Metabolic profiling of murine radiation-induced lung injury with Raman spectroscopy and comparative machine learning.

Radiation-induced lung injury (RILI) is a dose-limiting toxicity for cancer patients receiving thoracic radiotherapy. As such, it is important to characterize metabolic associations with the early and late stages of RILI, namely pneumonitis and pulmonary fibrosis. Recently, Raman spectroscopy has shown utility for the differentiation of pneumonitic and fibrotic tissue states in a mouse model; however, the specific metabolite-disease associations remain relatively unexplored from a Raman perspective. This work harnesses Raman spectroscopy and supervised machine learning to investigate metabolic associations with radiation pneumonitis and pulmonary fibrosis in a mouse model. To this end, Raman spectra were collected from lung tissues of irradiated/non-irradiated C3H/HeJ and C57BL/6J mice and labelled as normal, pneumonitis, or fibrosis, based on histological assessment. Spectra were decomposed into metabolic scores via group and basis restricted non-negative matrix factorization, classified with random forest (GBR-NMF-RF), and metabolites predictive of RILI were identified. To provide comparative context, spectra were decomposed and classified via principal component analysis with random forest (PCA-RF), and full spectra were classified with a convolutional neural network (CNN), as well as logistic regression (LR). Through leave-one-mouse-out cross-validation, we observed that GBR-NMF-RF was comparable to other methods by measure of accuracy and log-loss (p > 0.10 by Mann-Whitney U test), and no methodology was dominant across all classification tasks by measure of area under the receiver operating characteristic curve. Moreover, GBR-NMF-RF results were directly interpretable and identified collagen and specific collagen precursors as top fibrosis predictors, while metabolites with immune and inflammatory functions, such as serine and histidine, were top pneumonitis predictors. Further support for GBR-NMF-RF and the identified metabolite associations with RILI was found as CNN interpretation heatmaps revealed spectral regions consistent with these metabolites.

Development of a Radiation-induced Pulmonary Fibrosis Partial Body Irradiation Model in C57BL/6 Mice.

With the current volatile geopolitical climate, the threat of nuclear assault is high. Exposure to ionizing radiation from either nuclear incidents or radiological accidents often lead to major harmful consequences to human health. Depending on the absorbed dose, the symptoms of the acute radiation syndrome and delayed effects of acute radiation exposure (DEARE) can appear within hours, weeks to months. The lung is a relatively radiosensitive organ with manifestation of radiation pneumonitis as an acute effect, followed by apparent fibrosis in weeks or even months. A recently developed, first-of-its-kind murine model for partial-body irradiation (PBI) injury, which can be used to test potential countermeasures against multi-organ damage such as gastrointestinal (GI) tract and lungs was used for irradiation, with 2.5% bone marrow spared (BM2.5-PBI) from radiation exposure. Long-term damage to lungs from radiation was evaluated using µ-CT scans, pulmonary function testing, histopathological parameters and molecular biomarkers. Pulmonary fibrosis was detected by ground glass opacity observed in µ-CT scans of male and female C57BL/6J mice 6-7 months after BM2.5-PBI. Lung mechanics assessments pertaining to peripheral airways suggested fibrotic lungs with stiffer parenchymal lung tissue and reduced inspiratory capacity in irradiated animals 6-7 months after BM2.5-PBI. Histopathological evaluation of the irradiated lungs revealed presence of focal and diffuse pleural, and parenchymal inflammatory and fibrotic lesions. Fibrosis was confirmed by elevated levels of collagen when compared to lungs of age-matched naïve mice. These findings were validated by findings of elevated levels of pro-fibrotic biomarkers and reduction in anti-inflammatory proteins. In conclusion, a long-term model for radiation-induced pulmonary fibrosis was established, and countermeasures could be screened in this model for survival and protection/mitigation or recovery from radiation-induced pulmonary damage.

Optimizing lung cancer radiation therapy: A systematic review of multifactorial risk assessment for radiation-induced lung toxicity.

BACKGROUND: Radiation therapy (RT) is essential in treating advanced lung cancer, but may lead to radiation pneumonitis (RP). This systematic review investigates the use of pulmonary function tests (PFT) and other parameters to predict and mitigate RP, thereby improving RT planning. METHODS: A systematic review sifted through PubMed and on BioMed Central, targeting articles from September 2005 to December 2022 containing the keywords: Lung Cancer, Radiotherapy, and pulmonary function test. RESULTS: From 1153 articles, 80 were included. RP was assessed using CTCAEv.4 in 30 % of these. Six studies evaluated post-RT quality of life in lung cancer patients, reporting no decline. Patients with RP and chronic obstructive pulmonary disease (COPD) generally exhibited poorer overall survival. Notably, forced expiratory volume in one second (FEV1) and diffusing capacity of the lung for carbon monoxide (DLCO) declined 24 months post-RT, while forced vital capacity (FVC) stayed stable. In the majority of studies, age over 60, tumors located in the lower part of the lung, and low FEV1 before RT were associated with a higher risk of RP. Dosimetric factors (V5, V20, MLD) and metabolic imaging emerged as significant predictors of RP risk. A clinical checklist blending patient and tumor characteristics, PFT results, and dosimetric criteria was proposed for assessing RP risk before RT. CONCLUSION: The review reveals the multifactorial nature of RP development following RT in lung cancer. This approach should guide individualized management and calls for a prospective study to validate these findings and enhance RP prevention strategies.

Inhibition of TGFß1 activation prevents radiation-induced lung fibrosis.

BACKGROUND: Radiotherapy is the main treatment modality for thoracic tumours, but it may induce pulmonary fibrosis. Currently, the pathogenesis of radiation-induced pulmonary fibrosis (RIPF) is unclear, and effective treatments are lacking. Transforming growth factor beta 1 (TGFß1) plays a central role in RIPF. We found that activated TGFß1 had better performance for radiation pneumonitis (RP) risk prediction by detecting activated and total TGFß1 levels in patient serum. αv integrin plays key roles in TGFß1 activation, but the role of αv integrin-mediated TGFß1 activation in RIPF is unclear. Here, we investigated the role of αv integrin-mediated TGFß1 activation in RIPF and the application of the integrin antagonist cilengitide to prevent RIPF. METHODS: ItgavloxP/loxP ;Pdgfrb-Cre mice were generated by conditionally knocking out Itgav in myofibroblasts, and wild-type mice were treated with cilengitide or placebo. All mice received 16 Gy of radiation or underwent a sham radiation procedure. Lung fibrosis was measured by a modified Ashcroft score and microcomputed tomography (CT). An enzyme-linked immunosorbent assay (ELISA) was used to measure the serum TGFß1 concentration, and total Smad2/3 and p-Smad2/3 levels were determined via Western blotting. RESULTS: Conditional Itgav knockout significantly attenuated RIPF (p < .01). Hounsfield units (HUs) in the lungs were reduced in the knockout mice compared with the control mice (p < .001). Conditional Itgav knockout decreased active TGFß1 secretion and inhibited fibroblast p-Smad2/3 expression. Exogenous active TGFß1, but not latent TGFß1, reversed these reductions. Furthermore, cilengitide treatment elicited similar results and prevented RIPF. CONCLUSIONS: The present study revealed that conditional Itgav knockout and cilengitide treatment both significantly attenuated RIPF in mice by inhibiting αv integrin-mediated TGFß1 activation. HIGHLIGHTS: Activated TGFß1 has a superior capacity in predicting radiation pneumonitis (RP) risk and plays a vital role in the development of radiation-induced pulmonary fibrosis (RIPF). Conditional knock out Itgav in myofibroblasts prevented mice from developing RIPF. Cilengitide alleviated the development of RIPF by inhibiting αv integrin-mediated TGFß1 activation and may be used in targeted approaches for preventing RIPF.

Dosimetric predictors of radiation pneumonitis in patients with prior immunotherapy exposure: A multi-institutional analysis.

BACKGROUND AND PURPOSE: Combining immune checkpoint inhibitors (ICIs) and thoracic radiotherapy (TRT) may magnify the radiation pneumonitis (RP) risk. Dosimetric parameters can predict RP, but dosimetric data in context of immunotherapy are very scarce. To address this knowledge gap, we performed a large multicenter investigation to identify dosimetric predictors of RP in this under-studied population. MATERIALS AND METHODS: All lung cancer patients from five institutions who underwent conventionally-fractionated thoracic intensity-modulated radiotherapy with prior ICI receipt were retrospectively compiled. RP was defined per CTCAE v5.0. Statistics utilized logistic regression modeling and receiver operating characteristic (ROC) analysis. RESULTS: The vast majority of the 192 patients (median follow-up 14.7 months) had non-small cell lung cancer, received PD-1 inhibitors, and did not receive concurrent systemic therapy with TRT. Grades 1-5 RP occurred in 21.9%, 25.0%, 8.3%, 1.6%, and 1.0%, respectively. The mean MLD for patients with grades 1-5 RP was 10.7, 11.6, 12.6, 14.7, and 12.8 Gy, respectively. On multivariable analysis, tumor location and mean lung dose (MLD) significantly predicted for any-grade and grade ≥ 2 pneumonitis. Only MLD significantly predicted for grade ≥ 3 RP. ROC analysis was able to pictorially model RP risk probabilities for a variety of MLD thresholds, which can be an assistive tool during TRT treatment planning. CONCLUSION: This study, by far the largest to date of dosimetric predictors of RP in the immunotherapy era, illustrates that MLD is the most critical dose-volume parameter influencing RP risk. These data may provide a basis for revising lung dose constraints in efforts to better prevent RP in this rapidly expanding ICI/TRT population.

Prediction of Acute Radiation-Induced Lung Toxicity After Stereotactic Body Radiation Therapy Using Dose-Volume Parameters From Functional Mapping on Gallium 68 Perfusion Positron Emission Tomography/Computed Tomography.

PURPOSE: The aim of this work was to compare anatomic and functional dose-volume parameters as predictors of acute radiation-induced lung toxicity (RILT) in patients with lung tumors treated with stereotactic body radiation therapy. METHODS AND MATERIALS: Fifty-nine patients treated with stereotactic body radiation therapy were prospectively included. All patients underwent gallium 68 lung perfusion positron emission tomography (PET)/computed tomography (CT) imaging before treatment. Mean lung dose (MLD) and volumes receiving x Gy (VxGy, 5-30 Gy) were calculated in 5 lung volumes: the conventional anatomic volume (AV) delineated on CT images, 3 lung functional volumes (FVs) defined on lung perfusion PET imaging (FV50%, FV70%, and FV90%; ie, the minimal volume containing 50%, 70%, and 90% of the total activity within the AV), and a low FV (LFV; LFV = AV - FV90%). The primary endpoint of this analysis was grade ≥2 acute RILT at 3 months as assessed with National Cancer Institute Common Terminology Criteria for Adverse Events version 5. Dose-volume parameters in patients with and without acute RILT were compared. Receiver operating characteristic curves assessing the ability of dose-volume parameters to discriminate between patients with and without acute RILT were generated, and area under the curve (AUC) values were calculated. RESULTS: Of the 59 patients, 10 (17%) had grade ≥2 acute RILT. The MLD and the VxGy in the AV and LFV were not statistically different between patients with and without acute RILT (P > .05). All functional parameters were significantly higher in acute RILT patients (P < .05). AUC values (95% CI) for MLD AV, LFV, FV50%, FV70%, and FV90% were 0.66 (0.46-0.85), 0.60 (0.39-0.80), 0.77 (0.63-0.91), 0.77 (0.64-0.91), and 0.75 (0.58-0.91), respectively. AUC values for V20Gy AV, LFV, FV50%, FV70%, and FV90% were 0.65 (0.44-0.87), 0.64 (0.46-0.83), 0.82 (0.69-0.95), 0.81 (0.67-0.96), and 0.75 (0.57-0.94), respectively. CONCLUSIONS: The predictive value of PET perfusion-based functional parameters outperforms the standard CT-based dose-volume parameters for the risk of grade ≥2 acute RILT. Functional parameters could be useful for guiding radiation therapy planning and reducing the risk of acute RILT.

An interactive murine single-cell atlas of the lung responses to radiation injury.

Radiation Induced Lung Injury (RILI) is one of the main limiting factors of thorax irradiation, which can induce acute pneumonitis as well as pulmonary fibrosis, the latter being a life-threatening condition. The order of cellular and molecular events in the progression towards fibrosis is key to the physiopathogenesis of the disease, yet their coordination in space and time remains largely unexplored. Here, we present an interactive murine single cell atlas of the lung response to irradiation, generated from C57BL6/J female mice. This tool opens the door for exploration of the spatio-temporal dynamics of the mechanisms that lead to radiation-induced pulmonary fibrosis. It depicts with unprecedented detail cell type-specific radiation-induced responses associated with either lung regeneration or the failure thereof. A better understanding of the mechanisms leading to lung fibrosis will help finding new therapeutic options that could improve patients' quality of life.

A C57L/J Mouse Model of the Delayed Effects of Acute Radiation Exposure in the Context of Evolving Multi-Organ Dysfunction and Failure after Total-Body Irradiation with 2.5% Bone Marrow Sparing.

The objective of the current study was to establish a mouse model of acute radiation syndrome (ARS) after total-body irradiation with 2.5% bone marrow sparing (TBI/BM2.5) that progressed to the delayed effects of acute radiation exposure, specifically pneumonitis and/or pulmonary fibrosis (DEARE-lung), in animals surviving longer than 60 days. Two hundred age and sex matched C57L/J mice were assigned to one of six arms to receive a dose of 9.5 to 13.25 Gy of 320 kV X-ray TBI/BM2.5. A sham-irradiated cohort was included as an age- and sex-matched control. Blood was sampled from the facial vein prior to irradiation and on days 5, 10, 15, 20, 25, and 30 postirradiation for hematology. Respiratory function was monitored at regular intervals throughout the in-life phase. Animals with respiratory dysfunction were administered a single 12-day tapered regimen of dexamethasone, allometrically scaled from a similar regimen in the non-human primate. All animals were monitored daily for up to 224 days postirradiation for signs of organ dysfunction and morbidity/mortality. At euthanasia due to criteria or at the study endpoint, wet lung weights were recorded, and blood sampled for hematology and serum chemistry. The left lung, heart, spleen, small and large intestine, and kidneys were processed for histopathology. A dose-response curve with the estimated lethal dose for 10-99% of animals with 95% confidence intervals was established. The median survival time was significantly prolonged in males as compared to females across the 10.25 to 12.5 Gy dose range. Animal sex played a significant role in overall survival, with males 50% less likely to expire prior to the study endpoint compared to females. All animals developed pancytopenia within the first one- to two-weeks after TBI/BM2.5 followed by a progressive recovery through day 30. Fourteen percent of animals expired during the first 30-days postirradiation due to ARS (e.g., myelosuppression, gastrointestinal tissue abnormalities), with most deaths occurring prior to day 15. Microscopic findings show the presence of radiation pneumonitis as early as day 57. At time points later than day 70, pneumonitis was consistently present in the lungs of mice and the severity was comparable across radiation dose arms. Pulmonary fibrosis was first noted at day 64 but was not consistently present and stable in severity until after day 70. Fibrosis was comparable across radiation dose arms. In conclusion, this study established a multiple organ injury mouse model that progresses through the ARS phase to DEARE-lung, characterized by respiratory dysfunction, and microscopic abnormalities consistent with radiation pneumonitis/fibrosis. The model provides a platform for future development of medical countermeasures for approval and licensure by the U.S. Food and Drug Administration under the animal rule regulatory pathway.

Impact of palliative radiotherapy with or without lung irradiation in patients with interstitial lung disease.

BACKGROUND AND PURPOSE: Acute exacerbations or acute lung injury, including radiation pneumonitis (AE-ALI/RP) of interstitial lung disease (ILD), has a fatal prognosis. We evaluated the risk of palliative-intent radiotherapy (RT), with or without lung irradiation, for AE-ALI/RP of ILD. MATERIALS AND METHODS: The data of patients with ILD who received palliative-intent RT between January 2011 and January 2022 were retrospectively reviewed. Factors associated with AE-ALI/RP grade ≥ 3 were assessed using univariate and multivariate analyses. RESULTS: One hundred and three patients were examined, with median imaging and survival follow-up times of 88 (2-1440) and 144 (8-1441) days. The median time to onset of AE-ALI/RP grade ≥ 3 was 72 (5-206) days. In multivariate analysis, a higher pulmonary fibrosis score (PFS ≥ 3) (hazard ratio, HR: 2.16; 95% confidence interval, CI: 1.36-3.43; p < 0.01) and lung irradiation (lung-RT) (HR: 3.82; 95% CI: 1.01-15.73; p = 0.04) were significant factors for AE-ALI/RP grade ≥ 3. In patients who received lung-RT, the 100-day survival rate and cumulative incidence of AE-ALI/RP grade ≥ 3 were 56.8% and 13.7%, respectively. In patients with PFS ≥ 3 and who underwent lung-RT, the 100-day cumulative incidence of AE-ALI/RP grade ≥ 3 was 37.5%; all patients with AE-ALI/RP grade ≥ 3 had grade 5. In patients with PFS ≥ 3 without lung-RT, the 100-day cumulative incidence of AE-ALI/RP grade ≥ 3 was 4.8%. CONCLUSION: High PFS and lung-RT are significant risk factors for AE-ALI/RP grade ≥ 3. Even with relatively low doses, palliative-intent lung-RT carries an extremely high risk of AE-ALI/RP when PFS is high.

Amomum subulatum mitigates experimental thoracic radiation-induced lung injury by regulating antioxidant status and inflammatory responses.

Radiation-induced lung injury (RILI) is one of the most prominent complications of thoracic radiotherapy for which effective therapy is still lacking. This study investigates the nutraceutical potential of the culinary spice Amomum subulatum in mitigating thoracic radiation-induced pneumonitis (RP) and pulmonary fibrosis (PF). Mouse models of RP and PF were established by whole thorax irradiation at a dose of 25 gray. C57BL/6 mice were administered with 250 mg per kg body weight of methanolic extract of A. subulatum dry fruits (MEAS) for four consecutive weeks and observed for changes in lung tissue antioxidant activities, oxidative stress parameters, and expression of antioxidant, inflammation, and fibrosis-related genes by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) and real-time PCR analysis, and histology analysis. MEAS administration reduced radiation-induced oxidative stress by enhancing the expression of Nrf2 and its target genes. Irradiation increased gene expression of inflammatory mediators and lung histology further confirmed the characteristics of RP, which were reduced by MEAS treatment. Immunohistochemistry analysis revealed the potential of MEAS in reducing the radiation-induced elevation of cyclooxygenase 2 expression in the lungs. The late sequel of RILI was manifested as PF, characterized by the elevated expression of pro-fibrotic genes and increased collagen content. However, MEAS administration markedly reduced radiation-induced fibrotic changes in the lungs. These effects might be attributed to the synergistic effect of bioactive polyphenols in MEAS with antioxidant, anti-inflammatory, and anti-fibrotic efficacies. Taken together, this study demonstrates the potential of MEAS in mitigating RILI, suggesting the possible nutraceutical application of A. subulatum against radiation toxicities.

3D deep convolution neural network for radiation pneumonitis prediction following stereotactic body radiotherapy.

In this study, we investigated 3D convolutional neural networks (CNNs) with input from radiographic and dosimetric datasets of primary lung tumors and surrounding lung volumes to predict the likelihood of radiation pneumonitis (RP). Pre-treatment, 3- and 6-month follow-up computed tomography (CT) and 3D dose datasets from one hundred and ninety-three NSCLC patients treated with stereotactic body radiotherapy (SBRT) were retrospectively collected and analyzed for this study. DenseNet-121 and ResNet-50 models were selected for this study as they are deep neural networks and have been proven to have high accuracy for complex image classification tasks. Both were modified with 3D convolution and max pooling layers to accept 3D datasets. We used a minority class oversampling approach and data augmentation to address the challenges of data imbalance and data scarcity. We built two sets of models for classification of three (No RP, Grade 1 RP, Grade 2 RP) and two (No RP, Yes RP) classes as outputs. The 3D DenseNet-121 models performed better (F1 score [0.81], AUC [0.91] [three class]; F1 score [0.77], AUC [0.84] [two class]) than the 3D ResNet-50 models (F1 score [0.54], AUC [0.72] [three-class]; F1 score [0.68], AUC [0.71] [two-class]) (p = 0.017 for three class predictions). We also attempted to identify salient regions within the input 3D image dataset via integrated gradient (IG) techniques to assess the relevance of the tumor surrounding volume for RP stratification. These techniques appeared to indicate the significance of the tumor and surrounding regions in the prediction of RP. Overall, 3D CNNs performed well to predict clinical RP in our cohort based on the provided image sets and radiotherapy dose information.

Predictive role of circulatory levels of high-mobility group box 1 for radiation pneumonitis in patients with non-small cell lung cancer treated with definitive thoracic radiotherapy.

BACKGROUND: High-mobility group box 1 (HMGB1) is a pro-inflammatory protein associated with the pathophysiology of lung injury and lung tumorigenesis. Here, we investigated the predictive potential of serum HMGB1 levels for radiation pneumonitis in patients with lung cancer. METHODS: This was a retrospective biomarker study of 73 patients with non-small cell lung cancer treated with definitive thoracic radiotherapy between August 2007 and January 2021. We measured HMGB1 levels in serum stored before treatment, and analyzed its association with the development of grade ≥ 2 or grade ≥ 3 radiation pneumonitis. Additionally, baseline characteristics affecting HMGB1 levels were identified. RESULTS: Of the 73 patients, 21 (28.8%) and 6 (8.2%) patients experienced grade 2 and ≥ 3 radiation pneumonitis, respectively. Univariate and multivariate logistic regression analyses revealed that higher baseline levels of serum HMGB1 were significantly associated with a higher risk of grade ≥ 3, but not grade ≥ 2, radiation pneumonitis. The incidence of grade ≥ 3 radiation pneumonitis was higher in patients with HMGB1 levels ≥ 6.2 ng/mL than in those with levels < 6.2 ng/mL (25.0% vs. 3.5%, p = 0.019). Baseline serum levels of HMGB1 were independently and positively associated with gross tumor volume. CONCLUSIONS: Higher serum HMGB1 levels were significantly associated with the risk of grade ≥ 3 radiation pneumonitis in patients with lung cancer, and therefore, HMGB1 could be a potential blood biomarker for predicting severe radiation pneumonitis.

Circulating T Cell Activation and Exhaustion Markers Are Associated With Radiation Pneumonitis and Poor Survival in Non-Small-Cell Lung Cancer.

Introduction: Persistent inflammation and immune activation in the lungs are associated with adverse outcomes such as radiation pneumonitis (RP) and poor survival in non-small-cell lung cancer (NSCLC) patients. However, it is unknown how this is reflected by leukocyte activation markers in serum. Objective: The aim was to evaluate the serum levels of activation of different leukocyte subsets and to examine those in relation to the pathogenesis of RP and survival in NSCLC. Methods: We analyzed the serum levels of MPO, sCD25, sTIM-3, sPD-L1, sCD14, sCD163, CCL19 and CCL21 in 66 inoperable NSCLC patients with stage IA-IIIA disease. The patients were treated with stereotactic body radiation therapy (SBRT) or concurrent chemoradiation therapy (CCRT), followed by regular blood sampling for 12 months after treatment and for 5 years for survival. Results: Nineteen (29%) patients developed RP, which occurred more frequently and earlier in patients receiving CCRT than in those receiving SBRT. Increases in sCD25, sTIM-3 and CCL21 levels were observed at the last 6 months of follow-up in patients who had RP after SBRT. Patients who had RP after CCRT had higher sTIM-3 levels during the first 3 months of follow-up. Baseline sCD25 was independently associated with both 2- and 5-year mortality outcomes, while baseline sTIM-3 was independently associated with 2-year mortality. Conclusion: We showed that T cell activation and exhaustion markers such as sCD25 and sTIM-3 are enhanced in patients developing RP and are associated with poor survival in NSCLC.

Repeated Stereotactic Body Radiotherapy for Lung Malignancies: Toxicity Can Be Reduced by Sparing Lung Irradiation.

BACKGROUND/AIM: Evidence on the use of repeated stereotactic body radiotherapy (SBRT) is limited. We investigated the efficacy of repeated SBRT and predictors of lung toxicity. PATIENTS AND METHODS: We reviewed 20 patients (27 lesions) with primary or metastatic lung cancer who underwent repeated SBRT with CyberKnife® We generated a composite plan for dosimetric analysis based on equivalent doses in 2.0-Gy fractions (α/ß=3). Predictors of Grade 2+ radiation pneumonitis (RP) were examined. RESULTS: The median follow-up duration was 18.0 months. The 1-year and 2-year local control were both 95.2%. Five patients (25%) developed Grade 2+ RP, including a Grade 5 RP. The Grade 2+ RP group showed higher composite mean lung dose (MLD) and lower lung volumes spared from 5-20 Gy (VS5-VS20). CONCLUSION: Repeated SBRT with CyberKnife® showed favorable local control, but a high rate of Grade 2+ RP. Accumulated MLD and VS5-VS20 may predict RP.

A Prognostic Tool to Estimate the Risk of Pneumonitis in Patients Irradiated for Lung Cancer.

BACKGROUND/AIM: Radiotherapy of lung cancer can lead to pneumonitis. This study aimed to identify risk factors and create a prognostic tool. PATIENTS AND METHODS: Sixteen factors were evaluated in 169 patients irradiated for lung cancer including age, sex, lung function, primary tumor/nodal stage, histology, tumor location, surgery, systemic treatment, radiation volume, total dose, mean dose to ipsilateral lung, history of another malignancy, pack years, chronic inflammatory disease, and cardiovascular disease. RESULTS: Forty-one patients experienced pneumonitis. Significant associations were found for total doses >56 Gy (p=0.023), mean lung doses >20 Gy (p=0.002) or >13 Gy (p<0.001), and chronic inflammatory disease (p=0.034). Considering mean lung dose and chronic inflammatory disease, scores were 2, 3, 4, or 5 points. Pneumonitis rates were 0% (0/35), 24% (14/58), 32% (21/66), and 60% (6/10) (p=0.001), respectively. CONCLUSION: Based on significant risk factors, a prognostic tool was developed that can help estimate the risk of pneumonitis and contribute to personalized follow up of patients.

Radiation pneumonitis in patients with non-small-cell lung cancer receiving chemoradiotherapy and an immune checkpoint inhibitor: a retrospective study.

BACKGROUND: Immunotherapy has been administered to many patients with non-small-cell lung cancer (NSCLC). However, only few studies have examined toxicity in patients receiving an immune checkpoint inhibitor (ICI) after concurrent chemoradiotherapy (CCRT). Therefore, we performed a retrospective study to determine factors that predict radiation pneumonitis (RP) in these patients. METHODS: We evaluated the size of the planning target volume, mean lung dose (MLD), and the lung volume receiving more than a threshold radiation dose (VD) in 106 patients. The primary endpoint was RP ≥ grade 2, and toxicity was evaluated. RESULTS: After CCRT, 51/106 patients were treated with ICI. The median follow-up period was 11.5 months (range, 3.0-28.2), and RP ≥ grade 2 occurred in 47 (44.3%) patients: 27 and 20 in the ICI and non-ICI groups, respectively. Among the clinical factors, only the use of ICI was associated with RP (p = 0.043). Four dosimetric variables (MLD, V20, V30, and V40) had prognostic significance in univariate analysis for occurrence of pneumonitis (hazard ratio, p-value; MLD: 2.3, 0.009; V20: 2.9, 0.007; V30: 2.3, 0.004; V40: 2.5, 0.001). Only V20 was a significant risk factor in the non-ICI group, and MLD, V30, and V40 were significant risk factors in the ICI group. The survival and local control rates were superior in the ICI group than in the non-ICI group, but no significance was observed. CONCLUSIONS: Patients receiving ICI after definitive CCRT were more likely to develop RP, which may be related to the lung volume receiving high-dose radiation. Therefore, several factors should be carefully considered for patients with NSCLC.

Biological dosiomic features for the prediction of radiation pneumonitis in esophageal cancer patients.

OBJECTIVE: The purpose of this study was to develop a model using dose volume histogram (DVH) and dosiomic features to predict the risk of radiation pneumonitis (RP) in the treatment of esophageal cancer with radiation therapy and to compare the performance of DVH and dosiomic features after adjustment for the effect of fractionation by correcting the dose to the equivalent dose in 2 Gy (EQD2). MATERIALS AND METHODS: DVH features and dosiomic features were extracted from the 3D dose distribution of 101 esophageal cancer patients. The features were extracted with and without correction to EQD2. A predictive model was trained to predict RP grade ≥ 1 by logistic regression with L1 norm regularization. The models were then evaluated by the areas under the receiver operating characteristic curves (AUCs). RESULT: The AUCs of both DVH-based models with and without correction of the dose to EQD2 were 0.66 and 0.66, respectively. Both dosiomic-based models with correction of the dose to EQD2 (AUC = 0.70) and without correction of the dose to EQD2 (AUC = 0.71) showed significant improvement in performance when compared to both DVH-based models. There were no significant differences in the performance of the model by correcting the dose to EQD2. CONCLUSION: Dosiomic features can improve the performance of the predictive model for RP compared with that obtained with the DVH-based model.

High-dose thoracic radiation therapy for non-small cell lung cancer: a novel grading scale of radiation-induced lung injury for symptomatic radiation pneumonitis.

BACKGROUND: Symptomatic radiation pneumonitis (RP) may be a serious complication after thoracic radiation therapy (RT) for non-small cell lung cancer (NSCLC). This prospective observational study sought to evaluate the utility of a novel radiation-induced lung injury (RILI) grading scale (RGS) for the prediction of RP. MATERIALS AND METHODS: Data of 41 patients with NSCLC treated with thoracic RT of 60-66 Gy were analysed. CT scans were scheduled before RT, one month post-RT, and every three months thereafter for one year. Symptomatic RP was defined as Common Terminology Criteria for Adverse Events grade ≥ 2. RGS grading ranged from 0 to 3. The inter-observer variability of the RGS was assessed by four senior radiologists. CT scans performed 28 ± 10 days after RT were used to analyse the predictive value of the RGS. The change in the RGS severity was correlated to dosimetric parameters. RESULTS: The CT obtained one month post-RT showed RILI in 36 (88%) of patients (RGS grade 0 [5 patients], 1 [25 patients], 2 [6 patients], and 3 [5 patients]). The inter-observer agreement of the RGS grading was high (Kendall's W coefficient of concordance = 0.80, p < 0.01). Patients with RGS grades 2-3 had a significantly higher risk for development of RP (relative risk (RR): 2.4, 95% CI 1.6-3.7, p < 0.01) and RP symptoms within 8 weeks after RT (RR: 4.8, 95% CI 1.3-17.6, p < 0.01) compared to RGS grades 0-1. The specificity and sensitivity of the RGS grades 2-3 in predicting symptomatic RP was 100% (95% CI 80.5-100%) and 45.4% (95% CI 24.4-67.8%), respectively. Increase in RGS severity correlated to mean lung dose and the percentage of the total lung volume receiving 5 Gy. CONCLUSIONS: The RGS is a simple radiologic tool associated with symptomatic RP. A validation study is warranted.

Genetic variations in DNA repair gene NEIL1 associated with radiation pneumonitis risk in lung cancer patients.

BACKGROUND: Radiation pneumonitis (RP) is a common side effect in lung cancer patients who received radiotherapy. Our previous study found genetic variations in DNA repair gene NEIL1 may be a predictor of RP in patients with esophageal cancer. So, we hypothesis genetic variations in NEIL1 gene could affect the risk of RP in lung cancer patients following radiotherapy. METHODS: Genetic variations rs4462560 G>C and rs7402844 C>G in NEIL1 gene were genotyped in 174 lung cancer patients received radio(chemo)therapy. Luciferase assay, real-time PCR and Western blot were used to access the effect of the variants on NEIL1 in HELF and HEF cell lines which were transfected with plasmids containing rs4462560 G>C and rs7402844 C>G. RESULTS: Patients with rs4462560 CC genotype had a lower risk of RP grade ≥2 than GG genotype. Compared with the CC genotype, rs7402844 GG genotype was associated with an increased RP grade ≥2 risk. What is more, rs4462560 G decreased the relative luciferase activity of NEIL1 gene promoter compared with the negative control in vitro, while rs4462560 C can increase the relative luciferase activity. The mRNA and protein level of the NEIL1 gene in rs4462560 G were lower than rs4462560 C. CONCLUSIONS: Genetic variants of NEIL1 are associated with RP risk through regulation of NEIL1 expression and serve as independent biomarkers for prediction of RP in patients treated with thoracic radiotherapy.

Acute Radiation-Induced Hematopoietic Depletion Does Not Alter the Onset or Severity of Pneumonitis in Mice.

Survival from partial-body irradiation (PBI) may be limited by the development of the late lung injury response of pneumonitis. Herein we investigated the hypothesis that acute hematopoietic depletion alters the onset and severity of lung disease in a mouse model. To establish depletion, C3H/HeJ mice received 8 Gy PBI with shielding of only the tibiae, ankles and feet. One week after irradiation, blood lymphocyte and neutrophil counts were each significantly reduced (P < 0.04) in these mice compared to levels in untreated controls or in mice receiving 16 Gy to the whole thorax only. All 8 Gy PBI mice survived to the experimental end point of 16 weeks postirradiation. To determine whether the hematopoietic depletion affects lung disease, groups of mice received 8 Gy PBI plus 8 Gy whole-thorax irradiation (total lung dose of 16 Gy) or 16 Gy whole-thorax irradiation only. The weight loss, survival to onset of respiratory distress (P = 0.17) and pneumonitis score (P = 0.96) of mice that received 8 Gy PBI plus 8 Gy whole-thorax irradiation were not significantly different from those of mice receiving 16 Gy whole-thorax irradiation only. Mice in respiratory distress from PBI plus whole-thorax irradiation had significantly reduced (P = 0.02) blood monocyte counts compared to levels in distressed, whole-thorax irradiated mice, and symptomatic pneumonitis was associated with increased blood neutrophil counts (P = 0.04) relative to measures from irradiated, non-distressed mice. In conclusion, survivable acute hematopoietic depletion by partial-body irradiation did not alter the onset or severity of lethal pneumonitis in the C3H/HeJ mouse model.