were calculated by logistic regression. A total of 112 trials enrolling 80,134 patients were included, with publication dates between 2010 and 2019. Of these, off-protocol radiation therapy was allowed, not discussed, or prohibited during study systemic therapy in 52% (N =58), 25% (N = 28), and 23% (N = 26) of trials, respectively. However, only 2% (2 of 112) of trials reported off-protocol radiation therapy utilization rates, although no data were reported on the use of ablative off-protocol radiation therapy. No trials evaluated or adjusted for the potential influence of off-protocol radiation therapy on study endpoints. Among the subset of open-label studies, trials permissive toward off-protocol radiation therapy were more likely to meet their primary endpoint (adjusted odds ratio, 4.50; 95% CI, 1.23-20.23; P = .04). Although most trials allowed off-protocol radiation therapy during the receipt of the study systemic therapy, the influence of off-protocol radiation therapy, especially ablative radiation therapy, on study outcomes is underevaluated among phase 3 systemic therapy trials.

Stereotactic Ablative Radiation Therapy for Oligometastatic Ovarian Cancer Lymph Node Disease: The MITO-RT3/RAD Phase II Trial

PurposeMITO-RT3/RAD (NCT04593381) is a prospective multicenter Phase II trial designed to assess the effectiveness and safety of stereotactic body radiotherapy (SBRT) in patients diagnosed with oligometastatic ovarian cancer (oligo-MPR-OC). In this report, we provide the results of the trial in the setting of lymph node disease. MethodsThe primary endpoint was the complete response (CR) rate, secondary endpoints included local control (LC), progression-free survival (PFS), overall survival (OS), treatment-free interval (TFI), and toxicity rates. Sample size was based on a previous study reporting an average 70.0% CR with SBRT. The study was powered to detect an improvement in the CR rate from 70.0% to 85.0%, with an α error of 0.05 (one-side) and a β error of 0.1. ResultsThe study met its primary endpoint of a statistically significant improvement of CR. 135 patients with 249 lesions were enrolled across fifteen Institutions from May 2019 to November 2023. CR were observed in 194 lesions (77.9%), PR in 40 (16.1%), SD in 14 (5.6%), and Progressive Disease (PD) in one lesion (0.4%). The ORR was 94%, with an overall clinical benefit rate of 99.6%. CR lesions exhibited a significantly higher LC rate than partial or not responding lesions (12-month LC: 92.7% vs. 63.1%, p<0.001). The 12-months actuarial rates for PFS and for OS were 36.6% (CR 38.3% vs not-CR 18.8%; p: 0.022) and 97.2% (CR 97.8% vs not-CR 93.8%; p: 0.067), respectively. The 12-months actuarial rate for Treatment Free Interval was 52.7% (CR 58.4% vs not-CR 24.4%; p: 0.004). CR was substantially associated with higher PFS (p: 0.036) and TFI (p: 0.006) rates at the univariate analysis. Twenty-three patients (17.0%) experienced mild acute toxicity. Late toxicity was reported in 9 patients (6.7%), mostly Grade 1. ConclusionsThis trial confirms the efficacy of ablative SBRT, with minimal toxicity observed. SBRT offered a high CR rate, promising long-term outcomes and systemic-therapy-free survival rate for complete responders.

90 Effect of Treatment Delivery Schedule for Early-Stage Non-Small Cell Lung Cancer Patients Treated with Stereotactic Ablative Radiation Therapy: A Population-Based Analysis

90 Effect of Treatment Delivery Schedule for Early-Stage Non-Small Cell Lung Cancer Patients Treated with Stereotactic Ablative Radiation Therapy: A Population-Based Analysis

40 Impact of Clinical Target Volume Utilization on Outcomes in Patients with Non-Spine Bone Oligometastases Treated with Stereotactic Ablative Radiation Therapy

40 Impact of Clinical Target Volume Utilization on Outcomes in Patients with Non-Spine Bone Oligometastases Treated with Stereotactic Ablative Radiation Therapy

Effect of Treatment Delivery Schedule for Patients With Early-Stage Non-Small Cell Lung Cancer Treated With Stereotactic Ablative Radiation Therapy: A Population-Based Analysis

PurposeThe optimal stereotactic ablative body radiotherapy (SABR) delivery schedule in stage I non-small cell lung cancer (NSCLC) remains unclear. This population-based study investigated grade ≥ 2 toxicity rates, local failure (LF), and overall survival (OS) in patients treated with 48 Gy in 4 fractions scheduled every other day (QOD) versus daily with weekends (QDW) and consecutive daily without weekends (QD). Materials and MethodsBetween January 2019 and June 2022, treatment records using 48 Gy in 4 fractions were extracted from a provincial cancer registry and grouped by delivery as QOD, QDW, or QD. Toxicity events were recorded using CTCAE v5.0. The Kaplan-Meier method was used to compute OS while LF was calculated using cumulative incidence methods with death as a competing risk. Cox regression analyses and Fine-Gray modelling was used to assess for variables associated with OS and LF, respectively. ResultsOf 404 patients meeting study criteria, 190, 111, and 103 received QOD, QDW, and QD SABR, respectively. More patients receiving QDW SABR were medically inoperable and more patients receiving QD SABR had tumors abutting the chest wall. Median follow-up was 29.5 months (interquartile range [IQR] 19.2-38.4). Overall toxicity was low, with crude rates of acute and late grade ≥ 2 toxicity not being statistically different among the groups. No grade 4 or 5 toxicities were recorded. LF rates at 24 months were not different at 7.5% (95% confidence interval [CI] 3.7-11.3), 9.5% (95% CI 3.9-15.1), and 11.0% (95% CI 4.9-17.2) for the QOD, QDW, and QD groups, respectively (p = 0.60). QDW and QD schedules were not associated with LR. Similarly, no significant differences in median OS were found among the QOD, QDW, and QD groups at 47.5 months (95% CI 39.26-55,74), 52.7 (95% CI 34.7-70.7), and 49.0 months (95% CI 31.6-66.4), respectively. QDW and QD schedules were not associated with OS. ConclusionsThis population-based study demonstrated no statistically significant differences in grade ≥ 2 toxicity rates, LF, and OS for stage I NSCLC patients treated with lung SABR using 48 Gy in 4 fractions delivered QOD, QDW, and QD. Patient convenience and optimization of resources may be considered when choosing a lung SABR treatment delivery schedule.

Stereotactic Ablative Radiation Therapy (SABR) for Adolescent and Young Adult Malignancies.

There are limited studies examining local control (LC) and overall survival (OS) following stereotactic ablative radiation therapy (SABR) for adolescent and young adult (AYA) populations/histologies with local recurrences or metastatic disease. The RSSearch® Patient Registry, an international SABR registry, was evaluated for AYA patients treated with SABR. AYA patients with adult histologies/primaries were excluded. Kaplan-Meier analyses were employed to characterize LC and OS following SABR. Potential prognostic factors were assessed with log-rank tests for initial univariate analysis (UVA). For multivariate analyses (MVA), a Cox proportional hazards multivariate model was utilized. A total of 19 AYA patients with 39 lesions treated with SABR were identified and included in the analysis. Four lesions (10.3%) were treated with SABR for primary tumor recurrence and 35 lesions were treated for metastatic disease. The median patient age was 34 years (range: 16-39 years). Common lesion locations included lung (11 lesions; 28.2%), non-spinal bone (nine lesions; 23.1%), and spine (six lesions; 15.4%). The median biological effective dose (BED10) was 61.5 Gy (range: 26.4-180). One-year LC and OS following SABR were 77.7% (95% CI: 58.5-88.7) and 72.7% (95% CI: 46.3-87.6), respectively. On UVA, BED10 ≥ 60 Gy was associated with superior one-year LC (94.4% vs. 47.6%; p<0.0001) as were sarcoma primaries (two-year LC: 92.3% vs. 42.2%;p = 0.0002). Central nervous system (CNS) primaries had significantly poorer one-year LC (20% vs 87.5%; p<0.0001) as well as spinal metastases (33.3% vs. 87.0%; p<0.0001). On MVA, BED10 < 60 Gy was associated with inferior LC (hazard ratio (HR) = 5.51;p = 0.01) with sarcoma primaries associated with superior LC (HR = 0.04;p = 0.008). SABR with BED10 ≥ 60 Gy resulted in durable LC for AYA patients, particularly those with sarcoma primaries, though poor outcomes were noted in metastatic CNS malignancies.

Analysis of the periodic variation of pellet ablation radiation intensity in ASDEX Upgrade

Abstract In a future fusion reactor, the main fuelling method will likely rely on the injection of solid hydrogen pellets. Current predictions assume that this goal can be achieved, since being based on a technology which is already largely developed. However, this belief is founded on modelling tools that are usually aligned to the observation made in existing devices and then extrapolated to reactor conditions. This approach needs a sound consideration of its intrinsic restrictions and any observed feature not reproduced by the utilised codes should be applied to check their validation and possibly contribute to their refinement. One specific feature still lacking an explanation of a reasonable and self-consistent mechanism in the current models is the appearance of a phenomenon called striations, which are high frequency variations in the radiation emitted during the pellet ablation process. In order to provide a sound and reliable database for further considerations, a dedicated analysis of this effect has been performed on the mid-size tokamak ASDEX Upgrade. Therefore, such cases have been selected with the relevant signal recorded with sufficient temporal resolution during experiments covering a wide variation of plasma and pellet parameters which are regarded to be potentially influential on the striation pattern. In addition, it was ensured that for any specific case the observed behaviour was reproducible for several individual ablation events under identical conditions. In all cases considered, the observed radiation-intensity variations appear with a typical pattern showing a broad peak of frequencies in the range 50 to 150 kHz. This characteristic unveils a notable resilience against any parameter variation. This new collection of data can now act as firm basis to corroborate future modelling code-validation efforts. In addition, the analysis method can provide a relatively simple way of reviewing future modelling predictions.

Stereotactic centralized ablative radiation therapy: A novel methodology in treating bulky tumor and its technical realization.

159 Background: Bulky tumors pose significant challenges to traditional treatment modalities such as surgery, chemotherapy, and conventional radiotherapy. This study introduces a novel therapeutic approach named as Stereotactic-Core-Ablative-Radiation-Therapy (SCART), designed to deliver an ablative dose to a substantial core of the bulky tumor while quickly decreasing to a lower dose at the tumor periphery. Methods: A SCART-Treatment-Volume (STV) at the core of the GTV was predefined to administer an ablative radiation dose, aiming to induce DNA damage in cancer cells and potentially trigger biological cancer-killing effects. Utilizing Linac-based VMAT or Cyberknife techniques with 6MV photon beams, multiple radiation fields intersect and optimize at STV, generating an ablative dose at the STV. The dose rapidly diminishes to a safe level at the edge of GTV sparing the surrounding tissue. In the phase-1 trial, nineteen patients with 21 bulky tumors enrolled, receiving SCART at five dose levels (15GyX1, 15GyX2, 15GyX3, 18GyX3, 21GyX3, and 24GyX3), while maintaining the GTV's peripheral dose at 5Gy each fraction. Results: All patients completed treatment with average beam-on time of 8.9min and average treatment time of 18.5min. Mean follow-up time is 15.4 month. No grade-III or higher toxicity was observed. 7/19 patients still survive, with the overall survival of 40% at 30 months. Mean tumor volume shrinks by 60% between initial 301cc and post-SCART volumes of 118cc. Long-term follow-up revealed that 14/21 tumors achieved Partial Response, 2/21 Complete-Response, 3/21 Stable-Disease, and 1/21 Progressive-Disease, leading to an encouraging local control of 95%. Conclusions: SCART emerges as a safe and effective strategy for treating bulky malignant tumors, demonstrating excellent local control and overall survival. Multiple treatment courses were feasible. The results from phase-1 study suggest that SCART could revolutionize the treatment landscape for bulky tumors, offering a promising avenue for further exploration and application in clinical practice.

Y90 Radiation Segmentectomy versus Microwave Ablation for Hepatocellular Carcinoma in Locations Suboptimal for Percutaneous Ablation

Abstract Purpose The purpose of our study was to evaluate outcomes following percutaneous microwave ablation (MWA) versus yttrium-90 (Y90) radiation segmentectomy (RS) for tumors in suboptimal locations for ablation. Materials and Methods Retrospective review (January 2014–July 2019) was performed on patients who underwent Y90-RS or MWA (with or without prior transarterial chemoembolization [TACE]) with curative intent for early-stage hepatocellular carcinoma (HCC) lesions in suboptimal locations for percutaneous ablation, defined as locations in which needle placement is within 5 mm of critical structures (liver dome, liver capsule, gallbladder, and hilum). The primary endpoints were treatment response as per the modified Response Evaluation Criteria in Solid Tumors criteria and complications. Statistical Analysis Fischer's exact test was performed for categorical variables, and Student's t-tests for nominal variables. Results Twenty-three lesions in 20 patients (13 male, 67 ± 8.8 years) and 30 lesions in 30 patients (18 male, 62.5 ± 10.6 years) were treated with Y90-RS and MWA (19 with prior TACE), respectively. There were no differences in demographics (p &gt; 0.05). Mean tumor diameter was 2.9 ± 1.0 in those treated with Y90-RS and 2.3 ± 0.9 for MWA (p &lt; 0.05). Lesions were located adjacent to the following structures: dome (n = 22), capsule (n = 16), hilum (n = 9), and gallbladder (n = 6). All patients were Eastern Cooperative Oncology Group performance status 0 to 1. Of the MWA cohort, 19 were Child-Pugh class A, 5 were B, and 6 were C and the mean pretreatment laboratory values were as follows: Model for End-stage Liver Disease sodium (MELD-Na) 12.7 ± 4.6, alpha-fetoprotein (AFP) 848 ± 3168.0, aspartate aminotransferase (AST) 71.9 ± 49.1, alanine aminotransferase (ALT) 48.0 ± 32.4, and total bilirubin 2.4 ± 2.7. Of the Y90-RS cohort, 15 were Child-Pugh class A, 4 were B, and 1 was C and pretreatment laboratory values were as follows: MELD-Na 10.5 ± 3.3 (Y90-RS), AFP 762.2 ± 1793.8 (Y90), AST 50.3 ± 30.5 (Y90), ALT 30.1 ± 16.9 (Y90), and total bilirubin 1.6 ± 1.1 (Y90). Complete response rate following Y90 was 96 versus 76% for MWA, with no disease progression after Y90-RS within the follow-up period. Three (13%) lesions demonstrated progression of disease (time to progression 6.3 months) after MWA. No grade &gt; 2 toxicities or procedure-related complications were noted following Y90-RS. There were 7 major (arterioportal fistula with hemoperitoneum, pneumothorax, liver infarction, and capsular burn) and 3 minor complications following MWA. Conclusion Y90-RS is a valuable alternative to percutaneous MWA as a first-line therapy for early-stage HCC for tumors in suboptimal locations for ablation, offering a favorable treatment response and safety profile.

Comparison of resection, ablation and stereotactic body radiation therapy in treating solitary hepatocellular carcinoma ≤ 5 cm: a retrospective, multicenter, cohort study.

Few studies have focused on the efficacy of stereotactic body radiation therapy (SBRT) in treating early hepatocellular carcinoma (HCC) for curative intention. This study aims to determine the best option among resection, ablation and SBRT in dealing with single HCC no more than 5cm. This multicenter retrospective cohort study included 985 patients from 3 hospitals: 495, 335 and 155 in the resection, ablation and SBRT groups, respectively between January 2014 and December 2021. Subgroup analysis and propensity score matching (PSM) were performed. The SBRT group had unfavorable clinical features including larger tumor size, poorer liver function and more relapsed tumors. The 1-, 3-, and 5-year recurrence free survival (RFS) rates were 84.3%, 66.8% and 56.2% with resection, 73.3%, 49.8% and 37.2% with ablation and 73.2%, 56.4% and 53.6% with SBRT, respectively (P<0.001). The 3-year overall survival (OS) rates were 89.0%, 89.2% and 88.8% in the resection, ablation and SBRT group, respectively (P=0.590). The three modalities resulted in similar RFS and OS after adjusting for clinical factors. Resection provided ideal local tumor control, successively followed by SBRT and ablation. SBRT led to comparable RFS time compared to resection for tumors < 3cm (HR=0.75, P=0.205), relapsed tumors (HR=0.83, P=0.420) and patients with poor liver function (HR=0.70, P=0.330). In addition, SBRT was superior to ablation regarding RFS when tumors were adjacent to intra-hepatic vessels (HR=0.64, P=0.031). SBRT were more minimally invasive, however, gastrointestinal disorders, hepatic inflammation and myelosuppression occurred more frequently. All three approaches could be applied as curative options. Resection remains the best choice for preventing tumor recurrence, and SBRT showed advantages in treating small, recurrent and vascular-type lesions as well as patients with relatively poor liver function.