Lung Oligometastases Research Articles

Prognosis for local radical treatment in patients with esophageal squamous cell carcinoma with low-risk oligometastatic recurrence after curative resection: a retrospective cohort study.

Patients with esophageal carcinoma (EC) with recurrent disease have a poor prognosis. A limited numbers of metastases, safely treatable with curative intent, diagnosed after curative esophagectomy may be defined as oligometastatic recurrence (OLR). However, the appropriate number of metastases and metastatic organs involved remains incompletely characterized. And the role of local therapy in OLR after radical esophagectomy remains unknown. Therefore, this study aimed to more accurately define low-risk OLR in patients with esophageal squamous cell carcinoma (ESCC) treated with radical resection and investigate the role of chemotherapy combined with local treatment (CCLT) in these patients. A total of 83 sequential patients with ESCC who underwent radical esophagectomy, with an Eastern Cooperative Oncology Group (ECOG) performance status ≤2, with ability to tolerate chemotherapy (CT) and local treatment, and with newly diagnosed recurrence between January 2010 and May 2019 in our hospital were recruited. Overall survival (OS) curves after recurrence were analyzed using the Kaplan-Meier method, and a log-rank test was used to assess the OS differences. Cox proportional hazards regression analysis was performed to identify independent factors associated with 2-year OS. Regular follow-up examinations were assessed by thoracic and upper abdominal computed tomography (CT) scanning every 3 months in the first year, every 6 months over the next 2 years, and yearly thereafter. Of the 83 patients with ESCC (71 males and 12 females), the median age was 56 years (range, 37-79 years). Thirty-five patients with ESCC with ≤5 metastases safely treatable with curative intent located in a single organ had a favorable OS compared to 48 patients with metastases located in 2-3 organs with or without regional recurrence and/or regional lymph node (LN) metastases. In our study, low-risk OLR was defined as the presence of ≤5 metastases safely treatable with curative intent in a single organ and was compared to patients with 2-3 organs involved. The 2-year OS of patients with low-risk OLR with liver oligometastases was significantly worse than survival in patients with lung oligometastases (0% vs. 61.1%, P=0.009). Patients with ESCC in the low-risk OLR group treated with CCLT had a better 2-year OS after recurrence than those who received CT alone (66.7% vs. 30.4%, P=0.003). The multivariable Cox regression model identified treatment method [hazard ratio (HR) 3.920, P=0.02] as an independent factor affecting OS after recurrence for low-risk OLR. Low-risk OLR was defined as ≤5 metastases safely treatable with curative intent in a single organ. Patients with ESCC with low-risk OLR after curative resection treated with CCLT have a favorable OS compared to those treated with CT alone. CCLT is a promising treatment option for patients with ESCC and low-risk OLR.

Long-term outcomes of ablation versus surgery in patients with colorectal lung oligometastasis: A retrospective cohort study.

Long-term outcomes of ablation versus surgery in patients with colorectal lung oligometastasis: A retrospective cohort study.

Stereotactic body radiotherapy takes on Lung Oligometastases: Latest breakthroughs

AbstractLung oligometastases represent an intermediate state of cancer dissemination between localized and widespread metastases. Stereotactic body radiation therapy (SBRT) has emerged as an effective treatment option, with an efficacy comparable to that of surgical resection. This review aimed to provide a comprehensive summary of the latest advancements and controversial issues regarding SBRT for lung oligometastases. It focuses on four crucial perspectives: efficacy of SBRT, optimal patient selection criteria, technological innovations, and synergistic effects of SBRT combined with systemic therapy. Relevant clinical trials investigating SBRT for lung oligometastases have been conducted, with median 1‐ and 5‐year local control rates of 90% and 79%, respectively. The origin of the primary tumor, size and number of lesions, and biomarker profiles were highlighted as pivotal considerations in patient selection. The precise dose delivery was enhanced using robotic SBRT and optimized dose fractionation schemes. Evidence suggests that dose escalation above 100 Gy biologically effective dose may improve tumor control. Combined immunotherapy and SBRT have demonstrated synergistic effects in prolonging progression‐free survival and overall survival. This review provides valuable insights into the precise treatment of oligometastatic lung diseases using SBRT. Further multicenter randomized trials are warranted to develop definitive patient selection criteria and optimize the integration with systemic therapies.

Stereotactic ablative brachytherapy versus percutaneous microwave ablation as salvage treatments for lung oligometastasis from colorectal cancer

BackgroundThe treatment for lung oligometastasis from colorectal cancer (CRC) remains challenging. This retrospective study aimed to compare the local tumor control, survival and procedure-related complications in CRC patients undergoing low-dose rate stereotactic ablative brachytherapy (L-SABT) versus percutaneous microwave ablation (MWA) for lung oligometastasis.MethodsPatients between November 2017 and December 2020 were retrospectively analyzed. Local tumor progression-free survival (LTPFS) and overall survival (OS) were analyzed in the entire cohort as well as by stratified analysis based on the minimal ablation margin (MAM) around the tumor.ResultsThe final analysis included 122 patients: 74 and 48 in the brachytherapy and MWA groups, respectively, with a median follow-up of 30.5 and 35.3 months. The 1- and 3-year LTPFS rate was 54.1% and 40.5% in the brachytherapy group versus 58.3% and 41.7% in the MWA group (P = 0.524 and 0.889, respectively). The 1- and 3-year OS rate was 75.7% and 48.6% versus 75.0% and 50.0% (P = 0.775 and 0.918, respectively). Neither LTPFS nor OS differed significantly between the patients with MAM of 5–10 mm versus > 10 mm. Pulmonary complication rate did not differ in the overall analysis, but was significantly higher in the MWA group in the subgroup analysis that only included patients with lesion within 10 mm from the key structures (P = 0.005). The increased complications was primarily bronchopleural fistula.ConclusionsConsidering the caveats associated with radioisotope use in L-SABT, MWA is generally preferable. In patients with lesion within 10 mm from the key pulmonary structures, however, L-SABT could be considered as an alternative due to lower risk of bronchopleural fistula.

CT-guided radioactive 125I seeds brachytherapy for lung oligometastases from colorectal cancer: initial results.

To evaluate the safety and effectiveness of computed tomography (CT)-guided radioactive 125I seeds brachytherapy (RISB) for lung oligometastases (LO) from colorectal cancer (CRC). Data for 144 LOs from 70 CRC patients who underwent CT-guided RISB were retrospectively analyzed. The primary endpoints were progression-free survival (PFS) and overall survival (OS), and the secondary endpoints were technical success, local control rate (LCR), and complications. Kaplan-Meier method was used for survival analysis. Cox model was used to identify the independent predictors of poor prognosis. The RISB procedures were successfully performed in all patients, and the success rate was 100%. The median follow-up was 27.8months. The median PFS was 10.0months (95% CI: 8.9-11.1) and the 1- and 2-year PFS rates were 32.9% and 5.9%, respectively. On multivariate analysis, serum carcinoembryonic antigen (CEA) ≤ 15ng/ml (P = 0.048), middle-high differentiated pathological classification (P = 0.015), primary TNM stages I-III (P = 0.001), LO number ≤ 2 (P < 0.001) and cumulative gross tumor volume (GTV) ≤ 40 cm3 (P < 0.001) showed superior PFS. The median OS was 30.8months (95% CI: 27.1-34.4) and the 1-, 2-, and 3-year OS rates were 95.7%, 67.4%, and 42.5%, respectively. On multivariate analysis, serum CEA ≤ 15ng/ml (P = 0.004), middle-high differentiated pathological classification (P < 0.001), primary TNM stages I-III (P < 0.001), LO number ≤ 2 (P < 0.001), cumulative GTV ≤ 40 cm3 (P < 0.001) and system treatments combined with chemotherapy and target therapy (P < 0.001) showed superior OS. The LCR for 3, 6, and 12months was 97.9%, 91.0%, and 83.6%, respectively. There were 4 cases of pneumothorax at 5.7% that required drainage. RISB for LO from CRC is safe and effective, and serum CEA, TNM stage, LO number, cumulative GTV, and system treatments should be emphasized for long OS.

Lung Oligometastasis of Breast Cancer: Prospective Cohort Study of Treatment Strategies (SBP-06).

While local treatment of metastases is considered to be unrelated to prognosis, previous studies have suggested that local treatment of isolated lung metastases may have positive prognostic impact. We designed this prospective cohort study to investigate the clinical situation and its outcomes. We enrolled patients with fewer than 3 lung nodules suspected of being oligometastases after curative breast cancer surgery. Treatments, including local and systemic therapy, were selected by the physician and patient in consultation. The primary outcome was overall survival (OS); secondary outcomes were the efficacy and the safety of the surgery for lung oligometastases. Between May 2015 and May 2019, 14 patients were enrolled. Resection of lung nodules (metastasectomy) was performed in 11 (78.6%) of 14 patients, and one of these cases was diagnosed as primary lung cancer. Metastasectomies were all performed employing video-assisted thoracic surgery (VATS) without perioperative complications. Systemic therapies were administered to all patients except one. The respective 3-year and 5-year OS rates of patients with lung oligometastases were 91.6% and 81.5%, respectively. Progression occurred in 6 patients: 3 of the 10 with metastasectomy and all 3 without this surgical procedure. Lung metastasectomy was worthwhile as a diagnostic evaluation and may provide long-term benefit in some patients.

Clinical benefits of pulmonary resection for lung metastases from pancreatic cancer.

Systemic chemotherapy is generally used for metastatic pancreatic cancer; however, pulmonary resection may be a treatment option for lung oligometastases from pancreatic cancer. The current study aimed to clarify the oncological outcomes and clinical benefits of pulmonary resection for lung metastases. Of 510 patients who underwent pancreatic resection for pancreatic cancer, 44 patients with recurrence of isolated lung metastases and one patient with simultaneous lung metastases were evaluated. Of the 45 patients, 20 patients were selected as candidates for pulmonary resection based on clinical factors such as recurrence-free interval (RFI) from pancreatectomy to lung metastases, number of lung metastases, and serum CA19-9 level. The post-recurrent survival of patients with pulmonary resection was significantly better than that of patients without pulmonary resection. Fourteen of the 20 patients with pulmonary resection developed tumor recurrence with a median disease-free survival (DFS) of 15 months. Univariate analyses revealed that an RFI from pancreatectomy to lung metastases of ≥28 months was associated with better DFS after pulmonary resection. Of the 14 patients with an RFI of ≥28 months, pulmonary resection resulted in prolonged chemotherapy-free interval in 12 patients. Furthermore, repeat pulmonary resection for recurrent tumors after pulmonary resection led to further cancer-free interval in some cases. Although many patients had tumor recurrence after pulmonary resection, pulmonary resection for lung metastases from pancreatic cancer may provide prolonged cancer-free interval without the need for chemotherapy. Pulmonary resection should be performed for the patients with a long RFI from pancreatectomy to lung metastases.

Proton Beam Therapy for Lung Oligometastatic Recurrence in Patients With Esophageal Cancer.

Local treatment of oligometastatic esophagogastric cancer has been reported to improve overall survival (OS) compared to systemic therapy alone. This study evaluated the feasibility and safety of proton beam therapy (PBT) for the treatment of lung oligometastatic recurrence in esophageal cancer patients. This single-center historical cohort study enrolled 11 patients who underwent PBT for lung oligometastasis from esophageal cancer between 2010 and 2019. The selection criteria were that the primary esophageal cancer was controlled and no more than three lung metastases without outside lung tumors were present. OS, progression-free survival (PFS), and local control (LC) rates and adverse events (AEs) were assessed. Factors that may be related to OS were also investigated. The median follow-up period was 27.8 months (8.8-141.3 months). The one-, two-, and three-year OS rates were 81.8%, 72.7%, and 51.9%, respectively (median OS time: 43.7 months); PFS rates were 45.5%, 27.3%, and 27.3%, respectively (median PFS time: 8.8 months); and LC rates were 92.3%, 72.7%, and 72.7%, respectively. The eighth edition of tumor-node-metastasis (TNM) classification for esophageal cancer was the only significant OS-related factor (p = 0.0309). No grade ≥ 3 AEs were observed. Based on the low incidence of AEs and acceptable LC rate, PBT is a feasible option for the treatment oflung oligometastasis in esophageal cancer patients.

Clinical and genomic characterization of pancreatic ductal adenocarcinoma patients with lung oligometastasis

Clinical and genomic characterization of pancreatic ductal adenocarcinoma patients with lung oligometastasis

Outcomes of lung oligometastasis in pancreatic cancer.

Pancreatic cancer with lung oligometastasis may have favourable overall survival. The aim of this study was to evaluate outcomes of pancreatic cancer with lung oligometastases including both synchronous and metachronous metastases. Consecutive pancreatic cancer patients with lung metastasis treated at our institution between February 2015 and December 2021 were identified from our prospectively maintained database. Clinical characteristics and outcomes were compared and analysed according to the extent of lung metastases. Predictors for overall survival were analysed using the Cox proportional hazards model. A totoal of 171 patients were included (oligometastasis/polymetastasis/multi-organ metastasis: 34/50/87). Patients with oligometastases were more likely to undergo surgical resection (41% vs. 0% vs. 2%) and showed a longer median overall survival (41.3 vs. 17.6 vs. 13.1months) compared with those with other types of metastases. Oligometastasis (hazard ratio, 0.43; 95% confidence interval, 0.24-0.76; P=0.004) was identified as an independent factor predicting favourable overall survival in patients with lung-only metastasis. Disease status (synchronous vs. metachronous) was not associated with survival in patients with oligometastasis (29.4 vs. 41.3months, P=0.527) and polymetastasis (17.9 vs. 16.7months, P=0.545). Selected patients who underwent surgical resection showed a median overall survival of 52.7months. Patients with lung oligometastases presented a favourable prognosis. Surgical resection in selected patients was associated with a long median overall survival.

Concomitant electromagnetic navigation transbronchial microwave ablation of multiple lung nodules is safe, time-saving, and cost-effective

ObjectivesTransbronchial microwave ablation of lung nodules using electromagnetic navigation bronchoscopy is an emerging local therapy for lung oligometastases and multifocal lung cancers as part of a lung-preserving strategy. Concomitant ablation of multiple lung nodules in a single operating session may provide a one-stop solution. MethodsBetween April 2019 and April 2023, 25 patients had 2 or more lung nodules ablated concomitantly in our hybrid operating room. Nodules were proven or highly suspicious of malignancies or metastases. Feasibility and safety were retrospectively reviewed. ResultsA total of 56 nodules in 25 patients received concomitant multi-nodular ablation. The mean age of patients was 60 years, and the reasons for the lung-preserving strategy were multifocal lung cancers (80%) and lung oligometastases (20%). Among those with multifocal disease, 65% had previous major lung resection for lung cancer. Two to 4 nodules were ablated in each session. The mean nodule size was 9.9 mm (range, 5-20 mm), and the mean minimal margin was 5.9 mm. When comparing concomitant nodule ablation with the 103 single-nodule ablations performed in our institute, a mean of 86 minutes of operative time and 131 minutes of anesthetic time were saved. There were no increased complications despite overlapping ablation zones, and the mean hospital stay was 1.23 days. The rate of pneumothorax was 8%, and that of pleural effusion, pain, and fever was 4% respectively. ConclusionsConcomitant transbronchial microwave ablation of multiple lung nodules is feasible, safe, and associated with reduction in overall anesthetic and operative time. It is an important armamentarium in the contemporary lung-preserving strategy for battling multifocal lung cancers or lung oligometastases.

Cyberknife treatment for different types of tumor

CyberKnife radiosurgery is a frameless, image guided robotic stereotactic radiosurgical system (IGR-SRS) which uses potent, ablative radiation dose with limited treatment volume. The main aim of this study is to provide knowledge of this treatment for different types of tumor. To deliver radiation treatment from multiple angles, with real time target tracking through a combined orthogonal radiograph imaging and optic motion tracking system cyberKnife is a new and advanced technique. Radiation is delivered to the tumor within a predetermined range, for this an object recognition computer algorithm and a fudicial marker placed within a tumor. CyberKnife treatment cost USD 6,800 (Indian Rupees approx. 4,89,000). In this review you will get idea about different types of tumor get treated with cyberKnife radiosurgery (SRS). CyberKnife have submillimeter accuracy in metastatic brain tumor. By giving appropriate tracking method for stage I lung cancer and lung oligometastases stereotactic radiotherapy is an efficient treatment. So, at well-defined tumor sites cyberKnife is a new stereotactic body radiation therapy which delivers high dose of radiation in short period of time. For head and neck tumor treatment cyberKnife is most widely used. This treatment is helpful for adrenal gland tumor and prostate tumor, spinal metastases.

Stereotactic Body Radiotherapy for Lung Oligo-metastases: Systematic Review and International Stereotactic Radiosurgery Society Practice Guidelines

PurposeA systematic review of treatment characteristics, outcomes, and treatment-related toxicities of stereotactic body radiation therapy (SBRT) for pulmonary oligometastases served as the basis for development of this International Stereotactic Radiosurgery Society (ISRS) practice guideline. MethodsIn accordance with PRISMA guidelines, a systematic review was performed of retrospective series with ≥50 patients/lung metastases, prospective trials with ≥25 patients/lung metastases, analyses of specific high-risk situations, and all randomized trials published between 2012 and July 2022 in the MEDLINE or Embase database using the key words “lung oligometastases”, “lung metastases”, “pulmonary metastases”, “pulmonary oligometastases”, “stereotactic body radiation therapy (SBRT)” and “stereotactic ablative body radiotherapy (SBRT)”. Weighted random effects models were used to calculate pooled outcomes estimates. ResultsOf the 1884 articles screened, 35 analyses (27 retrospective-, 5 prospective, and 3 randomized trials) reporting on treatment of >3600 patients and >4650 metastases were included. The median local control was 90 % (Range: 57–100 %) at 1 year and 79 % (R: 70–96 %) at 5 years. Acute toxicity ≥3 was reported for 0.5 % and late toxicity ≥3 for 1.8 % of patients. A total of 21 practice recommendations covering the areas of staging & patient selection (n = 10), SBRT treatment (n = 10), and follow-up (n = 1) were developed, with agreements rates of 100 %, except for recommendation 13 (83 %). ConclusionSBRT represents an effective definitive local treatment modality combining high local control rates with low risk of radiation-induced toxicities.

CT-based radiomics prediction of complete response after stereotactic body radiation therapy for patients with lung metastases.

Stereotactic body radiotherapy (SBRT) is akey treatment modality for lung cancer patients. This study aims to develop amachine learning-based prediction model of complete response for lung oligometastatic cancer patients undergoing SBRT. CT images of 80pulmonary oligometastases from 56patients treated with SBRT were analyzed. The gross tumor volumes (GTV) were contoured on CT images. Patients that achieved complete response (CR) at 4months were defined as responders. For each GTV, 107radiomic features were extracted using the Pyradiomics software. The concordance correlation coefficients (CCC) between the region of interest (ROI)-based radiomics features obtained by the two segmentations were calculated. Pairwise feature interdependencies were evaluated using the Spearman rank correlation coefficient. The association of clinical variables and radiomics features with CR was evaluated with univariate logistic regression. Two supervised machine learning models, the logistic regression (LR) and the classification and regression tree analysis (CART), were trained to predict CR. The models were cross-validated using afive-fold cross-validation. The performance of models was assessed by receiver operating characteristic curve (ROC) and class-specific accuracy, precision, recall, and F1-measure evaluation metrics. Complete response was associated with four radiomics features, namely the surface to volume ratio (SVR; p = 0.003), the skewness (Skew; p = 0.027), the correlation (Corr; p = 0.024), and the grey normalized level uniformity (GNLU; p = 0.015). No significant relationship between clinical parameters and CR was found. In the validation set, the developed LR and CART machine learning models had an accuracy, precision, and recall of 0.644 and 0.750, 0.644 and 0.651, and 0.635 and 0.754, respectively. The area under the curve for CR prediction was 0.707 and 0.753 for the LR and CART models, respectively. This analysis demonstrates that radiomics features obtained from pretreatment CT could predict complete response of lung oligometastases following SBRT.

130 - Stereotactic ablative radiotherapy (SABR) for lung oligometastases can prevent or delay need for systemic anti-cancer treatment (SACT): single institution experience

130 - Stereotactic ablative radiotherapy (SABR) for lung oligometastases can prevent or delay need for systemic anti-cancer treatment (SACT): single institution experience

Stereotactic Body Radiotherapy versus Surgery for Lung Metastases from Colorectal Cancer: Single-Institution Results

Surgery and stereotactic body radiotherapy (SBRT) are two of the options available as local treatments for pulmonary oligometastases from colorectal cancer (CRC). We hypothesized that SBRT would have, at least, a similar local control rate to surgery. We identified an initial cohort of 100 patients with CRC who received SBRT or surgery for lung metastases. This was then narrowed down to 75 patients: those who underwent surgery (n = 50) or SBRT (n = 25) as their first local thoracic treatment between 1 January 2004 and 29 December 2017. The Kaplan-Meier method was used to calculate lung-progression-free survival (L-PFS) and overall survival (OS). The 1 and 2-year L-PFS was 85% and 70% in the surgical group and 87% and 71% in the SBRT group, respectively (p = 0.809). No significant differences were found between the two groups in terms of OS. The biologically effective dose (BED), age and initial CRC stage did not have a significant effect on local control or survival. No grade 3 or above acute- or late-toxicity events were reported. These results add retrospective evidence that SBRT and surgery have similar results in terms of OS and local control in patients with lung oligometastases from CRC.

Essential updates 2021/2022: Surgical outcomes of oligometastasis in pancreatic ductal adenocarcinoma.

Oligometastatic disease has been proposed as an intermediate state between localized and polymetastatic disease that can benefit from multimodal treatment, including surgery. There is a growing concern about performing surgery for oligometastatic pancreatic ductal adenocarcinoma, although there is still little evidence. We reviewed articles published between 2021 and 2022, focusing mainly on surgical outcomes. Furthermore, we summarized the current status of surgery in the multidisciplinary treatment of oligometastatic pancreatic cancer and discuss future perspectives. In liver oligometastasis, multimodal treatment including surgery achieved favorable long-term survival, especially in patients with good responses to preoperative chemotherapy, with a median survival time from 25.5 to 54.6months. In addition, the data from the National Cancer Database in the United States showed that patients who underwent surgery for oligometastatic liver metastases had a significantly longer overall survival than those who received chemotherapy alone. Prognostic biomarkers were identified, including carbohydrate antigen 19-9 (CA19-9) levels at diagnosis and preoperative chemotherapy with normalization of CA19-9 levels or favorable radiological response. Patients with lung oligometastasis had a more favorable long-term prognosis than those with other recurrence sites, and the updated literature further confirmed the previous studies. Overall survival was favorable, with 84 months after initial surgery and 29.2months after metastasectomy, and a 5-year survival rate of 60.6% was also reported. In peritoneal oligometastasis, the results of conversion surgery after good responses to preoperative treatment with intraperitoneal therapy or systematic chemotherapy were reported, and the conversion rate and long-term prognosis were favorable. There is a growing concern about performing surgery for oligometastatic pancreatic ductal adenocarcinoma. We reviewed articles published between 2021 and 2022, focusing mainly on surgical outcomes. Furthermore, we summarize the current status of surgery in multidisciplinary treatment of oligometastatic pancreatic cancer and discuss future perspectives.

CT radiomic predictors of local relapse after SBRT for lung oligometastases from colorectal cancer: asingle institute pilot study.

To assess the potential of radiomic features (RFs) extracted from simulation computed tomography (CT) images in discriminating local progression (LP) after stereotactic body radiotherapy (SBRT) in the management of lung oligometastases (LOM) from colorectal cancer (CRC). Thirty-eight patients with 70LOM treated with SBRT were analyzed. The largest LOM was considered as most representative for each patient and was manually delineated by two blinded radiation oncologists. In all, 141RFs were extracted from both contours according to IBSI (International Biomarker Standardization Initiative) recommendations. Based on the agreement between the two observers, 134/141 RFs were found to be robust against delineation (intraclass correlation coefficient [ICC] > 0.80); independent RFs were then assessed by Spearman correlation coefficients. The association between RFs and LP was assessed with Mann-Whitney test and univariate logistic regression (ULR): the discriminative power of the most informative RF was quantified by receiver-operating characteristics (ROC) analysis through area under curve (AUC). In all, 15/38patients presented LP. Median time to progression was 14.6months (range 2.4-66months); 5/141 RFs were significantly associated to LP at ULR analysis (p < 0.05); among them, 4RFs were selected as robust and independent: Statistical_Variance(AUC = 0.75, p = 0.002), Statistical_Range(AUC = 0.72, p = 0.013), Grey Level Size Zone Matrix (GLSZM) _zoneSizeNonUniformity(AUC = 0.70, p = 0.022), Grey Level Dependence Zone Matrix (GLDZM) _zoneDistanceEntropy (AUC = 0.70, p = 0.026). Importantly, the RF with the best performance (Statisical_Variance) is simply representative of density heterogeneity within LOM. Four RFs extracted from planning CT were significantly associated with LP of LOM from CRC treated with SBRT. Results encourage further research on alarger population aiming to define ausable radiomic score combining the most predictive RFs and, possibly, additional clinical features.

297P Transbronchial microwave ablation of early lung cancers and lung oligometastases: Mid-term results

Microwave ablation of lung nodules provides a faster, larger and more predictable ablation zone than its predecessor radiofrequency energy, while bronchoscopic ablation has advantage of less pleural-based complications than percutaneous approach. The combination of bronchoscopic approach and microwave ablation is a novel approach in local treatment of lung nodules.

Radioresistant Lung Oligometastases: Impact of Histology and Dose on Local Control

<h3>Purpose/Objective(s)</h3> While a prescribed biologically effective dose (BED) of 100 Gy optimizes local control in early-stage non-small cell lung cancer (NSCLC), pulmonary oligometastases from radioresistant primary tumors such as colorectal cancer are associated with higher local failure rates despite similar radiotherapy (RT) regimens. We hypothesized that (1) metastases from radioresistant primaries would have inferior local control than those from non-radioresistant non-NSCLC primaries, and that (2) higher BED would be associated with superior local control among radioresistant metastases. <h3>Materials/Methods</h3> We identified 102 patients treated with radiotherapy for oligometastatic pulmonary disease (1-3 lung metastases from non-NSCLC primaries) in 2013-2020 at a single institution. Radioresistant primary cancers included colorectal carcinoma, endometrial carcinoma, renal cell carcinoma, melanoma, and sarcoma. Non-radioresistant 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) and overall survival (OS) between radioresistant vs. non-radioresistant metastases, as well as between BED10≥100 Gy vs. BED10<100 Gy among radioresistant metastases. <h3>Results</h3> Among the 94 patients with complete records, 60 were identified as having pulmonary oligometastases from radioresistant primary cancers. The median total dose was 52 Gy (interquartile range [IQR] 50-54 Gy), and the median number of fractions was 5 (IQR 3-5). Median follow-up time was 62.9 months. 1 of 34 patients (2.9%) with a non-radioresistant metastasis experienced local failure compared to 14 of 60 (23.3%) patients with radiosensitive metastasis (log-rank p=0.038). Multivariable Cox regression analysis showed that radioresistant histology was associated with an increased risk of LRFS following lung RT (hazard ratio [HR]: 4.20, 95% CI: 1.11-15.9, p=0.034). Escalation of the lung RT dose (BED10≥100 vs. BED10<100) was associated with improved LRFS among patients with radioresistant tumors (HR 0.32, 95% CI 0.11-0.96, p=0.04, 1-year LRFS 93.7% vs. 66.7%, 2-year LRFS 78.3% vs. 50.0%). <h3>Conclusion</h3> For oligometastatic patients with lung metastases from non-NSCLC primaries, radioresistant histology was associated with an increased risk of local failure following lung RT. Among these patients, BED10≥100 Gy is associated with decreased risk of local recurrence, suggesting that dose escalation above this threshold should be strongly considered when feasible. In the context of ongoing oligometastatic trials that seek to increase the number of sites treated, our results emphasize that maintaining ablative doses may be necessary to optimize local disease control in this subset of patients.