The HILUS-Trial-a Prospective Nordic Multicenter Phase 2 Study of Ultracentral Lung Tumors Treated With Stereotactic Body Radiotherapy

Stereotactic body radiotherapy for early‑stage non‑small cell lung cancer: Comprehensive analysis of outcomes and recurrence from a single‑center experience

This study aimed to analyze prognostic factors in patients with early-stage non-small cell lung cancer (NSCLC) treated with stereotactic body radiotherapy (SBRT), focusing on symptomatic radiation pneumonitis (RP) and treatment failure patterns. This retrospective cohort study included 271 patients with early-stage NSCLC (276 lesions) treated with SBRT from May 2012 to January 2022. SBRT was administered according to standardized protocols with doses ranging from 28.5 to 80 Gy in 1 to 10 fractions. Tumor recurrence, RP, and failure patterns were assessed through imaging and clinical evaluations. Prognostic factors for overall survival (OS) and local control (LC) were identified using Kaplan-Meier survival analysis, Cox models, and logistic regression for RP risk. With a median follow-up of 30.8 months, the 1-, 2- and 3-year OS rates were 96.1, 91.8, and 86.5%, respectively, and LC rates were 98.8, 96.5, and 92.9%, respectively. The Eastern Cooperative Oncology Group performance status (P=0.002) and higher fractional dose (P=0.041) were significant predictors of OS. Larger tumor size (P<0.001) and higher solid-to-total tumor ratio (P=0.028) were associated with increased local recurrence risk. Symptomatic RP (7.2% of lesions) was associated with solid tumor size (P=0.050). Larger tumors with a higher solid component had more in-field recurrences, while marginal recurrences were often attributable to air space spread and pleural involvement. Higher fractional doses in SBRT benefit patients with early-stage NSCLC, especially those with larger tumors or significant solid components, suggesting that dose escalation or more biologically effective therapies could enhance outcomes and optimize SBRT protocols.

Are treatment plans optimized on the basis of acuros XB dose calculation robust against anatomic changes during online adaptive radiotherapy for lung cancer regarding dose homogeneity?

INTRODUCTION

The Acuros XB dose calculation algorithm implements advanced modelling of lateral electron transport, making dose distributions sensitive to density changes between source and subsequent CT. The aim of this study was to analyse the robustness of dose distribution in the central bronchial wall (CBW) of treatment plans from lung cancer patients treated with adaptive radiotherapy.

MATERIAL AND METHODS

IMRT or VMAT plans from patients with locally advanced lung cancer from a prospective registry cohort were analysed, who received definitive radiotherapy in surface-guided inspiratory breath-hold on the Ethos™ closed-bore linac, equipped with the HyperSight™ cone beam CT (CBCT). Dose homogeneity of the scheduled plans, optimized on planning CT (CTplan), was verified on the initial CBCT of a dose fraction (CBCT1). The adaptive plans were verified on a subsequent post-adaptation CBCT (CBCT2) of the same dose fraction. A predictive model was built for maximum dose (Dmax) in CBW in dependence on plan sensitivity in the central bronchial air lumen overlapping the planning target volume (CBALPTV) to water override (WOR) of the air lumen.

RESULTS

Ninety-one dose-fractions from 10 patients were analysed. Dmax values in the CBW of the scheduled plans showed over all significant inter-fractional increases from CTplan to subsequent CBCT1 (p < 0.0001, Wilcoxon test, stratified by patient) with significant heterogeneity between patients (p < 0.0001, Kruskal-Wallis Test). The median Dmax increase per dose fraction was 2.15% (-3.15 - 19.30%). Reducing the PTV overlap of scheduled plans with CBAL led to lower inter-fractional Dmax increases in CBW (p < 0.0001, signed rank test). Dose accumulation showed, that Dmax and D1cc values in CBW over the treatment course stayed in all patients below 110.5% and 107.5% and that the equivalent uniform dose in CTV around the CBW stayed > 95% for scheduled plans. A predictive model showed the dependence of inter-fractional Dmax increases in CBW of scheduled plans on an interaction between plan sensitivity on CTplan to WOR in CBALPTV and density change at the Dmax point in CBCT1 between CTplan and CBCT1 (p < 0.0001, t-test). Intra-fractional Dmax increases of adaptive plans in CBW amounted to only 20% +/- 1.1% of the inter-fractional increases of scheduled plans, as intra-fractional deformations were smaller than inter-fractional (p < 0.0001, signed rank test).

CONCLUSION

Dose homogeneity in CBW of Ethos plans were found sufficiently robust against intra-fractional deformations during course of online adaptive radiotherapy. Plan sensitivity to anatomic changes can be detected and controlled on the planning CT by the WOR of air in CBALPTV.

Stereotactic body radiation therapy (SBRT) of centrally located medically inoperable early-stage non-small cell lung cancer (T1-T3N0M0) - A subgroup analysis of the expanded HILUS study

INTRODUCTION

Centrally located early-stage non-small cell lung cancer (ES NSCLC) with tumors close to the bronchi is potentially curable with stereotactic body radiation therapy (SBRT). To evaluate the clinical benefit of the treatment, both the risk of high-grade toxicity as well as the treatment efficacy need to be assessed.

MATERIAL AND METHODS

From the expanded HILUS cohorts, 72 patients with T1-T3N0M0 NSCLC were included in the current analysis. All patients had been treated with SBRT in 8 fractions to 56 Gy for a tumor located within 2 cm from the tracheobronchial tree. Primary endpoint was progression free survival (PFS) and secondary endpoints included pattern of failure, local control (LC), lung cancer-specific survival (LCSS), overall survival (OS) and toxicity. The Kaplan-Meier method and Cox regression analysis were used.

RESULTS

The median age of the cohort was 73 years and all patients suffered from comorbidities prior to SBRT. T2-T3 tumors were seen in 65 % of the patients. Seventeen patients relapsed after SBRT and distant recurrence was the most common form of relapse. Three-year PFS was 31 % (95 % CI 22-44) and largely explained by the short overall survival (38 % (95 % CI 22-44) at 3 years). Three-year rates of LC and LCSS were 97 % (95 % CI 92-100) and 76 % (95 % CI 65-89), respectively. Twelve patients (17 %) suffered from grade 5 toxicity, of which 9 were bronchopulmonary bleedings.

CONCLUSION

The severe toxic profile limits the clinical benefit using SBRT with the investigated approach for patients with centrally located ES NSCLC.

Stereotactic Body Radiation Therapy for Primary Lung Cancer and Metastases: A Case-Based Discussion on Challenging Cases

PURPOSE

Data informing the safety, efficacy, treatment logistics, and dosimetry of stereotactic body radiation therapy (SBRT) for lung tumors has primarily been derived from patients with favorably located solitary tumors. SBRT is now considered a standard-of-care treatment for inoperable early-stage non-small cell lung cancer and lung metastases, and therefore extrapolation beyond this limited foundational patient population remains an active source of interest.

METHODS AND MATERIALS

This case-based discussion provides a practical framework for delivering SBRT to challenging, yet frequently encountered, cases in radiation oncology. The cases highlighted herein include the use of SBRT for ultracentral tumors, multiple tumors, and reirradiation. Patient characteristics, fractionation, prescription dose, treatment technique, and dose constraints are discussed. Relevant literature to these cases is summarized to provide a framework for the treatment of similar patients.

RESULTS

Treatment of challenging cases with lung SBRT requires many considerations, including treatment intent, fractionation selection, tumor localization, and plan optimization. In such scenarios, patient selection is critical to understanding the risk-benefit profile of an SBRT approach despite significant advances in delivery techniques and safety.

CONCLUSIONS

A case-based discussion was developed by the Radiosurgery Society to provide a practical guide to the common challenging scenarios noted above affecting patients with lung tumors. A multidisciplinary approach should guide the treatment of such cases to maximize the therapeutic window.

ESMO-ESTRO framework for assessing the interactions and safety of combining radiotherapy with targeted cancer therapies or immunotherapy

With the emergence of targeted therapies and immunotherapy, various cellular pathways are utilized to improve tumor control and patient survival. In patients receiving these new agents, radiotherapy is commonly applied with both radical and palliative intent. Combining radiotherapy with targeted therapies or immunotherapy may improve treatment outcomes, but may also lead to increased toxicity. High-quality toxicity data and evidence-based guidelines regarding combined therapy are very limited. The present framework, developed by ESMO and ESTRO, explores the main biological effects and interaction mechanisms of radiotherapy combined with targeted agents or immunotherapy. It addresses general clinical factors to take into consideration when deciding on whether and/or how to combine radiotherapy with these agents. Furthermore, it provides pragmatic, biological mechanism-based, clinical considerations for combining radiotherapy with various targeted agents or immunotherapy.

International Patterns of Practice for Stereotactic Ablative Radiotherapy for Early-Stage Non-Small Cell Lung Cancer: Are We All in Sync?: Global patterns of practice for SABR for early-stage NSCLC

PURPOSE

To generate an understanding of the similarities and variations in international practice patterns for stereotactic ablative radiotherapy (SABR) in early-stage non-small cell lung cancer (NSCLC).

METHODS

An online survey was conducted from October to December 2023, addressing general clinical and technical considerations for lung SABR, and for 5 specific anatomical NSCLC locations (peripheral, abutting chest wall, near brachial plexus, central, and ultra-central). Invitations to participate were extended through email and were distributed on social media.

RESULTS

The survey was completed by 255 radiation oncologists, each representing a single institution across 51 countries. Respondents reported treating a median of 20 cases annually. A total of 38% of participants reported using single-fraction SABR, and 54% applied an upper limit on the maximum dose (Dmax). Among those who applied a Dmax limit, 58% reported a Dmax threshold at ≥130% of the prescription, though this limit varied by region and national economy status. Respondents from low- and middle-income countries were less likely to set a Dmax limit at ≥130% (30% vs. 66%, p < 0.01) and less likely to use single-fraction SABR (14% vs. 44%, p < 0.01). Higher annual SABR patient volumes were associated with higher Dmax adoption (г = 0.23, p < 0.01). Across the 5 clinical scenarios presented; 57 distinct dose regimens were recommended. The most common regimen in each scenario was: 54 Gy in 3 fractions for peripheral tumors, 50 Gy in 5 fractions for apical, central, and abutment of chest wall, and 60 Gy in 8 fractions for ultra-central tumors. Approximately two-thirds of practices recommend a biologically effective dose (BED10) <100 Gy for one or more anatomical sites.

CONCLUSION

The findings reveal considerable variation in global SABR practice. These differences highlight the need for further data to guide prescription practices, and an international experts' consensus may be beneficial to standardize practice.

Organs at risk proximity in central lung stereotactic ablative radiotherapy: A comparison of four-dimensional computed tomography and magnetic resonance-guided breath-hold delivery techniques

Higher toxicity rates are associated with stereotactic ablative radiotherapy (SABR) to central lung tumors. Breath-hold (BH) magnetic resonance-guided SABR (MR-SABR) can reduce doses to organs at risk (OAR). We quantified the planning target volumes (PTV) to OAR distance in 45 lesions treated using MR-SABR and generated a corresponding four-dimensional computed tomography (4D-CT) based PTV (motion-encompassing internal target volume plus 5 mm). For lesions located ≦3 cm from airways, BH MR-SABR increased the median PTV distance to OAR by 3.7 mm. For lesions ≦3 cm from pericardium, median PTV-OAR separation increased by 2.0 mm with BH. These findings highlight the advantage of BH SABR for central lung tumors.

Risk-adapted stereotactic body radiation therapy for the treatment of large (>3 cm) primary lung cancer with or without histologic confirmation: A propensity score matched and weighted analysis

PURPOSE

Stereotactic body radiation therapy (SBRT) is a promising therapeutic approach for inoperable, small (≤3 cm) primary lung cancer. However, the efficacy and safety of risk-adapted SBRT for treating large (>3 cm) primary lung cancer remains inadequately characterized.

PATIENTS AND METHODS

Patients with large (>3 cm) primary lung cancer, diagnosed either clinically or histologically, were recruited between November 1, 2010 and December 31, 2022. Risk-adapted SBRT was administered in fractions (median, 5) for a total dose of 60 Gy (range, 45-63 Gy). The primary endpoint was overall survival (OS), and secondary endpoints included progression-free survival (PFS), local failure (LF), regional failure (RF), distant metastasis (DM), cancer-specific mortality (CSM), and toxicity. Differences in baseline characteristics were balanced via propensity score matching (PSM) with the logistic regression model, as well as 1:1 ratio matching and inverse probability of treatment weighting (IPTW). The Cox proportional hazards model was used for univariate and multivariate analyses aimed at identifying prognostic factors influencing OS and PFS.

RESULTS

The 126 enrolled patients included 61 cases (48.4 %) diagnosed clinically and 65 cases (51.6 %) diagnosed pathologically. Following PSM and IPTW, no differences were found between patients diagnosed clinically versus pathologically in OS, PFS, tumor failure, and CSM. Univariate and multivariate analyses identified a Charlson comorbidity index ≥5 as an adverse prognostic factor for OS and PFS. One patient (0.8 %) in the pathologically diagnosed group developed grade 5 pneumonitis 2 months after undergoing SBRT.

CONCLUSIONS

Risk-adapted SBRT may be an optimal treatment for appropriately selected patients with a large (>3 cm) primary lung cancer lacking histologic confirmation.

The Impact of Ultracentral Tumor Location on Outcomes in Patients with Pulmonary Oligometastases: A Secondary Analysis of the Single-Arm Phase 2 SABR-5 Trial

PURPOSE/OBJECTIVES

There are limited data on outcomes in patients with ultracentral pulmonary oligometastases treated with SABR. The purpose of this study was to determine whether ultracentral location was prognostic for toxicity and survival.

MATERIAL AND METHODS

Oligometastatic lung lesions treated on the single-arm phase 2 SABR-5 trial were retrospectively stratified into 2 cohorts: ultracentral tumors (UC), defined as planning target volume overlap or direct tumor abutment to the proximal bronchial tree, esophagus, great vessels, or heart, and nonultracentral tumors. Cohorts were compared with respect to grade ≥ 2 toxicity, progression-free survival (PFS), and overall survival (OS).

RESULTS

In total, 41 patients with 45 ultracentral metastases and 93 patients with 172 nonultracentral metastases underwent SABR. The most common primary histologies were colorectal (30%), lung (13%), and renal (13%), and these did not differ between groups. Patients with UC had a lower median PFS of 5.8 months compared with 15.8 months in patients with non ultracentral tumors (P < .001). OS was also worse in the UC cohort: median 29.0 months versus not yet reached (P < .001). On multivariable regression, UC remained prognostic for worse PFS (hazard ratio 2.18, P = .004) and OS (hazard ratio 3.45, P < .001). Groups had similar rates of local tumor control. Patients with UC had higher 2-year cumulative incidence of polymetastatic progression: 69.2% versus 31.4% (P < .001). The 2-year cumulative incidence of grade ≥ 2 toxicity was 14.6% for patients with UC and 9.8% for patients with nonultracentral tumors (P = .74). There were no grade 4 or 5 toxicities.

CONCLUSIONS

In this prospective patient cohort, SABR for ultracentral tumor had low toxicity rates and good local control. However, ultracentral location was an adverse prognostic feature for survival. This finding should be validated with larger studies and may be a factor when weighing the benefit versus risk of SABR in patients with pulmonary oligometastases.

SPECT/CT Dosimetry of Bronchial Artery 99mTc Macroaggregated Albumin Injection in Pulmonary Malignancies: Feasibility Evaluation of Bronchial Artery 90Y Radioembolization

Background External beam radiation therapy for primary and secondary pulmonary malignancies has limited utility for treating ultracentral tumors (ie, adjacent to the proximal bronchial tree or heart) or multiple metastases due to either radiation to central organs at risk (OARs) or extensive lung tissue exposure. Bronchial artery yttrium 90 (90Y) radioembolization may be a therapeutic option for these patients. Purpose To evaluate the feasibility of bronchial artery 90Y radioembolization using technetium 99m (99mTc) macroaggregated albumin (MAA) injection as a surrogate for 90Y microspheres and to use SPECT/CT dosimetry to assess 99mTc-MAA distribution and calculated anticipated 90Y doses to tumors and OARs. Materials and Methods In this prospective clinical trial, study participants with either primary lung cancer or pulmonary metastases were enrolled between August 2020 and October 2023 from a single academic medical center. All participants underwent bronchial artery embolization for malignancy-induced hemoptysis prophylaxis. 99mTc-MAA was injected via bronchial arteries, followed by bland embolization. SPECT/CT imaging and Monte Carlo simulations were used to evaluate 99mTc-MAA distribution and predict 90Y doses. Predicted 90Y doses to tumors and OARs are reported as means ± SDs. Results Eight participants (mean age, 63.0 years ± 13.58; six [75%] male participants) were included. All had ultracentral tumors, and four had four or more tumors. SPECT/CT revealed a concentrated 99mTc-MAA accumulation in tumors, with a mean tumor-to-normal tissue ratio of 22.71 ± 20.17. Simulations indicated that a 90Y biologically effective dose (α/β ratio of 10 Gy) of 175.7-3173.6 Gy (mean, 778.8 Gy ± 981.9) could be delivered to all tumors while remaining under OAR toxicity thresholds. Conclusion SPECT/CT dosimetric analysis of 99mTc-MAA injected via the bronchial artery for pulmonary malignancy suggests that bronchial artery 90Y radioembolization is feasible and could be an alternative treatment for patients unable to receive external beam radiation therapy. ClinicalTrials.gov Identifier: NCT04105283 © RSNA, 2025 Supplemental material is available for this article.

Deep learning-based synthetic CT for dosimetric monitoring of combined conventional radiotherapy and lattice boost in large lung tumors

PURPOSE

Conventional radiotherapy (CRT) has limited local control and poses a high risk of severe toxicity in large lung tumors. This study aimed to develop an integrated treatment plan that combines CRT with lattice boost radiotherapy (LRT) and monitors its dosimetric characteristics.

METHODS

This study employed cone-beam computed tomography from 115 lung cancer patients to develop a U-Net +  + deep learning model for generating synthetic CT (sCT). The clinical feasibility of sCT was thoroughly evaluated in terms of image clarity, Hounsfield Unit (HU) consistency, and computational accuracy. For large lung tumors, accumulated doses to the gross tumor volume (GTV) and organs at risk (OARs) during 20 fractions of CRT were precisely monitored using matrices derived from the deformable registration of sCT and planning CT (pCT). Additionally, for patients with minimal tumor shrinkage during CRT, an sCT-based adaptive LRT boost plan was introduced, with its dosimetric properties, treatment safety in high dose regions, and delivery accuracy quantitatively assessed.

RESULTS

The image quality and HU consistency of sCT improved significantly, with dose deviations ranging from 0.15% to 1.25%. These results indicated that sCT is feasible for inter-fraction dose monitoring and adaptive planning. After rigid and hybrid deformable registration of sCT and pCT, the mean distance-to-agreement was 0.80 ± 0.18 mm, and the mean Dice similarity coefficient was 0.97 ± 0.01. Monitoring dose accumulation over 20 CRT fractions showed an increase in high-dose regions of the GTV (P < 0.05) and a reduction in low-dose regions (P < 0.05). Dosimetric parameters of all OARs were significantly higher than those in the original treatment plan (P < 0.01). The sCT based adaptive LRT boost plan, when combined with CRT, significantly reduced the dose to OARs compared to CRT alone (P < 0.05). In LRT plan, high-dose regions for the GTV and D95% exhibited displacements greater than 5 mm from the tumor boundary in 19 randomly scanned sCT sequences under free breathing conditions. Validation of dose delivery using TLD phantom measurements showed that more than half of the dose points in the sCT based LRT plan had deviations below 2%, with a maximum deviation of 5.89%.

CONCLUSIONS

The sCT generated by the U-Net +  + model enhanced the accuracy of monitoring the actual accumulated dose, thereby facilitating the evaluation of therapeutic efficacy and toxicity. Additionally, the sCT-based LRT boost plan, combined with CRT, further minimized the dose delivered to OARs while ensuring safe and precise treatment delivery.

Centralized Quality Assurance of Stereotactic Body Radiation Therapy for the Veterans Affairs Cooperative Studies Program Study Number 2005: A Phase 3 Randomized Trial of Lung Cancer Surgery or Stereotactic Radiotherapy for Operable Early-Stage Non-Small Cell Lung Cancer (VALOR)

PURPOSE

The phase 3 Veterans Affairs Lung Cancer Surgery Or Stereotactic Radiotherapy study implemented centralized quality assurance (QA) to mitigate risks of protocol deviations. This report summarizes the quality and compliance of the first 100 participants treated with stereotactic body radiation therapy (SBRT) in this study.

METHODS AND MATERIALS

A centralized QA program was developed to credential and monitor study sites to ensure standard-of-care lung SBRT treatments are delivered to participants. Requirements were adapted from protocols established by the National Cancer Institute's Image and Radiation Oncology Core, which provides oversight for clinical trials sponsored by the National Cancer Institute's National Clinical Trials Network.

RESULTS

The first 100 lung SBRT treatment plans were reviewed from April 2017 to October 2022. Tumor contours were appropriate in all submissions. Planning target volume (PTV) expansions were less than the minimum 5 mm requirement in 2% of cases. Critical organ-at-risk structures were contoured accurately for the proximal bronchial tree, trachea, esophagus, spinal cord, and brachial plexus in 75%, 92%, 100%, 100%, and 95% of cases, respectively. Prescriptions were appropriate in 98% of cases; 2 central tumors were treated using a peripheral tumor dose prescription while meeting organ-at-risk constraints. PTV V100% (the percentage of target volume that receives 100% or more of the prescription) values were above the protocol-defined minimum of 94% in all but 1 submission. The median dose maximum (Dmax) within the PTV was 125.4% (105.8%-149.0%; SD ± 8.7%), where values reference the percentage of the prescription dose. High-dose conformality (ratio of the volume of the prescription isodose to the volume of the PTV) and intermediate-dose compactness [R50% (ratio of the volume of the half prescription isodose to the volume of the PTV) and D2cm (the maximum dose beyond a 2 cm expansion of the PTV expressed as a percentage of the prescription dose)] were acceptable or deviation acceptable in 100% and 94% of cases, respectively.

CONCLUSIONS

The first 100 participants randomized to SBRT in this study were appropriately treated without safety concerns. A response to the incorrect prescriptions led to preventative measures without further recurrences. The program was developed in a health care system without prior experience with a centralized radiation therapy QA program and may serve as a reference for other institutions.

Exploring the Current Challenges and Pioneering Clinical Applications of Stereotactic Radiotherapy in Cancer Treatment

Stereotactic radiotherapy (SRT) has become integral to modern oncology, offering the ability to deliver ablative doses while minimizing damage to surrounding normal tissues. Recent advancements in imaging integration, treatment planning, and dose delivery have expanded their clinical applications across various tumor types. However, challenges such as toxicity in anatomically critical regions, optimal margin determination, and the lack of standardized protocols persist. This review explores key issues in contemporary practice and highlights emerging clinical evidence across lung, liver, prostate, brain, and oligometastatic diseases. Further refinement in patient selection and treatment strategies is essential to maximize therapeutic efficacy and ensure safe implementation in broader clinical settings.

Primary lung tumour stereotactic body radiotherapy followed by concurrent mediastinal chemoradiotherapy and adjuvant immunotherapy for locally advanced non-small-cell lung cancer: a multicentre, single-arm, phase 2 trial

BACKGROUND

Patients with locally advanced non-small-cell lung cancer (NSCLC) who undergo concurrent chemotherapy and radiotherapy often experience synergistic toxicity, and local regional control rates remain poor. We assessed the activity and safety outcomes of primary tumour stereotactic body radiotherapy (SBRT) followed by conventional chemoradiotherapy to the lymph nodes and consolidation immunotherapy in patients with unresectable locally advanced NSCLC.

METHODS

In this multicentre, single-arm, phase 2 trial, patients aged 18 years and older were enrolled at eight regional cancer centres in North Carolina and South Carolina, USA. Patients were eligible if they had stage II-III, unresectable, locally advanced NSCLC (any histology), with peripheral or central primary tumours that were 7 cm or smaller, excluding central tumours within 2 cm of involved nodal disease, and an Eastern Cooperative Oncology Group performance status of 0-2. Patients who had previously received systemic therapy or radiotherapy were excluded. Participants received SBRT to the primary tumour (50-54 Gy in three to five fractions) followed by standard radiotherapy (planned up to 60 Gy in 30 2 Gy fractions) to the involved lymph nodes with concurrent platinum doublet chemotherapy (either paclitaxel 50 mg/m2 intravenously plus carboplatin area under the curve 2 mg/mL per min every 7 days for a total of six 1-week cycles or etoposide 50 mg/m2 intravenously on days 1-5 and days 29-33 plus cisplatin 50 mg/m2 intravenously on days 1, 8, 29, and 36 for two cycles of 4 weeks). An amendment to the protocol (Dec 11, 2017) permitted the administration of consolidation durvalumab at the discretion of the treating investigator. An additional protocol amendment on Jan 13, 2021, directed patients without disease progression after chemoradiotherapy to receive consolidation durvalumab (10 mg/kg intravenously on day 1 and day 15 of a 4-week cycle for up to 12 cycles or 1500 mg intravenously on day 1 of a 4-week cycle for up to 12 cycles). The primary endpoint was 1-year progression-free survival (per Response Evaluation Criteria in Solid Tumours version 1.1), assessed in all participants who received at least one fraction of SBRT and had radiological follow-up data up to 1 year. A 1-year progression-free survival rate of greater than 60% was required to reject the null hypothesis and show significant improvement in 1-year progression-free survival. One-sided exact binomial tests were used to compare the primary endpoint versus the historical control 1-year progression-free survival rate used to determine the sample size. Safety was assessed in all patients who received at least one fraction of SBRT. This study is registered with ClinicalTrials.gov, NCT03141359, and is closed to accrual.

FINDINGS

Between May 11, 2017, and June 27, 2022, 61 patients were enrolled and received at least one dose of fractionated SBRT, of whom 59 were evaluable for the primary endpoint. Median age was 67 years (IQR 61-72), 28 (46%) of 61 were female, 33 (54%) were male, 51 (84%) were White, seven (11%) were Black, and three (5%) were of other or unknown race. Of the 61 patients enrolled, 47 received at least one dose of consolidation durvalumab. As of data cutoff (July 12, 2023), median follow-up was 29·5 months (IQR 14·9-47·1). 1-year progression-free survival was 62·7% (90% CI 51·2-73·2; one-sided p=0·39, compared with the historical control rate), with 37 of 59 evaluable participants progression free and alive 1 year after enrolment (n=14 progressed, n=8 died). The most common grade 3-4 treatment-related adverse events were decreased neutrophil count (nine [15%] of 61 patients), decreased white blood cell count (five [8%]), and anaemia (four [7%]). Treatment-related serious adverse events occurred in 11 (18%) of 61 patients, which included lung infection (three [5%]), pneumonitis (two [3%]), decreased neutrophil count (two [3%]), febrile neutropenia (two [3%]), and dyspnoea, hypoxia, respiratory failure, sinus tachycardia, bronchial infection, and acute kidney injury (each in one [2%] patient). Treatment-related deaths occurred in four (7%) of 61 patients (one each of respiratory failure, respiratory failure and dyspnoea, lung infection, and pneumonitis).

INTERPRETATION

Although this study did not meet the primary endpoint, activity and safety profiles of primary lung tumour SBRT followed by concurrent mediastinal chemoradiotherapy were favourable compared with other modern trials treating locally advanced NSCLC with chemoradiotherapy. These findings serve as the basis for the ongoing randomised phase 3 study NRG Oncology LU008 (NCT05624996).

FUNDING

AstraZeneca and Atrium Health Levine Cancer Institute.

The Treatment of Patients with Early-Stage Non-Small Cell Lung Cancer Who Are Not Candidates or Decline Surgical Resection: The Role of Radiation and Image-Guided Thermal Ablation

The standard of care for early-stage NSCLC has historically been surgical resection. Given the association of lung cancer with smoking, a large number of early-stage patients also have active smoking-related medical comorbidities such as COPD precluding surgery. The current approach for treating such inoperable patients is frequently considered to be stereotactic body radiation therapy (SBRT). SBRT (also known as stereotactic ablative radiation therapy or SABR) is a curative modality that precisely delivers very high dose radiation in few (typically <5) sessions. That said, because of their minimal invasiveness and repeatable nature, image-guided thermal ablation therapies such as radiofrequency ablation (RFA), microwave ablation (MWA), and cryoablation (CA) have also been used to treat early-stage lung tumors. For those patients deemed to have "high operative risk" (i.e., those who cannot tolerate lobectomy, but are candidates for sublobar resection), the appropriateness of potential alternatives [e.g., SBRT; ablation] to surgery is an active area of investigation. In the absence of completed randomized phase III trials, the approach to comparing outcomes between surgery, SBRT, or ablative therapies by their efficacy or equivalence is complex. An overview of the role of SBRT and other non-surgical modalities in the management of early-stage lung cancer is the subject of the present review.

Multi-institutional study using sbrt to treat mediastinal and hilar lymphadenopathy

Mediastinal and hilar lymphadenopathy (MHL) is a common pattern of cancer spread, particularly in lung disease. Recently, there has been interest in the use of SBRT for MHL, especially in the oligometastatic setting. The goal is to improve local control (LC) and to achieve shorter treatment durations to minimize systemic treatment interruptions. The primary endpoint of this study was local control (LC). The secondary endpoints were distant metastasis-free survival (DMFS), progression-free survival (PFS), and overall survival (OS) and predictive factors of response. This is a retrospective study. It analyses a group of patients treated with SBRT for MHL with different primary tumours and histologies. From November 2007 to June 2023, we treated 159 MHL in 128 patients. The primary most represented was lung cancer. A single fraction was used in 16% of cases and multiple fractions in 84% of cases. The medium BED 10 was 75.06 Gy (range: 37-120 Gy). Actuarial LC rates at 1, 2 and 5 years were 80.0%, 78.8% and 75.2%. The actuarial DMFS rates at 1, 2 and 5 years were 43.9%, 34.1% and 14.1%, respectively. Actuarial PFS rates at 1, 2 and 5 years were 37.2%, 23.9% and 8.3%, respectively. Actuarial OS rates at 1, 2 and 5 years were 68.8%, 52.7% and 26.9%, respectively. SBRT may be an option for the treatment of MHL. In addition, achieving a complete response is one of the most important predictors of our endpoints, in addition to tumour burden and volume.

Systematic Review of Stereotactic Ablative Radiotherapy (SABR)/Stereotactic Body Radiation Therapy (SBRT) for Treatment of High-Risk Patients with Stage I Non-Small Cell Lung Cancer

Stereotactic ablative radiotherapy (SABR) has emerged as an alternative, non-surgical treatment for high-risk patients with stage I non-small cell lung cancer (NSCLC) with increased use over time. The American Association for Thoracic Surgery (AATS) Clinical Practice Standards Committee (CPSC) assembled an expert panel and conducted a systematic review of the literature evaluating the results of SABR, which is also referred to as stereotactic body radiation therapy (SBRT) or stereotactic radiosurgery (SRS), prior to developing treatment recommendations for high-risk patients with stage I NSCLC based on expert consensus. Publications detailing the findings of 16 prospective studies of SABR and 14 retrospective studies of SABR for the management of early-stage lung cancer in 54,697 patients were identified by systematic review of the literature with further review by members of our expert panel. Medical inoperability (93-95%) was the primary reason for utilizing SABR. The median rate of histologically confirmed cancer in treated patients was 67% (range 57-86%). In retrospective studies and prospective studies, the most common dosing regimens were 48-54Gy in 3-5 fractions and 44-66Gy in 3-5 fractions respectively. The median follow-up after SABR was 30 months (range 15-50). The complications, oncological results and quality of life after SABR in high-risk patients with early-stage NSCLC are summarized in this Expert Review article. Further prospective randomized trials are needed and are currently underway to compare outcomes after SABR with outcomes after sublobar resection to fully evaluate treatment options applicable this high-risk group of patients.

Recent Advances and Current Challenges in Stereotactic Body Radiotherapy for Ultra-Central Lung Tumors

Stereotactic body radiotherapy has been established as a viable treatment option for inoperable early-stage non-small cell lung cancer or secondary lesions mainly in oligoprogressive/oligometastatic scenarios. Treating lesions in the so-called "no flight zone" has always been challenging and conflicting data never cleared how to safely treat these lesions. This is truer considering ultra-central lesions, i.e., directly abutting or whose PTV is overlapping critical mediastinal organs. While historical retrospective data are abundant but mostly heterogenous in terms of the definition of ultra-central lesions, dosing regimens and outcomes, prospective data remain scarce, even though recently published studies have given new encouraging results for such delicate treatment scenarios. For this reason, we aimed to review and summarize current knowledge on stereotactic radiation treatment for ultra-central thoracic lesions, highlighting the most recent advances and the messages that can be taken from them. Lastly, we propose a workflow of the necessary steps to identify and treat such patients, therefore helping in elucidating the advantages and caveats of such treatment options.

Treatment Selection for the High-Risk Patient with Stage I Non-Small Cell Lung Cancer: Sublobar Resection, Stereotactic Ablative Radiotherapy or Image-Guided Thermal Ablation?

A significant proportion of patients with stage I non-small cell lung cancer (NSCLC) are considered at high risk for complications or mortality after lobectomy. The American Association for Thoracic Surgery (AATS) previously published an expert consensus document detailing important considerations in determining who is at high risk. The current objective was to evaluate treatment options and important factors to consider during treatment selection for these high-risk patients. After systematic review of the literature, treatment options for high-risk patients with stage I NSCLC were reviewed by an AATS expert panel. Expert consensus statements and vignettes pertaining to treatment selection were then developed using discussion and a modified Delphi method. The expert panel identified sublobar resection, stereotactic ablative radiotherapy (SABR), and image-guided thermal ablation (IGTA) as modalities applicable in the treatment of high-risk patients with stage I NSCLC. The panel also identified lung-nodule-related factors that are important to consider in treatment selection. Using this information, the panel formulated 14 consensus statements and 5 vignettes illustrating clinical scenarios. This article summarizes important factors to consider in treatment selection using these modalities, which are applicable in high-risk patients with stage I NSCLC. The choice of which modality (sublobar resection, SABR, or IGTA) is optimal in high-risk patients with stage I NSCLC is complex, but a surgical approach is generally favored when deemed safe. SABR and IGTA are reasonable options in select patients. SABR is more commonly used than IGTA and is likely the next-best choice. A multi-disciplinary review of patient and tumor characteristics is essential for achieving an optimal decision. The clinical treatment decision should also take patient perspectives, preferences, and quality of life into consideration.

Appropriate Use Criteria (AUC) for the Management of Non-Small Cell Lung Cancer in a Central/Ultra-Central Location: Guidelines from the American Radium Society

INTRODUCTION

Definitive radiation therapy is considered standard therapy for medically inoperable early-stage NSCLC. Nevertheless, for patients with tumors located near structures such as the proximal tracheobronchial tree, esophagus, heart, spinal cord, and brachial plexus, the optimal management regimen is controversial. The objective was to develop expert multidisciplinary consensus guidelines on managing medically inoperable NSCLC located in a central or ultracentral location relative to critical organs at risk.

METHODS

Case variants regarding centrally and ultracentrally located lung tumors were developed by the 15-member multidisciplinary American Radium Society (ARS) Thoracic Appropriate Use Criteria (AUC) expert panel. A comprehensive review of the English medical literature was performed from January 1 1946 to December 31 2023 to inform consensus guidelines. Modified Delphi methods were used by the panel to evaluate the variants and procedures, with at least three rating points from median defining agreement/consensus. The guideline was then approved by the ARS Executive Committee and released for public comment per established ARS procedures.

RESULTS

The Thoracic ARS AUC Panel identified 90 relevant references and obtained consensus in all variants. Radiotherapy alone was considered appropriate, with additional immunotherapy to be considered primarily in the clinical trial setting. Hypofractionated radiotherapy in eight to 18 fractions was considered appropriate for ultracentral lesions near the proximal tracheobronchial tree, upper trachea, and esophagus. For other ultracentral lesions near the heart, great vessels, brachial plexus, and spine, or for non-ultracentral but still central lesions, five-fraction stereotactic body radiation therapy was also considered an appropriate option. Intensity-modulated radiotherapy was considered appropriate and three-dimensional-conformal radiotherapy inappropriate for all variants. Other treatment planning techniques to decrease the risk of overdosing critical organs at risk were also considered.

CONCLUSIONS

The ARS Thoracic AUC panel has developed multidisciplinary consensus guidelines for various presentations of stage I NSCLC in a central or ultracentral location.

Stereotactic Radiation for Ultra-Central Non-Small Cell Lung Cancer: A Safety and Efficacy Trial (SUNSET)

PURPOSE

The use of stereotactic body radiation therapy for tumors in close proximity to the central mediastinal structures has been associated with a high risk of toxicity. This study (NCT03306680) aimed to determine the maximally tolerated dose of stereotactic body radiation therapy for ultracentral non-small cell lung carcinoma, using a time-to-event continual reassessment methodology.

METHODS AND MATERIALS

Patients with T1-3N0M0 (≤6 cm) non-small cell lung carcinoma were eligible. The maximally tolerated dose was defined as the dose of radiation therapy associated with a ≤30% rate of grade (G) 3 to 5 prespecified treatment-related toxicity occurring within 2 years of treatment. The starting dose level was 60 Gy in 8 daily fractions. The dose-maximum hotspot was limited to 120% and within the planning tumor volume; tumors with endobronchial invasion were excluded. This primary analysis occurred 2 years after completion of accrual.

RESULTS

Between March 2018 and April 2021, 30 patients were enrolled at 5 institutions. The median age was 73 years (range, 65-87) and 17 (57%) were female. Planning tumor volume was abutting proximal bronchial tree in 19 (63%), esophagus 5 (17%), pulmonary vein 1 (3.3%), and pulmonary artery 14 (47%). All patients received 60 Gy in 8 fractions. The median follow-up was 37 months (range, 8.9-51). Two patients (6.7%) experienced G3-5 adverse events related to treatment: 1 patient with G3 dyspnea and 1 G5 pneumonia. The latter had computed tomography findings consistent with a background of interstitial lung disease. Three-year overall survival was 72.5% (95% CI, 52.3%-85.3%), progression-free survival 66.1% (95% CI, 46.1%-80.2%), local control 89.6% (95% CI, 71.2%-96.5%), regional control 96.4% (95% CI, 77.2%-99.5%), and distant control 85.9% (95% CI, 66.7%-94.5%). Quality-of-life scores declined numerically over time, but the decreases were not clinically or statistically significant.

CONCLUSIONS

Sixty Gy in 8 fractions, planned and delivered with only a moderate hotspot, has a favorable adverse event rate within the prespecified acceptability criteria and results in excellent control for ultracentral tumors.

Daily CBCT-based dose calculations for enhancing the safety of dose-escalation in lung cancer radiotherapy

PURPOSE

Dose-escalation in lung cancer comes with a high risk of severe toxicity. This study aimed to calculate the delivered dose in a Scandinavian phase-III dose-escalation trial.

METHODS

The delivered dose was evaluated for 21 locally-advanced non-small cell lung cancer (LA-NSCLC) patients treated as part of the NARLAL2 dose-escalation trial. The patients were randomized between standard and escalated heterogeneous dose-delivery. Both treatment plans were created and approved before randomization. Daily cone-beam CT (CBCT) for patient positioning, and adaptive radiotherapy were mandatory. Standard and escalated plans, including adaptive re-plans, were recalculated on each daily CBCT and accumulated on the planning CT for each patient. Dose to the clinical target volume (CTV), organs at risk (OAR), and the effects of plan adaptions were evaluated for the accumulated dose and on each treated fraction scaled to full treatment.

RESULTS

For the standard treatment, plan adaptations reduced the number of patients with CTV-T underdosage from six to one, and the total number of fractions with CTV-T underdosage from 161 to 56; while for the escalated treatment, the number of patients was reduced from five to zero and number of fractions from 81 to 11. For dose-escalation, three patients had fractions exceeding trial constraints for heart, bronchi, or esophagus, and one had an accumulated heart dose above the constraints.

CONCLUSION

Dose-escalation for LA-NSCLC patients, using daily image guidance and adaptive radiotherapy, is dosimetrically safe for the majority of patients. Dose calculation on daily CBCTs is an efficient tool to monitor target coverage and OAR doses.

Advances in Stereotactic Body Radiation Therapy for Lung Cancer

ABSTRACT

Stereotactic body radiation therapy (SBRT) delivers curative-intent radiation to patients with early-stage non-small cell lung cancer and inoperable thoracic lesions. With improved techniques in tumor delineation, motion management, and delivery of radiation treatments, the therapeutic window within the thorax is able to be maximized. Ongoing technological advances enable highly targeted ablative radiation therapy while sparing adjacent sensitive organs at risk. Further applications of SBRT with combinatorial immunotherapy, the usage of particle therapy, and for patients with more advanced stages of lung cancer and other histologies mark exciting possibilities for the role of SBRT within the thorax.

Stereotactic vs Hypofractionated Radiotherapy for Inoperable Stage I Non-Small Cell Lung Cancer: The LUSTRE Phase 3 Randomized Clinical Trial

Importance

Stereotactic body radiotherapy (SBRT) is widely used for stage I medically inoperable non-small cell lung cancer (NSCLC), yet varied results from randomized clinical trials (RCTs) and concerns in treating centrally located tumors persist.

Objective

To examine whether SBRT would improve local control (LC) compared with hypofractionated conventional radiotherapy (CRT).

Design Setting and Participants

This phase 3 RCT was conducted in 16 Canadian centers. Patients with medically inoperable stage I (≤5 cm) NSCLC were randomized 2:1 to SBRT of 48 Gy in 4 fractions (peripheral NSCLC) or 60 Gy in 8 fractions (central NSCLC) vs CRT of 60 Gy in 15 fractions. Data were collected from May 2014 to January 2020, and data were analyzed from July 2022 to July 2023.

Interventions

SBRT or CRT.

Main Outcomes and Measures

The primary objective was to determine the effectiveness of SBRT compared with CRT based on LC at 3 years. Secondary outcomes included event-free survival, overall survival, and toxic effects. All radiation plans were subject to real-time/final review. Local failures were centrally adjudicated. The study was designed to detect a 3-year LC improvement of SBRT from 75% to 87.5%. The target sample size was 324 patients.

Results

Of 233 included patients, 119 (51.1%) were male, and the mean (SD) age was 75.4 (7.7) years; the median (IQR) follow-up was 36.1 (26.4-52.8) months. A total of 154 patients received SBRT and 79 received CRT. The 3-year LC was 87.6% (95% CI, 81.9%-93.4%) for SBRT and 81.2% (95% CI, 71.9%-90.5%) for CRT (hazard ratio [HR], 0.61; 95% CI, 0.31-1.20; P = .15). The HR was 1.02 (95% CI, 0.72-1.45; P = .87) for event-free survival and 1.18 (95% CI, 0.80-1.76; P = .40) for overall survival. Minimal acute toxic effects were observed. Among those randomized to SBRT, late grade 3 or 4 toxic effects occurred in 5 of 45 (11%) with central NSCLC and 2 of 109 (1.8%) with peripheral NSCLC; among those randomized to CRT, in 1 of 19 (5%) with central NSCLC and 1 of 60 (2%) with peripheral NSCLC. One patient who received SBRT for an ultracentral lesion (target overlapping proximal bronchus) experienced a possible treatment-related grade 5 event (hemoptysis).

Conclusions and Relevance

This RCT compared lung SBRT with hypofractionated CRT that included central/ultracentral tumors. No difference was detected in LC between groups. Severe toxic effects were limited, including patients with central tumors. The trial provides important prospective data evaluating SBRT; however, further research is necessary to determine if SBRT is more effective than CRT for peripheral and central NSCLC.

Trial Registration

ClinicalTrials.gov Identifier: NCT03924869.

Safety and Efficacy of Stereotactic Body Radiation Therapy for Ultra-central Thoracic Tumors: A Single Center Retrospective Review

PURPOSE

We sought to evaluate the toxicity and efficacy of stereotactic body radiation therapy (SBRT) for ultracentral thoracic tumors at our institution.

METHODS AND MATERIALS

Patients with ultracentral lung tumors or nodes, defined as having the planning target volume (PTV) overlapping or abutting the central bronchial tree and/or esophagus, treated at our institution with SBRT between 2009 and 2019 were retrospectively reviewed. All SBRT plans were generated with the goal of creating homogenous dose distributions. The primary endpoint was incidence of SBRT-related grade ≥3 toxicity, defined using the Common Terminology Criteria for Adverse Events (V5.0). Secondary endpoints included local failure (LF), progression-free survival (PFS), and overall survival. Competing risk analysis was used to estimate incidence and identify predictors of severe toxicity and LF, while the Kaplan-Meier method was used to estimate PFS and OS.

RESULTS

A total of 154 patients receiving 162 ultracentral courses of SBRT were included. The most common prescription was 50 Gy in 5 fractions (42%), with doses ranging from 30 to 55 Gy in 5 fractions (BED10 range, 48-115 Gy). The incidence of severe toxicity was 9.4% at 3 years. The most common severe toxicity was pneumonitis (n = 4). There was 1 possible treatment-related death from pneumonitis/pneumonia. Predictors of severe toxicity included increased PTV size, decreased PTV V95%, lung V5 Gy, and lung V20 Gy. The incidence of LF was 14% at 3 years. Predictors of LF included younger age and greater volume of overlap between the PTV and esophagus. The median PFS was 8.8 months, while the median overall survival was 44.0 months.

CONCLUSIONS

In the largest case series of ultracentral thoracic SBRT to date, homogenously prescribed SBRT was associated with relatively low rates of severe toxicity and LF. Predictors of toxicity should be interpreted in the context of the heterogeneity in toxicities observed.

Stereotactic Body Radiotherapy for Centrally Located Inoperable Early-Stage NSCLC: EORTC 22113-08113 LungTech Phase II Trial Results

INTRODUCTION

The international phase II single-arm LungTech trial 22113-08113 of the European Organization for Research and Treatment of Cancer assessed the safety and efficacy of stereotactic body radiotherapy (SBRT) in patients with centrally located early-stage NSCLC.

METHODS

Patients with inoperable non-metastatic central NSCLC (T1-T3 N0 M0, ≤7cm) were included. After prospective central imaging review and radiation therapy quality assurance for any eligible patient, SBRT (8 × 7.5 Gy) was delivered. The primary endpoint was freedom from local progression probability three years after the start of SBRT.

RESULTS

The trial was closed early due to poor accrual related to repeated safety-related pauses in recruitment. Between August 2015 and December 2017, 39 patients from six European countries were included and 31 were treated per protocol and analyzed. Patients were mainly male (58%) with a median age of 75 years. Baseline comorbidities were mainly respiratory (68%) and cardiac (48%). Median tumor size was 2.6 cm (range 1.2-5.5) and most cancers were T1 (51.6%) or T2a (38.7%) N0 M0 and of squamous cell origin (48.4%). Six patients (19.4%) had an ultracentral tumor location. The median follow-up was 3.6 years. The rates of 3-year freedom from local progression and overall survival were 81.5% (90% confidence interval [CI]: 62.7%-91.4%) and 61.1% (90% CI: 44.1%-74.4%), respectively. Cumulative incidence rates of local, regional, and distant progression at three years were 6.7% (90% CI: 1.6%-17.1%), 3.3% (90% CI: 0.4%-12.4%), and 29.8% (90% CI: 16.8%-44.1%), respectively. SBRT-related acute adverse events and late adverse events ≥ G3 were reported in 6.5% (n = 2, including one G5 pneumonitis in a patient with prior interstitial lung disease) and 19.4% (n = 6, including one lethal hemoptysis after a lung biopsy in a patient receiving anticoagulants), respectively.

CONCLUSIONS

The LungTech trial suggests that SBRT with 8 × 7.5Gy for central lung tumors in inoperable patients is associated with acceptable local control rates. However, late severe adverse events may occur after completion of treatment. This SBRT regimen is a viable treatment option after a thorough risk-benefit discussion with patients. To minimize potentially fatal toxicity, careful management of dose constraints, and post-SBRT interventions is crucial.

Dose prescription for stereotactic body radiotherapy: general and organ-specific consensus statement from the DEGRO/DGMP Working Group Stereotactic Radiotherapy and Radiosurgery

PURPOSE AND OBJECTIVE

To develop expert consensus statements on multiparametric dose prescriptions for stereotactic body radiotherapy (SBRT) aligning with ICRU report 91. These statements serve as a foundational step towards harmonizing current SBRT practices and refining dose prescription and documentation requirements for clinical trial designs.

MATERIALS AND METHODS

Based on the results of a literature review by the working group, a two-tier Delphi consensus process was conducted among 24 physicians and physics experts from three European countries. The degree of consensus was predefined for overarching (OA) and organ-specific (OS) statements (≥ 80%, 60-79%, < 60% for high, intermediate, and poor consensus, respectively). Post-first round statements were refined in a live discussion for the second round of the Delphi process.

RESULTS

Experts consented on a total of 14 OA and 17 OS statements regarding SBRT of primary and secondary lung, liver, pancreatic, adrenal, and kidney tumors regarding dose prescription, target coverage, and organ at risk dose limitations. Degree of consent was ≥ 80% in 79% and 41% of OA and OS statements, respectively, with higher consensus for lung compared to the upper abdomen. In round 2, the degree of consent was ≥ 80 to 100% for OA and 88% in OS statements. No consensus was reached for dose escalation to liver metastases after chemotherapy (47%) or single-fraction SBRT for kidney primaries (13%). In round 2, no statement had 60-79% consensus.

CONCLUSION

In 29 of 31 statements a high consensus was achieved after a two-tier Delphi process and one statement (kidney) was clearly refused. The Delphi process was able to achieve a high degree of consensus for SBRT dose prescription. In summary, clear recommendations for both OA and OS could be defined. This contributes significantly to harmonization of SBRT practice and facilitates dose prescription and reporting in clinical trials investigating SBRT.

Palliative Thoracic Radiotherapy in the Era of Modern Cancer Care for NSCLC

Palliative thoracic radiotherapy provides rapid and effective symptom relief in approximately two-thirds of NSCLC patients treated. In patients with poor performance status, the degree of palliation appears unrelated to the radiation dose or fractionation schedule. Conversely, in patients with good performance status, higher radiation doses administered over longer periods have shown modest survival benefits. These findings stem from studies conducted before the advent of immunotherapy and targeted therapy in clinical practice. Currently, there are no large prospective studies specifically dedicated to palliative radiotherapy conducted in this new treatment era. Modern radiotherapy technologies are now widely available and are increasingly used for palliative purposes in selected patients, reflecting the expanded array of therapeutic options for disseminated NSCLC and improved prognosis. Some traditional tenets of palliative thoracic radiotherapy, such as the improvement of overall survival with a protracted radiation schedule and the use of simple, cost-effective radiation techniques for palliative purposes, may no longer hold true for patients receiving immunotherapy or targeted therapy. The application of IMRT or SBRT in the context of palliative radiotherapy for NSCLC is not yet sufficiently explored, and this is addressed in this review. Moreover, new risks associated with combining palliative radiotherapy with these systemic treatments are being explored and are discussed within the context of palliative care. The optimal timing, doses, fractionation schedules, and treatment volumes for radiotherapy combined with immunotherapy or targeted therapy are currently subjects of investigation. In emergencies, radiotherapy should be used as a life-saving measure without delay. However, for other indications of palliative thoracic radiotherapy, decisions regarding doses, timing relative to systemic treatments, and treatment volumes should be made in a multidisciplinary context, considering the patient's prognosis, anticipated outcomes, and access to potentially effective treatments. We still lack robust data from prospective studies on this matter. This review examines and discusses available evidence on the use of palliative thoracic radiotherapy within the framework of modern treatment strategies for NSCLC.

Prospective phase II trial on ablative stereotactic body radiation therapy (SBRT) for medically inoperable thoracic nodes metastases

BACKGROUND

Oligometastases in mediastinal nodes are increasingly prevalent, posing challenges for treatment with stereotactic body radiotherapy (SBRT) due to proximity to organs at risk (OARs). We report the results of a single prospective observational phase II trial on ablative SBRT for medically inoperable thoracic nodes metastases (NCT02970955).

MATERIAL AND METHODS

Since 2017, patients with < 3 nodal metastases were evaluated by the tumor board and included if deemed inoperable. SBRT was delivered using risk adaptive approach based on number, site and size of metastatic nodes (50 Gy/5fractions, 60 Gy/8fractions, 70 Gy/10 fractions). Planning target volume (PTV) partial underdosage was allowed. The primary end point was local control (LC) at 12 months. Secondary end points were: acute and late toxicities, overall survival (OS), progression free survival (PFS), and time to next systemic therapy (TTNS).

RESULTS

Between 03/2017-11/2021, 32 patients (41 nodal metastases) were included. NSCLC (13pts), breast (5pts) and colorectal cancer (4pts) were the most represented primary tumour. In 66 % cases, partial PTV undercoverage was necessary. LC at 1 and 2 years was 93.5 % and 82.3 %, respectively. Treatment was well-tolerated with no acute or late toxicity ≥ G3. Median OS was 59.7 months. OS at 1 and 2 years was 96.9 % and 83.8 % respectively. Median PFS was 12.2 months. PFS at 1 and 2 years was 53.1 % and 31.3 %, respectively.

CONCLUSION

This trial supported the feasibility and safety of ablative SBRT for thoracic nodes metastases thanks to risk adaptive approach allowing to delay of new systemic therapies. Larger studies are needed to confirm these observations.

[New Radiation Therapy Concepts in Non-Metastatic Lung Cancer]

Radiotherapy plays a critical role in the management of non-metastatic lung cancer, offering curative potential and symptom relief. It serves as a primary treatment modality or adjuvant therapy post-surgery, enhancing local control and survival rates. Modern techniques like Stereotactic Body Radiotherapy (SBRT) enable precise tumor targeting, minimizing damage to healthy tissue and reducing treatment duration. The synergy between radiotherapy and systemic treatments, including immunotherapy, holds promise in improving outcomes. Immunotherapy augments the immune response against cancer cells, potentially enhancing radiotherapy's efficacy. Furthermore, radiotherapy's ability to modulate the tumor microenvironment complements the immunotherapy's mechanism of action. As a result, the combination of radiotherapy and immunotherapy may offer superior tumor control and survival benefits. Moreover, the integration of radiotherapy with surgery and chemotherapy in multidisciplinary approaches maximizes treatment efficacy while minimizing toxicity. Herein we present an overview on modern radiotherapy and potential developments in the close future.

Harnessing the Power of Radiotherapy for Lung Cancer: A Narrative Review of the Evolving Role of Magnetic Resonance Imaging Guidance

Compared with computed tomography (CT), magnetic resonance imaging (MRI) traditionally plays a very limited role in lung cancer management, although there is plenty of room for improvement in the current CT-based workflow, for example, in structures such as the brachial plexus and chest wall invasion, which are difficult to visualize with CT alone. Furthermore, in the treatment of high-risk tumors such as ultracentral lung cancer, treatment-associated toxicity currently still outweighs its benefits. The advent of MR-Linac, an MRI-guided radiotherapy (RT) that combines MRI with a linear accelerator, could potentially address these limitations. Compared with CT-based technologies, MR-Linac could offer superior soft tissue visualization, daily adaptive capability, real-time target tracking, and an early assessment of treatment response. Clinically, it could be especially advantageous in the treatment of central/ultracentral lung cancer, early-stage lung cancer, and locally advanced lung cancer. Increasing demands for stereotactic body radiotherapy (SBRT) for lung cancer have led to MR-Linac adoption in some cancer centers. In this review, a broad overview of the latest research on imaging-guided radiotherapy (IGRT) with MR-Linac for lung cancer management is provided, and development pertaining to artificial intelligence is also highlighted. New avenues of research are also discussed.

Motion-Inclusive Treatment Planning to Assess Normal Tissue Dose for Central Lung Stereotactic Body Radiation Therapy

Purpose

For lung stereotactic body radiation therapy, 4-dimensional computed tomography is often used to delineate target volumes, whereas organs at risk (OARs) are typically outlined on either average intensity projection (AIP) or midventilation (MidV = 30% phase) images. AIP has been widely adopted as it represents a true average, but image blurring often precludes accurate contouring of critical structures such as central airways. Here, we compare AIP versus MidV planning for centrally located tumors via respiratory motion-inclusive (RMI) plans to better evaluate dose delivered throughout the breathing cycle.

Methods and Materials

Independently contoured and optimized AIP and MidV plans were created for 16 treatments and rigidly copied to each of the 10 breathing phase-specific computed tomography image sets. Resulting dose distributions were deformably registered back to the MidV image set (used as reference because of clearer depiction of anatomy compared with motion-blurred AIP) and averaged to create RMI plans. Doses to central OARs were compared between plans.

Results

Mean absolute dose differences were low for all comparisons (range, 0.01-2.87 Gy); however, individual plans exhibited differences >20 Gy. Dose differences >5 Gy were observed most often for plan comparisons involving AIP-based plans (MidV vs AIP 23, AIP RMI vs AIP 12, MidV RMI vs AIP RMI 7, and MidV RMI vs MidV 8 times). Inclusion of respiratory motion reduced large dose differences. Standard OAR thresholds were exceeded up to 5 times for each plan comparison scenario and always involved proximal bronchial tree D4 cc tolerance dose. AIP-based contours were larger by, on average, 3% to 15%.

Conclusions

Large dose differences were observed when plans with AIP-based contours were compared with MidV-based contours, indicating that observed dose differences were likely due to contoured volume differences rather than the effect of motion. Because of blurring with AIP images, MidV RMI-based planning may offer a more accurate method to determine dose to critical OARs in the presence of respiratory motion.

Local-Regional Therapy for Oligometastatic Colorectal Cancer

ABSTRACT

Colorectal cancer is one of the most common malignancies in the United States as well as a leading cause of cancer-related death. Upward of 30% of patients ultimately develop metastatic disease, most commonly to the liver and lung. Untreated, patients have poor survival. Historically, patients with oligometastatic disease were treated with resection leading to long-term survival; however, there are many patients who are not surgical candidates. Innovations in thermal ablation, hepatic artery infusions, chemoembolization and radioembolization, and stereotactic ablative radiation have led to an expansion of patients eligible for local therapy. This review examines the evidence behind each modality for the most common locations of oligometastatic colorectal cancer.

A Novel Inverse Algorithm To Solve the Integrated Optimization of Dose, Dose Rate, and Linear Energy Transfer of Proton FLASH Therapy With Sparse Filters

PURPOSE

The recently proposed Integrated Physical Optimization Intensity Modulated Proton Therapy (IPO-IMPT) framework allows simultaneous optimization of dose, dose rate, and linear energy transfer (LET) for ultra-high dose rate (FLASH) treatment planning. Finding solutions to IPO-IMPT is difficult because of computational intensiveness. Nevertheless, an inverse solution that simultaneously specifies the geometry of a sparse filter and weights of a proton intensity map is desirable for both clinical and preclinical applications. Such solutions can reduce effective biologic dose to organs at risk in patients with cancer as well as reduce the number of animal irradiations needed to derive extra biologic dose models in preclinical studies.

METHODS AND MATERIALS

Unlike the initial forward heuristic, this inverse IPO-IMPT solution includes simultaneous optimization of sparse range compensation, sparse range modulation, and spot intensity. The daunting computational tasks vital to this endeavor were resolved iteratively with a distributed computing framework to enable Simultaneous Intensity and Energy Modulation and Compensation (SIEMAC). SIEMAC was demonstrated on a human patient with central lung cancer and a minipig.

RESULTS

SIEMAC simultaneously improves maps of spot intensities and patient-field-specific sparse range compensators and range modulators. For the patient with lung cancer, at our maximum nozzle current of 300 nA, dose rate coverage above 100 Gy/s increased from 57% to 96% in the lung and from 93% to 100% in the heart, and LET coverage above 4 keV/µm dropped from 68% to 9% in the lung and from 26% to <1% in the heart. For a simple minipig plan, the full-width half-maximum of the dose, dose rate, and LET distributions decreased by 30%, 1.6%, and 57%, respectively, again with similar target dose coverage, thus reducing uncertainty in these quantities for preclinical studies.

CONCLUSIONS

The inverse solution to IPO-IMPT demonstrated the capability to simultaneously modulate subspot proton energy and intensity distributions for clinical and preclinical studies.

Epidemiology and Survival of Malignant Central Airway Obstruction in Lung Cancer Identified on Cross-Sectional Imaging

BACKGROUND

The prevalence of malignant central airway obstruction at diagnosis and its 5-year incidence are largely unknown, as are basic epidemiological data pertaining to this serious condition. To address these data limitations, we retrospectively collected data from the cohort of patients diagnosed with lung cancer at our institution in 2015 and followed cohort patients 5 years forward, until 2020.

METHODS

We reviewed index PET/CT or CT scans at the time of lung cancer diagnosis to identify the presence, subtype, and severity of malignant central airway obstruction as well as progression/development over the next 5 years.

RESULTS

The prevalence of malignant central airway obstruction affecting the airway lumen by 25% or greater was 17%, and its 5-year incidence of development was 8.2%. Notable associations from the multivariate analysis included a younger age and a stepwise increase in obstruction with increasing stage of disease. Squamous cell carcinoma and small-cell lung cancer were the 2 histologic subtypes with the strongest association with obstruction. The presence of malignant central airway obstruction either at time of diagnosis or on follow-up imaging was associated with significantly shortened survival (multivariate Cox proportional HR for MCAO=1.702, P<0.001).

CONCLUSION

This study provides the first systematic characterization of fundamental epidemiological data on malignant central airway obstructions at a tertiary cancer center in the United States. This data is important to inform research directions and funding efforts of this serious complication. It also serves as a baseline value against which to compare for future studies.

Single institution experience of MRI-guided radiotherapy for thoracic tumors and clinical characteristics impacting treatment duty cycle

Introduction

MRI-guided radiotherapy (MRgRT) allows for direct motion management and real-time radiation treatment plan adaptation. We report our institutional experience using low strength 0.35T MRgRT for thoracic malignancies, and evaluate changes in treatment duty cycle between first and final MRgRT fractions.

Methods

All patients with intrathoracic tumors treated with MRgRT were included. The primary reason for MRgRT (adjacent organ at risk [OAR] vs. motion management [MM] vs. other) was recorded. Tumor location was classified as central (within 2cm of tracheobronchial tree) vs. non-central, and further classified by the Expanded HILUS grouping. Gross tumor volume (GTV) motion, planning target volume expansions, dose/fractionation, treatment plan time, and total delivery time were extracted from the treatment planning system. Treatment plan time was defined as the time for beam delivery, including multileaf collimator (MLC) motion, and gantry rotation. Treatment delivery time was defined as the time from beam on to completion of treatment, including treatment plan time and patient respiratory breath holds. Duty cycle was calculated as treatment plan time/treatment delivery time. Duty cycles were compared between first and final fraction using a two-sample t-test.

Results

Twenty-seven patients with thoracic tumors (16 non-small cell lung cancer and 11 thoracic metastases) were treated with MRgRT between 12/2021 and 06/2023. Fifteen patients received MRgRT due to OAR and 11 patients received MRgRT for motion management. 11 patients had central tumors and all were treated with MRgRT due to OAR risk. The median dose/fractionation was 50 Gy/5 fractions. For patients treated due to OAR (n=15), 80% had at least 1 adapted fraction during their course of radiotherapy. There was no plan adaptation for patients treated due to motion management (n=11). Mean GTV motion was significantly higher for patients treated due to motion management compared to OAR (16.1mm vs. 6.5mm, p=0.011). Mean duty cycle for fraction 1 was 54.2% compared to 62.1% with final fraction (p=0.004). Mean fraction 1 duty cycle was higher for patients treated due to OAR compared to patients treated for MM (61% vs. 45.0%, p=0.012).

Discussion

Duty cycle improved from first fraction to final fraction possibly due to patient familiarity with treatment. Duty cycle was improved for patients treated due to OAR risk, likely due to more central location and thus decreased target motion.

The First Reported Case of Treating the Ultra-Central Thorax With Cone Beam Computed Tomography-Guided Stereotactic Adaptive Radiotherapy (CT-STAR)

Stereotactic body radiotherapy (SBRT) to the central and ultra-central thorax is associated with infrequent but potentially serious adverse events. Adaptive SBRT, which provides more precise treatment planning and inter-fraction motion management, may allow the delivery of ablative doses to ultra-central tumors with effective local control and improved toxicity profiles. Herein, we describe the first reported case of cone beam computed tomography (CBCT)-guided stereotactic adaptive radiotherapy (CT-STAR) in the treatment of ultra-central non-small cell lung cancer (NSCLC) in a prospective clinical trial (NCT05785845). An 80-year-old man with radiographically diagnosed early-stage NSCLC presented for definitive management of an enlarging ultra-central lung nodule. He was prescribed 55 Gy in five fractions with CT-STAR. A simulation was performed using four-dimensional CT, and patients were planned for treatment at end-exhale breath-hold. Treatment plans were generated using a strict isotoxicity approach, which prioritized organ at risk (OAR) constraints over target coverage. During treatment, daily CBCTs were acquired and used to generate adapted contours and treatment plans based on the patient's anatomy-of-the-day, all while the patient was on the treatment table. The initial and adapted plans were compared using dose-volume histograms, and the superior plan was selected for treatment. The adapted plan was deemed superior and used for treatment in three out of five fractions. The adapted plan provided improved target coverage in two fractions and resolved an OAR hard constraint violation in one fraction. We report the successful treatment of a patient with ultra-central NSCLC utilizing CT-STAR. This case report builds on previously published in silico data to support the viability and dosimetric advantages of CT-STAR in the ablative treatment of this challenging tumor location. Further data are needed to confirm the toxicity and efficacy of this technique.

Structure-specific rigid dose accumulation dosimetric analysis of ablative stereotactic MRI-guided adaptive radiation therapy in ultracentral lung lesions

BACKGROUND

Definitive local therapy with stereotactic ablative radiation therapy (SABR) for ultracentral lung lesions is associated with a high risk of toxicity, including treatment related death. Stereotactic MR-guided adaptive radiation therapy (SMART) can overcome many of the challenges associated with SABR treatment of ultracentral lesions.

METHODS

We retrospectively identified 14 consecutive patients who received SMART to ultracentral lung lesions from 10/2019 to 01/2021. Patients had a median distance from the proximal bronchial tree (PBT) of 0.38 cm. Tumors were most often lung primary (64.3%) and HILUS group A (85.7%). A structure-specific rigid registration approach was used for cumulative dose analysis. Kaplan-Meier log-rank analysis was used for clinical outcome data and the Wilcoxon Signed Rank test was used for dosimetric data.

RESULTS

Here we show that SMART dosimetric improvements in favor of delivered plans over predicted non-adapted plans for PBT, with improvements in proximal bronchial tree DMax of 5.7 Gy (p = 0.002) and gross tumor 100% prescription coverage of 7.3% (p = 0.002). The mean estimated follow-up is 17.2 months and 2-year local control and local failure free survival rates are 92.9% and 85.7%, respectively. There are no grade ≥ 3 toxicities.

CONCLUSIONS

SMART has dosimetric advantages and excellent clinical outcomes for ultracentral lung tumors. Daily plan adaptation reliably improves target coverage while simultaneously reducing doses to the proximal airways. These results further characterize the therapeutic window improvements for SMART. Structure-specific rigid dose accumulation dosimetric analysis provides insights that elucidate the dosimetric advantages of SMART more so than per fractional analysis alone.

Correlation of Bronchoscopy and CT in Characterizing Malignant Central Airway Obstruction

BACKGROUND

Malignant Central Airway Obstruction (MCAO) presents a significant challenge in lung cancer management, with notable morbidity and mortality implications. While bronchoscopy is the established diagnostic standard for confirming MCAO and assessing obstruction subtype (intrinsic, extrinsic, mixed) and severity, Computed Tomography (CT) serves as an initial screening tool. However, the extent of agreement between CT and bronchoscopy findings for MCAO remains unclear.

METHODS

To assess the correlation between bronchoscopy and CT, we conducted a retrospective review of 108 patients at Roswell Park Comprehensive Cancer Center, analyzing CT and bronchoscopy results to document MCAO presence, severity, and subtype.

RESULTS

CT correctly identified MCAO in 99% of cases (107/108). Agreement regarding obstruction subtype (80.8%, Cohen's κ = 0.683, p < 0.001), and severity (65%, Quadratic κ = 0.657, p < 0.001) was moderate. CT tended to equally overestimate (7/19) and underestimate (7/19) the degree of obstruction. CT was also poor in identifying mucosal involvement in mixed MCAO.

CONCLUSIONS

CT demonstrates reasonable agreement with bronchoscopy in detecting obstruction. Nevertheless, when CT indicates a positive finding for MCAO, it is advisable to conduct bronchoscopy. This is because CT lacks reliability in determining the severity of obstruction and identifying the mucosal component of mixed disease.

Protocol of a phase II study to evaluate the efficacy and safety of deep-inspiration breath-hold daily online adaptive radiotherapy for centrally located lung tumours (PUDDING study)

BACKGROUND

Centrally located lung tumours present a challenge because of their tendency to exhibit symptoms such as airway obstruction, atelectasis, and bleeding. Surgical resection of these tumours often requires sacrificing the lungs, making definitive radiotherapy the preferred alternative to avoid pneumonectomy. However, the proximity of these tumours to mediastinal organs at risk increases the potential for severe adverse events. To mitigate this risk, we propose a dual-method approach: deep inspiration breath-hold (DIBH) radiotherapy combined with adaptive radiotherapy. The aim of this single-centre, single-arm phase II study is to investigate the efficacy and safety of DIBH daily online adaptive radiotherapy.

METHODS

Patients diagnosed with centrally located lung tumours according to the International Association for the Study of Lung Cancer recommendations, are enrolled and subjected to DIBH daily online adaptive radiotherapy. The primary endpoint is the one-year cumulative incidence of grade 3 or more severe adverse events, as classified by the Common Terminology Criteria for Adverse Events (CTCAE v5.0).

DISCUSSION

Delivering definitive radiotherapy for centrally located lung tumours presents a dilemma between ensuring optimal dose coverage for the planning target volume and the associated increased risk of adverse events. DIBH provides measurable dosimetric benefits by increasing the normal lung volume and distancing the tumour from critical mediastinal organs at risk, leading to reduced toxicity. DIBH adaptive radiotherapy has been proposed as an adjunct treatment option for abdominal and pelvic cancers. If the application of DIBH adaptive radiotherapy to centrally located lung tumours proves successful, this approach could shape future phase III trials and offer novel perspectives in lung tumour radiotherapy.

TRIAL REGISTRATION

Registered at the Japan Registry of Clinical Trials (jRCT; https://jrct.niph.go.jp/ ); registration number: jRCT1052230085 ( https://jrct.niph.go.jp/en-latest-detail/jRCT1052230085 ).

Dose-Volume Predictors of Radiation Pneumonitis After Thoracic Hypofractionated Radiation Therapy

PURPOSE

Hypofractionated radiation therapy (HFRT) is a common treatment for thoracic tumors, typically delivered as 60 Gy in 15 fractions. We aimed to identify dosimetric risk factors associated with radiation pneumonitis in patients receiving HFRT at 4 Gy per fraction, focusing on lung V20, mean lung dose (MLD), and lung V5 as potential predictors of grade ≥2 pneumonitis.

METHODS AND MATERIALS

All patients were treated with thoracic HFRT to 60 Gy in 15 fractions or 72 Gy in 18 fractions at a single health care system from 2013 to 2020. Tumors near critical structures (trachea, proximal tracheobronchial tree, esophagus, spinal cord, or heart) were considered central (within 2 cm), and those closer were classified as ultracentral (within 1 cm). The primary endpoint was grade ≥2 pneumonitis. Logistic regression analyses, adjusting for target size and dosimetric variables, were used to establish a dose threshold associated with <20% risk of grade ≥2 pneumonitis.

RESULTS

During a median 24.3-month follow-up, 18 patients (16.8%) developed grade ≥2 radiation pneumonitis, with no significant difference between the 2 dose regimens (17.3% vs 16.3%, P = .88). Four patients (3.7%) experienced grade ≥3 pneumonitis, including 2 grade 5 cases. Patients with grade ≥2 pneumonitis had significantly higher lung V20 (mean 23.4% vs 14.5%, P < .001), MLD (mean 13.0 Gy vs 9.5 Gy, P < .001), and lung V5 (mean 49.6% vs 40.6%, P = .01). Dose thresholds for a 20% risk of grade ≥2 pneumonitis were lung V20 <17.7%, MLD <10.6 Gy, and V5 <41.3%. Multivariable analysis revealed a significant association between lung V20 and grade ≥2 pneumonitis (adjusted odds ratio, 1.48, P = .03).

CONCLUSIONS

To minimize the risk of grade ≥2 radiation pneumonitis when delivering 4 Gy per fraction at either 60 Gy or 72 Gy, it is advisable to maintain lung V20<17.7%. MLD <10.6 Gy and V5<41.3% can also be considered as lower-priority constraints. However, additional validation is necessary before incorporating these constraints into clinical practice or trial planning guidelines.