Multi-centre evaluation of variation in cumulative dose assessment in reirradiation scenarios.

BACKGROUND AND PURPOSE: Safe reirradiation relies on assessment of cumulative doses to organs at risk (OARs) across multiple treatments. Different clinical pathways can result in inconsistent estimates. Here, we quantified the consistency of cumulative dose to OARs across multi-centre clinical pathways. MATERIAL AND METHODS: We provided DICOM planning CT, structures and doses for two reirradiation cases: head & neck (HN) and lung. Participants followed their standard pathway to assess the cumulative physical and EQD2 doses (with provided α/ß values), and submitted DVH metrics and a description of their pathways. Participants could also submit physical dose distributions from Course 1 mapped onto the CT of Course 2 using their best available tools. To assess isolated impact of image registrations, a single observer accumulated each submitted spatially mapped physical dose for every participating centre. RESULTS: Cumulative dose assessment was performed by 24 participants. Pathways included rigid (n = 15), or deformable (n = 5) image registration-based 3D dose summation, visual inspection of isodose line contours (n = 1), or summation of dose metrics extracted from each course (n = 3). Largest variations were observed in near-maximum cumulative doses (25.4 - 41.8 Gy for HN, 2.4 - 33.8 Gy for lung OARs), with lower variations in volume/dose metrics to large organs. A standardised process involving spatial mapping of the first course dose to the second course CT followed by summation improved consistency for most near-maximum dose metrics in both cases. CONCLUSION: Large variations highlight the uncertainty in reporting cumulative doses in reirradiation scenarios, with implications for outcome analysis and understanding of published doses. Using a standardised workflow potentially including spatially mapped doses improves consistency in determination of accumulated dose in reirradiation scenarios.

Dosimetric evaluation in Helical TomoTherapy for lung SBRT using Monte Carlo-based independent dose verification software.

PURPOSE: To elucidate the dosimetric errors caused by a model-based algorithm in lung stereotactic body radiation therapy (SBRT) with Helical TomoTherapy (HT) using Monte Carlo (MC)-based dose verification software. METHODS: For 38 plans of lung SBRT, the dose calculation accuracy of a treatment planning system (TPS) of HT was compared with the results of DoseCHECK, the commercial MC-based independent verification software. The following indices were extracted to evaluate the correlation of dosimetric errors: (1) target volume, (2) average computed tomography (CT) value of the planning target volume (PTV) margin, and (3) average CT value of surrounding 2-mm area of the PTV (PTV ring). Receiver operating characteristic (ROC) analyses determined the threshold for 5% of differences in PTV D95%. Then, the 38 plans were classified into two groups using the cutoff values of ROC analysis for these three indices. Dosimetric differences between groups were statistically compared using the Mann-Whitney U test. RESULTS: TPS of HT overestimated by more than 5% in the PTV D95% in 16 of 38 plans. The PTV ring showed the strongest correlation with dosimetric differences. The cutoff value for the target volume, the PTV margin, and the PTV ring was 14.7 cc, -754 HU, and -708 HU, respectively. The area under the curve (AUC) for the target volume, the PTV margin, and the PTV ring were 0.835, 0.878, and 0.932, respectively. Dosimetric errors more than 5% were observed when the PTV volume was less than 15 cc or when the CT value around the target was less than -700 HU. CONCLUSION: The TPS of HT might overestimate the PTV dose by more than 5% if any the three indices in this study were below threshold. Therefore, independent verification with an MC-based algorithm should be strongly recommended for lung SBRT in HT.

Equity of travel to access surgery and radiation therapy for lung cancer in New Zealand.

PURPOSE: Centralisation of lung cancer treatment can improve outcomes, but may result in differential access to care for those who do not reside within treatment centres. METHODS: We used national-level cancer registration and health care access data and used Geographic Information Systems (GIS) methods to determine the distance and time to access first relevant surgery and first radiation therapy among all New Zealanders diagnosed with lung cancer (2007-2019; N = 27,869), and compared these outcomes between ethnic groups. We also explored the likelihood of being treated at a high-, medium-, or low-volume hospital. Analysis involved both descriptive and adjusted logistic regression modelling. RESULTS: We found that Maori tend to need to travel further (with longer travel times) to access both surgery (median travel distance: Maori 57 km, European 34 km) and radiation therapy (Maori 75 km, European 35 km) than Europeans. Maori have greater odds of living more than 200 km away from both surgery (adjusted odds ratio [aOR] 1.83, 95% CI 1.49-2.25) and radiation therapy (aOR 1.41, 95% CI 1.25-1.60). CONCLUSIONS: Centralisation of care may often improve treatment outcomes, but it also makes accessing treatment even more difficult for populations who are more likely to live rurally and in deprivation, such as Maori.

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.

Comparative assessment of radiation therapy-induced vasculitis using [18F]FDG-PET/CT in patients with non-small cell lung cancer treated with proton versus photon radiotherapy.

PURPOSE: To assess radiation therapy (RT)-induced vasculitis in patients with non-small cell lung cancer (NSCLC) by examining changes in the uptake of 18F-fluoro-D-deoxyglucose ([18F]FDG) by positron emission tomography/computed tomography (PET/CT) images of the ascending aorta (AA), descending aorta (DA), and aortic arch (AoA) before and after proton and photon RT. METHOD: Thirty-five consecutive locally advanced NSCLC patients were definitively treated with proton (n = 27) or photon (n = 8) RT and concurrent chemotherapy. The patients were prospectively enrolled to undergo [18F]FDG-PET/CT imaging before and 3 months after RT. An adaptive contrast-oriented thresholding algorithm was applied to generate mean standardized uptake values (SUVmean) for regions of interest (ROIs) 3 mm outside and 3 mm inside the outer perimeter of the AA, DA, and AoA. These ROIs were employed to exclusively select the aortic wall and remove the influence of blood pool activity. SUVmeans before and after RT were compared using two-tailed paired t-tests. RESULTS: RT treatments were associated with increased SUVmeans in the AA, DA, and AoA-1.9%, 0.3%, and 1.3% for proton and 15.8%, 9.5%, and 15.5% for photon, respectively. There was a statistically significant difference in the ∆SUVmean (post-RT SUVmean - pre-RT SUVmean) in patients treated with photon RT when compared to ∆SUVmean in patients treated with proton RT in the AA (p = 0.043) and AoA (p = 0.015). There was an average increase in SUVmean that was related to dose for photon patients (across structures), but that was not seen for proton patients, although the increase was not statistically significant. CONCLUSION: Our results suggest that patients treated with photon RT for NSCLC may exhibit significantly more RT-induced inflammation (measured as ∆SUVmean) in the AA and AoA when compared to patients who received proton RT. Knowledge gained from further analyses in larger cohorts could aid in treatment planning and help prevent the significant morbidity and mortality associated with RT-induced vascular complications. TRIAL REGISTRATION: NCT02135679.

Secondary cancer risk assessments following the proton therapy of lung cancer as the functions of field characteristics and patient age.

INTRODUCTION: Radiation-induced secondary cancers relevant to proton therapy are still a main concern among cancer survivors. This study aims to determine the effects of age at exposure and treatment field size on radiation-induced secondary tumors following the proton therapy of lung cancer within out of field organs through the Monte Carlo (MC) simulation approach. MATERIAL AND METHODS: A full MC model of ICRP-110 male phantom was simulated to calculate the absorbed dose corresponding to secondary radiations within distant organs from the tumor volume. Then, the risks of secondary malignancies were estimated by employing the recommended risk model by the Committee of Biological Effects of Ionizing Radiation (BEIR) for different treatment field sizes and various patient ages at exposure. RESULTS: The results revealed that by increasing the patient age from 25 to 45 years, lifetime attributable risk (LAR) values were decreased. Maximum and minimum mortality rates were obtained for the liver and thyroid at the fixed age of 25 years, respectively. Calculated risk values for most near organs to the tumor were higher than those for distant organs. Changing the aperture size from 5 × 5 cm2 to 8 × 10 cm2 resulted in LAR increments with maximum variations of 12.5% for the stomach and a rough variation of 1.12 times in LAR for all exposure ages. CONCLUSION: Our work on whole-body phantom addresses the impact of age at exposure and aperture size on LAR during the proton therapy of lung cancer. To minimize secondary cancer risks relevant to proton therapy of lung cancer, extra attention should be considered.

4D Monte Carlo dose reconstructions using surface motion measurements.

PURPOSE: To investigate the feasibility of a 4D Monte Carlo based dose reconstruction method to study the dosimetric impact of respiratory motion using surface motion measurements for patients undergoing VMAT treatments for Non-Small Cell Lung Cancer. METHODS: The 4Ddefdosxyznrc/EGSnrc algorithm was used to reconstruct VMAT doses delivered to the patients using machine log files and respiratory traces measured with the RADPOS 4D dosimetry system. The RADPOS sensor was adhered to the patient's abdomen prior to each treatment fraction and its position was used as a surrogate for tumour motion. Treatment log files were synchronized with the patient respiratory traces. Patient specific respiratory models were generated from deformable registration of the inhale and exhale 4DCT images and the respiratory traces. The reconstructed doses were compared to planned doses calculated with DOSXYZnrc/EGSnrc on the average-intensity and the exhale phase CT images. RESULTS: Respiratory motion measurements and log files were acquired for 2 patients over 5 treatment fractions each. The motion was predominantly along the anterior/posterior direction (A/P). The average respiratory amplitudes were 8.7 ± 2.7 mm and 10.0 ± 1.2 mm for Patient 1 and 2, respectively. Both patients displayed inter- and intra-fractional variations in the baseline position. Small inter-fractional differences were observed in the reconstructed doses for each patient. Differences between the reconstructed and planned doses were attributed to differences in organ volumes. CONCLUSION: The 4D reconstruction method was successfully implemented for the two patients studied. Small differences between the planned and reconstructed doses were observed due to the small tumour motion of these patients.

Measuring dose in lung identifies peripheral tumour dose inaccuracy in SBRT audit.

PURPOSE: Stereotactic Body Radiotherapy (SBRT) for lung tumours has become a mainstay of clinical practice worldwide. Measurements in anthropomorphic phantoms enable verification of patient dose in clinically realistic scenarios. Correction factors for reporting dose to the tissue equivalent materials in a lung phantom are presented in the context of a national dosimetry audit for SBRT. Analysis of dosimetry audit results is performed showing inaccuracies of common dose calculation algorithms in soft tissue lung target, inhale lung material and at tissue interfaces. METHODS: Monte Carlo based simulation of correction factors for detectors in non-water tissue was performed for the soft tissue lung target and inhale lung materials of a modified CIRS SBRT thorax phantom. The corrections were determined for Gafchromic EBT3 Film and PTW 60019 microDiamond detectors used for measurements of 168 SBRT lung plans in an end-to-end dosimetry audit. Corrections were derived for dose to medium (Dm,m) and dose to water (Dw,w) scenarios. RESULTS: Correction factors were up to -3.4% and 9.2% for in field and out of field lung respectively. Overall, application of the correction factors improved the measurement-to-plan dose discrepancy. For the soft tissue lung target, agreement between planned and measured dose was within average of 3% for both film and microDiamond measurements. CONCLUSIONS: The correction factors developed for this work are provided for clinical users to apply to commissioning measurements using a commercially available thorax phantom where inhomogeneity is present. The end-to-end dosimetry audit demonstrates dose calculation algorithms can underestimate dose at lung tumour/lung tissue interfaces by an average of 2-5%.

A review article on the dosimetry in intraluminal HDR brachytherapy of lung carcinoma.

Lung cancer is one of the most common cancers in the world. Intraluminal brachytherapy (BT) is one of the most adopted treatment modalities for lung malignancies with Ir-192 source in radiotherapy. In intraluminal BT, treatment delivery is required to be very accurate and precise with respect to the plan created in the treatment planning system (TPS). The BT dosimetry is necessary for better treatment outcomes. Therefore in this review article, some relevant studies were identified and analyzed for dosimetric outcomes in intraluminal BT in lung malignancies. The dosimetry in BT for plan verification is not presently in practice, which needs to be performed to check the variation between the planned and measured doses. The necessary dosimetric work done by the various researchers in intraluminal BT such as the Monte Carlo CYLTRAN code was used to calculate and measure the dose rate in any medium. Anthropomorphic phantom was used to measure doses at some distance from the source with Thermo luminescence dosimeters (TLDs). The dosimetric influence of air passage in the bronchus was evaluated with the GEANT4 Monte Carlo method. A pinpoint chamber was used to measure and quantify the impact of inhomogeneity in wax phantom for the Ir-192 source. The Gafchromic films and Monte Carlo methods were used to find the phantom and heterogeneities, which were found to underestimate the dose for the lungs and overestimated for the bones in TPS. The exact tool to quantify the variation in planned and delivered doses should be cost-effective and easy to use possibly with tissue equivalent phantoms and Gafchromic films in lung malignancies treatment.

Prediction of dose deposition matrix using voxel features driven machine learning approach.

OBJECTIVES: A dose deposition matrix (DDM) prediction method using several voxel features and a machine learning (ML) approach is proposed for plan optimization in radiation therapy. METHODS: Head and lung cases with the inhomogeneous medium are used as training and testing data. The prediction model is a cascade forward backprop neural network where the input is the features of the voxel, including 1) voxel to body surface distance along the beamlet axis, 2) voxel to beamlet axis distance, 3) voxel density, 4) heterogeneity corrected voxel to body surface distance, 5) heterogeneity corrected voxel to beamlet axis, and (6) the dose of voxel obtained from the pencil beam (PB) algorithm. The output is the predicted voxel dose corresponding to a beamlet. The predicted DDM was used for plan optimization (ML method) and compared with the dose of MC-based plan optimization (MC method) and the dose of pencil beam-based plan optimization (PB method). The mean absolute error (MAE) value was calculated for full volume relative to the dose of the MC method to evaluate the overall dose performance of the final plan. RESULTS: For patient with head tumor, the ML method achieves MAE value 0.49 × 10-4 and PB has MAE 1.86 × 10-4. For patient with lung tumor, the ML method has MAE 1.42 × 10-4 and PB has MAE 3.72 × 10-4. The maximum percentage difference in PTV dose coverage (D98) between ML and MC methods is no more than 1.2% for patient with head tumor, while the difference is larger than 10% using the PB method. For patient with lung tumor, the maximum percentage difference in PTV dose coverage (D98) between ML and MC methods is no more than 2.1%, while the difference is larger than 16% using the PB method. CONCLUSIONS: In this work, a reliable DDM prediction method is established for plan optimization by applying several voxel features and the ML approach. The results show that the ML method based on voxel features can obtain plans comparable to the MC method and is better than the PB method in achieving accurate dose to the patient, which is helpful for rapid plan optimization and accurate dose calculation. ADVANCES IN KNOWLEDGE: Establishment of a new machine learning method based on the relationship between the voxel and beamlet features for dose deposition matrix prediction in radiation therapy.

Health Economic Evaluation of Proton Therapy for Lung Cancer: A Systematic Review.

BACKGROUND: To our knowledge, there have been no systematic reviews of health economic evaluations of proton therapy specific to lung cancer. METHODS: We conducted this systematic review according to the predefined protocol [PROSPERO CRD42022365869]. We summarized the results of the included studies via structured narrative synthesis. RESULTS: We identified four studies (all used passively scattered proton therapy) from 787 searches. Two cost analyses reported that proton therapy was more costly than photon therapy for early- or locally advanced-stage non-small cell lung cancer, one cost-utility analysis reported that proton therapy was dominated by nonproton therapy in early-stage non-small cell lung cancer, and one cost-utility analysis reported that proton therapy was not cost-effective (vs. photon) in locally advanced non-small cell lung cancer. CONCLUSIONS: Passively scattered proton therapy was more costly and not cost-effective than photon therapy for early- and locally advanced-stage non-small cell lung cancer. Further health economic evaluations regarding modern proton therapy (such as scanning beam) for common radiotherapy indications of lung cancer are eagerly awaited.

Clinical 3D/4D cumulative proton dose assessment methods for thoracic tumours with large motion.

PURPOSE: Despite the anticipated clinical benefits of intensity-modulated proton therapy (IMPT), plan robustness may be compromised due to its sensitivity to patient treatment uncertainties, especially for tumours with large motion. In this study, we investigated treatment course-wise plan robustness for intra-thoracic tumours with large motion comparing a 4D pre-clinical evaluation method (4DREM) to our clinical 3D/4D dose reconstruction and accumulation methods. MATERIALS AND METHODS: Twenty patients with large target motion (>10 mm) were treated with five times layered rescanned IMPT. The 3D-robust optimised plans were generated on the averaged planning 4DCT. Using multiple 4DCTs, treatment plan robustness was assessed on a weekly and treatment course-wise basis through the 3D robustness evaluation method (3DREM, based on averaged 4DCTs), the 4D robustness evaluation method (4DREM, including the time structure of treatment delivery and 4DCT phases) and 4D dose reconstruction and accumulation (4DREAL, based on fraction-wise information). RESULTS: Baseline target motion for all patients ranged from 11-17 mm. For the offline adapted course-wise dose assessment, adequate target dose coverage was found for all patients. The target volume receiving 95% of the prescription dose was consistent between methods with 16/20 patients showing differences < 1%. 4DREAL showed the highest target coverage (99.8 ± 0.6%, p < 0.001), while no differences were observed between 3DREM and 4DREM (99.3 ± 1.3% and 99.4 ± 1.1%, respectively). CONCLUSION: Our results show that intra-thoracic tumours can be adequately treated with IMPT in free breathing for target motion amplitudes up to 17 mm employing any of the accumulation methods. Anatomical changes, setup and range errors demonstrated a more severe impact on target coverage than motion in these patients treated with fractionated proton radiotherapy.

Lack of Adherence to Guideline-Based Imaging Before Subsequent Radiation in Patients with Non-Small Cell Lung Cancer: Impact on Patient Outcomes.

Lung cancer is the leading cause of cancer death within the United States, yet prior studies have shown a lack of adherence to imaging and treatment guidelines in patients with lung cancer. This study evaluated the use of 18F-FDG PET/CT imaging before subsequent radiation therapy (RT) in patients with non-small cell lung cancer (NSCLC), as recommended by National Comprehensive Cancer Network guidelines, and whether the use of this imaging modality impacts cancer-specific survival. Methods: This was a retrospective study of the National Cancer Institute's Surveillance, Epidemiology, and End Results program of Medicare-linked data in patients with NSCLC. Hazard ratios and 95% CIs for overall and cancer-specific survival were estimated for patients diagnosed between 2006 and 2015 who underwent either 18F-FDG PET/CT-based or CT-based imaging before subsequent RT. Results: Significant improvement in cancer-specific survival was found in patients who underwent 18F-FDG PET/CT imaging before subsequent RT, compared with those who underwent CT (hazard ratio, 1.43 [95% CI, 1.32-1.55; P < 0.0001]). Although the National Comprehensive Cancer Network recommends 18F-FDG PET/CT before subsequent RT, 43.6% of patients were imaged with CT alone. Conclusion: Many patients with NSCLC are not being imaged according to national guidelines before subsequent RT, and this omission is associated with a lower cancer-specific survival.

Assessment of the Implementation of Lung Cancer Consensus Statements From the Royal College of Radiologists in 2021; Progress and Barriers.

BACKGROUND: Lung cancer outcomes in the UK are worse than those in many similar countries. The RCR developed a series of 43 consensus statements (CS) to facilitate improvements in care for patients treated with radiotherapy. METHODS: We asked all 61 UK radiotherapy centres to self-assess the implementation of the CS and to describe their departmental key strengths and weaknesses in September 2021. RESULTS: 87% of centres returned their assessments. Whilst developmental activity was seen in most areas for most centres, 24 of the statements were felt to be difficult to implement within the next 2 years by at least one centre. The most frequently reported strengths were in the implementation of SABR (stereotactic body radiotherapy), concurrent chemoradiation for non-small cell lung cancer and technological aspects of treatment planning. The most frequently described departmental weaknesses were in pre-habilitation, timeliness of PET/CT scans and prophylaxis for Pneumocystis jiroveci Pneumonia (PJP). Barriers to implementation were often due to insufficient resource, a requirement for organisations to work together, and a perceived lack of evidence base. Strengths were often attributed to good team working, a local champion and being an early adopter. CONCLUSIONS: This work confirms the commitment of lung cancer radiotherapy teams across the UK to improve outcomes for their patients. Most of the statements have been implemented at least partially. Themes have been identified to aid further progress, one of which is a requirement for significant investment.

Statistical breathing curve sampling to quantify interplay effects of moving lung tumors in a 4D Monte Carlo dose calculation framework.

PURPOSE: The interplay between respiratory tumor motion and dose application by intensity modulated radiotherapy (IMRT) techniques can potentially lead to undesirable and non-intuitive deviations from the planned dose distribution. We developed a 4D Monte Carlo (MC) dose recalculation framework featuring statistical breathing curve sampling, to precisely simulate the dose distribution for moving target volumes aiming at a comprehensive assessment of interplay effects. METHODS: We implemented a dose accumulation tool that enables dose recalculations of arbitrary breathing curves including the actual breathing curve of the patient. This MC dose recalculation framework is based on linac log-files, facilitating a high temporal resolution up to 0.1 s. By statistical analysis of 128 different breathing curves, interplay susceptibility of different treatment parameters was evaluated for an exemplary patient case. To facilitate prospective clinical application in the treatment planning stage, in which patient breathing curves or linac log-files are not available, we derived a log-file free version with breathing curves generated by a random walk approach. Interplay was quantified by standard deviations σ in D5%, D50% and D95%. RESULTS: Interplay induced dose deviations for single fractions were observed and evaluated for IMRT and volumetric arc therapy (σD95% up to 1.3 %) showing a decrease with higher fraction doses and an increase with higher MU rates. Interplay effects for conformal treatment techniques were negligible (σ<0.1%). The log-file free version and the random walk generated breathing curves yielded similar results (deviations in σ< 0.1 %) and can be used as substitutes for interplay assessment. CONCLUSION: It is feasible to combine statistically sampled breathing curves with MC dose calculations. The universality of the presented framework allows comprehensive assessment of interplay effects in retrospective and prospective clinically relevant scenarios.

Race is a Risk Factor for the Deferral of Resection and Radiation for Early-Stage Lung Cancer.

PURPOSE: There remain profound race-related disparities in the treatment of non-small cell lung cancer (NSCLC). Deferral of operative management for early-stage disease is recognized as driver of this disparity. Black race has been associated with higher rates of surgical deferral. It remains unclear how race impacts likelihood of receiving radiation therapy after declining surgical management of NSCLC. PATIENTS AND METHODS: A retrospective cohort analysis was completed using data from the National Cancer Database (NCBD) for patients 18 and over with stage I NSCLC offered surgical resection from 2004 to 2015 (N = 89,462). Multivariable logistic regression identified predictors of surgical deferral and predictors for deferral of radiation after deferral of surgery. Kaplan-Meier survival analysis with log-rank tests and multivariable Cox proportional hazards regressions were performed. RESULTS: 87,293 (97.6%) patients underwent surgery, 2169 (2.4%) deferred. Patients who deferred had 2.1 times higher hazard ratio for mortality, (HR = 2.08, [1.97, 2.29], P < .001). Of those that deferred, 1250 (57.6%) received postdeferral radiation. Compared to White patients, Black patients had OR of 1.82 for deferring both surgery and radiation (aOR: 1.82, [1.31, 2.53], P < .001) and Asian and Pacific Island (API) patients had an OR of 2.67 (aOR: 2.67, [1.27, 4.64], P = .008). Other predictors of deferral of therapy included: Medicare or lack of insurance, and treatment at nonacademic medical centers. CONCLUSION: Insurance status and Black race, and API race are associated with deferring surgical therapy and radiation therapy for NSCLC. These findings are consistent with the large body of work showing worse outcomes for treatment of NSCLC in minority patients.

Assessment of a computed tomography-based radiomics approach for assessing lung function in lung cancer patients.

PURPOSE: We aimed to assess radiomics approaches for estimating three pulmonary function test (PFT) results (forced expiratory volume in one second [FEV1], forced vital capacity [FVC], and the ratio of FEV1 to FVC [FEV1/FVC]) using data extracted from chest computed tomography (CT) images. METHODS: This retrospective study included 85 lung cancer patients (mean age, 75 years ±8; 69 men) who underwent stereotactic body radiotherapy between 2012 and 2020. Their pretreatment chest breath-hold CT and PFT data before radiotherapy were obtained. A total of 107 radiomics features (Shape: 14, Intensity: 18, Texture: 75) were extracted using two methods: extraction of the lung tissue (<-250 HU) (APPROACH 1), and extraction of small blood vessels and lung tissue (APPROACH 2). The PFT results were estimated using the least absolute shrinkage and selection operator regression. Pearson's correlation coefficients (r) were determined for all PFT results, and the area under the curve (AUC) was calculated for FEV1/FVC (<70 %). Finally, we compared our approaches with the conventional formula (Conventional). RESULTS: For the estimated FEV1/FVC, the Pearson's r were 0.21 (P =.06), 0.69 (P <.01), and 0.73 (P <.01) for Conventional, APPROACH 1, and APPROACH 2, respectively; the AUCs for FEV1/FVC (<70 %) were 0.67 (95 % confidence interval [CI]: 0.55, 0.79), 0.82 (CI: 0.72, 0.91; P =.047) and 0.86 (CI: 0.78, 0.94; P =.01), respectively. CONCLUSIONS: The radiomics approach performed better than the conventional equation and may be useful for assessing lung function based on CT images.

Assessment of Organ Dose Reduction Using Dynamic Conformal Arc and Static Field with FFF Beams for SBRT in Lung Cancer.

BACKGROUND: The aim of this study is to compare the dose delivered to the organs at risk (OAR), using static beams (SF) and a dynamic conformational arc (DCA) with flattening filter free (FFF) beams, for lung stereotactic body radiation therapy (SBRT). METHODS: 100 patients with lung cancer were treated with SBRT, using FF beams (TrueBeam STx, 6 MV, IQ = 0.67, 600 MU/min), separated into two groups: DCA (50 patients) and SF (50 patients). These patients were retrospectively re-planned using 6XFFF beams, IQ = 0.63, 1400 MU/min. The beam-on time and dosimetric gain on planning target volume (PTV) and OARs (heart, spinal cord, planning risk volume (PRV) of spinal cord, esophagus, lungs and ribs) were analyzed according to tumor location. The comparison of median values was performed using the non-parametric Wilcoxon test (significance level: p < 0.05). RESULTS: PTV coverage was 98.90% versus 98.40% (DCA) and 98.8% versus 98.3% (SF) for the FF and FFF beams, respectively. The median dosimetric gain to the heart, spinal cord, PRV spinal cord, esophagus and lungs was 6% (4-11%) in the central region and 8% (2-23%) in the peripheral region, using FFF (p < 0.05). The dose received by the ribs decreases by 5-6 Gy, using FFF beams. The median gain in beam-on time ranged from 31% to 34% for SF and from 44 to 52% for DCA using FFF beams. CONCLUSIONS: The FFF beams reduce the dose received by all OARs, regardless of the used technique or tumor location, reducing treatment delivery time as well.