Stereotactic body radiation therapy (SBRT) for early stage non-small cell lung cancer (NSCLC): contemporary insights and advances

Improved commissioning of lung stereotactic body radiotherapy using a customized respiratory motion Phantom: a single- institutional study

Stereotactic body radiation therapy (SBRT) involves delivering high doses of radiation with geometric precision in a few hypofractionated schedules. In lung SBRT, respiratory motion is an additional concern as it could cause the delivered dose distribution to deviate from the treatment plan. Therefore, it is crucial to conduct accurate commissioning tests on a dynamic phantom. In this study, the QUASAR™ Respiratory Motion Phantom was customized using 3D-printed parts to minimize motion-induced errors in measurements. The customisations included a specialized ion chamber insert designed to move with the tumour and measure the average dose at its centre. A film insert was also developed for secure fixation, enabling precise dose verification on a static plane while minimizing the risk of friction-related damage. The quality assurance (QA) tests were performed on the plans created for phantom studies indicated that ion chamber measurements were within 1.9% of the planned dose, and film gamma analysis demonstrated pass rates over 95% using the 3%/1 mm criteria. A set of SBRT volumetric modulated arc therapy (VMAT) plans were created for a suite of test patients using both flattened and flattening filter free (FFF) 6 MV beams and utilising robust optimization. A standardized patient-specific QA protocol was used to evaluate the treatment plans of 20 test patients, yielding film gamma pass rates above 98.8%. The suggested approach, using the 3D-printed inserts, effectively mitigated dose-blurring, providing a robust tool for lung SBRT commissioning and ensuring the reliability of lung cancer treatment with SBRT.

Effect of Treatment Delivery Schedule for Patients With Early-Stage Non-Small Cell Lung Cancer Treated With Stereotactic Ablative Radiation Therapy: A Population-Based Analysis

PURPOSE

The optimal SABR treatment delivery schedule in stage I non-small cell lung cancer (NSCLC) remains unclear. This population-based study investigated grade ≥2 toxicity rates, local failure (LF), and overall survival (OS) in patients treated with 48 Gy in 4 fractions scheduled every other day versus daily with weekends and consecutive daily without weekends.

METHODS AND MATERIALS

Between January 2019 and June 2022, treatment records using 48 Gy in 4 fractions were extracted from a provincial cancer registry and grouped by delivery as every other day, daily with weekends, or consecutive daily without weekends. Toxicity events were recorded using National Cancer Institute Common Terminology Criteria for Adverse Events, version 5.0. The Kaplan-Meier method was used to compute OS and LF was calculated using cumulative incidence methods with death as a competing risk. Cox regression analyses and Fine-Gray modeling was used to assess for variables associated with OS and LF, respectively.

RESULTS

Of 404 patients meeting study criteria, 190, 111, and 103 received SABR every other day, daily with weekends, and consecutive daily without weekends, respectively. More patients receiving SABR daily with weekends were medically inoperable and more patients receiving SABR consecutive daily without weekends had tumors abutting the chest wall. Median follow-up time was 29.5 months (IQR, 19.2-38.4 months). Overall toxicity was low, with crude rates of acute and late grade ≥2 toxicity not being statistically different among the groups. No grade 4 or 5 toxicities were recorded. LF rates at 24 months were not different at 7.5% (95% CI, 3.7-11.3), 9.5% (95% CI, 3.9-15.1), and 11.0% (95% CI, 4.9-17.2) for the every other day, daily with weekends, and consecutive daily without weekends groups, respectively (P = .60). Schedules of daily with weekends and consecutive daily without weekends were not associated with LF. Similarly, no significant differences in median OS were found among the every other day, daily with weekends, and consecutive daily without weekends groups at 47.5 months (95% CI, 39.26-55.74), 52.7 months (95% CI, 34.7-70.7), and 49.0 months (95% CI, 31.6-66.4), respectively. Schedules of daily with weekends and consecutive daily without weekends were not associated with OS.

CONCLUSIONS

This population-based study demonstrated no statistically significant differences in grade ≥2 toxicity rates, LF, and OS for patients with stage I NSCLC treated with lung SABR using 48 Gy in 4 fractions delivered every other day, daily with weekends, and consecutive daily without weekends. Patient convenience and optimization of resources may be considered when choosing a lung SABR treatment delivery schedule.

High barriers to treatment are associated with stereotactic radiation instead of surgery for patients with operable stage I non-small cell lung cancer†

OBJECTIVES

Although surgery is considered the standard of care for early-stage lung cancer, there has been increased use of stereotactic radiotherapy for operable patients in recent years. Given that this modality may be perceived as a more practical treatment, we hypothesized that it might be more often delivered to patients who experience barriers to care.

METHODS

The National Cancer Database (2018-2020) was queried for patients with clinical stage IA non-small cell lung cancer treated with surgery or stereotactic radiotherapy (48-60 Gy, 3-5 fractions), excluding patients with contraindications to surgery. Patients who had all the following characteristics were categorized as experiencing 'high barriers' to treatment: income below median national levels, lack of private insurance, treatment at a community facility and residence in non-metropolitan areas. Using multivariable logistic regression, the association between high barriers to treatment and stereotactic radiotherapy use was estimated.

RESULTS

A total of 60 829 patients were included, of whom 3382 (5.6%) experienced high barriers to treatment. Among them, 13 535 (22.3%) underwent stereotactic radiotherapy and 47 294 (77.7%) underwent surgery. Overall, more patients undergoing stereotactic radiotherapy faced high barriers to treatment compared to those who received surgery (8.6% vs 4.7%, P < 0.001). Geographic region was associated with the delivery of stereotactic radiotherapy (P < 0.001). The magnitude of such association was stronger among those who faced high barriers. In multivariable analysis, experiencing high barriers to treatment remained associated with receiving stereotactic radiotherapy (OR: 1.46, 95% CI 1.35-1.58).

CONCLUSIONS

The use of stereotactic radiotherapy is more prevalent among patients facing barriers to care. Further research is needed to clarify the role of this treatment modality in early-stage lung cancer.

Consecutive Daily Versus Every Other Day Stereotactic Body Radiation Therapy Scheduling for Stage I Non-small Cell Lung Cancer

Purpose

The optimal delivery schedule for stereotactic body radiation therapy (SBRT) in treating stage I non-small cell lung cancer (NSCLC) is unknown. This study used the National Cancer Database to examine daily versus every other day (QOD) SBRT scheduling, including trends over time and association with survival.

Methods and Materials

The National Cancer Database was used to retrospectively identify patients with stage I NSCLC treated with 3-, 4-, or 5-fraction of SBRT between 2004 and 2016. Survival analysis was performed using the Kaplan-Meier method and Cox regression modeling.

Results

Of 15,269 patients, 3927 (25.7%) received SBRT daily, and 11,342 (74.3%) received treatment QOD. The use of QOD treatment increased from 63.2% in 2007 to 78.3% in 2016, and 5-fraction SBRT increased from 3.7% in 2004 to 51.4% in 2016 (both P < .0001). QOD 5-fraction became the most prevalent scheduling from 2012 to 2016 (28.5% in 2012 to 41.6% in 2016). Factors significantly associated with daily SBRT scheduling included number of fractions, race, lower income, lower comorbidities, and treatment at academic/research programs (all P ≤ .01).Median survival for daily SBRT was 37.9 months versus 38.4 months for QOD (P = .4). On multivariable analysis, no difference was found in overall survival between daily versus QOD scheduling (adjusted hazard ratio [aHR], 0.99; 95% confidence interval [CI], 0.94-1.04; P = .55). Five-fraction SBRT was associated with worse survival versus 3 fractions (aHR, 1.09; 95% CI, 1.03-1.15; P = .002). With 3-fraction SBRT, QOD treatment was associated with improved survival versus daily treatment (aHR, 0.91; 95% CI, 0.84-0.98; P = .02). With 5-fraction SBRT, QOD treatment was associated with worse survival versus daily treatment (aHR, 1.11; 95% CI, 1.02-1.22; P = .02).

Conclusions

QOD SBRT schedules were more frequently used to treat stage I NSCLC than daily regimens by a factor of 3:1, and QOD 5-fraction SBRT became the most common dose schedule after 2012. Three-fraction QOD SBRT was associated with improved survival versus daily, whereas 5-fraction QOD SBRT was associated with worse survival versus daily.

Non-homogenous intratumor ionizing radiation doses synergize with PD1 and CXCR2 blockade

The efficacy and side effects of radiotherapy (RT) depend on parameters like dose and the volume of irradiated tissue. RT induces modulations of the tumor immune microenvironment (TIME) that are dependent on the dose. Low dose RT (LDRT, i.e., single doses of 0.5-2 Gy) has been shown to promote immune infiltration into the tumor. Here we hypothesize that partial tumor irradiation combining the immunostimulatory/non-lethal properties of LDRT with cell killing/shrinkage properties of high dose RT (HDRT) within the same tumor mass could enhance anti-tumor responses when combined with immunomodulators. In models of colorectal and breast cancer in immunocompetent female mice, partial irradiation (PI) with millimetric precision to deliver LDRT (2 Gy) and HDRT (16 Gy) within the same tumor induces substantial tumor control when combined with anti-PD1. Using flow cytometry, cytokine profiling and single-cell RNA sequencing, we identify a crosstalk between the TIME of the differentially irradiated tumor volumes. PI reshapes tumor-infiltrating CD8+ T cells into more cytotoxic and interferon-activated phenotypes but also increases the infiltration of pro-tumor neutrophils driven by CXCR2. The combination of the CXCR2 antagonist SB225002 with PD1 blockade and PI improves tumor control and mouse survival. Our results suggest a strategy to reduce RT toxicity and improve the therapeutic index of RT and immune checkpoint combinations.

Use of Personalized Ultra-Fractionated Stereotactic Adaptive Radiotherapy for Oligometastatic Lung Adenocarcinoma: Leveraging CT-Guided Online Adaptive Radiotherapy

Management of oligometastatic non-small cell lung cancer (OM-NSCLC) has changed considerably in recent years, as these patients were found to have better survival with systemic therapy followed by consolidative radiation. Stereotactic body radiotherapy (SBRT), characterized by high doses of radiation delivered in a limited number of fractions, has been shown to have improved local control compared to conventionally fractionated radiation in early-stage lung cancer, but its use in large tumors, ultra-central tumors, or mediastinal nodal regions is limited due to concerns of toxicity to nearby serial mediastinal structures. Recent improvements in image guidance and fast replanning allow adaptive radiotherapy to be used to personalize treatment to the patient's daily anatomy and ensure accurate dose delivery to the tumor while minimizing dose and toxicity to normal. Adaptive SBRT can expand its use into ultra-central tumors that otherwise may not be amenable to SBRT or enable alternative fractionation schedules such as personalized ultra-fractionated stereotactic adaptive radiotherapy (PULSAR) with one-month intervals between fractions. In this case, we report a patient initially presenting with bulky OM-NSCLC of the left lung and mediastinum with an isolated left femur metastasis who was referred for consolidative radiotherapy after systemic therapy. We demonstrate how CT-guided online adaptive radiotherapy to the lung and mediastinum can be used despite the long time interval between treatments. In addition, adaptive plans lead to a substantial decrease in the heart dose, with moderate decreases in other organs compared to non-adaptive plans. This case demonstrates the feasibility of using adaptive radiotherapy for PULSAR of ultra-central OM-NSCLC.

Acute Large Dose Irradiation Sensitizes Surviving Cells to Subsequent Irradiation; Implications for Stereotactic Body Radiation Therapy

To determine if the radiation sensitivity of cells that survive acute high-dose radiation exposure used in stereotactic body radiation therapy (SBRT), differs from the sensitivity of non-irradiated cells and cells that survive multiple 2 Gy doses of radiation. Isogenic rodent and two human tumor cell lines were exposed to 14 × 2 Gy of radiation, or a single acute dose of 12 Gy. The most resistant cell line was also exposed to an acute dose of 15 Gy. One week after 12 Gy, and 4 days after 14 × 2 Gy, surviving cells were exposed to 0-8 Gy in 2 Gy doses and cell survival was assessed by colony formation. In addition, the colony forming efficiency of 12 Gy survivors was evaluated for 1 month postirradiation. For cells exposed to 15 Gy, the response of surviving cells to 6 Gy was determined for up to 35 days postirradiation and compared to the 6 Gy surviving fraction of control cells. The radiation sensitivity of cells that survived 12 Gy exposure, and cells that survived 14 fractions of 2 Gy irradiation did not differ from the response of unirradiated control cells. However, the growth rate and colony forming efficiency of 12 Gy survivors was transiently reduced for greater than 2 weeks postirradiation. In contrast to the unchanged sensitivity of 12 Gy surviving cells at day 7 postirradiation, 15 Gy survivors exhibited enhanced sensitivity to radiation for up to 21 days postirradiation and suggests a biological basis for SBRT.

Adjuvant Novel Nanocarrier-Based Targeted Therapy for Lung Cancer

Lung cancer has the lowest survival rate due to its late-stage diagnosis, poor prognosis, and intra-tumoral heterogeneity. These factors decrease the effectiveness of treatment. They release chemokines and cytokines from the tumor microenvironment (TME). To improve the effectiveness of treatment, researchers emphasize personalized adjuvant therapies along with conventional ones. Targeted chemotherapeutic drug delivery systems and specific pathway-blocking agents using nanocarriers are a few of them. This study explored the nanocarrier roles and strategies to improve the treatment profile's effectiveness by striving for TME. A biofunctionalized nanocarrier stimulates biosystem interaction, cellular uptake, immune system escape, and vascular changes for penetration into the TME. Inorganic metal compounds scavenge reactive oxygen species (ROS) through their photothermal effect. Stroma, hypoxia, pH, and immunity-modulating agents conjugated or modified nanocarriers co-administered with pathway-blocking or condition-modulating agents can regulate extracellular matrix (ECM), Cancer-associated fibroblasts (CAF),Tyro3, Axl, and Mertk receptors (TAM) regulation, regulatory T-cell (Treg) inhibition, and myeloid-derived suppressor cells (MDSC) inhibition. Again, biomimetic conjugation or the surface modification of nanocarriers using ligands can enhance active targeting efficacy by bypassing the TME. A carrier system with biofunctionalized inorganic metal compounds and organic compound complex-loaded drugs is convenient for NSCLC-targeted therapy.

Faster and lower dose imaging: evaluating adaptive, constant gantry velocity and angular separation in fast low-dose 4D cone beam CT imaging

BACKGROUND

The adoption of four-dimensional cone beam computed tomography (4DCBCT) for image-guided lung cancer radiotherapy is increasing, especially for hypofractionated treatments. However, the drawbacks of 4DCBCT include long scan times (∼240 s), inconsistent image quality, higher imaging dose than necessary, and streaking artifacts. With the emergence of linear accelerators that can acquire 4DCBCT scans in a short period of time (9.2 s) there is a need to examine the impact that these very fast gantry rotations have on 4DCBCT image quality.

PURPOSE

This study investigates the impact of gantry velocity and angular separation between x-ray projections on image quality and its implication for fast low-dose 4DCBCT with emerging systems, such as the Varian Halcyon that provide fast gantry rotation and imaging. Large and uneven angular separation between x-ray projections is known to reduce 4DCBCT image quality through increased streaking artifacts. However, it is not known when angular separation starts degrading image quality. The study assesses the impact of constant and adaptive gantry velocity and determines the level when angular gaps impair image quality using state-of-the-art reconstruction methods.

METHODS

This study considers fast low-dose 4DCBCT acquisitions (60-80 s, 200-projection scans). To assess the impact of adaptive gantry rotations, the angular position of x-ray projections from adaptive 4DCBCT acquisitions from a 30-patient clinical trial were analyzed (referred to as patient angular gaps). To assess the impact of angular gaps, variable and static angular gaps (20°, 30°, 40°) were introduced into evenly separated 200 projections (ideal angular separation). To simulate fast gantry rotations, which are on emerging linacs, constant gantry velocity acquisitions (9.2 s, 60 s, 120 s, 240 s) were simulated by sampling x-ray projections at constant intervals using the patient breathing traces from the ADAPT clinical trial (ACTRN12618001440213). The 4D Extended Cardiac-Torso (XCAT) digital phantom was used to simulate projections to remove patient-specific image quality variables. Image reconstruction was performed using Feldkamp-Davis-Kress (FDK), McKinnon-Bates (MKB), and Motion-Compensated-MKB (MCMKB) algorithms. Image quality was assessed using Structural Similarity-Index-Measure (SSIM), Contrast-to-Noise-Ratio (CNR), Signal-to-Noise-Ratio (SNR), Tissue-Interface-Width-Diaphragm (TIW-D), and Tissue-Interface-Width-Tumor (TIW-T).

RESULTS

Patient angular gaps and variable angular gap reconstructions produced similar results to ideal angular separation reconstructions, while static angular gap reconstructions produced lower image quality metrics. For MCMKB-reconstructions, average patient angular gaps produced SSIM-0.98, CNR-13.6, SNR-34.8, TIW-D-1.5 mm, and TIW-T-2.0 mm, static angular gap 40° produced SSIM-0.92, CNR-6.8, SNR-6.7, TIW-D-5.7 mm, and TIW-T-5.9 mm and ideal produced SSIM-1.00, CNR-13.6, SNR-34.8, TIW-D-1.5 mm, and TIW-T-2.0 mm. All constant gantry velocity reconstructions produced lower image quality metrics than ideal angular separation reconstructions regardless of the acquisition time. Motion compensated reconstruction (MCMKB) produced the highest contrast images with low streaking artifacts.

CONCLUSION

Very fast 4DCBCT scans can be acquired provided that the entire scan range is adaptively sampled, and motion-compensated reconstruction is performed. Importantly, the angular separation between x-ray projections within each individual respiratory bin had minimal effect on the image quality of fast low-dose 4DCBCT imaging. The results will assist the development of future 4DCBCT acquisition protocols that can now be achieved in very short time frames with emerging linear accelerators.

Stereotactic body radiotherapy for early-stage lung cancer: a systematic review on the choice of photon energy and linac flattened/unflattened beams

SBRT is an effective local treatment for patients with early-stage non-small cell lung cancer (NSCLC). This treatment is currently used in patients who have poor lung function or who decline surgery. As SBRT usually has small PTV margins, reducing the beam-on-time (BOT) is beneficial for accurate dose delivery by minimising intrafraction motion as well as improved patient comfort. Removal of the linear accelerator flattening filter can provide a higher dose rate which results in a faster treatment. In addition, the choice of photon energy can also affect the dose distribution to the target and the organs-at-risk (OAR). In this systematic review, studies analysing the choice of various photon beam energies, with a flattening filter or flattening filter free (FFF), were compared for their overall dosimetric benefit in the SBRT treatment for early-stage NSCLC. It was found that FFF treatment delivers a comparatively more conformal dose distribution, as well as a better homogeneity index and conformity index, and typically reduces BOT by between 30 and 50%. The trade-off may be a minor increase in monitor units for FFF treatment found in some studies but not others. Target conformity and OAR sparing, particularly lung doses appear better with 6MV FFF, but 10MV FFF was marginally more advantageous for skin sparing and BOT reduction. The favourable beam modality for clinical use would depend on the individual case, for which tumour size and depth, radiotherapy technique, as well as fractionation scheme need to be taken into account.

AI/ML advances in non-small cell lung cancer biomarker discovery

Lung cancer is the leading cause of cancer deaths among both men and women, representing approximately 25% of cancer fatalities each year. The treatment landscape for non-small cell lung cancer (NSCLC) is rapidly evolving due to the progress made in biomarker-driven targeted therapies. While advancements in targeted treatments have improved survival rates for NSCLC patients with actionable biomarkers, long-term survival remains low, with an overall 5-year relative survival rate below 20%. Artificial intelligence/machine learning (AI/ML) algorithms have shown promise in biomarker discovery, yet NSCLC-specific studies capturing the clinical challenges targeted and emerging patterns identified using AI/ML approaches are lacking. Here, we employed a text-mining approach and identified 215 studies that reported potential biomarkers of NSCLC using AI/ML algorithms. We catalogued these studies with respect to BEST (Biomarkers, EndpointS, and other Tools) biomarker sub-types and summarized emerging patterns and trends in AI/ML-driven NSCLC biomarker discovery. We anticipate that our comprehensive review will contribute to the current understanding of AI/ML advances in NSCLC biomarker research and provide an important catalogue that may facilitate clinical adoption of AI/ML-derived biomarkers.

Long-Term Survival and Failure Outcomes of Single-Fraction Stereotactic Body Radiation Therapy in Early Stage NSCLC

INTRODUCTION

This study aims to report our 13-year institutional experience with single-fraction stereotactic body radiation therapy (SF-SBRT) for early stage NSCLC.

METHODS

A single-institutional retrospective review of patients with biopsy-proven peripheral cT1-2N0M0 NSCLC undergoing definitive SF-SBRT between September 2008 and May 2022 was performed. All patients were treated to 27 Gy with heterogeneity corrections or 30 Gy without. Primary outcomes were overall survival and progression-free survival. Secondary outcomes included local failure, nodal failure, distant failure, and second primary lung cancer.

RESULTS

Among 263 eligible patients, the median age was 76 years (interquartile range [IQR]: 70-81 y) and median follow-up time was 27.2 months (IQR: 14.25-44.9 mo). Median tumor size was 1.9 cm (IQR: 1.4-2.6 cm), and 224 (85%) tumors were T1. There were 92 patients (35%) alive at the time of analysis with a median follow-up of 34.0 months (IQR: 16.6-50.0 mo). Two- and five-year overall survival was 65% and 26%, respectively. A total of 74 patients (28%) developed disease progression. Rates of five-year local failure, nodal failure, distant failure, and second primary lung cancer were 12.7%, 14.7%, 23.5%, and 12.0%, respectively.

CONCLUSIONS

Consistent with multiple prospective randomized trials, in a large real-world retrospective cohort, SF-SBRT for peripheral early stage NSCLC was an effective treatment approach.

Development of a multi-feature-combined model: proof-of-concept with application to local failure prediction of post-SBRT or surgery early-stage NSCLC patients

Objective

To develop a Multi-Feature-Combined (MFC) model for proof-of-concept in predicting local failure (LR) in NSCLC patients after surgery or SBRT using pre-treatment CT images. This MFC model combines handcrafted radiomic features, deep radiomic features, and patient demographic information in an integrated machine learning workflow.

Methods

The MFC model comprised three key steps. (1) Extraction of 92 handcrafted radiomic features from the GTV segmented on pre-treatment CT images. (2) Extraction of 512 deep radiomic features from pre-trained U-Net encoder. (3) The extracted handcrafted radiomic features, deep radiomic features, along with 4 patient demographic information (i.e., gender, age, tumor volume, and Charlson comorbidity index), were concatenated as a multi-dimensional input to the classifiers for LR prediction. Two NSCLC patient cohorts from our institution were investigated: (1) the surgery cohort includes 83 patients with segmentectomy or wedge resection (7 LR), and (2) the SBRT cohort includes 84 patients with lung SBRT (9 LR). The MFC model was developed and evaluated independently for both cohorts, and was subsequently compared against the prediction models based on only handcrafted radiomic features (R models), patient demographic information (PI models), and deep learning modeling (DL models). ROC with AUC was adopted to evaluate model performance with leave-one-out cross-validation (LOOCV) and 100-fold Monte Carlo random validation (MCRV). The t-test was performed to identify the statistically significant differences.

Results

In LOOCV, the AUC range (surgery/SBRT) of the MFC model was 0.858-0.895/0.868-0.913, which was higher than the three other models: 0.356-0.480/0.322-0.650 for PI models, 0.559-0.618/0.639-0.682 for R models, and 0.809/0.843 for DL models. In 100-fold MCRV, the MFC model again showed the highest AUC results (surgery/SBRT): 0.742-0.825/0.888-0.920, which were significantly higher than PI models: 0.464-0.564/0.538-0.628, R models: 0.557-0.652/0.551-0.732, and DL models: 0.702/0.791.

Conclusion

We successfully developed an MFC model that combines feature information from multiple sources for proof-of-concept prediction of LR in patients with surgical and SBRT early-stage NSCLC. Initial results suggested that incorporating pre-treatment patient information from multiple sources improves the ability to predict the risk of local failure.

Clinical Nomogram Using Novel Computed Tomography-Based Radiomics Predicts Survival in Patients With Non-Small-Cell Lung Cancer Treated With Stereotactic Body Radiation Therapy

PURPOSE

Improved survival prediction and risk stratification in non-small-cell lung cancer (NSCLC) would lead to better prognosis counseling, adjuvant therapy selection, and clinical trial design. We propose the persistent homology (PHOM) score, the radiomic quantification of solid tumor topology, as a solution.

MATERIALS AND METHODS

Patients diagnosed with stage I or II NSCLC primarily treated with stereotactic body radiation therapy (SBRT) were selected (N = 554). The PHOM score was calculated for each patient's pretreatment computed tomography scan (October 2008-November 2019). PHOM score, age, sex, stage, Karnofsky Performance Status, Charlson Comorbidity Index, and post-SBRT chemotherapy were predictors in the Cox proportional hazards models for OS and cancer-specific survival. Patients were split into high- and low-PHOM score groups and compared using Kaplan-Meier curves for overall survival (OS) and cumulative incidence curves for cause-specific death. Finally, we generated a validated nomogram to predict OS, which is publicly available at Eashwarsoma.Shinyapps.

RESULTS

PHOM score was a significant predictor for OS (hazard ratio [HR], 1.17; 95% CI, 1.07 to 1.28) and was the only significant predictor for cancer-specific survival (1.31; 95% CI, 1.11 to 1.56) in the multivariable Cox model. The median survival for the high-PHOM group was 29.2 months (95% CI, 23.6 to 34.3), which was significantly worse compared with the low-PHOM group (45.4 months; 95% CI, 40.1 to 51.8; P < .001). The high-PHOM group had a significantly greater chance of cancer-specific death at post-treatment month 65 (0.244; 95% CI, 0.192 to 0.296) compared with the low-PHOM group (0.171; 95% CI, 0.123 to 0.218; P = .029).

CONCLUSION

The PHOM score is associated with cancer-specific survival and predictive of OS. Our developed nomogram can be used to inform clinical prognosis and assist in making post-SBRT treatment considerations.

Stereotactic Magnetic Resonance-Guided Adaptive and Non-Adaptive Radiotherapy on Combination MR-Linear Accelerators: Current Practice and Future Directions

Stereotactic body radiotherapy (SBRT) is an effective radiation therapy technique that has allowed for shorter treatment courses, as compared to conventionally dosed radiation therapy. As its name implies, SBRT relies on daily image guidance to ensure that each fraction targets a tumor, instead of healthy tissue. Magnetic resonance imaging (MRI) offers improved soft-tissue visualization, allowing for better tumor and normal tissue delineation. MR-guided RT (MRgRT) has traditionally been defined by the use of offline MRI to aid in defining the RT volumes during the initial planning stages in order to ensure accurate tumor targeting while sparing critical normal tissues. However, the ViewRay MRIdian and Elekta Unity have improved upon and revolutionized the MRgRT by creating a combined MRI and linear accelerator (MRL), allowing MRgRT to incorporate online MRI in RT. MRL-based MR-guided SBRT (MRgSBRT) represents a novel solution to deliver higher doses to larger volumes of gross disease, regardless of the proximity of at-risk organs due to the (1) superior soft-tissue visualization for patient positioning, (2) real-time continuous intrafraction assessment of internal structures, and (3) daily online adaptive replanning. Stereotactic MR-guided adaptive radiation therapy (SMART) has enabled the safe delivery of ablative doses to tumors adjacent to radiosensitive tissues throughout the body. Although it is still a relatively new RT technique, SMART has demonstrated significant opportunities to improve disease control and reduce toxicity. In this review, we included the current clinical applications and the active prospective trials related to SMART. We highlighted the most impactful clinical studies at various tumor sites. In addition, we explored how MRL-based multiparametric MRI could potentially synergize with SMART to significantly change the current treatment paradigm and to improve personalized cancer care.

Emerging precision neoadjuvant systemic therapy for patients with resectable non-small cell lung cancer: current status and perspectives

Over the past decade, targeted therapy for oncogene-driven NSCLC and immune checkpoint inhibitors for non-oncogene-driven NSCLC, respectively, have greatly improved the survival and quality of life for patients with unresectable NSCLC. Increasingly, these biomarker-guided systemic therapies given before or after surgery have been used in patients with early-stage NSCLC. In March 2022, the US FDA granted the approval of neoadjuvant nivolumab and chemotherapy for patients with stage IB-IIIA NSCLC. Several phase II/III trials are evaluating the clinical efficacy of various neoadjuvant immune checkpoint inhibitor combinations for non-oncogene-driven NSCLC and neoadjuvant molecular targeted therapies for oncogene-driven NSCLC, respectively. However, clinical application of precision neoadjuvant treatment requires a paradigm shift in the biomarker testing and multidisciplinary collaboration at the diagnosis of early-stage NSCLC. In this comprehensive review, we summarize the current diagnosis and treatment landscape, recent advances, new challenges in biomarker testing and endpoint selections, practical considerations for a timely multidisciplinary collaboration at diagnosis, and perspectives in emerging neoadjuvant precision systemic therapy for patients with resectable, early-stage NSCLC. These biomarker-guided neoadjuvant therapies hold the promise to improve surgical and pathological outcomes, reduce systemic recurrences, guide postoperative therapy, and improve cure rates in patients with resectable NSCLC.

Effect of Ablative Dose Irradiation on Redistribution and Radioresponse in a Mouse Xenograft Model

We investigated the effects of ablative dose irradiation on redistribution and radioresponse after the second irradiation in a mouse xenograft model, assuming stereotactic body radiotherapy (SBRT). A human tongue cancer cell line, SAS-Fucci, expressing the fluorescent ubiquitination-based cell cycle indicator (Fucci) that visualizes the cell cycle, was employed in this study. Tumor xenografts formed subcutaneously in nude mice (approximately 6 mm in diameter), with essentially no hypoxic regions, were irradiated at 10 Gy and G2 arrest kinetics were determined using histology sections and a real-time detection method. The second irradiation (10 Gy) was given at intervals of 0 h, 3 h, 1 day, and 4 days after the first irradiation, and tumor regrowth curves were obtained. It was revealed that the ratio of G2-arrested cells showed a much higher peak at 1 day postirradiation compared to 2 Gy, assuming conventional radiotherapy, and gradually decreased thereafter up to 4 days. Tumors irradiated at intervals of 0 h and 1 day demonstrated significantly higher radioresponses than other timings. We conclude that redistribution could contribute to the efficacy of SBRT.

Manifestations of radiation toxicity in the head, neck, and spine: An image-based review

BACKGROUND AND PURPOSE

Radiation therapy is an important component of treatment in patients with malignancies of the head, neck, and spine. However, radiation to these regions has well-known potential side effects, many of which can be encountered on imaging. In this manuscript, we review selected radiographic manifestations of therapeutic radiation to the head, neck, and spine that may be encountered in the practice of radiology.

METHODS

We conducted an extensive literature review of known complications of radiation therapy in the head, neck, and spine. We excluded intracranial and pulmonary radiation effects from our search. We selected complications that had salient, recognizable imaging findings. We searched our imaging database for illustrative examples of these complications.

RESULTS

Based on our initial literature search and imaging database review, we selected cases of radiation-induced tumors, radiation tissue necrosis (osteoradionecrosis and soft tissue necrosis), carotid stenosis and blowout secondary to radiation, enlarging thyroglossal duct cysts, radiation myelopathy, and radiation-induced vertebral compression fractures.

CONCLUSIONS

We describe the clinical and imaging features of selected sequelae of radiation therapy to the head, neck, and spine, with a focus on those with characteristic imaging findings that can be instrumental in helping to make the diagnosis. Knowledge of these entities and their imaging findings is crucial for accurate diagnosis. Not only do radiologists play a key role in early detection of these entities, but many of these entities can be misinterpreted if one is not familiar with them.

Pneumonitis after Stereotactic Thoracic Radioimmunotherapy with Checkpoint Inhibitors: Exploration of the Dose-Volume-Effect Correlation

Simple Summary

Stereotactic body radiation therapy (SBRT) is widely applied for treatment of early stage lung cancer and pulmonary metastases. Modern immune checkpoint blockade (ICB) is progressively used in cancer treatment. Pneumonitis is a relevant side effect of both thoracic SBRT and ICB. Currently, it remains unclear whether we can presume the same radiation dose–volume–effect correlations and dose constraints for safe application of SBRT + ICB. We present a dose–volume–effect correlation analysis method using pneumonitis contours and dose–volume histograms (DVH). We showed dosimetric differences for pneumonitis volumes between SBRT + ICB and SBRT alone. We found a large extent of pneumonitis, even bilateral and apart from the radiation field for combined SBRT + ICB. We noticed a shift in pneumonitis DVHs towards lower doses and a trend towards decreased areas under the curve (AUC) for SBRT + ICB. This provides a direction for re-evaluation and potential adaptation of lung dose constraints for combined SBRT and ICB.

Abstract

Thoracic stereotactic body radiation therapy (SBRT) is extensively used in combination with immune checkpoint blockade (ICB). While current evidence suggests that the occurrence of pneumonitis as a side effect of both treatments is not enhanced for the combination, the dose–volume correlation remains unclear. We investigate dose–volume–effect correlations for pneumonitis after combined SBRT + ICB. We analyzed patient clinical characteristics and dosimetric data for 42 data sets for thoracic SBRT with ICB treatment (13) and without (29). Dose volumes were converted into 2 Gy equivalent doses (EQD2), allowing for dosimetric comparison of different fractionation regimes. Pneumonitis volumes were delineated and corresponding DVHs were analyzed. We noticed a shift towards lower doses for combined SBRT + ICB treatment, supported by a trend of smaller areas under the curve (AUC) for SBRT+ ICB (median AUC 1337.37 vs. 5799.10, p = 0.317). We present a DVH-based dose–volume–effect correlation method and observed large pneumonitis volumes, even with bilateral extent in the SBRT + ICB group. We conclude that further studies using this method with enhanced statistical power are needed to clarify whether adjustments of the radiation dose constraints are required to better estimate risks of pneumonitis after the combination of SBRT and ICB.

Peer review quality assurance in stereotactic body radiotherapy planning: the impact of case volume

Purpose:

Peer review is an essential quality assurance component of radiation therapy planning. A growing body of literature has demonstrated substantial rates of suggested plan changes resulting from peer review. There remains a paucity of data on the impact of peer review rounds for stereotactic body radiation therapy (SBRT). We therefore aim to evaluate the outcomes of peer review in this specific patient cohort.

Methods and materials:

We conducted a retrospective review of all SBRT cases that underwent peer review from July 2015 to June 2018 at a single institution. Weekly peer review rounds are grouped according to cancer subsite and attended by radiation oncologists, medical physicists and medical radiation technologists. We prospectively compiled ‘learning moments’, defined as cases with suggested changes or where an educational discussion occurred beyond routine management, and critical errors, defined as errors which could alter clinical outcomes, recorded prospectively during peer review. Plan changes implemented after peer review were documented.

Results:

Nine hundred thirty-four SBRT cases were included. The most common treatment sites were lung (518, 55%), liver (196, 21%) and spine (119, 13%). Learning moments were identified in 161 cases (17%) and translated into plan changes in 28 cases (3%). Two critical errors (0.2%) were identified: an inadequate planning target volume margin and an incorrect image set used for contouring. There was a statistically significantly higher rate of learning moments for lower-volume SBRT sites (defined as ≤30 cases/year) versus higher-volume SBRT sites (29% vs 16%, respectively; p = 0.001).

Conclusions:

Peer review for SBRT cases revealed a low rate of critical errors, but did result in implemented plan changes in 3% of cases, and either educational discussion or suggestions of plan changes in 17% of cases. All SBRT sites appear to benefit from peer review, though lower-volume sites may require particular attention.

Patterns of Pretreatment Diagnostic Assessment in Patients Treated with Stereotactic Body Radiation Therapy (SBRT) for Non-Small Cell Lung Cancer (NSCLC): Special Characteristics in the COVID Pandemic and Influence on Outcomes

The pandemic raised a discussion about the postponement of medical interventions for non-small cell lung cancer (NSCLC). We analyzed the characteristics of pretreatment diagnostic assessment in the pandemic and the influence of diagnostic assessment on outcomes. A total of 96 patients with stereotactic body radiation therapy (SBRT) for NSCLC were included. The number of patients increased from mean 0.9 (2012–2019) to 1.45 per month in the COVID era (p < 0.05). Pandemic-related factors (contact reduction, limited intensive care unit resources) might have influenced clinical decision making towards SBRT. The time from pretreatment assessment (multidisciplinary tumor board decision, bronchoscopy, planning CT) to SBRT was longer during the COVID period (p < 0.05). Reduced services, staff shortage, or appointment management to mitigate infection risks might explain this finding. Overall survival, progression-free survival, locoregional progression-free survival, and distant progression-free survival were superior in patients who received a PET/CT scan prior to SBRT (p < 0.05). This supports that SBRT guidelines advocate the acquisition of a PET/CT scan. A longer time from PET/CT scan/conventional staging to SBRT (<10 vs. ≥10 weeks) was associated with worse locoregional control (p < 0.05). The postponement of diagnostic or therapeutic measures in the pandemic should be discussed cautiously. Patient- and tumor-related features should be evaluated in detail.

Impact of Dosimetric Parameters on Interplay Effects in 6 MV Flattening Filter-Free Photon Beams to Treat Lung Cancer

CONTEXT

Interplay effects have become the significant problem in lung cancer radiotherapy. Since these effects yield dose variation within the target and surrounding tissues.

AIM

The aim of this study is to investigate the effect of the dosimetric parameters of interplay effects in 6 MV flattening filter-free (FFF) photon beams for lung cancer.

SETTINGS AND DESIGN

This study performed planning, measurement, and data analysis sections for examining different breathing amplitudes and phases, doses, dose rates, field sizes, and fractionations.

SUBJECTS AND METHODS

Standard and clinical plans were created on the eclipse treatment planning system. The static and dynamic measurements were performed using a robotic platform and two-dimensional (2D) diode array. The gamma passing rates were defined as the percent of dose variation caused by the interplay effects.

STATISTICAL ANALYSIS USED

Unpaired t-test.

RESULTS

The outcomes showed three trends between gamma passing rates (γ) and dosimetric parameters. First, a decreasing trend was breathing amplitudes. The lowest γ of maximum amplitudes (2 cm) in both one dimensional and 2D were <25%. Second, an increasing trend was field sizes. The lowest γ of minimum field size (4 cm × 4 cm²) was <55%. Third, constant outcomes were breathing phases, doses, dose rates, and a number of fractions. The γ values of these factors were 53.1%, 55.1%, 34.7%, and 36.7%, respectively.

CONCLUSIONS

Lung tumor motion-induced interplay effects in 6 MV FFF photon beams are more pronounced for higher breathing amplitudes and smaller field sizes.

Single Institution Experience of Stereotactic Body Radiation Therapy in Non-small Cell Lung Cancer: Comparison of Two Dose Regimes and a Perspective on Ideal Dose Regimens

Introduction Stereotactic body radiation therapy (SBRT) is an effective treatment for early-stage non-small cell lung cancer (NSCLC) patients who are either medically inoperable or who decline surgery. SBRT improves tumor control and overall survival (OS) in medically inoperable, early-stage, NSCLC patients. In this study, we investigated the effectiveness of two different SBRT doses commonly used and present our institutional experience. Purpose To determine the clinical outcomes between two treatment regiments (50 Gray [Gy] vs. 55 Gy in five fractions) among Stage I NSCLC patients treated with SBRT at a state academic medical center. Methods We performed a retrospective analysis of 114 patients with Stage I (T1-2 N0 M0) NSCLC treated at a state academic medical center between October 2009 and April 2019. Survival analyses with treatment regimens of 50 Gy and 55 Gy in five fractions were conducted to detect any improvement in outcomes associated with the higher dose. The primary endpoints of this study included OS, local control (LC), and disease-free survival (DFS). Log-rank test and the Kaplan-Meier method were used to analyze the survival curves of the two treatment doses. The SPSS v.24.0 (IBM Corp., Armonk, NY, USA) was used for statistical analyses. Results The 114 early-stage NSCLC patients (median age, 68 years; range 12 to 87 years) had a median follow-up of 25 months (range two to 86 months). The number of males (n = 72; 63.2 %) exceeded the number of females (n = 42; 36.8 %). The majority of patients in this study were Caucasians (n = 68; 59.6 %) and 46 patients were African Americans (40.4 %). Two-thirds of the patients (n = 76; 66.7 %) were treated with 50 Gy in five fractions, and 38 patients (33.3 %) with 55 Gy in five fractions. The one-, two-, and three-year OS and DFS rates were improved in the patients treated with 55 Gy [OS, 81.7 % vs. 72.8 %; 81.7 % vs. 58.9 %; 81.7 % vs. 46.7 % (p = 0.049)], [DFS, 69.7 % vs. 69.7 %; 61.9 % vs. 55.7 %; 61.9 % vs. 52.0 % (p = 0.842)], compared to those treated with 50 Gy. Adenocarcinoma was the most common histology in both groups (51.3 % and 68.4 %). Failure rates were elevated for the 50 Gy regimen [39 (34.2 %) vs. 12 (8.5 %)]. Three year control rates were (66.3 % vs. 96.6 %; p = 0.002) local control; (63.3 % vs. 94.4 %; p = 0.000) regional control; and (65.7 % vs. 97.1 %; p = 0.000) distant control, compared to those treated with 55 Gy. Conclusion Early-stage NSCLC patients treated with SBRT 55 Gy in five fractions did better in terms of local control, overall survival, and disease-free survival rates compared to the 50 Gy in five fractions group.

Dosimetric evaluation of different planning techniques based on flattening filter-free beams for central and peripheral lung stereotactic body radiotherapy

This study aimed to dosimetrically compare and evaluate the flattening filter-free (FFF) photon beam-based three-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT) for lung stereotactic body radiotherapy (SBRT). RANDO phantom computed tomography (CT) images were used for treatment planning. Gross tumor volumes (GTVs) were delineated in the central and peripheral lung locations. Planning target volumes (PTVs) was determined by adding a 5 mm margin to the GTV. 3DCRT, IMRT, and VMAT plans were generated using a 6-MV FFF photon beam. Dose calculations for all plans were performed using the anisotropic analytical algorithm (AAA) and Acuros XB algorithms. The accuracy of the algorithms was validated using the dose measured in a CIRS thorax phantom. The conformity index (CI), high dose volume (HDV), low dose location (D_2cm), and homogeneity index (HI) improved with FFF-VMAT compared to FFF-IMRT and FFF-3DCRT, while low dose volume (R_50%) and gradient index (GI) showed improvement with FFF-3DCRT. Compared with FFF-3DCRT, a drastic decrease in the mean treatment time (TT) value was observed with FFF-VMAT for different lung sites between 57.09% and 60.39%, while with FFF-IMRT it increased between 10.78% and 17.49%. The dose calculation with Acuros XB was found to be superior to that of AAA. Based on the comparison of dosimetric indices in this study, FFF-VMAT provides a superior treatment plan to FFF-IMRT and FFF-3DCRT in the treatment of peripheral and central lung PTVs. This study suggests that Acuros XB is a more accurate algorithm than AAA in the lung region.

On the evaluation of mobile target trajectory between four-dimensional computer tomography and four-dimensional cone-beam computer tomography

Purpose

For mobile lung tumors, four‐dimensional computer tomography (4D CT) is often used for simulation and treatment planning. Localization accuracy remains a challenge in lung stereotactic body radiation therapy (SBRT) treatments. An attractive image guidance method to increase localization accuracy is 4D cone‐beam CT (CBCT) as it allows for visualization of tumor motion with reduced motion artifacts. However, acquisition and reconstruction of 4D CBCT differ from that of 4D CT. This study evaluates the discrepancies between the reconstructed motion of 4D CBCT and 4D CT imaging over a wide range of sine target motion parameters and patient waveforms.

Methods

A thorax motion phantom was used to examine 24 sine motions with varying amplitudes and cycle times and seven patient waveforms. Each programmed motion was imaged using 4D CT and 4D CBCT. The images were processed to auto segment the target. For sine motion, the target centroid at each phase was fitted to a sinusoidal curve to evaluate equivalence in amplitude between the two imaging modalities. The patient waveform motion was evaluated based on the average 4D data sets.

Results

The mean difference and root‐mean‐square‐error between the two modalities for sine motion were −0.35 ± 0.22 and 0.60 mm, respectively, with 4D CBCT slightly overestimating amplitude compared with 4D CT. The two imaging methods were determined to be significantly equivalent within ±1 mm based on two one‐sided t tests (p < 0.001). For patient‐specific motion, the mean difference was 1.5 ± 2.1 (0.8 ± 0.6 without outlier), 0.4 ± 0.3, and 0.8 ± 0.6 mm for superior/inferior (SI), anterior/posterior (AP), and left/right (LR), respectively.

Conclusion

In cases where 4D CT is used to image mobile tumors, 4D CBCT is an attractive localization method due to its assessment of motion with respect to 4D CT, particularly for lung SBRT treatments where accuracy is paramount.

Radiation and Modulation of the Tumor Immune Microenvironment in Non-Small Cell Lung Cancer

Immune checkpoint inhibitors are approved for a variety of indications for locally advanced and metastatic non-small cell lung cancer (NSCLC), and trials are ongoing in the early-stage setting. There is an unmet need to understand which patients may derive benefit from immunotherapies and how to harness combined modality therapies to improve overall response rates and durability. Here, we review studies from the bench-to-bedside to examine the role of radiation therapy (RT) on the tumor immune microenvironment in NSCLC with an eye toward augmenting antitumor immunity. Together, these data provide a foundation for developing future clinical trials harnessing RT to augment antitumor immunity and highlight the need for correlative translational studies to directly characterize the impact of RT on the human NSCLC tumor immune microenvironment.

Radiation Modalities Used in Lung Cancer: An Overview for Thoracic Surgeons

Radiation is a constantly evolving technology which plays a role in the management of lung cancer in a variety of settings: as an adjunct to surgery, definitively, and palliatively. Key aspects of radiation oncology-including acute and chronic toxicities of thoracic radiation and rationale for choosing one modality of radiation over another-may be obscure to those outside the field. We aim to provide a useful overview relevant for the thoracic surgeon of radiation technology and delivery. A review was performed of salient articles identifying radiation technologies used in lung cancer which were summarized and expounded upon with focus on integrating their history, evolution, and landmark trials establishing basis of their use. This article reviews the four fundamental means of external beam radiation employed in managing lung cancer and provides visual examples of comparison plans. We also touch on potential practice-changing developments in regards to proton therapy and radiation in the era of immunotherapy. Radiation oncology has evolved considerably over time to become a critical part of lung cancer management, particularly in early-stage inoperable disease and locally advanced disease. Maximizing tumor control while minimizing toxicity drives treatment strategies. Knowledge of these fundamentals will help the thoracic surgeon answer many questions patients pose regarding radiation.

Minimizing 4DCBCT imaging dose and scan time with Respiratory Motion Guided 4DCBCT: a pre-clinical investigation

Current conventional 4D Cone Beam Computed Tomography (4DCBCT) imaging is hampered by inconsistent patient breathing that leads to long scan times, reduced image quality and high imaging dose. To address these limitations, Respiratory Motion Guided 4D cone beam computed tomography (RMG-4DCBCT) uses mathematical optimization to adapt the gantry rotation speed and projection acquisition rate in real-time in response to changes in the patient's breathing rate. Here, RMG-4DCBCT is implemented on an Elekta Synergy linear accelerator to determine the minimum achievable imaging dose. 8 patient-measured breathing traces were programmed into a 1D motion stage supporting a 3D-printed anthropomorphic thorax phantom. The respiratory phase and current gantry position were calculated in real-time with the RMG-4DCBCT software, which in turn modulated the gantry rotation speed and suppressed projection acquisition. Specifically, the effect of acquiring 20, 25, 30, 35 and 40 projections/respiratory phase bin RMG scans on scan time and image quality was assessed. Reconstructed image quality was assessed via the contrast-to-noise ratio (CNR) and the Edge Response Width (ERW) metrics. The performance of the system in terms of gantry control accuracy was also assessed via an analysis of the angular separation between adjacent projections. The median CNR increased linearly from 5.90 (20 projections/bin) to 8.39 (40 projections/bin). The ERW did not significantly change from 1.08 mm (20 projections/bin) to 1.07 mm (40 projections/bin), indicating the sharpness is not dependent on the total number of projections acquired. Scan times increased with increasing total projections and slower breathing rates. Across all 40 RMG-4DCBCT scans performed, the average difference in the acquired and desired angular separation between projections was 0.64°. RMG-4DCBCT provides the opportunity to enable fast low-dose 4DCBCT (∼70 s, 200 projections), without compromising on current clinical image quality.

Long-term Overall Survival Outcomes in Patients with Early Stage, Peripherally Located, Non-small Cell Lung Cancer Treated with Stereotactic Ablative Radiotherapy in a Non-academic Cancer Centre

AIMS

To report long-term outcomes of patients treated with stereotactic ablative radiotherapy (SABR) for early stage, peripherally located non-small cell lung cancer.

MATERIALS AND METHODS

Data were collected retrospectively between September 2009 and May 2019. Electronic medical records were reviewed for baseline characteristics, treatment details and outcomes. All patients were treated according to local protocol based on the national UK SABR Consortium guidelines. Risk-adapted treatment schedules were used depending on the size and the location of the tumour (54 Gy in three fractions, 55 Gy in five fractions, 60 Gy in eight fractions or 50 Gy in 10 fractions). Overall survival outcomes were evaluated using the Kaplan-Meier method.

RESULTS

In total, 412 patients were included in the analysis. The median age was 76 years (range 48-93 years). Histological confirmation was obtained in 233 cases (56.6%). The median overall survival for all patients was 42.3 months (95% confidence interval 37.3-47.3 months), with 3- and 5-year overall survival of 52.8% and 37.3%, respectively. For biopsy-proven patients (56.6%), 3- and 5-year overall survival was 57.3% and 40.1%, respectively. With respect to overall survival, univariate and multivariate analysis revealed no significant difference in survival by technique (volume-modulated arc therapy versus conformal; three-dimensional computed tomography versus four-dimensional computed tomography), tumour location, smoking status at first contact, pre-treatment tumour stage or pre-treatment standardised uptake value. Survival was poorer for patients who received the 50 Gy in 10 fractions schedule. Treatment was very well tolerated with very low rates of grade 3-4 toxicity (1%).

CONCLUSIONS

SABR for peripherally located, medically inoperable non-small cell lung cancer can be safely and effectively implemented in a non-academic institution with appropriate equipment and training. Overall survival outcomes and toxicity rates are comparable with internationally published studies. Patients treated with 50 Gy in 10 fractions had a poorer survival outcome.

The impact of stereotactic body radiation therapy on the overall survival of patients diagnosed with early-stage non-small cell lung cancer

BACKGROUND AND PURPOSE

Stereotactic Body Radiotherapy (SBRT) has emerged as a standard treatment for inoperable early-stage non-small cell lung cancer (NSCLC) with remarkable local control. However, it is not clear if this local control translates to overall survival (OS). The objective of this study is to investigate the impact of SBRT on the OS of early-stage NSCLC patients and examine if the extent of this impact changes with the era of diagnosis, T stage, age, and comorbidity status.

MATERIALS AND METHODS

Using the National Cancer Database, we compared the OS of cT1-3 cN0 cM0 NSCLC patients with SBRT or observation. Multivariable analyses were adjusted for age, race, sex, income, education, place of living, hospital type, insurance status, comorbidity score, histology types, and diagnosis year.

RESULTS

Among 50,819 patients, 27,027 (53.18%) received SBRT and 23,792 (46.82%) were observed. Multivariable Cox Proportional-Hazards analysis demonstrated SBRT was associated with an improved OS compared to observation (HR:0.56, p < 0.001). Subset multivariable Cox Proportional-Hazards analyses stratified by T stage, year of diagnosis, age, or Charlson Score revealed that HRs of SBRT vs. observation decrease from cT1 to cT3 (0.73-0.68), from 2004 to 2015 (0.65-0.51), from <50 to ≥80 years old (1.04-0.58) and from a Charlson Score 0 to 2 (0.69-0.58).

CONCLUSION

SBRT was associated with improved OS compared to no treatment in early-stage NSCLC. The magnitude of the impact of SBRT on OS increases in patients with advanced age, higher T stages, higher comorbidity scores and more recent treatment eras.

Predicting High-Grade Esophagus Toxicity After Treating Central Lung Tumors With Stereotactic Radiation Therapy Using a Normal Tissue Complication Probability Model

PURPOSE

The treatment of central lung tumors with stereotactic body radiation therapy (SBRT) is challenged by the risk of excessive esophageal toxicity. To improve clinical decision making, we aimed to derive normal tissue complication probability (NTCP) models in a patient cohort with central lung tumors treated with SBRT and to evaluate the currently used esophagus dose constraints.

METHODS AND MATERIALS

Patients with a central lung tumor who received SBRT (8 fractions of 7.5 Gy or 12 fractions of 5 Gy) were included. Doses were recalculated to an equivalent dose of 2 Gy with an α/β-ratio of 10 Gy for acute and 3 Gy for late toxicity (the cut-off was 3 months). The esophagus was manually delineated. NTCP modeling based on logistic regression was used to relate dose-volume histogram parameters (D_max, D_1cc, D_2cc, D_5cc) to acute and late toxicity. Parameters with a P < .05 were included in the model. Based on the NTCP models, we determined the probability of toxicity for the currently used dose constraints: D_1cc ≤40 Gy for 8 fractions and D_1cc ≤48 Gy for 12 fractions.

RESULTS

For this study, 188 patients with 203 tumors were eligible. Esophagus toxicity occurred in 33 patients (18%). Late high-grade toxicity consisted of 2 possible treatment-related deaths (grade 5) and 2 patients with grade 3 toxicity. Acute toxicity consisted of only grade 1 (n = 19) and grade 2 toxicity (n = 10). All investigated dose-volume histogram parameters were significantly correlated to acute and late toxicity. The probability of late high-grade toxicity is 1.1% for 8 fractions and 1.4% for 12 fractions when applying the current dose constraints.

CONCLUSIONS

High-grade esophageal toxicity occurred in 2.1% of the patients, including 2 possible treatment-related deaths. The currently used dose constraints correspond to a low risk of high-grade toxicity.

Strengths and limitations of large databases in lung cancer radiation oncology research

There has been a substantial rise in the utilization of large databases in radiation oncology research. The advantages of these datasets include a large sample size and inclusion of a diverse population of patients in a real-world setting. Such observational studies hold promise in enhancing our understanding of questions for which evidence is conflicting or absent in lung cancer radiotherapy. However, it is critical that investigators understand the strengths and limitations of large databases in order to avoid the common pitfalls that beset observational analyses. This review begins by outlining the data variables available in major registries that are used most often in observational analyses. This is followed by a discussion of the type of radiotherapy-related questions that can be addressed using such datasets, accompanied by examples from the lung cancer literature. Finally, we describe some limitations of observational research and techniques to mitigate bias and confounding. We hope that clinicians and researchers find this review helpful for designing new research studies and interpreting published analyses in the literature.

Differential inflammatory response dynamics in normal lung following stereotactic body radiation therapy with protons versus photons

BACKGROUND AND PURPOSE

To compare time-dependent changes in lung parenchyma of early-stage non-small cell lung carcinoma (NSCLC) patients after stereotactic body radiation therapy with protons (SBPT) or photons (SBRT).

MATERIALS AND METHOD

We retrospectively identified NSCLC patients treated with SBPT and matched each one with a SBRT patient by patient, tumor, and treatment characteristics. Lung parenchyma on serial post-treatment chest computer tomography (CT) scans was deformably registered with the treatment plan to analyze lung density changes as function of dose, quantified by Houndsfield Unit (HU)/Gy. A thoracic radiologist also evaluated the CTs using an established grading system.

RESULTS

We matched 23 SBPT/SBRT pairs, including 5 patients treated with both modalities (internally matched cohort). Normal lung response following SBPT significantly increased in the early time period (CTs acquired <6 months, median 3 months) post-treatment, and then did not change significantly in the later time period (CTs acquired 6-14 months, median 9 months). For SBRT, the normal lung response was similar to SBPT in the early time period, but then increased significantly from the early to the late time period (p = 0.007). These differences were most pronounced in sensitive (response >6 HU/Gy) patients and in the internally matched cohort. However, there was no significant difference in the maximum observed response in the entire cohort over all time periods, median 3.4 [IQR, 1.0-5.4] HU/Gy (SBPT) versus 2.5 [1.6-5.2] HU/Gy (SBRT). Qualitative radiological evaluation was highly correlated with the quantitative analysis (p < 0.0001).

CONCLUSION

While there was no significant difference in maximum response after SBPT versus SBRT, dose-defined lung inflammation occurred earlier after proton irradiation. Further investigation is warranted into the mechanisms of inflammation and therapeutic consequences after proton versus photon irradiation.

Multiple primary lung cancer: a rising challenge

With the use of high-resolution chest imaging system and lung cancer screening program, patients with multiple primary lung cancers (MPLCs) are becoming a growing population in clinical practice worldwide. The diagnostic criteria for MPLCs has been established and modified by three major lung cancer research institutes. However, due to the fact that the differential diagnosis between MPLCs and a recurrence, metastatic, or satellite lesion arising from the original lesion remains ambiguous and confusing, there is still insufficient evidence to support a uniform guideline. Newly developed molecular and genomic methods have the potential to better define the relationship among multiple lesions and bring the possibility of targeted therapy. Surgical resection remains the first choice for the treatment of MPLCs and detailed strategy should be carefully planned taking characteristics of the tumor and status of patients into consideration. For those who are intolerant to surgery, a new technology called stereotactic body radiation therapy (SBRT) is now an optional therapeutic strategy. Furthermore, multiple GGOs are unique MPLCs that need special attentions in the clinical practice.