Stereotactic ablative radiotherapy for the comprehensive treatment of 4-10 oligometastatic tumors (SABR-COMET-10): study protocol for a randomized phase III trial

Spine Stereotactic Body Radiation Therapy in Geriatric Patients: Implications of Age and Dose on Iatrogenic Vertebral Compression Fracture Risk

PURPOSE

Stereotactic body radiation therapy (SBRT) is an effective treatment for spinal metastases; however, outcomes specific to a geriatric population have not been described. This study aims to investigate the efficacy and safety of spine SBRT, in particular the rate of iatrogenic vertebral compression fracture (VCF), in patients aged 70 and older.

PATIENTS AND METHODS

From a prospectively maintained single-institutional database of 976 patients and 2407 spinal segments treated with SBRT for vertebral metastases between 2008 and 2021, all patients aged 70 or above were retrospectively reviewed. The primary outcome is the risk of VCF. Secondary outcomes included magnetic resonance imaging-based local failure and overall survival.

RESULTS

A total of 252 consecutive patients with 580 spinal segments treated with spine SBRT were reviewed. The median age was 75.8 (range: 70-90.3) years and the median (interquartile range) follow-up duration was 16.9 (6.4-41.3) months. The median overall survival of the entire cohort was 20.3 months and the 2-year local failure rate was 14.3%. The cumulative risk of VCF at 12 and 24 months were 8.4% and 12.3%, respectively. Significant predictors of VCF on multivariable analyses included greater biologically equivalent dose, baseline fracture, and increasing age. In particular, the 2-year VCF rate and median time to VCF were 30.3% and 3.4 months for those 86 and older, compared with 11.2% and 12.8 months for those younger than 86, respectively (P = .0011).

CONCLUSION AND RELEVANCE

Spine SBRT should be considered in a geriatric population; however, for those 86 and older, we suggest caution due to the significant risk of VCF.

Oligometastatic granulosa cell tumor treated with stereotactic body radiation therapy with a radiographic and tumor marker response

Stereotactic body radiation therapy (SBRT) is a safe and effective treatment for oligometastatic gynecologic cancers. This report details the case of a 75-year-old woman with recurrent granulosa cell tumor of the left ovary. The patient was diagnosed with a peritoneal recurrence after her inhibin-B level increased to 39.7 pg/mL, and a subsequent computed tomography (CT) scan of the abdomen and pelvis revealed an enlarging left-sided soft tissue mass in the sigmoid mesentery measuring 1.2 × 1.2 cm. She underwent SBRT, delivering 37.5 Gy in 5 fractions to the soft tissue mass. A CT scan post-treatment indicated the mass had decreased to 0.8 cm and that her inhibin B level decreased to < 7 pg/mL. This case highlights the effectiveness of SBRT in the management of oligometastatic ovarian cancer, achieving a marked radiographic and tumor marker response in patients with disease not amenable to surgical resection.

Validation and development of a refined M1 category for nasopharyngeal carcinoma based on the version-nine of AJCC/UICC TNM staging system in the immunotherapy era: A multicenter cohort study

OBJECTIVE

To evaluate the applicability of the M1 category of the version-nine of AJCC/UICC TNM staging system (TNM-9) for M1 nasopharyngeal carcinoma (M1-NPC) in immunotherapy era and propose potential refinements.

METHODS

M1-NPC patients who underwent palliative chemotherapy and immune checkpoint inhibitors (ICIs) between January 2019 and June 2023 across five institutions were included and re-staged according to TNM-9. Overall survival (OS) and Progression-free survival (PFS) were analyzed. A recursive partitioning analysis (RPA) model was employed to derive a new RPA-M1 category.

RESULTS

Among the 472 patients included, 219 were M1a and 253 were M1b. With a median follow-up time of 27 months, the M1a subgroup exhibited significantly higher 2-year OS (90.4 % vs. 73.7 %) and PFS (69.2 % vs. 40.6 %) than M1b subgroup (all P<0.001), which was further confirmed by multivariate analysis (MVA). Additionally, number of involved organs was found to be another independent predictor. New RPA-M1 category were then developed: RPA-M1a (≤3 metastatic lesions and confined to one single organ), RPA-M1b (≤3 metastatic lesions but involving multiple organs or >3 lesions and confined to one single organ), and RPA-M1c (patients with >3 metastatic lesions and involving multiple organs), with 2-year OS rates of 91.5 %, 81.4 %, and 69.8 %, respectively (P < 0.05) and PFS rates of 72.4 %, 54.3 % and 29.1 %, respectively (P < 0.005). Compared to the M1 Category in TNM-9, RPA-M1 category had a lower Akaike Information Criterion (AIC) and a higher concordance index (C-index) for OS and PFS.

CONCLUSION

The M1 category in the TNM-9 is applicable in the immunotherapy era. The RPA-M1 category offers improve depiction of survival outcomes compared to TNM-9, allowing for more refined stratification of patient outcomes and individulized decision-tailoring.

The 2024 State of Science report from the European Organisation for Research and Treatment of Cancer's Radiation Oncology Scientific Council

BACKGROUND

Radiotherapy (RT) is a central pillar of a multimodal cancer treatment approach. The ongoing advances in the fields of RT, imaging technologies, cancer biology, and others yield the potential to refine the use of RT. The European Organisation for Research and Treatment of Cancer (EORTC) hosted a dedicated workshop to identify and prioritize key research questions and to define future RT-based treatment strategies to improve the survival and quality of life of cancer patients.

METHODS

An initial call for relevant RT research topics led to the formation of workgroups to develop these into new clinical research proposals and projects. The EORTC Radiation Oncology Scientific Council (ROSC) State of Science workshop was held in Brussels, Belgium, in February 2024, bringing together EORTC members and international stakeholders to connect and work on the proposals.

RESULTS

Four topics of interest were identified: I) De-escalation of RT, minimizing toxicity while maintaining patients' quality of life, II) Technology-driven RT utilizing advances in treatment techniques, such as spatially fractionated RT to improve outcomes in patients with bulky disease and localized high tumor burden, III) Biology-driven RT, integrating the rapid advances in cancer biology and functional imaging to guide and personalize RT, and IV) New indications adding value and expanding the use of RT.

CONCLUSION

The EORTC ROSC State of Science workshop prioritized clinical questions to be addressed in prospective clinical research projects to advance RT care and improve patient outcomes.

Comparison of metastasis and treatment patterns among different histopathologic types of lung cancer: analysis of 6 years of nationwide lung cancer cohort data in Korea

Background

Personalized management of stage IV lung cancer requires a deeper understanding of metastatic patterns and the potential benefits of localized treatments for each histologic type. This study aims to identify patterns of both intrathoracic and extrathoracic metastases across various histologic types of lung cancer using a nationwide Korean lung cancer database.

Methods

The study analyzed data from patients diagnosed with lung cancer between 2014 and 2019, sourced from the Korean Association of Lung Cancer Registry (KALC-R). Patients with stage IV lung cancer, indicated by M staging, were included to focus on metastatic patterns.

Results

The cohort included 7,562 stage IV lung cancer patients, with adenocarcinoma being the most prevalent histologic type, comprising 49.22% of cases (3,722 patients). M stage categorization showed that 27.3% were M1a, 56.3% M1b, 15.7% M1c, and 0.6% unspecified. The adenosquamous type had the highest proportion of patients with metastases in three or more organs (42.9%). Metastases to the liver and bones were consistently associated with decreased survival across histologic types. In adenocarcinoma, strong associations were observed between extrathoracic metastatic sites, particularly between bone and liver [odds ratio (OR) =3.93] and liver and adrenal glands (OR =2.85). Multivariate analysis revealed that patients receiving radiotherapy to lung lesions had significantly better overall survival (OS) [hazard ratio (HR) =0.68; 95% confidence interval (CI): 0.60-0.78; P<0.001] compared to those who did not. Radiotherapy to extrathoracic metastases also significantly improved survival (HR =0.84; 95% CI: 0.77-0.93; P<0.001).

Conclusions

Understanding metastasis patterns and treatment options specific to each lung cancer histologic type is essential for improving treatment strategies.

Total Tumor Irradiation for Multiple Lung Metastases Using Carbon Ion Radiotherapy and High-Frequency Oscillatory Ventilation: A Case Report of Two Patients

Curative-intent radiotherapy for multiple lung metastases with more than 10 lesions is limited by lung dose constraints and respiratory motion. Carbon ion radiotherapy (CIRT) leverages the Bragg peak for precision and hypofractionation, while high-frequency oscillatory ventilation (HFOV) minimizes motion under anesthesia. This study evaluates the feasibility of combining CIRT and HFOV in treating ≥15 lung metastases. Two patients received single-fraction CIRT (50 Gy(RBE)) targeting all lesions. Case 1 (16 metastases of bilateral lung, hepatocellular carcinoma) and Case 2 (15 metastases of the left lung, colorectal adenocarcinoma) underwent four-dimensional (4D)-CT simulation with HFOV and CIRT in one single dose. Diaphragm motion reduced from 1.15 and 3.09 cm for Cases 1 and 2 (free-breathing) to 0.1 and 0.2 cm, respectively. Lung dose constraint parameters (V30: 3.57% to 12.35%; V20: 6.06% to 15.3%) met safety thresholds. Both patients achieved 22-month survival with continued local control (complete response in Case 1; partial response in Case 2). Case 1 developed grade II pneumonitis (resolved with steroids) and asymptomatic fibrosis; Case 2 had no toxicity. Some new lesions were managed with additional CIRT. Outcomes compare favorably to published photon trials in which up to 10 lung lesions were irradiated, underscoring CIRT's precision and HFOV's motion control. Success relied on three factors: CIRT's dosimetric advantages, HFOV-driven motion reduction, and anesthesia-enabled tolerability of the longer irradiation time span. Despite cost barriers, CIRT seems to extend survival in patients with multiple lung metastases that were refractory to conventional local therapy. This approach demonstrates the feasibility of irradiating more than 15 lesions in patients with polymetastatic lung disease, offering durable control with manageable toxicity. Larger studies are needed to validate its role in multimodal therapy.

Predicting the 3-Dimensional Dose Distribution of Multilesion Lung Stereotactic Ablative Radiation Therapy With Generative Adversarial Networks

PURPOSE

Because SABR therapy is being used to treat greater numbers of lung metastases, selecting the optimal dose and fractionation to balance local failure and treatment toxicity becomes increasingly challenging. Multilesion lung SABR therapy plans include spatially diverse lesions with heterogeneous prescriptions and interacting dose distributions. In this study, we developed and evaluated a generative adversarial network (GAN) to provide real-time dosimetry predictions for these complex cases.

METHODS AND MATERIALS

A GAN was trained to predict dosimetry on a data set of patients who received SABR therapy for lung lesions at a tertiary center. Model input included the planning computed tomography scan, the organs at risk (OARs) and target structures, and an initial estimate of exponential dose fall-off. Multilesion plans were split 80/20 for training and evaluation. Models were evaluated on voxel-voxel, clinical dose-volume histogram, and conformality metrics. An out-of-sample validation and analysis of model variance were performed.

RESULTS

There were 125 multilesion plans from 102 patients with 357 lesions. Patients were treated for 2 to 7 lesions, with 19 unique dose-fractionation schemes over 1 to 3 courses of treatment. The out-of-sample validation set contained an additional 90 plans from 80 patients. The mean absolute difference and gamma pass fraction between the predicted and true dosimetry was <3 Gy and >90% for all OARs. The absolute differences in lung V20 and CV14 were 1.40% ± 0.99% and 75.8 ± 42.0 cc, respectively. The ratios of predicted to true R50%, R100%, and D2cm were 1.00 ± 0.16, 0.96 ± 0.32, and 1.01 ± 0.36, respectively. The out-of-sample validation set maintained mean absolute difference and gamma pass fraction of <3 Gy and >90%, respectively for all OARs. The median standard deviation of variance in V20 and CV14 prediction was 0.49% and 22.2 cc, respectively.

CONCLUSIONS

A GAN for predicting the 3-D dosimetry of complex multilesion lung SABR therapy is presented. Rapid dosimetry prediction can be used to assess treatment feasibility and explore dosimetric differences between varying prescriptions.

The Role of Stereotactic Body Radiotherapy in Oligometastatic Non-Small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) is a major cause of mortality in Canada, with many patients presenting with metastatic disease. The oligometastatic state (OM-NSCLC) may be amenable to cure using aggressive local consolidative therapies. Stereotactic body radiotherapy (SBRT), which entails the utilization of a high dose of radiation in one or few fractions, has many benefits in this setting, including its applicability in varied patient populations to ablate lesions in varied anatomical locations. It has also been demonstrated to prolong the time to next-line systemic therapy, to reduce financial burden, to improve quality-adjusted life years, and reduce adverse events caused by these lesions. This review outlines the published phase II and III trials that have already demonstrated the utility of SBRT in OM-NSCLC, as well as the many ongoing trials aiming to further define its role, including the largest phase II/III trial to date, NRG-LU002. Overall, SBRT appears to improve outcomes when combined with a broad range of standard-of-care therapies and is generally well tolerated; however, careful patient selection is necessary to maximize benefits while minimizing harm. Ongoing trials will help define the optimal patients for SBRT and the best timing for this intervention.

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

PURPOSE

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.

METHODS AND MATERIALS

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.

RESULTS

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).

CONCLUSIONS

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.

Ablative Radiation Therapy to Restrain Everything Safely Treatable (ARREST): A Phase 1 Study of Stereotactic Ablative Radiation Therapy for Polymetastatic Disease

PURPOSE

This phase 1 study aimed to assess the safety and feasibility of SABR therapy delivery to all sites of polymetastatic disease (>10 metastases).

METHODS AND MATERIALS

A 3 + 3 study design was used with 5 dose levels from 6 Gy (6 Gy × 1) to 30 Gy (6 Gy weekly × 5). Dose-limiting toxicity (DLT) was defined as any grade 4 or 5 toxicity or more than 3 grade 3 toxicities within 6 weeks of treatment. The primary endpoint was the maximal tolerated dose, defined as the dose level where ≥2/6 of patients experienced DLT. Secondary endpoints included quality of life (Functional Assessment of Cancer Therapy - General and European Quality of Life 5 Dimension 5 Level) at 6 weeks posttreatment, progression-free survival, and overall survival.

RESULTS

Thirteen patients were accrued: 12 Gy (n = 3), 18 Gy (n = 3), 24 Gy (n = 4), and 30 Gy (n = 3), and 207 lesions were treated. Nine patients (69%) had acute toxicity: grade 1 (n = 6, 46%), grade 2 (n = 2, 15%; n = 1 pneumonitis and n = 1 fatigue), and grade 3 (n = 1, 7.7% neutropenia). There were no grade 4 or 5 toxicities. Mean ± SD quality of life (Functional Assessment of Cancer Therapy - General and European Quality of Life 5 Dimension 5 Level health state) was 80.4 ± 21.9 and 77.4 ± 20.9 at baseline versus 76.4 ± 21.8 and 68.0 ± 24.2 at 6-week follow-up, respectively (p = .009 and p = .055, respectively). With a median follow-up of 8.7 months posttreatment (IQR, 2.4-24 months), 8 of 13 patients had disease progression (62%). The median and 12-month progression-free survival were 3.6 months and 11.3%, respectively. The median and 12-month overall survival were 13.8 months and 62%, respectively.

CONCLUSIONS

In this phase 1 trial, SABR therapy for polymetastatic disease was technically feasible with acceptable acute toxicity at dose levels up to 30 Gy (6 Gy weekly × 5). DLT was not observed.

Multidisciplinary Canadian consensus on the multimodal management of high-risk and radioactive iodine-refractory thyroid carcinoma

Most follicular cell-derived differentiated thyroid carcinomas are regarded as low-risk neoplasms prompting conservative therapeutic management. Here, we provide consensus recommendations reached by a multidisciplinary group of endocrinologists, medical oncologists, pathologists, radiation oncology specialists, a surgeon and a medication reimbursement specialist, addressing more challenging forms of this malignancy, focused on radioactive iodine (RAI)-resistant or -refractory differentiated thyroid carcinoma (RAIRTC). In this document we highlight clinical, radiographic, and molecular features providing the basis for these management plans. We distinguish differentiated thyroid cancers associated with more aggressive behavior from thyroid cancers manifesting as poorly differentiated and/or anaplastic carcinomas. Treatment algorithms based on risk-benefit assessments of different multimodal therapy approaches are also discussed. Given the scarcity of data supporting management of this rare yet aggressive disease entity, these consensus recommendations provide much needed guidance for multidisciplinary teams to optimally manage RAIRTC.

Feasibility and safety of single-fraction sub-ablative radiotherapy with systemic therapy in colorectal cancer patients with ≤ 10 metastases: A multicenter pilot study (NCT05375708)

Colorectal cancer patients with ≤10 unresectable metastases were treated with single-fraction sub-ablative radiotherapy in addition to standard of care systemic therapy in a single-arm, open-label, multicenter, pilot study (SIRIUS) to assess feasibility and safety. Results indicate that radiotherapy combined with systemic therapy is feasible and safe in this population.

Sharing the Burden: The Case for Definitive Local Therapy in Place of Immune Checkpoint Blockade for Patients With a Low-Volume Burden of Metastatic Disease

COMMENTARY

Sharing the burden of low-volume metastatic cancer between ICB and local treatments.

CT-Guided Adaptive Radiotherapy for the Treatment of Technically Challenging Oligometastatic Disease: A Case Report

There is a growing interest in the application of stereotactic body radiotherapy (SBRT) for the treatment of oligometastatic cancers. This increasing appeal of SBRT has highlighted the need for more sophisticated radiotherapy techniques that allow high doses of radiation to be delivered to multiple sites while limiting the exposure of neighboring healthy tissue. A major obstacle to achieving this aim has been the occurrence of interfraction target variability: the tendency of both the tumor and the surrounding tissue to undergo day-to-day non-synchronous shifts in position. Such changes in the conformation of the tumor field often compromise the effectiveness of conventional SBRT prescribed for a fixed target. We report a case of oligometastatic pelvic disease where the challenge of an unusually mobile tumor was overcome with the use of a novel technique employing cone beam CT (CBCT)-based online adaptive radiotherapy (OART). The Phase I "Adaptive Radiation for Abdominopelvic Metastases (ARAM)" clinical trial was designed to determine if OART can achieve dosing targets superior to those attained using conventional radiotherapy techniques. In this case, CT adaptive planning enabled the treatment of a pelvic target prescribed per protocol to 45Gy that would otherwise have not been amenable to treatment with conventional SBRT planning. Adaptive plans showed significant improvements in target coverage while respecting critical organ constraints, resulting in a total treatment V35Gy of 89.3% and V45Gy of 52.8%, whereas the scheduled plan would have achieved V35Gy of 67.4% and V45Gy of 13.6%. Treatment times were variable (38.1-96.7 mins), and correlated with the magnitude of daily translation which ranged from 4 to 7 cm of total linear translation. The patient tolerated treatment without any adverse events. These results demonstrate a novel application of CBCT-guided OART that allowed for the administration of ablative treatment to an unexpectedly mobile target unamenable to conventional SBRT. CBCT-guided OART currently requires increased treatment time, a need which might be reduced by optimization of daily contouring. The phase 1 clinical trial NCT05880667 is ongoing and may provide further evidence that CBCT-guided OART can meet the technical challenges posed by radiotherapy for oligometastatic abdominal and pelvic disease.

Five-year outcomes of fractionated stereotactic body radiotherapy for oligometastatic prostate cancer from the TRANSFORM phase II trial

Metastasis-directed therapy (MDT) for oligometastatic prostate cancer (PCa), including stereotactic body radiotherapy (SBRT), has shown promise but is still considered investigational. This is the 5-year analysis of the TRANSFORM trial, the largest prospective cohort of men with oligometastatic PCa treated with SBRT-based MDT. The primary endpoint was 5-year treatment escalation-free survival (TE-FS), defined as freedom from any new cancer therapy other than further SBRT. In total, 199 men received SBRT; 76.4% were hormone-naïve at baseline. The rate of 5-year TE-FS was 21.7% (95% confidence interval [CI]: 15.7%-28.7%) overall and 25.4% (95% CI: 18.1%-33.9%) in the hormone-naïve subgroup. The subgroups with International Society of Urological Pathology Grade Groups 4-5 disease (hazard ratio [HR] = 1.48, 95% CI: 1.05-2.01, p = .026), a higher baseline prostate-specific antigen (PSA) (HR = 1.06, 95% CI: 1.03-1.09, p < .001) and those who received prior androgen deprivation therapy (ADT) (HR = 2.13, 95% CI: 1.40-3.26, p < .001), were at greater risk of treatment escalation. Outcomes for participants with four or five initial lesions were comparable to those with one to three lesions. At last follow-up, 18.9% (95% CI: 13.2%-25.7%) of participants were free from treatment escalation (median follow-up of 67.9 months) and two participants had an undetectable PSA level. No treatment-related grade three or higher adverse events were reported. The findings of this study demonstrate that SBRT-based MDT is an effective option for delaying systemic treatment escalation in the context of oligometastatic PCa. Future randomised trials comparing SBRT-based MDT to standard-of-care ADT-based approaches are required to evaluate the impact of delaying ADT on survival.

Challenges in the Understanding of Oligometastatic Disease in Clinical Practice

Introduction: There is little data describing oligometastatic disease (OMD) and decision-making. We sought to understand the knowledge gaps and challenges in deciphering and delivering treatments.

MATERIALS AND METHODS

 This is a quality improvement (QI) study conducted via an anonymous survey. Three different clinical scenarios of OMD (oligo-recurrence disease, synchronous de-novo OMD, and oligo-progressive disease) were presented to assess participants' comprehension. A qualitative approach was used, involving four open-ended questions. Summary statistics and descriptive analysis were utilized to describe survey answers.

RESULTS

 The survey was answered by 70 clinicians, 56% (n=39) medical oncologists, 24% (n=17) radiation oncologists, 7% (n=5) surgeons, and the remaining 13% (n=9) from anatomical pathology, radiology, and palliative care. The three clinical cases were correctly identified as oligo-recurrence, de-novo, and oligo-progression disease in 63% (n=44), 94% (n=66), and 76% (n=53) of responses, respectively. Additionally, for each case, the majority of respondents indicated that they would offer local treatment (n=59, 84%; n=57, 81%; n=55, 79%, respectively). Seventy-nine percent (n=49) perceived differences between each modality of local therapies. Physicians perceived challenges including the lack of prospective trial data and unclear approach to OMD. An important determinant in deciding whether patients may benefit from treatment was tumor histology.

CONCLUSION

 The term OMD involves certain difficulties in definition and management. Positive and negative trials have further added uncertainty regarding who would best benefit from local treatment. The discordance in outcome expectations from physicians and patients will need to be addressed to ensure that patient's goals of care are met.

Machine learning predicts conventional imaging metastasis-free survival (MFS) for oligometastatic castration-sensitive prostate cancer (omCSPC) using prostate-specific membrane antigen (PSMA) PET radiomics

PURPOSE

This study investigated imaging biomarkers derived from PSMA-PET acquired pre- and post-metastasis-directed therapy (MDT) to predict 2-year metastasis-free survival (MFS), which provides valuable early response assessment to improve patient outcomes.

MATERIALS/METHODS

An international cohort of 117 oligometastatic castration-sensitive prostate cancer (omCSPC) patients, comprising 34 from John Hopkins Hospital (JHH) and 83 from Baskent University (BU), were treated with stereotactic ablative radiation therapy (SABR) MDT with both pre- and post-MDT PSMA-PET/CT scans acquired. PET radiomic features were analyzed from a CT-PET fusion defined gross tumor volume ((GTV) or zone 1), and a 5 mm expansion ring area outside the GTV (zone 2). A total of 1748 PET radiomic features were extracted from these zones. The six most significant features selected using the Chi2 method, along with five clinical parameters (age, Gleason score, number of total lesions, untreated lesions, and pre-MDT prostate-specific antigen (PSA)) were extracted as inputs to the models. Various machine learning models, including Random Forest, Decision Tree, Support Vector Machine, and Naïve Bayesian, were employed for 2-year MFS prediction and tested using leave-one-out and cross-institution validation.

RESULTS

Six radiomic features, including Total Energy, Entropy, and Standard Deviation from pre-PSMA-PET zone 1, Total Energy and Contrast from post-PSMA-PET zone 1, and Entropy from pre-PSMA-PET zone 2, along with five clinical parameters were selected for predicting 2-year MFS. In a leave-one-out test with all the patients, random forest achieved an accuracy of 80 % and an AUC of 0.82 in predicting 2-year MFS. In cross-institution validation, the model correctly predicted 2-year MFS events with an accuracy of 75 % and an AUC of 0.77 for patients from JHH, and an accuracy of 78 % and an AUC of 0.80 for BU patients, respectively.

CONCLUSION

Our study demonstrated the promise of using pre- and post-MDT PSMA-PET-based imaging biomarkers for MFS prediction for omCSPC patients.

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.

A randomized phase III trial of stereotactic ablative radiotherapy for patients with up to 10 oligometastases and a synchronous primary tumor (SABR-SYNC): study protocol

BACKGROUND

Emerging randomized data, mostly from phase II trials, have suggested that patients with oligometastatic cancers may benefit from ablative treatments such as stereotactic ablative radiotherapy (SABR). However, phase III data testing this paradigm are lacking, and many studies have examined SABR in the setting of metachronous oligometastatic disease. The goal of the SABR-SYNC trial is to assess the effect of SABR in patients with oligometastatic cancers and a synchronous primary tumor.

METHODS

One hundred and eighty patients will be randomized in a 1:2 ratio between standard of care (SOC) palliative-intent treatments vs. SOC + ablative therapy (SABR preferred) to all sites of known disease. Randomization will be stratified based on histology and number of metastases at enrollment. SABR may be delivered in 1-, 3- and 5-fraction regimens, with recommended doses of 20 Gy, 30 Gy, and 35 Gy, respectively. Non-SABR local modalities (e.g. surgery, thermal ablation, conventional radiation) may be used for treatment of the primary or metastases at the discretion of the treating physicians, if those modalities are clinically preferred. The primary endpoint is overall survival, and secondary endpoints include progression-free survival, time to development of new metastatic lesions, time to initiation of next systemic therapy, quality of life, and toxicity. Translational endpoints include assessment of circulating tumor DNA and immunological predictors of outcomes.

DISCUSSION

SABR-SYNC will provide phase III data to assess the impact of SABR on overall survival in a population of patients with synchronous oligometastases. The translational component will attempt to identify novel prognostic and predictive biomarkers to aid in clinical decision making.

TRIAL REGISTRATION

Clinicaltrials.gov NCT05717166 (registration date: Feb. 8, 2023).

Challenges and Opportunities in Developing an Oncology Clinical Trial Network in the United States Veterans Affairs Health Care System: The VA STARPORT Experience

The United States Veterans Affairs (VA) Health Care System has a strong history of conducting impactful oncology randomized clinical trials (RCTs). We developed a phase II/III RCT to test the use of metastasis-directed therapy in Veterans with oligometastatic prostate cancer (OMPC)-the first VA RCT in OMPC that leverages novel imaging and advanced radiotherapy techniques. To accomplish this, we developed a clinical trial network to conduct the study. In this manuscript, we describe several challenges we encountered in study development/conduct and our strategies to address them, with the goal of helping investigators establish robust study networks to conduct clinical trials. In the study start-up, we encountered challenges in timely site activation, and leveraged project management to maximize efficiency. Additionally, there were several changes in the clinical paradigms in imaging and treatment that led to protocol amendments to ensure maximum equipoise, recruitment, and impact of the study. Specifically, we amended the trial to add de novo OMPC patients (from initially only recurrent OMPC) and expanded the study to allow up to 10 metastases (from initially five). Finally, in order to maintain local study team engagement, we developed initiatives to maximize collaboration and add value to the overall clinical program through study participation.

Radiotherapy, immunity, and immune checkpoint inhibitors

Radiotherapy exerts immunostimulatory and immunosuppressive effects, both locally, within the irradiated tumour microenvironment, and systemically, outside the radiation field. Inspired by preclinical data that showed synergy between radiotherapy and immune checkpoint inhibitors, multiple clinical trials were initiated with the hypothesis that combined treatment with radiotherapy and immune checkpoint inhibitors could stimulate a robust systemic immune response and improve clinical outcomes. However, despite early optimism, radioimmunotherapy trials in the curative and metastatic settings have met with little success. In this Review, we summarise the immunostimulatory effects of radiotherapy that provided the theoretical basis for trials of combination radiotherapy and immune checkpoint inhibitors. We also discuss findings from clinical trials incorporating radiotherapy and immune checkpoint inhibitors and examine the success of these trials in the context of the immunosuppressive effects of radiotherapy. We conclude by highlighting targets for relieving radiotherapy-induced immunosuppression with the goal of enhancing the combined effects of radiotherapy and immune checkpoint inhibitors.

Radiotherapy and immunology

The majority of cancer patients receive radiotherapy during the course of treatment, delivered with curative intent for local tumor control or as part of a multimodality regimen aimed at eliminating distant metastasis. A major focus of research has been DNA damage; however, in the past two decades, emphasis has shifted to the important role the immune system plays in radiotherapy-induced anti-tumor effects. Radiotherapy reprograms the tumor microenvironment, triggering DNA and RNA sensing cascades that activate innate immunity and ultimately enhance adaptive immunity. In opposition, radiotherapy also induces suppression of anti-tumor immunity, including recruitment of regulatory T cells, myeloid-derived suppressor cells, and suppressive macrophages. The balance of pro- and anti-tumor immunity is regulated in part by radiotherapy-induced chemokines and cytokines. Microbiota can also influence radiotherapy outcomes and is under clinical investigation. Blockade of the PD-1/PD-L1 axis and CTLA-4 has been extensively investigated in combination with radiotherapy; we include a review of clinical trials involving inhibition of these immune checkpoints and radiotherapy.

Local Therapy for Metastatic Colorectal Cancer: A Case-Based Review

ABSTRACT

The oligometastatic disease state, defined as a cancer with 5 or fewer sites of metastasis, is a therapeutic opportunity to improve oncologic outcomes. Colorectal cancer (CRC) was among the first for which oligometastatic treatment was used in routine clinical practice, and recent studies have shown potential for improved overall survival with metastasis-directed therapies. As CRC is the third most common cause of cancer death in men and women, improving oncologic outcomes in this population is of paramount importance. The relatively recent identification of this treatment paradigm and paucity of high-quality data have led to heterogeneity in clinical practice. This review will explore perspectives of a panel of surgical and radiation oncologists for complex or controversial cases of metastatic CRC.

Evaluation of chest CT-scans following lung stereotactic ablative radiotherapy: Challenges and new insights

Stereotactic ablative radiotherapy (SABR) is increasingly used for the treatment of early-stage non-small cell lung cancer (ES-NSCLC) and for pulmonary metastases. In patients with ES-NSCLC, SABR is highly successful with reported 5-year local control rates of approximately 90%. However, the assessment of local control following lung SABR can be challenging as radiological changes arising from radiation-induced lung injury (RILI) can be observed in up to 90% of patients. These so-called 'benign' radiological changes evolve with time and are often asymptomatic. Several radiological and metabolic features have been explored to help distinguish RILI from local recurrences (LR). These include the Response Evaluation Criteria for Solid Tumors (RECIST), high-risk features (HRF's) and maximum standardized uptake value (SUVmax) on FDG-PET-CT. However, use of some of these approaches have poor predictive values and low specificity for recurrence. A proposed new workflow for the evaluation of post-lung SABR radiological changes will be reviewed which uses the presence of so-called 'actionable radiological features' to trigger changes to imaging schedules and identifies the need for a multidisciplinary board review. Furthermore, this critical review of post-lung SABR imaging will highlight current challenges, new insights, and unknowns in this field.

Radioresistant Pulmonary Oligometastatic and Oligoprogressive Lesions From Nonlung Primaries: Impact of Histology and Dose-Fractionation on Local Control After Radiation Therapy

Purpose

We investigated whether pulmonary metastases from historically considered radioresistant primaries would have inferior local control after radiation therapy than those from nonradioresistant nonlung primaries, and whether higher biologically effective dose assuming alpha/beta=10 (BED10) would be associated with superior local control.

Methods and Materials

We identified patients treated with radiation therapy for oligometastatic or oligoprogressive pulmonary disease to 1 to 5 lung metastases from nonlung primaries in 2013 to 2020 at a single health care system. Radioresistant primary cancers included colorectal carcinoma, endometrial carcinoma, renal cell carcinoma, melanoma, and sarcoma. Nonradioresistant primary cancers included breast, bladder, esophageal, pancreas, and head and neck carcinomas. The Kaplan-Meier estimator, log-rank test, and multivariable Cox proportional hazards regression were used to compare local recurrence-free survival (LRFS), new metastasis-free survival, progression-free survival, and overall survival.

Results

Among 114 patients, 73 had radioresistant primary cancers. The median total dose was 50 Gy (IQR, 50-54 Gy) and the median number of fractions was 5 (IQR, 3-5). Median follow-up time was 59.6 months. One of 41 (2.4%) patients with a nonradioresistant metastasis experienced local failure compared with 18 of 73 (24.7%) patients with radioresistant metastasis (log-rank P = .004). Among radioresistant metastases, 12 of 41 (29.2%) patients with colorectal carcinoma experienced local failure compared with 6 of 32 (18.8%) with other primaries (log-rank P = .018). BED10 ≥100 Gy was associated with decreased risk of local recurrence. On univariable analysis, BED10 ≥100 Gy (hazard ratio [HR], 0.263; 95% CI, 0.105-0.656; P = .004) was associated with higher LRFS, and colorectal primary (HR, 3.060; 95% CI, 1.204-7.777; P = .019) was associated with lower LRFS, though these were not statistically significant on multivariable analysis. Among colorectal primary patients, BED10 ≥100 Gy was associated with higher LRFS (HR, 0.266; 95% CI, 0.072-0.985; P = .047) on multivariable analysis.

Conclusions

Local control after radiation therapy was encouraging for pulmonary metastases from most nonlung primaries, even for many of those classically considered to be radioresistant. Those from colorectal primaries may benefit from testing additional strategies, such as resection or systemic treatment concurrent with radiation.

Survival outcomes for women with a solitary extracranial metastasis from breast cancer

BACKGROUND

Aggressive metastasis directed treatment of extracranial oligometastatic breast cancer with the aim of increasing disease-free survival has emerged as a new potential treatment paradigm, however there is currently a lack of data to assist in identifying the subset of patients who will potentially benefit most. This single-institute retrospective cohort study aimed to evaluate survival outcomes for patients with a solitary extracranial metastasis from breast cancer and to assess for significant prognostic factors.

METHODS AND MATERIALS

Medical records of 70 female breast cancer patients with a solitary extracranial metastasis actively managed at the Peter MacCallum Cancer Centre (PMCC) Melbourne Campus between 2000 and 2019 were reviewed. Kaplan-Meier curves were used to estimate overall survival (OS), local progression free survival (LPFS) and distant progression free survival (DPFS).

RESULTS

Median follow-up period was 9.4 years. The study included 40 hormone receptor positive/HER2 negative (HR+HER2-), 14 hormone receptor positive/HER2 positive (HR+HER2+), 3 hormone receptor negative/HER2 positive (HR-HER2+), 9 triple negative (TNBC) and 4 unclassified breast cancer patients. 5-year OS rate for all patients was 46%, LPFS rate was 56% and DPFS was 20%. Tumour receptor group had a statistically significant association with OS and DPFS rates. TNBC patients had significantly poorer OS and DPFS rates in comparison to HR+HER2-patients.

CONCLUSION

Among patients with a solitary extracranial metastasis from breast cancer, TNBC was associated with the poorest OS and DPFS rates. Identification of other significant prognostic factors for oligometastatic breast cancer patients may inform guidelines for metastasis directed treatments.

Assessing the effect of metastasis-directed therapy in oligometastatic disease using the restricted mean survival time

BACKGROUND

Metastasis-directed therapy (MDT) with stereotactic body radiotherapy (SBRT) is emerging as an effective therapeutic option for oligometastatic disease (OMD). However, a lack of phase III data, consensus guidelines, and toxicity concerns limit its widespread use. Randomized controlled trials (RCTs) routinely report hazard ratios (HRs) and medians that lack clear clinical and robust interpretation. Restricted-mean survival time (RMST) is the duration of time a patient is expected to survive over the follow-up period, providing a robust and interpretable alternative. We analyzed the efficacy of SBRT using RMST.

METHODS

All registered RCTs of ablative radiotherapy in OMD in ClinicalTrials.gov through 2022 were identified. Data were reconstructed from Kaplan-Meier curves, and the HRs and RMST differences were estimated for surrogate endpoints (SEs) and overall survival (OS).

RESULTS

Six studies comprising 426 patients met the inclusion criteria. The RMST differences for SEs ranged from 4.6 months in a study by Iyengar et al. to 11.1 months in SABR-COMET. The RMST differences for OS in SABR-COMET, Gomez et al., and SINDAS studies were 12.6, 15 and 7.9 months, respectively.

CONCLUSION

RMST demonstrates the efficacy of local treatment in OMD. Representing the expected survival time, this method effectively communicates outcomes to patients and clinicians.

Stereotactic ablative radiation therapy in metastatic prostate cancer

PURPOSE OF REVIEW

The evolving role of stereotactic ablative radiation therapy (SABR) as metastasis-directed therapy (MDT) for oligometastatic prostate cancer (omPCa) will be discussed.

RECENT FINDINGS

Oligometastatic disease (OMD) is an intermediate state between localized and wide-spread malignant disease. OMD has recently been spotlighted given the increasing demonstration of clinical benefit from local therapies despite presence of metastatic disease and allure of the curative potential of MDT in select cases. Among the different forms of MDT, SABR has rapidly become a widely adopted treatment modality. Significant efforts in this space have focused on omPCa, owing to its relatively indolent biology, presence of a sensitive and specific serum biomarker and recent advances in molecular imaging. While most studies have evaluated the role of SABR MDT in hormone sensitive omPCa, new emerging clinical data also suggests benefits of SABR MDT for even castration-resistant disease.

SUMMARY

Treating omPCa with SABR MDT appears to generate an efficacy signal with minimal morbidity across both hormone-sensitive and castration-resistant disease. However, additional definitive omPCa trial data are needed. Future research efforts should investigate biomarkers for this heterogeneous disease space and the role of SABR MDT in combination with systemic agents to improve upon standard of care treatments.

An in-silico planning study of stereotactic body radiation therapy for polymetastatic patients with more than ten extra-cranial lesions

Background and purpose

Limited data is available about the feasibility of stereotactic body radiation therapy (SBRT) for treating more than five extra-cranial metastases, and almost no data for treating more than ten. The aim of this study was to investigate the feasibility of SBRT in this polymetatstatic setting.

Materials and methods

Consecutive metastatic melanoma patients with more than ten extra-cranial metastases and a maximum lesion diameter below 11 cm were selected from a single-center prospective registry for this in-silico planning study. For each patient, SBRT plans were generated to treat all metastases with a prescribed dose of 5x7Gy, and dose-limiting organs (OARs) were analyzed. A cell-kill based inverse planning approach was used to automatically determine the maximum deliverable dose to each lesion individually, while respecting all OARs constraints.

Results

A total of 23 polymetastatic patients with a medium of 17 metastases (range, 11-51) per patient were selected. SBRT plans with sufficient target coverage and respected OARs dose constraints were achieved in 16 out of 23 patients. In the remaining seven patients, the lungs V5Gy < 80 % and the liver D700 cm3 < 15Gy were most frequently the dose-limiting constraints. The cell-kill based planning approach allowed optimizing the dose administration depending on metastases total volume and location.

Conclusion

This retrospective planning study shows the feasibility of definitive SBRT for 70% of polymetastatic patients with more than ten extra-cranial lesions and proposes the cell-killing planning approach as an approach to individualize treatment planning in polymetastatic patients'.

Long-Term Results of a Phase 1 Dose Escalation Trial of Ablative Stereotactic Body Radiation Therapy

PURPOSE

Stereotactic body radiation therapy is increasingly used for oligometastatic disease as well as palliation, but treatment protocols for nonspine bone and nodal metastases are lacking, with a wide variety of schedules applied.

METHODS AND MATERIALS

A prospective dose-escalation trial was initiated, involving 90 patients, among whom 52 (58%) had primary prostate tumors, 13 had breast tumors (14%), and 25 (28%) had other primary tumor types. All visible lymph node or nonspine bone oligometastases were treated in 3 consecutive cohorts: 5 × 7.0 Gy, 3 × 10.0 Gy, or 1 × 20.0 Gy.

RESULTS

Initial results revealed no dose-limiting toxicity after a median follow-up of 17.2 months. This update provides information on long-term toxicity, local failure (LF), and progression-free survival (PFS). After a median follow-up of 50 months, no new safety signals were observed. Grade 2 toxicity was 13%, 7% and 10% in the respective cohorts (P = .9), without grade 3 to 5 toxicities. LF rates were 9%, 3%, and 6% (P = .5) for the respective treatment groups, with an overall cumulative risk of LF of 7% (95% CI, 2-12) at 4 years. Median PFS was 16.5 months (95% CI, 9.8-21.5), and 4-year PFS was 21% (95% CI, 14-32). Median overall survival across groups was not reached (95% CI, 52.8 - not reached), 4-year OS was 68% (95% CI, 59-78). A subset of patients (23%) remained long-term disease-free, 37% had oligoprogressive disease at first recurrence and 40% developed polymetastatic relapse.

CONCLUSIONS

The safe and effective use of dose-escalated single-fraction stereotactic body radiation therapy for bone and lymph node metastases is supported by this trial, especially considering patient-convenience and cost-effectiveness. Caution is needed when generalizing these outcomes beyond breast and prostate cancer, given their underrepresentation in our study.

An Update on the Management of Bone Metastases

PURPOSE OF REVIEW

Increasing life expectancy among patients with advanced cancer has placed a greater emphasis on optimizing pain control and quality of life. Concurrently, significant advancements in radiotherapy for bone metastases have permitted for dose escalation strategies such as stereotactic radiotherapy. This review aims to provide updated information on the management of bone metastases in light of these developments.

RECENT FINDINGS

We reviewed recent studies regarding the role and details of external beam radiotherapy for bone metastases, with emphasis on differences by treatment site as well as intention (palliative versus ablative for oligometastases). Conventional palliative radiotherapy remains a mainstay of management. While stereotactic radiotherapy may augment durability of pain relief and even survival time, there are significant questions remaining regarding optimal dosing and patient selection. Radiotherapy for bone metastases continues to evolve, particularly with increasing use of stereotactic radiotherapy. Future studies are needed to clarify optimal dose, fractionation, modality, and patient selection criteria among different radiotherapy approaches.

Definitive single fraction spine stereotactic radiosurgery for metastatic sarcoma: Simultaneous integrated boost is associated with high tumor control and low vertebral fracture risk

INTRODUCTION

Sarcoma spinal metastases (SSM) are particularly difficult to manage given their poor response rates to chemotherapy and inherent radioresistance. We evaluated outcomes in a cohort of patients with SSM uniformly treated using single-fraction simultaneous-integrated-boost (SIB) spine stereotactic radiosurgery (SSRS).

MATERIALS AND METHODS

A retrospective review was conducted at a single tertiary institution treated with SSRS for SSM between April 2007-April 2023. 16-24 Gy was delivered to the GTV and 16 Gy uniformly to the CTV. Kaplan-Meier analysis was conducted to assess time to progression of disease (PD) with proportionate hazards modelling used to determine hazard ratios (HR) and respective 95 % confidence intervals (CI).

RESULTS

70 patients with 100 lesions underwent SSRS for SSM. Median follow-up was 19.3 months (IQR 7.7-27.8). Median age was 55 years (IQR42-63). Median GTV and CTVs were 14.5 cm3 (IQR 5-32) and 52.7 cm3 (IQR 29.5-87.5) respectively. Median GTV prescription dose and biologically equivalent dose (BED) [α/β = 10] was 24 Gy and 81.6 Gy respectively. 85 lesions received 24 Gy to the GTV. 27 % of patients had Bilsky 1b or greater disease. 16 of 100 lesions recurred representing a crude local failure rate of 16 % with a median time to failure of 10.4 months (IQR 5.7-18) in cases which failed locally. 1-year actuarial local control (LC) was 89 %. Median overall survival (OS) was 15.3 months (IQR 7.7-25) from SSRS. Every 1 Gy increase in GTV absolute minimum dose (DMin) across the range (5.8-25 Gy) was associated with a reduced risk of local failure (HR = 0.871 [95 % CI 0.782-0.97], p = 0.009). 9 % of patients developed vertebral compression fractures at a median of 13 months post SSRS (IQR 7-25).

CONCLUSION

This study represents one of the most homogenously treated and the largest cohorts of patients with SSM treated with single-fraction SSRS. Despite inherent radioresistance, SSRS confers durable and high rates of local control in SSM without unexpected long-term toxicity rates.

Upfront Versus Delayed Systemic Therapy in Patients With Oligometastatic Cancer Treated With SABR in the Phase 2 SABR-5 Trial

PURPOSE

The optimal sequencing of local and systemic therapy for oligometastatic cancer has not been established. This study retrospectively compared progression-free survival (PFS), overall survival (OS), and SABR-related toxicity between upfront versus delay of systemic treatment until progression in patients in the SABR-5 trial.

METHODS AND MATERIALS

The single-arm phase 2 SABR-5 trial accrued patients with up to 5 oligometastases across SABR-5 between November 2016 and July 2020. Patients received SABR to all lesions. Two cohorts were retrospectively identified: those receiving upfront systemic treatment along with SABR and those for whom systemic treatment was delayed until disease progression. Patients treated for oligoprogression were excluded. Propensity score analysis with overlap weighting balanced baseline characteristics of cohorts. Bootstrap sampling and Cox regression models estimated the association of delayed systemic treatment with PFS, OS, and grade ≥2 toxicity.

RESULTS

A total of 319 patients with oligometastases underwent treatment on SABR-5, including 121 (38%) and 198 (62%) who received upfront and delayed systemic treatment, respectively. In the weighted sample, prostate cancer was the most common primary tumor histology (48%) followed by colorectal (18%), breast (13%), and lung (4%). Most patients (93%) were treated for 1 to 2 metastases. The median follow-up time was 34 months (IQR, 24-45). Delayed systemic treatment was associated with shorter PFS (hazard ratio [HR], 1.56; 95% CI, 1.15-2.13; P = .005) but similar OS (HR, 0.90; 95% CI, 0.51-1.59; P = .65) compared with upfront systemic treatment. Risk of grade 2 or higher SABR-related toxicity was reduced with delayed systemic treatment (odds ratio, 0.35; 95% CI, 0.15-0.70; P < .001).

CONCLUSIONS

Delayed systemic treatment is associated with shorter PFS without reduction in OS and with reduced SABR-related toxicity and may be a favorable option for select patients seeking to avoid initial systemic treatment. Efforts should continue to accrue patients to histology-specific trials examining a delayed systemic treatment approach.

Stereotactic body radiotherapy for distant metastases to the head and neck

PURPOSE

To report clinical outcomes for patients with metastatic disease to the head and neck (HN) treated with stereotactic body radiation therapy (SBRT).

METHODS

A retrospective review of patients treated with SBRT to HN sites from 2012 to 2020 was conducted. Treatment indications included the following: oligometastases, oligoprogression, and control a dominant area of progression (DAP). Kaplan-Meier method was used to estimate local control (LC), regional control (RC), overall survival (OS), and progression-free survival (PFS). Univariable (UVA) and multivariable analyses (MVA) were performed. Grade 3-4 acute and late toxicities were reported by the Common Terminology Criteria for Adverse Events v5.0.

RESULTS

Fifty-six patients (58 lesions) were analysed with a median follow-up of 16 months. Primary sites included lung (25.0%), kidney (19.6%), breast (19.6%) and other (35.8%). SBRT indications were as follows: oligometastases (42.9%), oligoprogression (19.6%) and local control of a dominant area of progression (37.5%). Most patients received SBRT to a single neck node (n = 47, 81.0%). Median SBRT dose was 40 Gy (range 25-50 Gy) in five fractions, with a median biologically effective dose (BED10) of 72 Gy (range 37.5-100 Gy). One- and 2-year LC and RC rates were 97.6% and 72.7% as well as 100% and 86.7%, respectively. Median OS was 19.2 months (95% [CI] 14.8-69.4), and median PFS was 7.4 months (95% [CI] 5.2-11.9). The 1-year OS and PFS rates for oligometastases, oligoprogression and DAP were 95.8%, 63.6% and 38.1% (p = 0.0039) as well as 56.5%, 27.3% and 19.1% (p = 0.0004), respectively. On MVA, treatment indication and histology were predictive for OS, while indication and prior systemic therapy were predictive for PFS. Cumulative late grade 3 + toxicity rate was 11.3%, without grade 5 events.

CONCLUSION

The use of SBRT for metastatic disease to the HN provided excellent LC rates with low rates of regional failure and an acceptable toxicity profile, highlighting its utility in these patients. Patients with oligometastatic disease had better OS and PFS than others.

Uncovering the armpit of SBRT: An institutional experience with stereotactic radiation of axillary metastases

Purpose/objectives

The growing use of stereotactic body radiotherapy (SBRT) in metastatic cancer has led to its use in varying anatomic locations. The objective of this study was to review our institutional SBRT experience for axillary metastases (AM), focusing on outcomes and process.

Materials/methods

Patients treated with SBRT to AM from 2014 to 2022 were reviewed. Cumulative incidence functions were used to estimate the incidence of local failure (LF), with death as competing risk. Kaplan-Meier method was used to estimate progression-free (PFS) and overall survival (OS). Univariate regression analysis examined predictors of LF.

Results

We analyzed 37 patients with 39 AM who received SBRT. Patients were predominantly female (60 %) and elderly (median age: 72). Median follow-up was 14.6 months. Common primary cancers included breast (43 %), skin (19 %), and lung (14 %). Treatment indication included oligoprogression (46 %), oligometastases (35 %) and symptomatic progression (19 %). A minority had prior overlapping radiation (18 %) or surgery (11 %). Most had prior systemic therapy (70 %).Significant heterogeneity in planning technique was identified; a minority of patient received 4-D CT scans (46 %), MR-simulation (21 %), or contrast (10 %). Median dose was 40 Gy (interquartile range (IQR): 35-40) in 5 fractions, (BED10 = 72 Gy). Seventeen cases (44 %) utilized a low-dose elective volume to cover remaining axilla.At first assessment, 87 % had partial or complete response, with a single progression. Of symptomatic patients (n = 14), 57 % had complete resolution and 21 % had improvement. One and 2-year LF rate were 16 % and 20 %, respectively. Univariable analysis showed increasing BED reduced risk of LF. Median OS was 21.0 months (95 % [Confidence Interval (CI)] 17.3-not reached) and median PFS was 7.0 months (95 % [CI] 4.3-11.3). Two grade 3 events were identified, and no grade 4/5.

Conclusion

Using SBRT for AM demonstrated low rates of toxicity and LF, and respectable symptom improvement. Variation in treatment delivery has prompted development of an institutional protocol to standardize technique and increase efficiency. Limited followup may limit detection of local failure and late toxicity.

Metastases-directed local therapies (MDT) beyond genuine oligometastatic disease (OMD): Indications, endpoints and the role of imaging

To further personalise treatment in metastatic cancer, the indications for metastases-directed local therapy (MDT) and the biology of oligometastatic disease (OMD) should be kept conceptually apart. Both need to be vigorously investigated. Tumour growth dynamics - growth rate combined with metastatic seeding efficiency - is the single most important biological feature determining the likelihood of success of MDT in an individual patient, which might even be beneficial in slowly developing polymetastatic disease. This can be reasonably well assessed using appropriate clinical imaging. In the context of considering appropriate indications for MDT, detecting metastases at the edge of image resolution should therefore suggest postponing MDT. While three to five lesions are typically used to define OMD, it could be argued that countability throughout the course of metastatic disease, rather than a specific maximum number of lesions, could serve as a better parameter for guiding MDT. Here we argue that the unit of MDT as a treatment option in metastatic cancer might best be defined not as a single procedure at a single point in time, but as a series of treatments that can be delivered in a single or multiple sessions to different lesions over time. Newly emerging lesions that remain amenable to MDT without triggering the start of a new systemic treatment, a change in systemic therapy, or initiation of best supportive care, would thus not constitute a failure of MDT. This would have implications for defining endpoints in clinical trials and registries: Rather than with any disease progression, failure of MDT would only be declared when there is progression to polymetastatic disease, which then precludes further options for MDT.

Patterns of metastatic spread and tumor burden in unselected cancer patients using PET imaging: Implications for the oligometastatic spectrum theory

Introduction and background

Metastatic disease has been proposed as a continuum, with no clear cut-off between oligometastatic and polymetastatic disease. This study aims to quantify tumor burden and patterns of spread in unselected metastatic cancer patients referred for PET-based staging, response assessment of restaging.

Materials and methods

All oncological fluorodeoxyglucose (FDG-) and prostate-specific membrane antigen (PSMA-) positron emission tomography (PET) scans conducted at a single academic center in 2020 were analyzed. Imaging reports of all patients with metastatic disease were reviewed and assessed.

Results

For this study, 7,000 PET scans were screened. One third of PET scans (n = 1,754; 33 %) from 1,155 unique patients showed presence of metastatic disease from solid malignancies, of which 601 (52 %) and 554 (48 %) were classified as oligometastatic (maximum 5 metastases) and polymetastatic (>5 metastases), respectively. Lung and pleural cancer, skin cancer, and breast cancer were the most common primary tumor histologies with 132 (23.8 %), 88 (15.9 %), and 72 (13.0 %) cases, respectively. Analysis of the number of distant metastases showed a strong bimodal distribution of the metastatic burden with 26 % of patients having one solitary metastasis and 43 % of patients harboring >10 metastases. Yet, despite 43 % of polymetastatic patients having >10 distant metastases, their pattern of distribution was restricted to one or two organs in about two thirds of patients, and there was no association between the number of distant metastases and the number of involved organs.

Conclusion

The majority of metastatic cancer patients are characterized by either a solitary metastasis or a high tumor burden with >10 metastases, the latter was often associated with affecting a limited number of organs. These findings support both the spectrum theory of metastasis and the seed and soil hypothesis and can support in designing the next generation of clinical trials in the field of oligometastatic disease.

Stereotactic Body Radiotherapy for Extracranial Oligometastatic Disease from Head and Neck Primary Cancers: A Systematic Review and Meta-Analysis

INTRODUCTION

Stereotactic body radiotherapy (SBRT) is increasingly used to treat disease in the oligometastatic (OM) setting due to mounting evidence demonstrating its efficacy and safety. Given the low population representation in prospective studies, we performed a systematic review and meta-analysis of outcomes of HNC patients with extracranial OM disease treated with SBRT.

METHODS

A systematic review was conducted with Cochrane, Medline, and Embase databases queried from inception to August 2022 for studies with extracranial OM HNC treated with stereotactic radiotherapy. Polymetastatic patients (>five lesions), mixed-primary cohorts failing to report HNC separately, lack of treatment to all lesions, nonquantitative endpoints, and other definitive treatments (surgery, conventional radiotherapy, and radioablation) were excluded. The meta-analysis examined the pooled effects of 12- and 24-month local control (LC) per lesion, progression-free survival (PFS), and overall survival (OS). Weighted random-effects were assessed using the DerSimonian and Laird method, with heterogeneity evaluated using the I2 statistic and Cochran Qtest. Forest plots were generated for each endpoint.

RESULTS

Fifteen studies met the inclusion criteria (639 patients, 831 lesions), with twelve eligible for quantitative synthesis with common endpoints and sufficient reporting. Fourteen studies were retrospective, with a single prospective trial. Studies were small, with a median of 32 patients (range: 6-81) and 63 lesions (range: 6-126). The OM definition varied, with a maximum of two to five metastases, mixed synchronous and metachronous lesions, and a few studies including oligoprogressive lesions. The most common site of metastasis was the lung. Radiation was delivered in 1-10 fractions (20-70 Gy). The one-year LC (LC1), reported in 12 studies, was 86.9% (95% confidence interval [CI]: 79.3-91.9%). LC2 was 77.9% (95% CI: 66.4-86.3%), with heterogeneity across studies. PFS was reported in five studies, with a PFS1 of 43.0% (95% CI: 35.0-51.4%) and PFS2 of 23.9% (95% CI: 17.8-31.2%), with homogeneity across studies. OS was analyzed in nine studies, demonstrating an OS1 of 80.1% (95% CI: 74.2-85.0%) and OS2 of 60.7% (95% CI: 51.3-69.4%). Treatment was well tolerated with no reported grade 4 or 5 toxicities. Grade 3 toxicity rates were uniformly below 5% when reported.

CONCLUSIONS

SBRT offers excellent LC and promising OS, with acceptable toxicities in OM HNC. Durable PFS remains rare, highlighting the need for effective local or systemic therapies in this population. Further investigations on concurrent and adjuvant therapies are warranted.

Stereotactic body radiation therapy for bone oligometastases

Stereotactic body radiation therapy is effective for the local management of oligometastases (at most five metastases) with a benefit in survival and local control. Most studies on the management of oligometastases focus on all oligometastatic sites in primary cancer and very few focus on a single oligometastatic site. In particular, there are few data on bone oligometastases, which represent one of the preferred sites for secondary cancer locations. This article focuses on the benefit of stereotactic radiotherapy for bone oligometastases of all cancers by histological types, and reviews the results of major studies in this field.

Management of head and neck carcinomas with synchronous or metachronous oligometastatic disease: Role of locoregional radiotherapy and metastasis-directed radiotherapy

Head and neck carcinomas are initially metastatic in about 15% of cases. Radiotherapy is a cornerstone in the multimodal strategy at the locoregional phase. In patients with head and neck cancer, often heavily pretreated and with comorbidities, who relapse locoregionally or at distant sites, radiotherapy has also become increasingly important at the metastatic phase. Data on the optimal sequence of systemic treatments and metastasis-directed treatments including stereotactic irradiation are still lacking. Several randomized head and neck trials have been initiated that should provide important answers, including one recent GORTEC trial.

Safety and efficacy of radiotherapy combined with chemotherapy for recurrent metastatic renal pelvic and ureteral carcinoma

PURPOSE

To retrospectively investigate the safety and efficacy of radiotherapy combined with chemotherapy for recurrent metastatic renal pelvic and ureteral carcinoma.

METHODS

109 patients were enrolled in this study, including 44 patients in the radiochemotherapy group and 65 patients in the chemotherapy group. Propensity score matching (PSM) was used to balance the baseline characteristics of the two groups by 1:1 matching. Kaplan-Meier method was used to calculate PFS and OS. Cox regression model was used for multivariate analysis. The side effects were evaluated by CTCAE v5.0 RESULTS: The median follow-up time was 14.5 months. Multivariate analysis showed that radiotherapy was a good independent prognostic factor for OS (HR: 0.327, 95% CI 0.157-0.680, P = 0.003). After matching, there were 40 patients in both groups, and the median PFS and OS in the radiochemotherapy group were longer than those in the chemotherapy group (PFS: 10.4 vs. 6.7 months, P = 0.035; OS: 43.5 vs. 18.8 months, P < 0.001). In addition, in the radiochemotherapy group, patients treated with radiotherapy before first-line chemotherapy failure had a longer PFS than those treated with radiotherapy after chemotherapy failure (median PFS: 15.7 vs. 6 months, P = 0.003). There was no significant difference in the incidence of grade 3-4 toxicities between the two groups (52.3% vs. 50.8%, P = 0.878).

CONCLUSION

For patients with recurrent metastatic renal pelvic and ureteral carcinoma, radiotherapy combined with chemotherapy is well tolerable and expected to bring long-term survival benefits, and the benefits of early interventional radiotherapy may be more obvious.

Intensity-Modulated Radiation Therapy for Uterine Cervical Cancer to Reduce Toxicity and Enhance Efficacy - an Option or a Must?: A Narrative Review

Radiotherapy (RT) is a fundamental modality in treatment of cervical cancer. With advancement of technology, conventional RT used for external beam radiotherapy (EBRT) for over half a century has been rapidly replaced with intensity-modulated radiation therapy (IMRT) especially during the last decade. This newer technique is able to differentiate the intensity of radiation within the same field, thus reduces the inevitable exposure of radiation to normal organs and enables better dose delivery to tumors. Recently, the American Society for Radiation Oncology has released a guideline for RT in cervical cancer. Although a section of the guideline recommends IMRT for the purpose of toxicity reduction, a thorough review of the literature is necessary to understand the current status of IMRT in cervical cancer. This narrative review updates the recent high-level evidences regarding the efficacy and toxicity of IMRT and provides a better understanding of the most innovative techniques currently available for EBRT enabled by IMRT.

Association of follow-up imaging frequency with temporal incidence and patterns of distant failure following (chemo) radiotherapy for HPV related oropharyngeal cancer

OBJECTIVES

Emerging data supports radical intent therapy for oligometastatic (OM) relapsed human papilloma virus (HPV+) related oropharyngeal cancer (OPC). We assess the association of follow-up imaging frequency amongst HPV + OPC, with temporal and spatial patterns of distant relapse, to inform rationalisation of routine post-treatment imaging.

MATERIALS AND METHODS

A retrospective single centre cohort study was carried out of consecutive HPV + OPC patients treated with radical intent (chemo)radiotherapy ((CT)RT) between 2011 and 2019. OM state was defined as ≤ 5 metastasis, none larger than 3 cm (OMs) or, if interval from last negative surveillance imaging > 6-months, then ≤ 10 metastasis, none larger than 5 cm, (OMp). Patients not meeting OMs / OMp criteria were deemed to have incurable diffuse metastatic disease (DMdiffuse).

RESULTS

793 HPV-OPC patients were identified with median follow-up 3.15years (range 0.2-8.9). 52 (6.6 %) patients had radiologically identified DM at first failure and were considered for analysis. The median time to recurrence was 15.1 months (range: 2.6-63 months). 87 % of distant metastasis (DM) occurred in the first two years after treatment. Twenty-seven (52 %) patients had OM (OMs or OMp) at time of failure, with 31 % having OMs. The median time from completion of treatment to diagnosis of DMdiffuse vs OM was 22.2 months (range: 2.6-63.1 months) vs 11.6 months (range: 3.5-32.5 months). The probability of being diagnosed with OM vs DMdiffuse increased with reducing interval from last negative surveillance scan to imaging identifying DM (≤6 months 88.9 %, 7-12 months 71.4 %, 13-24 months 35 %, > 24 months 22.2 %).

CONCLUSION

We demonstrate that a reduced interval between last negative imaging and subsequent radiological diagnosis of DM is associated with increased likelihood of identification of OM disease. Consideration of increased frequency of surveillance imaging during the first two years of follow up is supported, particularly for patients at high risk of distant failure.

Multimodality local consolidative treatment versus conventional care of advanced lung cancer after first-line systemic anti-cancer treatment: study protocol for the RAMON multicentre randomised controlled trial with an internal pilot

INTRODUCTION

Lung cancer is the most common cause of cancer death worldwide and most patients present with extensive disease. One-year survival is improving but remains low (37%) despite novel systemic anti-cancer treatments forming the current standard of care. Although new therapies improve survival, most patients have residual disease after treatment, and little is known on how best to manage it. Therefore, residual disease management varies across the UK, with some patients receiving only maintenance systemic anti-cancer treatment while others receive local consolidative treatment (LCT), alongside maintenance systemic anti-cancer treatment. LCT can be a combination of surgery, radiotherapy and/or ablation to remove all remaining cancer within the lung and throughout the body. This is intensive, expensive and impacts quality of life, but we do not know if it results in better survival, nor the extent of impact on quality of life and what the cost might be for healthcare providers. The RAMON study (RAdical Management Of Advanced Non-small cell lung cancer) will evaluate the acceptability, effectiveness and cost-effectiveness of LCT versus no LCT after first-line systemic treatment for advanced lung cancer.

METHODS AND ANALYSIS

RAMON is a pragmatic open multicentre, parallel group, superiority randomised controlled trial. We aim to recruit 244 patients aged 18 years and over with advanced non-small-cell lung cancer from 40 UK NHS hospitals. Participants will be randomised in a 1:1 ratio to receive LCT alongside maintenance treatment, or maintenance treatment alone. LCT will be tailored to each patient's specific disease sites. Participants will be followed up for a minimum of 2 years. The primary outcome is overall survival from randomisation.

ETHICS AND DISSEMINATION

The West of Scotland Research Ethics Committee (22/WS/0121) gave ethical approval in August 2022 and the Health Research Authority in September 2022. Participants will provide written informed consent before participating in the study. Findings will be presented at international meetings, in peer-reviewed publications, through patient organisations and notifications to patients.

TRIAL REGISTRATION NUMBER

ISRCTN11613852.

Oligometastatic Colorectal Cancer: A Review of Definitions and Patient Selection for Local Therapies

PURPOSE

Nearly one-third of patients diagnosed with colorectal cancer (CRC) will ultimately develop metastatic disease. While a small percentage of patients can be considered for curative resection, more patients have limited disease that can be considered for local therapy. Challenges remain in defining oligometastatic CRC as well as developing treatment strategies guided by high level evidence.

METHODS

In this review, we present the challenges in defining oligometastatic CRC and summarize the current literature on treatment and outcomes of local therapy in patients with metastatic CRC.

RESULTS

For patients with liver- and/or lung-confined CRC metastases, surgical resection is the standard of care given the potential for long-term progression-free and overall survival. For patients with liver- or lung-confined disease not amenable to surgical resection, non-surgical local therapies, such as thermal ablation, hepatic arterial infusion pump (HAIP), or stereotactic body radiation therapy (SBRT), should be considered. For patients with more advanced disease, such as lymph node or bony metastases, the role of metastasis-directed therapy is controversial. Emerging data suggests that SBRT to ablate all metastases can improve progression-free and overall survival.

CONCLUSION

Multidisciplinary management is critical for patients with metastatic CRC due to the complexity of their cases and the nuanced patient, tumor, biological, and anatomical factors that must be weighed when considering local therapy. High-quality prospective randomized data in CRC are needed to further clarify the role of local ablative therapy in patients with unresectable oligometastatic CRC with ongoing studies including the RESOLUTE trial (ACTRN12621001198819) and the upcoming NCTN ERASur trial (NCT05673148).

TORCH-R trial protocol: hypofractionated radiotherapy combined with chemotherapy and toripalimab for locally recurrent rectal cancer: a prospective, single-arm, two-cohort, phase II trial

For patients with locally recurrent rectal cancer (LRRC), the response rate to chemoradiotherapy is 40%-50%. Additionally, only approximately 40%-50% of patients with recurrent rectal cancer are able to undergo R0 resection. Recent studies in locally advanced rectal cancer (LARC) have shown promising synergistic effects when combining immunotherapy (PD-1/PD-L1 antibodies) with neoadjuvant chemoradiotherapy (nCRT). Therefore, incorporating immunotherapy into the treatment regimen for LRRC patients has the potential to further improve response rates and prognosis. To investigate this, the TORCH-R trial was conducted. This prospective, single-arm, two-cohort, phase II trial focuses on the use of hypofractionated radiotherapy, chemotherapy, and immunotherapy in LRRC patients without or with oligometastases. The trial will include two cohorts: cohort A consists of rectal cancer patients who are treatment-naive for local recurrence, and cohort B includes patients with progressive disease after first-line chemotherapy. Cohort A and cohort B patients will receive 25-40 Gy/5 Fx irradiation or 15-30 Gy/5 Fx reirradiation for pelvic recurrence, respectively. Subsequently, they will undergo 18 weeks of chemotherapy, toripalimab, and stereotactic ablative radiotherapy (SABR) for all metastatic lesions between chemoimmunotherapy cycles. Decisions regarding follow-up of complete response (CR), radical surgery, sustained treatment of non-resection, or exiting the trial are made by a multidisciplinary team (MDT). The primary endpoint of this study is the local objective response rate (ORR). The secondary endpoints include the extrapelvic response rate, duration of response, local recurrence R0 resection rate, progression-free survival (PFS), overall survival (OS), and safety and tolerability. Notably, this trial represents the first clinical exploration of inducing hypofractionated radiotherapy, chemotherapy, and immunotherapy in LRRC patients.

Clinical trial registration

https://clinicaltrials.gov/study/NCT05628038, identifier NCT05628038.

Clinical outcomes of MR-guided adrenal stereotactic ablative radiotherapy with preferential sparing of organs at risk

Background and purpose

The optimal stereotactic ablative radiotherapy (SABR) doses for adrenal tumors are unknown. Some trials have specified that organ at risk (OAR) dose constraints should take priority over target coverage. We performed a retrospective review of the outcomes of MR-guided adrenal SABR (MRgRT) delivered with OAR sparing.

Materials and methods

Patients who underwent adrenal MRgRT between 2016 and 2023 were identified from our Ethics-approved institutional database. Dose ranged between 8 and 24 Gy per fraction, delivered in 1-5 fractions. A 3 mm margin was added to the breath-hold gross tumor volume (GTV) to derive a PTV. Plan were delivered to an 'optimized' PTV that was generated by excluding any overlap with OARs.

Results

Adrenal SABR was performed in 107 patients (114 metastases). The commonest scheme used 5 fractions of 10 Gy (53.5 %); 82 % of plans delivered a BED10 ≧ 80 Gy. Systemic therapy was administered within 3 months preceding or following SABR in 53.5 % of patients. Grade 3 acute toxicity (CTCAE v5.0) occurred in 0.9 % of patients, and 4.4 % reported late toxicity, consisting of adrenal insufficiency and a vertebral collapse. Median follow-up was 13.8 months (range, 0.0-73.4 months). Local progression occurred in 7.4 % of evaluable patients. PTV underdosage was frequent, with a coverage compromise index (D99/prescription dose) of < 0.90 in 52 % of all plans. Recurrences were independent of the prescription doses.

Conclusion

MRgRT for adrenal metastases is well tolerated with high local control rates despite prioritizing OAR sparing over PTV coverage. Studies using deformable dose accumulation may lead to a better understanding of dose-response relationship with adaptive SABR.

Pre-radiotherapy ctDNA liquid biopsy for risk stratification of oligometastatic non-small cell lung cancer

The optimal treatment paradigm for patients with oligometastatic non-small cell lung cancer (NSCLC) remains unclear. Some patients with oligometastatic disease experience prolonged remission after locally consolidative radiation therapy (RT), while others harbor micrometastatic disease (below limits of detection by imaging) and benefit from systemic therapy. To risk-stratify and identify the patients most likely to benefit from locally consolidative RT, we performed a multi-institutional cohort study of 1487 patients with oligometastatic NSCLC undergoing liquid biopsy analysis of circulating tumor DNA (ctDNA). In total, 1880 liquid biopsies were performed and approximately 20% of patients (n = 309) had ctDNA measured prior to RT and after their diagnosis of oligometastatic disease. Patients with undetectable ctDNA (pathogenic or likely pathogenic variants in plasma using the Tempus xF assay) before RT had significantly improved progression-free survival (PFS) (P = 0.004) and overall survival (OS) (P = 0.030). ctDNA maximum variant allele frequency (VAF) pre-RT and ctDNA mutational burden pre-RT were both significantly inversely correlated with PFS (maximum VAF P = 0.008, mutational burden P = 0.003) and OS (maximum VAF P = 0.007, mutational burden P = 0.045). These findings were corroborated by multivariate Cox proportional hazards models that included eight additional clinical and genomic parameters. Overall, these data suggest that in patients with oligometastatic NSCLC, pre-RT ctDNA can potentially identify the patients most likely to benefit from locally consolidative RT and experience prolonged PFS and OS. Similarly, ctDNA may be useful to identify undiagnosed micrometastatic disease where it may be appropriate to prioritize systemic therapies.