Stereotactic ablative radiation therapy for centrally located early stage or isolated parenchymal recurrences of non-small cell lung cancer: how to fly in a "no fly zone"

Surgery Versus Stereotactic Radiotherapy in Patients over 75 Years Treated for Stage IA-IIA NSCLC

INTRODUCTION

Lobectomy with lymph node dissection is the gold standard treatment for stage IA-IIA Non-Small Cell Lung Cancer (NSCLC). Surgery is responsible for higher early mortality but offers better overall long-term survival. The patient population concerned is often elderly and combines the comorbidities of smoking and age. Several trials have shown good results of stereotactic radiotherapy (SABR) in terms of local control and tolerance in elderly subjects. Our objective is to study the survival and regional control of patients over 75 years treated by surgery or SABR for localized NSCLC.

MATERIALS AND METHOD

We conducted a single-center retrospective study between January 2012 and December 2022 including elderly patients who received surgery or SABR for NSCLC less than 5 cm in size, N0, M0. A cumulative comorbidity index was calculated for each patient, considering severity and impact of treatment. We performed subgroup analyses using CART method to identify factors impacting survival and early death.

RESULTS

After propensity score matching, 127 operated patients were matched to 85 patients treated with SABR. Overall survival at 1 and 5 years for the operated patients was 83.87% and 47.30% compared with 88.8% and 31.5% in the radiotherapy group (p = 0.068). We have identified four factors influencing the incidence of early mortality: gender, World Health Organization Performance status (WHO status), Forced Expiratory Volume in 1 s (FEV1), and treatment group.

CONCLUSIONS

Surgery seems to remain the standard of treatment in terms of overall survival and locoregional recurrence, in a context where SABR nevertheless provides excellent local control and tolerance in the short and long term. In order to improve patient selection, we are proposing for the first time a tool to aid therapeutic decision-making.

The Treatment of Patients with Early-Stage Non-Small Cell Lung Cancer Who Are Not Candidates or Decline Surgical Resection: The Role of Radiation and Image-Guided Thermal Ablation

The standard of care for early-stage NSCLC has historically been surgical resection. Given the association of lung cancer with smoking, a large number of early-stage patients also have active smoking-related medical comorbidities such as COPD precluding surgery. The current approach for treating such inoperable patients is frequently considered to be stereotactic body radiation therapy (SBRT). SBRT (also known as stereotactic ablative radiation therapy or SABR) is a curative modality that precisely delivers very high dose radiation in few (typically <5) sessions. That said, because of their minimal invasiveness and repeatable nature, image-guided thermal ablation therapies such as radiofrequency ablation (RFA), microwave ablation (MWA), and cryoablation (CA) have also been used to treat early-stage lung tumors. For those patients deemed to have "high operative risk" (i.e., those who cannot tolerate lobectomy, but are candidates for sublobar resection), the appropriateness of potential alternatives [e.g., SBRT; ablation] to surgery is an active area of investigation. In the absence of completed randomized phase III trials, the approach to comparing outcomes between surgery, SBRT, or ablative therapies by their efficacy or equivalence is complex. An overview of the role of SBRT and other non-surgical modalities in the management of early-stage lung cancer is the subject of the present review.

Appropriate Use Criteria (AUC) for the Management of Non-Small Cell Lung Cancer in a Central/Ultra-Central Location: Guidelines from the American Radium Society

INTRODUCTION

Definitive radiation therapy is considered standard therapy for medically inoperable early-stage NSCLC. Nevertheless, for patients with tumors located near structures such as the proximal tracheobronchial tree, esophagus, heart, spinal cord, and brachial plexus, the optimal management regimen is controversial. The objective was to develop expert multidisciplinary consensus guidelines on managing medically inoperable NSCLC located in a central or ultracentral location relative to critical organs at risk.

METHODS

Case variants regarding centrally and ultracentrally located lung tumors were developed by the 15-member multidisciplinary American Radium Society (ARS) Thoracic Appropriate Use Criteria (AUC) expert panel. A comprehensive review of the English medical literature was performed from January 1 1946 to December 31 2023 to inform consensus guidelines. Modified Delphi methods were used by the panel to evaluate the variants and procedures, with at least three rating points from median defining agreement/consensus. The guideline was then approved by the ARS Executive Committee and released for public comment per established ARS procedures.

RESULTS

The Thoracic ARS AUC Panel identified 90 relevant references and obtained consensus in all variants. Radiotherapy alone was considered appropriate, with additional immunotherapy to be considered primarily in the clinical trial setting. Hypofractionated radiotherapy in eight to 18 fractions was considered appropriate for ultracentral lesions near the proximal tracheobronchial tree, upper trachea, and esophagus. For other ultracentral lesions near the heart, great vessels, brachial plexus, and spine, or for non-ultracentral but still central lesions, five-fraction stereotactic body radiation therapy was also considered an appropriate option. Intensity-modulated radiotherapy was considered appropriate and three-dimensional-conformal radiotherapy inappropriate for all variants. Other treatment planning techniques to decrease the risk of overdosing critical organs at risk were also considered.

CONCLUSIONS

The ARS Thoracic AUC panel has developed multidisciplinary consensus guidelines for various presentations of stage I NSCLC in a central or ultracentral location.

Dose-averaged linear energy transfer within the gross tumor volume of non-small-cell lung cancer affects the local control in carbon-ion radiotherapy

BACKGROUND AND PURPOSE

High linear energy transfer (LET) radiation exhibits stronger tumor-killing effect. However, the correlation between LET and the therapeutic efficacy in Carbon-ion radiotherapy (CIRT) for locally advanced non-small-cell lung cancer (LA-NSCLC) is currently not clear. This study aimed to investigate the relationship between the dose-averaged LET (LETd) distribution within tumor and local recurrence for LA-NSCLC treated with CIRT.

METHODS AND MATERIALS

An analysis of 62 consecutive patients with LA-NSCLC who underwent CIRT from 2018 to 2022 was conducted. The LETd distribution was calculated based on their treated plans, and the correlation between local recurrence and LETd, relative biological effectiveness (RBE)-weighted doses (DRBE) and clinical factors was investigated. Receiver operating characteristic (ROC) curve, log-rank test, and Cox regression analysis were performed based on that.

RESULTS

16 patients were defined as local recurrence. Overall survival (OS) and local control (LC) at 24 months were 76.9 % and 73.2 %, respectively. The mean LETd in internal gross tumor volume (iGTV) in the local recurrence group was 48.7 keV/µm, significantly lower than the mean LETd of 53.2 keV/µm in the local control group (p = 0.016). No significant difference was observed in DRBE between the local recurrence and local control groups. ROC curve analysis indicated that a percentage of 88 % of volume in iGTV receiving at least 40 keV/µm (V40keV/μm) is the optimal threshold for predicting local recurrence (Area under curve (AUC) = 0.7636). The log-rank test and Cox regression analysis revealed that the LETd value covering 98 % volume of iGTV (LETd98%) was a significant risk factor for LC (p = 0.020).

CONCLUSIONS

Our study revealed an association between LETd distribution and local recurrence in patients with LA-NSCLC. These findings suggest that lower LETd may increase the probability of local recurrence. We suggest that LETd distribution within iGTV should be routinely assessed in CIRT for lung cancer.

A Comparison of Stereotactic Radiation Therapy in Elderly Patients with Central or Peripheral Stage I-II (T1-3 N0 M0) Non-Small Cell Lung Cancer

Purpose

The objective of this study was to compare the clinical outcomes of stereotactic body radiation therapy (SBRT) in elderly patients aged 65 or older with clinical stage I-II non-small-cell lung cancer (NSCLC), specifically examining the differences between centrally located lung tumors and peripherally located lung tumors.

Methods

From April 2009 to January 2020, a total of 136 patients with 136 tumors (65 central, 71 peripheral; NSCLC) at an early stage (T1-3N0M0) were treated with SBRT at a single institution. Central/peripheral location was assessed retrospectively on planning CT scans. A propensity score matching analysis was utilized to compare the two groups. In addition, the prognosis and related toxicity were compared between the two study arms.

Results

A total of 33 central tumors and 33 peripheral tumors were matched and analyzed. The results showed no significant differences in overall survival (OS) and progression-free survival (PFS) between the two groups. The 2-year OS was 71.88% (95% CI, 57.87%-89.27%) in the central lung cancer group, while it was 93.94% (95% CI, 86.14%-100.00%) in the peripheral lung cancer group (P=0.462). The 2-year PFS was 43.75% in the central lung cancer group, while it was 78.79% in the peripheral lung cancer group (P=0.279). Further subgroup analysis indicated that the location of peripheral tumor have a positive impact on OS in patients with adenocarcinoma. The occurrence of local failure, regional failure, or distant failure was comparable between central and peripheral tumors. There was no statistically significant difference in toxicity between the central and the peripheral tumor groups.

Conclusion

The outcomes of SBRT for central tumors versus peripheral lung tumors in elderly patients with early-stage NSCLC were similar. SBRT demonstrated a similar level of safety in terms of toxicity for both central and peripheral lung tumors.

Advances in Stereotactic Body Radiation Therapy for Lung Cancer

ABSTRACT

Stereotactic body radiation therapy (SBRT) delivers curative-intent radiation to patients with early-stage non-small cell lung cancer and inoperable thoracic lesions. With improved techniques in tumor delineation, motion management, and delivery of radiation treatments, the therapeutic window within the thorax is able to be maximized. Ongoing technological advances enable highly targeted ablative radiation therapy while sparing adjacent sensitive organs at risk. Further applications of SBRT with combinatorial immunotherapy, the usage of particle therapy, and for patients with more advanced stages of lung cancer and other histologies mark exciting possibilities for the role of SBRT within the thorax.

New perspectives on inoperable early-stage lung cancer management: Clinicians, physicists, and biologists unveil strategies and insights

This work provides a comprehensive overview of the current landscape of lung cancer, emphasizing the global significance of the disease and the challenges associated with its diagnosis and treatment. The authors highlight the prevalence of lung cancer, with non-small cell lung cancer (NSCLC) and small cell lung cancer (SCC) being the predominant histological subtypes. Advanced-stage diagnosis is common due to the asymptomatic nature of the disease, leading to a systemic treatment approach involving chemotherapy and radiotherapy.The authors discuss the evolution of treatment strategies, with a focus on the emergence of targeted therapies for advanced-stage NSCLC. A panel of predictive biomarkers, both DNA-based (e.g., EGFR, BRAF, KRAS) and RNA-based (e.g., ALK, ROS1, RET, MET), is highlighted as crucial for molecular analysis in diagnostic specimens. While advanced NSCLC patients benefit from targeted therapy, early-stage patients may undergo surgery followed by adjuvant cisplatin-based chemotherapy or stereotactic body radiotherapy (SBRT). The work emphasizes the importance of screening programs for early detection, with a particular focus on the Italian Lung Cancer Screening Network (RISP). RISP aims to recruit high-risk individuals for screening using low-dose computed tomography (LDCT) and implements primary prevention interventions, such as smoking cessation support. The program's objectives include reducing lung cancer mortality, developing a recruitment system for suitable candidates, and integrating radiological, clinical, and molecular data for individual risk profiling. The review also delves into the perspectives of clinicians, physicists, and biologists in the management of lung cancer. Clinicians focus on risk stratification and treatment options, physicists discuss the role of medical physicists in SBRT, and biologists explore precision medicine, biomarkers, and challenges inearly detection.The comparison between surgery and SBRT for early-stage NSCLC patients is discussed, emphasizing the efficacy of SBRT as a non-invasive approach for patients ineligible for surgery. The authors also touch upon ongoing trials addressing the clinical performance of SBRT in comparison to surgery and the challenges posed by preexisting treatment preferences. The physicist's perspective emphasizes the role of medical physicists in lung SBRT, covering aspects from treatment planning to quality assurance. The importance of radiation physics expertise, advanced imaging techniques, image-guided radiation therapy (IGRT), and adaptive radiotherapy is highlighted. Customized models for tumor control and toxicity evaluation, derived from dosimetric analysis, contribute to treatment optimization and patient care. The biologist's viewpoint explores precision medicine in advanced NSCLC treatment, emphasizing the role of somatic alterations as predictive biomarkers. Challenges in early detection are discussed, and the ideal screening tool is proposed to integrate radiological, pathological, and clinical data. Various blood-derived biomarkers and diagnostic assays, such as EarlyCDT-Lung, Nodify XL2, and miRNA-based signatures, are presented as potential tools for early-stage lung cancer detection. In conclusion, the review underscores the multidisciplinary approach required for effective lung cancer management. Advances in early detection, personalized treatment, and the integration of technology and biomarkers offer hope for improving outcomes and reducing the global burden of lung cancer.

Prospective phase II trial on ablative stereotactic body radiation therapy (SBRT) for medically inoperable thoracic nodes metastases

BACKGROUND

Oligometastases in mediastinal nodes are increasingly prevalent, posing challenges for treatment with stereotactic body radiotherapy (SBRT) due to proximity to organs at risk (OARs). We report the results of a single prospective observational phase II trial on ablative SBRT for medically inoperable thoracic nodes metastases (NCT02970955).

MATERIAL AND METHODS

Since 2017, patients with < 3 nodal metastases were evaluated by the tumor board and included if deemed inoperable. SBRT was delivered using risk adaptive approach based on number, site and size of metastatic nodes (50 Gy/5fractions, 60 Gy/8fractions, 70 Gy/10 fractions). Planning target volume (PTV) partial underdosage was allowed. The primary end point was local control (LC) at 12 months. Secondary end points were: acute and late toxicities, overall survival (OS), progression free survival (PFS), and time to next systemic therapy (TTNS).

RESULTS

Between 03/2017-11/2021, 32 patients (41 nodal metastases) were included. NSCLC (13pts), breast (5pts) and colorectal cancer (4pts) were the most represented primary tumour. In 66 % cases, partial PTV undercoverage was necessary. LC at 1 and 2 years was 93.5 % and 82.3 %, respectively. Treatment was well-tolerated with no acute or late toxicity ≥ G3. Median OS was 59.7 months. OS at 1 and 2 years was 96.9 % and 83.8 % respectively. Median PFS was 12.2 months. PFS at 1 and 2 years was 53.1 % and 31.3 %, respectively.

CONCLUSION

This trial supported the feasibility and safety of ablative SBRT for thoracic nodes metastases thanks to risk adaptive approach allowing to delay of new systemic therapies. Larger studies are needed to confirm these observations.

The role of surgery in the management of radiation-induced brachial plexopathy: a systematic review

This systematic literature review of the clinical characteristics of radiation-induced brachial plexopathy and outcomes after intervention includes 30 trials with 611 patients. The mean radiation dose to the brachial plexus was 56 Gy, and the mean duration of radiation was 4 weeks. The mean time from radiation to the onset of symptoms was 35 months. The most commonly reported symptom was sensory loss (n = 323, 62%), followed by motor deficits (n = 294, 56%) and neuropathic pain (n = 284, 54%). In total, 65 (56%) patients had panplexus involvement and 51 (44%) patients had partial plexus involvement. The most common surgical procedure was neurolysis with flap coverage (n = 108, 6%), followed by neurolysis alone (n = 71, 30%). Of the 237 patients who underwent surgery, 125 (53%) reported an improvement in pain. Motor and sensory deficits were improved in 46 (19%) and 39 (16%) patients, respectively, suggesting that surgery is beneficial in relieving pain, but not as beneficial in restoring motor and sensory function.

SABR for Sarcoma Lung Metastases: Indications for Treatment and Guidance for Patient Selection

PURPOSE

The lungs are the most common site of metastasis for patients with soft tissue sarcoma. SABR is commonly employed to treat lung metastases among select patients with sarcoma with limited disease burden. We sought to evaluate outcomes and patterns of failure among patients with sarcoma treated with SABR for their lung metastases.

METHODS AND MATERIALS

We performed a retrospective review of patients treated at a tertiary cancer center between 2006 and 2020. Patient disease status at the time of SABR was categorized as either oligorecurrent or oligoprogressive. The Kaplan-Meier method was used to estimate disease outcomes. Uni- and multivariable analyses were conducted using the Cox proportional hazards model.

RESULTS

We identified 70 patients with soft tissue sarcoma treated with SABR to 98 metastatic lung lesions. Local recurrence-free survival after SABR treatment was 83% at 2 years. On univariable analysis, receipt of comprehensive SABR to all sites of pulmonary metastatic disease at the time of treatment was associated with improved progression-free survival (PFS; hazard ratio [HR], 0.51 [0.29-0.88]; P = .02). On multivariable analysis, only having systemic disease controlled at the time of SABR predicted improved PFS (median PFS, 14 vs 4 months; HR, 0.37 [0.20-0.69]; P = .002) and overall survival (median overall survival, 51 vs 14 months; HR, 0.17 [0.08-0.35]; P < .0001).

CONCLUSIONS

SABR provides durable long-term local control for sarcoma lung metastases. The most important predictor for improved outcomes was systemic disease control. Careful consideration of these factors should help guide decisions in a multidisciplinary setting to appropriately select the optimal candidates for SABR.

Hypofractionated Stereotactic Radiation Therapy Dosimetric Tolerances for the Inferior Aspect of the Brachial Plexus: A Systematic Review

We sought to systematically review and summarize dosimetric factors associated with radiation-induced brachial plexopathy (RIBP) after stereotactic body radiation therapy (SBRT) or hypofractionated image guided radiation therapy (HIGRT). From published studies identified from searches of PubMed and Embase databases, data quantifying risks of RIBP after 1- to 10-fraction SBRT/HIGRT were extracted and summarized. Published studies have reported <10% risks of RIBP with maximum doses (Dmax) to the inferior aspect of the brachial plexus of 32 Gy in 5 fractions and 25 Gy in 3 fractions. For 10-fraction HIGRT, risks of RIBP appear to be low with Dmax < 40 to 50 Gy. For a given dose value, greater risks are anticipated with point volume-based metrics (ie, D0.03-0.035cc: minimum dose to hottest 0.03-0.035 cc) versus Dmax. With SBRT/HIGRT, there were insufficient published data to predict risks of RIBP relative to brachial plexus dose-volume exposure. Minimizing maximum doses and possibly volume exposure of the brachial plexus can reduce risks of RIBP after SBRT/HIGRT. Further study is needed to better understand the effect of volume exposure on the brachial plexus and whether there are location-specific susceptibilities along or within the brachial plexus structure.

Stereotactic body radiotherapy in lung cancer: a contemporary review

The treatment of early stage non-small cell lung cancer (NSCLC) has improved enormously in the last two decades. Although surgery is not the only choice, lobectomy is still the gold standard treatment type for operable patients. For inoperable patients stereotactic body radiotherapy (SBRT) should be offered, reaching very high local control and overall survival rates. With SBRT we can precisely irradiate small, well-defined lesions with high doses. To select the appropriate fractionation schedule it is important to determine the size, localization and extent of the lung tumor. The introduction of novel and further developed planning (contouring guidelines, diagnostic image application, planning systems) and delivery techniques (motion management, image guided radiotherapy) led to lower rates of side effects and more conformal target volume coverage. The purpose of this study is to summarize the current developments, randomised studies, guidelines about lung SBRT, with emphasis on the possibility of increasing local control and overall rates in "fit," operable patients as well, so SBRT would be eligible in place of surgery.

Long-Term Outcomes of Ablative Carbon-Ion Radiotherapy for Central Non-Small Cell Lung Cancer: A Single-Center, Retrospective Study

The aim of this study is to assess the efficacy and safety of ablative carbon ion radiotherapy (CIRT) for early stage central non-small cell lung cancer (NSCLC). We retrospectively reviewed 30 patients who had received CIRT at 68.4 Gy in 12 fractions for central NSCLC in 2006-2019. The median age was 75 years, and the median Karnofsky Performance Scale score was 90%. All patients had concomitant chronic obstructive pulmonary disease, and 20 patients (67%) were considered inoperable. In DVH analysis, the median lung V5 and V20 were 15.5% and 10.4%, and the median Dmax, D0.5cc, D2cc of proximal bronchial tree was 65.6 Gy, 52.8 Gy, and 10.0 Gy, respectively. At a median follow-up of 43 months, the 3-year overall survival, disease-specific survival, and local control rates were 72.4, 75.8, and 88.7%, respectively. Two patients experienced grade 3 pneumonitis, but no grade ≥3 adverse events involving the mediastinal organs occurred. Ablative CIRT is feasible and effective for central NSCLC and could be considered as a treatment option, especially for patients who are intolerant of other curative treatments.

Radiotherapy in the management of lung oligometastases

In recent years, the development of both medical imaging and new systemic agents (targeted therapy and immunotherapy) have revolutionized the field of oncology, leading to a new entity: oligometastatic disease. Adding local treatment of oligometastases to systemic treatment could lead to prolonged survival with no significant impact on quality of life. Given the high prevalence of lung oligometastases and the new systemic agents coming with increased pulmonary toxicity, this article provides a comprehensive review of the current state-of-art for radiotherapy of lung oligometastases. After reviewing pretreatment workup, the authors define several radiotherapy regimen based on the localization and size of the oligometastases. A comment on the synergistic combination of medical treatment and radiotherapy is also made, projecting on future steps in this specific clinical setting.

Dosimetric analysis of brachial plexopathy after stereotactic body radiotherapy: Significance of organ delineation

OBJECTIVES

Examine the significance of contouring the brachial plexus (BP) for toxicity estimation and select metrics for predicting radiation-induced brachial plexopathy (RIBP) after stereotactic body radiotherapy.

MATERIALS AND METHODS

Patients with planning target volume (PTV) ≤ 2 cm from the BP were eligible. The BP was contoured primarily according to the RTOG 1106 atlas, while subclavian-axillary veins (SAV) were contoured according to RTOG 0236. Apical PTVs were classified as anterior (PTV-A) or posterior (PTV-B) PTVs. Variables predicting grade 2 or higher RIBP (RIBP2) were selected through least absolute shrinkage and selection operator regression and logistic regression.

RESULTS

Among 137 patients with 140 BPs (median follow-up, 32.1 months), 11 experienced RIBP2. For patients with RIBP2, the maximum physical dose to the BP (BP-Dmax) was 46.5 Gy (median; range, 35.7 to 60.7 Gy). Of these patients, 54.5 % (6/11) satisfied the RTOG limits when using SAV delineation; among them, 83.3 % (5/6) had PTV-B. For patients with PTV-B, the maximum physical dose to SAV (SAV-Dmax) was 11.2 Gy (median) lower than BP-Dmax. Maximum and 0.3 cc biologically effective doses to the BP based on the linear-quadratic-linear model (BP-BEDmax LQL and BP-BED0.3cc LQL, α/β = 3) were selected as predictive variables with thresholds of 118 and 73 Gy, respectively.

CONCLUSION

Contouring SAV may significantly underestimate the RIBP2 risk in dosimetry, especially for patients with PTV-B. BP contouring indicated BP-BED0.3cc LQL and BP-BEDmax LQL as potential predictors of RIBP2.

Obtaining organ-specific radiobiological parameters from clinical data for radiation therapy planning of head and neck cancers

Objective.Different radiation therapy (RT) strategies, e.g. conventional fractionation RT (CFRT), hypofractionation RT (HFRT), stereotactic body RT (SBRT), adaptive RT, and re-irradiation are often used to treat head and neck (HN) cancers. Combining and/or comparing these strategies requires calculating biological effective dose (BED). The purpose of this study is to develop a practical process to estimate organ-specific radiobiologic model parameters that may be used for BED calculations in individualized RT planning for HN cancers.Approach.Clinical dose constraint data for CFRT, HFRT and SBRT for 5 organs at risk (OARs) namely spinal cord, brainstem, brachial plexus, optic pathway, and esophagus obtained from literature were analyzed. These clinical data correspond to a particular endpoint. The linear-quadratic (LQ) and linear-quadratic-linear (LQ-L) models were used to fit these clinical data and extract relevant model parameters (alpha/beta ratio, gamma/alpha,dTand BED) from the iso-effective curve. The dose constraints in terms of equivalent physical dose in 2 Gy-fraction (EQD2) were calculated using the obtained parameters.Main results.The LQ-L and LQ models fitted clinical data well from the CFRT to SBRT with the LQ-L representing a better fit for most of the OARs. The alpha/beta values for LQ-L (LQ) were found to be 2.72 (2.11) Gy, 0.55 (0.30) Gy, 2.82 (2.90) Gy, 6.57 (3.86) Gy, 5.38 (4.71) Gy, and the dose constraint EQD2 were 55.91 (54.90) Gy, 57.35 (56.79) Gy, 57.54 (56.35) Gy, 60.13 (59.72) Gy and 65.66 (64.50) Gy for spinal cord, optic pathway, brainstem, brachial plexus, and esophagus, respectively. Additional two LQ-L parametersdTwere 5.24 Gy, 5.09 Gy, 7.00 Gy, 5.23 Gy, and 6.16 Gy, and gamma/alpha were 7.91, 34.02, 8.67, 5.62 and 4.95.Significance.A practical process was developed to extract organ-specific radiobiological model parameters from clinical data. The obtained parameters can be used for biologically based radiation planning such as calculating dose constraints of different fractionation regimens.

An optimal dose-fractionation for stereotactic body radiotherapy in peripherally, centrally and ultracentrally located early-stage non-small lung cancer

Stereotactic body radiotherapy (SBRT), also known as stereotactic ablative radiotherapy (SABR), is commonly used in inoperable patients with early-stage non-small lung cancer (NSCLC). This treatment has good outcomes and low toxicity in peripherally located tumors. However, in lesions which are located close to structures such as the bronchial tree or mediastinum the risk of severe toxicity increases. This review summarizes the evidence of dose-fractionation in SBRT of NSCLC patients in various locations.

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.

A competing risk analysis of the patterns and risk factors of recurrence in early-stage non-small cell lung cancer treated with stereotactic ablative radiotherapy

INTRODUCTION

To assess patterns of recurrence after stereotactic ablative radiotherapy (SABR) in patient ineligible to surgery with early-stage non-small cell lung cancer (ES-NSCLC), report survival and treatment after first recurrence.

METHODS

We performed a retrospective analysis on 1068 patients with ES-NSCLC and 1143 lesions. Between group differences were estimated using competing risk analysis and cause-specific hazard ratios were calculated. Overall survival (OS) after first recurrence was calculated.

RESULTS

Median follow-up was 37.6 months. Univariate analysis demonstrated that ultra-central location was associated with higher risk of regional recurrence (RR) and distant metastasis (DM) (p = 0.004 and 0.01). Central lesions were associated with higher risk of local recurrence (LR) and RR (p < 0.001). Ultra-central lesions were associated with shorter OS (p = 0.002) compared to peripheral lesions. In multivariate analysis, central location was the only factor associated with increased LR and RR risks (p = 0.016 and 0.005). Median OS after first recurrence was 14.8 months. There was no difference in OS after first recurrence between ultra-central, central, and peripheral lesions (p = 0.83). Patients who received a second SABR course had an OS of 51.3 months, compared to 19.5 months with systemic therapy and 8.1 months with supportive care (p < 0.0001).

DISCUSSION

The main prognostic factor for LR and RR risks was central location. Ultra-central and central tumors might benefit from treatment intensification strategies such as dose escalation and/or addition of systemic therapy to improve radiotherapy outcomes. After a first recurrence post SABR, patients with contralateral lung recurrences and those who were eligible to receive a second course of SABR had improved OS.

Clinical and dosimetric factors for symptomatic radiation pneumonitis after stereotactic body radiotherapy for early-stage non-small cell lung cancer

Background and purpose

The present study attempted to identify risk factors for symptomatic radiation pneumonitis (RP) after stereotactic body radiotherapy (SBRT) in patients with early-stage non-small cell lung cancer (NSCLC).

Materials and methods

We reviewed 244 patients with early-stage NSCLC treated with SBRT. The primary endpoint was the incidence of grade ≥2 RP. Gray's test was performed to examine the relationship between clinical risk factors and grade ≥2 RP, and the Fine-Gray model was used for a multivariate analysis. The effects of each dose parameter on grade ≥2 RP were evaluated with the Fine-Gray model and optimal thresholds were tested using receiver operating characteristic (ROC) curves.

Results

With a median follow-up period of 48 months, the 4-year cumulative incidence of grade ≥2 RP was 15.3%. Gray's test revealed that tumor size, a central tumor, interstitial pneumonia, and the biologically effective dose correlated with RP. In the multivariate analysis, a central tumor and interstitial pneumonia remained significant factors (p < 0.001, p = 0.002). Among dose parameters, the total lung volume (%) receiving at least 8 Gy (V8), V10, V20, and the mean lung dose correlated with RP (p = 0.012, 0.011, 0.022, and 0.014, respectively). The results of the Fine-Gray model and ROC curve analyses showed that V10 >16.7% was the best indicator of symptomatic RP among dose parameters.

Conclusion

The present results suggest that a central tumor and interstitial pneumonia are independent risk factors for symptomatic RP and lung V10 ≤16.7% is recommended as the threshold in SBRT.

Retrospective comparison between definitive stereotactic body radiotherapy and radical surgery for 538 patients with early-stage non-small cell lung cancer in a single institution

Introduction

Survival information for stereotactic body radiotherapy (SBRT) and surgery for stage I non-small cell lung cancer (NSCLC) was examined.

Methods

Stage I NSCLC patients who underwent surgery or SBRT between 2012 and 2016 were retrospectively enrolled in this single-institution study. Using the Kaplan--Meier method and Cox regression model, overall survival (OS) was estimated and compared.

Results

Among 538 enrolled patients, compared to the surgery group (443), the SBRT group (95) had more complications (P = 0.01), worse performance status (P = 0.001), and were older (P < 0.001). Three-year OS was 70.5% post SBRT and 90.1% postsurgery. The 3-year cancer-specific survival (CSS) and disease-free survival (DFS) post SBRT and postsurgery were 92.7% vs. 92.3% and 61.1% vs 79.3%, respectively. Three-year locoregional and distant control rates post SBRT and postsurgery were 85.6% vs. 90.1% and 82.5% vs. 86.4%, respectively. Multivariate analysis using the Cox model, including age, T-stage, CCI, and C/T ratio and treatment, showed the surgery group's OS to be significantly superior to that of the SBRT group (HR of SBRT per surgery: 1.90, 95%CI: 1.12-3.21, P = 0.017). No significant differences were observed in rates of adverse events.

Conclusion

Although OS was better in the surgery group, no differences in CSS existed. This analysis suggests the need for future studies that compare specific radical surgeries and SBRT in a prospective and randomized setting.

[Limits of dose constraint definition for organs at risk specific to stereotactic radiotherapy]

Stereotactic radiotherapy is a very hypofractionated radiotherapy (>7.5Gy per fraction), and therefore is more likely to induce late toxicities than conventional normofractionated irradiations. The present study examines four frequent and potentially serious late toxicities: brain radionecrosis, radiation pneumonitis, radiation myelitis, and radiation-induced pelvic toxicities. The critical review focuses on the toxicity scales, the definition of the dose constrained volume, the dosimetric parameters, and the non-dosimetric risk factors. The most commonly used toxicity scales remain: RTOG/EORTC or common terminology criteria for adverse events (CTCAE). The definition of organ-at-risk volume requiring protection is often controversial, which limits the comparability of studies and the possibility of accurate dose constraints. Nevertheless, for the brain, whatever the indication (arteriovenous malformation, benign tumor, metastasis of solid tumors...), the association between the volume of brain receiving 12Gy (V12Gy) and the risk of cerebral radionecrosis is well established for both single and multi-fraction stereotactic irradiation. For the lung, the average dose received by both lungs and the V20 seem to correlate well with the risk of radiation-induced pneumonitis. For the spinal cord, the maximum dose is the most consensual parameter. Clinical trial protocols are useful for nonconsensual dose constraints. Non-dosimetric risk factors should be considered when validating the treatment plan.

STereotactic Ablative RadioTherapy in NEWly Diagnosed and Recurrent Locally Advanced Non-Small Cell Lung Cancer Patients Unfit for ConcurrEnt RAdio-Chemotherapy: Early Analysis of the START-NEW-ERA Non-Randomised Phase II Trial

PURPOSE

This is a single arm phase 2 trial (Clinical trials.gov NCT05291780) to assess local control (LC) and safety of SAbR in patients with unresectable locally advanced non-small cell lung cancer (LA-NSCLC) unfit for concurrent chemo-radiation therapy (ChT-RT).

METHODS

Neoadjuvant ChT was prescribed in fit patients. The tumor volume included primary tumor and any regionally positive node/s. The coprimary study endpoints were LC and safety.

RESULTS

Between December 31, 2015, and December 31, 2020, 50 patients with LA-NSCLC were enrolled. Histology was squamous cell carcinoma and adenocarcinoma (ADC) in 52% and 48%, respectively. Forty (80%) patients had ultracentral tumor. Twenty-seven (54%) received neoadjuvant ChT and 7 (14%) adjuvant durvalumab. Median prescribed dose was 45 Gy (range, 35-55) and 40 Gy (35-45) in 5 daily fractions to tumor and node/s, respectively. After a median follow-up of 38 months (range, 12-80), 19 (38%) patients had experienced local recurrence (LR) at a median time of 13 months (range, 7-34). The median LR-free survival (FS) was not reached (95% confidence interval [CI], 28 to not reached). The 1-, 2-, and 3-year LR-FS rates were 86% ± 5%, 66% ± 7%, and 56% ± 8%, respectively. At last follow-up, 33 (66%) patients were alive. Median overall survival (OS) was 55 months (95% CI, 43-55 months). The 1-, 2-, and 3-year OS rates were 94% ± 3%, 79% ± 6%, and 72% ± 7%, respectively. No patients developed ≥ grade (G) 3 toxicity. ADC (hazard ratio [HR], 3.61; 95% CI, 1.15-11.35) was a significant predictor of better LC, while OS was significantly conditioned by smaller planning target volumes (HR, 1.004; 95% CI, 1.001-1.010) and tumor, node, and metastasis stage (HR, 4.8; 95% CI, 1.34-17).

CONCLUSIONS

Patients with LA-NSCLC treated with SABR had optimal LC and promising OS in absence of ≥G3 toxicity. Our early outcomes would suggest the feasibility of using this approach in patients with LA-NSCLC unfit for concurrent ChT-RT.

Deep inspiratory breath hold assisted by continuous positive airway pressure ventilation for lung stereotactic body radiotherapy

PURPOSE

Continuous positive airway pressure (CPAP) ventilation hyperinflates the lungs and reduces diaphragmatic motion. We hypothesized that CPAP could be safely combined with deep inspiratory breath hold (CPAP-DIBH) during lung stereotactic radiotherapy (SBRT).

MATERIAL AND METHODS

Patients with stage-1 lung cancer or lung metastasis treated with CPAP-DIBH SBRT between 3/2017-5/2021 were analyzed retrospectively. Patient characteristics, treatment parameters, duration of breath holds in all sessions and tolerance to CPAP-DIBH were recorded. Local control (LC) was assessed from CT or PET-CT imaging. The distances between the tumor and mediastinal organs at risk (OAR) in centrally located tumors using either free breathing (FB) or CPAP-DIBH were compared. Toxicity was graded retrospectively.

RESULTS

Forty-five patients with 71 lesions were treated with CPAP-DIBH SBRT. Indications for CPAP-DIBH were prior radiation (35/71, 65%), lower lobe location (34/71, 48%), multiple lesions (26/71, 36.6%) and proximity to mediastinal OAR (7/71, 10%). Patient characteristics were: F:M 43%: 57%; mean gross tumor volume 4.5cm³ (SD 7.9), mean planning target volume 20cm³ (SD 27), primary: metastatic lesions (7%:93%). Mean radiation dose was 52.5 Gray (SD3.5). Mean lung volume was 5292cm³ (SD 1106). Mean duration of CPAP-DIBH was 41.3s (IQR 31-46.8). LC at 2 years was 89.5% (95% CI 76-95.5). In patients with central lesions, the distance between the tumor and mediastinal OAR increased from 0.84cm (SD 0.65) with FB to 1.23cm (SD 0.8) with CPAP-DIBH (p=0.002). Most patients tolerated CPAP well and completed all treatments after starting therapy. Three patients did not receive treatment: 2 were unable to tolerate CPAP and 1 had syncope (pre-existing). Toxicity was grade 2 in 4/65 (6%) and grade 3 in 1/65 (1.5%). There was no grade 2 or higher esophageal or tracheal toxicities.

CONCLUSION

CPAP-DIBH assisted lung SBRT was tolerated well and was associated with minimal toxicity and favorable LC. This technique may be considered when treating multiple lung lesions, lesions located in the lower lobes or adjacent to mediastinal OAR.

Derived Neutrophil-Lymphocyte Ratio and C-Reactive Protein as Prognostic Factors for Early-Stage Non-Small Cell Lung Cancer Treated with Stereotactic Body Radiation Therapy

Objectives: To explore the relationship between peripheral blood inflammation parameters and overall survival (OS) and progression-free survival (PFS) of early-stage non-small cell lung cancer patients who underwent stereotactic body radiotherapy (SBRT). Patients and methods: In this study, eligible patients treated with SBRT from 2013 to 2018, and both serum complete blood count and blood biochemical results were available prior to (within 60 days) radiotherapy were included. Results: A review of hospital registries identified 148 patients, and the 5-year OS and PFS of the entire cohort were 69.8% and 65.6%, respectively, with the median follow-up time was 52.8 months. Multivariable analysis showed that derived neutrophil-lymphocyte ratio (dNLR) ≥1.4 and C-reactive protein (CRP) ≥2.9 were statistically and independently associated with worse OS (HR = 4.62, 95% CI 1.89-11.27, p = 0.001; HR = 2.92, 95% CI 1.49-5.70, p = 0.002, respectively). The 5-year OS for patients with dNLR below and equal to or above the 1.4 were 85.3% and 62.9% (p = 0.002), respectively, and 76.7% for the low CRP group versus 58.5% for the high CRP group (p = 0.030). Higher serum level of post-treatment CRP also independent parameters for inferior PFS (HR = 4.83, 95% CI 1.28-18.25, p = 0.020). Conclusions: Our results demonstrate that dNLR and CRP are associated with the outcomes of early-stage NSCLC patients treated with SBRT, which may assist in selecting optimal nursing care and therapeutic scheme for every individual.

Image-Guided Percutaneous and Transarterial Therapies for Primary and Metastatic Lung Cancer

Lung cancer is the leading cause of cancer mortality in the world. A significant proportion of patients with lung cancer are not candidates for surgery and must resort to other treatment alternatives. Rapid technological advancements in fields like interventional radiology have paved the way for valid treatment modalities like image-guided percutaneous and transarterial therapies for treatment of both primary and metastatic lung cancer. The rationale of ablative therapies relies on the fact that focused delivery of energy induces tumor destruction and pathological necrosis. Image-guided percutaneous thermal ablation therapies are established techniques in the local treatment of hepatic, renal, bone, thyroid, or uterine lesions. In the lung, the 3 main indications for lung ablation include local curative intent, a strategy to achieve a chemoholiday in oligometastatic disease, and recently, oligoprogressive disease. Transarterial therapies include a set of catheter-based treatments that involve delivering embolic and/or chemotherapeutic agents directed into the target tumor via the supplying arteries. This article provides a comprehensive review of the various techniques available and discusses their applications and associated complications in primary and metastatic lung cancer.

Research landscape and trends of lung cancer radiotherapy: A bibliometric analysis

BACKGROUND

radiotherapy is one of the major treatments for lung cancer and has been a hot research area for years. This bibliometric analysis aims to present the research trends on lung cancer radiotherapy.

METHOD

On August 31, 2022, the authors identified 9868 articles on lung cancer radiotherapy by the Web of Science (Science Citation Indexing Expanded database) and extracted their general information and the total number of citations. A bibliometric analysis was carried out to present the research landscape, demonstrate the research trends, and determine the most cited papers (top-papers) as well as top-journals on lung cancer radiotherapy. After that, the authors analyzed the recent research hotspots based on the latest publications in top-journals.

RESULTS

These 9868 papers were cited a total of 268,068 times. "Durvalumab after chemoradiotherapy in stage III non-small-cell lung cancer" published in 2017 by Antonia et al.was the most cited article (2110 citations). Among the journals, New England Journal of Medicine was most influential. Moreover, J. Clin. Oncol. and Int. J. Radiat. Oncol. Biol. Phys. was both influential and productive. Corresponding authors represented the USA (2610 articles) and China mainland (2060 articles) took part in most publications and articles with corresponding authors from Netherlands were most cited (46.12 citations per paper). Chemoradiotherapy was the hottest research area, and stereotactic body radiotherapy has become a research hotspot since 2006. Radiotherapy plus immunotherapy has been highly focused since 2019.

CONCLUSIONS

This bibliometric analysis comprehensively and quantitatively presents the research trends and hotspots based on 9868 relevant articles, and further suggests future research directions. The researchers can benefit in selecting journals and in finding potential collaborators. This study can help researchers gain a comprehensive picture of the research landscape, historical development, and recent hotspots in lung cancer radiotherapy and can provide inspiration for future research.

Stereotactic Body Radiation Therapy for Lung and Liver Oligometastases from Breast Cancer: Toxicity Data of a Prospective Non-Randomized Phase II Trial

AIMS

We report the mature toxicity data of a phase II non-randomized trial on the use of SBRT for lung and liver oligometastases.

METHODS

Oligometastatic patients from breast cancer were treated with SBRT for up to five lung and/or liver lesions. Inclusion criteria were: age > 18 years, ECOG 0-2, diagnosis of breast cancer, less than five lung/liver lesions (with a maximum diameter <5 cm), metastatic disease confined to the lungs and liver or extrapulmonary or extrahepatic disease stable or responding to systemic therapy. Various dose-fractionation schedules were used. Then, a 4D-CT scan and FDG-CTPET were acquired for simulation and fused for target definition.

RESULTS

From 2015 to 2021, 64 patients and a total of 90 lesions were irradiated. Treatment was well tolerated, with no G 3-4 toxicities. No grade ≥3 toxicities were registered and the coprimary endpoint of the study was met. Median follow-up was 19.4 months (range 2.6-73.1).

CONCLUSIONS

The co-primary endpoint of this phase II trial was met, showing excellent tolerability of SBRT for lung and liver oligometastatic in breast cancer patients. Until efficacy data will mature with longer follow-up, SBRT should be regarded as an opportunity for oligometastatic breast cancer patients.

The potential of biology-guided radiation therapy in thoracic cancer: A preliminary treatment planning study

Purpose

We investigated the feasibility of biology-guided radiotherapy (BgRT), a technique that utilizes real-time positron emission imaging to minimize tumor motion uncertainties, to spare nearby organs at risk.

Methods

Volumetric modulated arc therapy (VMAT), intensity-modulated proton (IMPT) therapy, and BgRT plans were created for a paratracheal node recurrence (case 1; 60 Gy in 10 fractions) and a primary peripheral left upper lobe adenocarcinoma (case 2; 50 Gy in four fractions).

Results

For case 1, BgRT produced lower bronchus V40 values compared to VMAT and IMPT. For case 2, total lung V20 was lower in the BgRT case compared to VMAT and IMPT.

Conclusions

BgRT has the potential to reduce the radiation dose to proximal critical structures but requires further detailed investigation.

Proton Beam Therapy versus Photon Radiotherapy for Stage I Non-Small Cell Lung Cancer

Simple Summary

Stereotactic body radiotherapy (SABR) is accepted as a standard of care for patients who are not candidates for surgery in stage I non-small cell lung cancer (NSCLC). SABR has shown encouraging disease control and acceptable toxicity in peripherally located stage I NSCLC. However, for centrally located tumors around the proximal bronchial tree or for tumors located close to the chest wall, toxicities by SABR are not negligible. Therefore, proton beam therapy (PBT), which provides better organ at risk (OAR) sparing than photon radiotherapy by the Bragg peak, was tested and investigated to reduce radiation-induced toxicities in stage I NSCLC. Here, we compared 112 and 117 stage I NSCLC patients who underwent PBT and photon radiotherapy, respectively. PBT showed significantly lower lung and heart radiation exposure than photon radiotherapy without worsening disease control. PBT could be an effective treatment to reduce long-term toxicities of the lung and heart.

Abstract

Proton beam therapy (PBT) and photon radiotherapy for stage I non-small cell lung cancer (NSCLC) were compared in terms of clinical outcomes and dosimetry. Data were obtained from patients who underwent PBT or photon radiotherapy at two institutions—the only two facilities where PBT is available in the Republic of Korea. Multivariate Cox proportional hazards models and propensity score-matched analyses were used to compare local progression-free survival (PFS) and overall survival (OS). Survival and radiation exposure to the lungs were compared in the matched population. Of 289 patients included in the analyses, 112 and 177 underwent PBT and photon radiotherapy, respectively. With a median follow-up duration of 27 months, the 2-year local PFS and OS rates were 94.0% and 83.0%, respectively. In the multivariate analysis, a biologically effective dose (BED₁₀, using α/β = 10 Gy) of ≥125 cobalt gray equivalents was significantly associated with improved local PFS and OS. In the matched analyses, the local PFS and OS did not differ between groups. However, PBT showed significantly lower lung and heart radiation exposure in the mean dose, V5, and V10 than photon radiotherapy. PBT significantly reduced radiation exposure to the heart and lungs without worsening disease control in stage I NSCLC patients.

Treatment plan comparison of volumetric-modulated arc therapy to intensity-modulated radiotherapy in lung stereotactic body radiotherapy using either 6- or 10-MV photon energies

Purpose

The aim of this study was to dosimetrically compare volumetric‐modulated arc therapy (VMAT) with intensity‐modulated radiotherapy (IMRT) techniques using either 6‐ or 10‐MV photon beam energies in lung stereotactic body radiation therapy (SBRT) plans.

Methods

Thirty patients with primary or metastatic lung tumors eligible for SBRT were randomly selected. VMAT and IMRT treatment plans using either 6‐ or 10‐MV photon energies were generated through automatic SBRT planning software in the RayStation treatment planning system.

Results

For planning target volume, there was no difference in D_95% for all plans, whereas D_2% and D_50% were significantly increased by 5.22%–5.98% and 2.47%–2.59%, respectively, using VMAT_6/10‐MV plans compared to IMRT_6/10‐MV plans. When comparing the D_max of organs at risk (OARs), VMAT_6/10‐MV was 18.32%–47.95% lower than IMRT_6/10‐MV for almost all OARs. VMAT_6/10‐MV obviously decreased D_mean, V_5Gy, V_10Gy, and V_20Gy of whole lung by 9.68%–20.92% than IMRT_6/10‐MV. Similar results were found when comparing VMAT_6‐MV with IMRT_10‐MV or VMAT_10‐MV with IMRT_6‐MV. The differences in the D_2%, heterogeneity index, and conformity index between 6‐ and 10‐MV plans are not statistically significant. Plans using 6‐MV performed 4.68%–8.91% lower levels of D_max of spinal cord, esophagus, great vessels, and trachea and proximal bronchial tree than those using 10‐MV plans. Similarly, D_mean, V_5Gy, V_10Gy, and V_20Gy of whole lung were also reduced by 2.79%–5.25% using 6‐MV. For dose fall‐off analysis, the D_2cm and R_50% of VMAT_6/10‐MV were lower than those of IMRT_6/10‐MV. Dose fall‐off curve based on 10 rings was steeper for VMAT plans than IMRT plans regardless of the energy used.

Conclusions

For lung SBRT plans, VMAT‐based plans significantly reduced OARs dose and steepened dose fall‐off curves compared to IMRT‐based plans. A 6‐MV energy level was a better choice than 10‐MV for lung SBRT. In addition, the dose differences between different techniques were more obvious than those between different energy levels.

Practical considerations of single-fraction stereotactic ablative radiotherapy to the lung

Stereotactic ablative radiotherapy (SABR) is a well-established treatment for patients with medically inoperable early-stage non-small cell lung cancer (NSCLC) and pulmonary oligometastases. The use of single-fraction SABR in this setting is supported by excellent local control and safety profiles which appear equivalent to multi-fraction SABR based on the available data. The resource efficiency and reduction in hospital outpatient visits associated with single-fraction SABR have been particularly advantageous during the COVID-19 pandemic. Despite the increased interest, single-fraction SABR in subgroups of patients remains controversial, including those with centrally located tumours, synchronous targets, proximity to dose-limiting organs at risk, and concomitant severe respiratory illness. This review provides an overview of the published randomised evidence evaluating single-fraction SABR in primary lung cancer and pulmonary oligometastases, the common clinical challenges faced, immunogenic effect of SABR, as well as technical and cost-utility considerations.

How to Improve SBRT Outcomes in NSCLC: From Pre-Clinical Modeling to Successful Clinical Translation

Simple Summary

Despite major research and clinical efforts, lung cancer remains the leading cause of cancer-related death. Stereotactic body radiotherapy (SBRT) has emerged as a major treatment modality for lung cancer in the last decade. Additional research is needed to elucidate underlying mechanisms of resistance and to develop improved therapeutic strategies. Clinical progress relies on accurate preclinical modelling of human disease in order to yield clinically meaningful results; however, successful translation of pre-clinical research is still lagging behind. In this review, we summarize the major clinical developments of radiation therapy for non-small-cell lung cancer (NSCLC), and we discuss the pre-clinical research models at our disposal, highlighting ongoing translational challenges and future perspectives.

Abstract

Despite major research and clinical efforts, lung cancer remains the leading cause of cancer-related death. While the delivery of conformal radiotherapy and image guidance of stereotactic body radiotherapy (SBRT) have revolutionized the treatment of early-stage non-small-cell lung cancer (NSCLC), additional research is needed to elucidate underlying mechanisms of resistance and identify novel therapeutic combinations. Clinical progress relies on the successful translation of pre-clinical work, which so far has not always yielded expected results. Improved clinical modelling involves characterizing the preclinical models and selecting appropriate experimental designs that faithfully mimic precise clinical scenarios. Here, we review the current role of SBRT and the scope of pre-clinical armamentarium at our disposal to improve successful clinical translation of pre-clinical research in the radiation oncology of NSCLC.

Stereotactic radiotherapy for lung oligometastases

30-60% of cancer patients develop lung metastases, mostly from primary tumors in the colon-rectum, lung, head and neck area, breast and kidney. Nowadays, stereotactic radiotherapy (SRT ) is considered the ideal modality for treating pulmonary metastases. When lung metastases are suspected, complete disease staging includes a total body computed tomography (CT ) and/or positron emission tomography-computed tomography (PET -CT ) scan. PET -CT has higher specificity and sensitivity than a CT scan when investigating mediastinal lymph nodes, diagnosing a solitary lung lesion and detecting distant metastases. For treatment planning, a multi-detector planning CT scan of the entire chest is usually performed, with or without intravenous contrast media or esophageal lumen opacification, especially when central lesions have to be irradiated. Respiratory management is recommended in lung SRT, taking the breath cycle into account in planning and delivery. For contouring, co-registration and/or matching planning CT and diagnostic images (as provided by contrast enhanced CT or PET-CT ) are useful, particularly for central tumors. Doses and fractionation schedules are heterogeneous, ranging from 33 to 60 Gy in 3-6 fractions. Independently of fractionation schedule, a BED10 > 100 Gy is recommended for high local control rates. Single fraction SRT (ranges 15-30 Gy) is occasionally administered, particularly for small lesions. SRT provides tumor control rates of up to 91% at 3 years, with limited toxicities. The present overview focuses on technical and clinical aspects related to treatment planning, dose constraints, outcome and toxicity of SRT for lung metastases.

Bibliometric Analysis of the Top-Cited Publications and Research Trends for Stereotactic Body Radiotherapy

Objective

This study aims to analyze the 100 most cited papers and research trends on stereotactic body radiotherapy (SBRT).

Methods

We used Web of Science to identify the 100 most frequently cited papers on SBRT on September 29, 2021 and extracted the following data: publication year, source title, country/region, organization, total citations, and average number of citations per year. The research type and research domain were classified independently by the authors. Then we carried out a bibliometric analysis to determine the trends in research on SBRT.

Results

These 100 papers were cited a total of 26,540 times, and the median number of citations was 190 (range, 138-1688). “Stereotactic body radiation therapy for inoperable early stage lung cancer” by Timmerman et al. had the highest number of total citations (1688 times). International Journal of Radiation Oncology, Biology, Physics published the largest number of papers (37 papers), followed by Journal of Clinical Oncology (13 papers). The USA contributed the most papers (67 papers), followed by Canada (18 papers). Primary lung cancer (33 papers, 10,683 citations) and oligometastases (30 papers, 7,147 citations) were the most cited research areas.

Conclusions

To the best of our knowledge, this is the first bibliometric analysis of the most frequently cited papers on SBRT. Our results provide insight into the historical development of SBRT and important advances in its application to cancer treatment. Early-stage non–small-cell lung cancer and oligometastases were the most cited research areas in the top 100 publications on SBRT, and SBRT combined with immunotherapy was a hot topic in the past few years. This study is helpful for researchers to identify the most influential papers and current research hotspots on SBRT.

Dosimetric Comparisons between Proton Beam Therapy and Modern Photon Radiation Techniques for Stage I Non-Small Cell Lung Cancer According to Tumor Location

Simple Summary

Stereotactic ablative radiotherapy (SABR) is a well-established technique used to treat stage I non-small cell lung cancer (NSCLC). Proton beam therapy (PBT) offers dosimetric advantages over photon SABR techniques by reducing doses to normal organs. Hence, it is believed that PBT is helpful for patients with tumors located centrally in stage I NSCLC. However, the benefits of PBT for other locations, such as peripherally located tumors, have not been well-described. We investigated dosimetric benefits for PBT over modern photon radiation techniques for stage I NSCLC according to tumor locations. A total of 42 patients’ (including tumors that were central (11), peripheral (nine), and close to the chest wall (22)) PBT plans were compared with those of modern photon radiation techniques. In all locations, PBT significantly reduced radiation exposure to the lung and heart. To reduce potential lung and heart toxicities, PBT is ideal, even in the peripherally located stage I NSCLC.

Abstract

Herein, we investigated the dosimetric benefits for proton beam therapy (PBT) over modern photon radiation techniques according to tumor location (central, peripheral, and close to the chest wall) for stage I non-small cell lung cancer (NSCLC) patients. A total of 42 patients with stage I NSCLC were treated with PBT with a total dose of 50–70 Gy in four or 10 fractions considering the risk of treatment-related toxicities. Simulation plans for three-dimensional conformal radiation therapy (3D-CRT), static-field intensity-modulated radiotherapy (IMRT), and volumetric-modulated arc therapy (VMAT) were retrospectively generated using the same treatment volumes as implemented in the PBT plans for these patients. Dosimetric improvements were observed with PBT as compared with all the photon-based radiation techniques with regards to the mean lung dose, lung V5 and V10, mean heart dose, and heart V5 and V10 in all locations. Moreover, lower radiation exposure to the chest wall was observed within PBT for peripherally located and close to the chest wall tumors. All radiotherapy modalities achieved clinically satisfactory treatment plans in the current study. Notably, the usage of PBT resulted in significant dosimetric improvements in the lung and heart over photon-based techniques at all tumor locations, including the periphery, for stage I NSCLC.

Stereotactic body radiotherapy for apical lung tumors: Dosimetric analysis of the brachial plexus and preliminary clinical outcomes

BACKGROUND

Dosimetric constraints of the brachial plexus have not yet been well-established for patients undergoing stereotactic body radiotherapy (SBRT). This study evaluated long-term experience with the treatment of early stage apical lung tumors with SBRT and reports on dosimetric correlates of outcome.

METHODS

Between 2009 and 2018, a total of 78 consecutive patients with 81 apical lung tumors underwent SBRT for T1-3N0 non-small cell lung cancer. Apical tumors were those with tumor epicenter superior to the aortic arch. The brachial plexus (BP) was anatomically contoured according to the Radiation Therapy Oncology Group (RTOG) atlas. Patient medical records were retrospectively reviewed to determine incidence of brachial plexus injury (BPI) and a normal tissue complication probability model (NTCP) was applied to the dosimetric data.

RESULTS

Five patients (6.4%) reported neuropathic symptoms consistent with BPI and occurred a median 11.9 months after treatment (range, 5.2 to 28.1 months). Most common dose and fractionation in those developing BPI were 50 Gy in 5 fractions (4 patients). Symptoms consisted of pain in 2 patients (40.0%), numbness in the hand or axilla in 4 patients (80.0%), and ipsilateral hand weakness in 1 patient (20.0%). In the overall cohort the median BP Dmax (EQD2_{3 Gy}) was 5.13 Gy (range, 0.18 to 217.2 Gy) and in patients with BPI the median BP Dmax (EQD2_{3 Gy}) was 32.14 Gy (range, 13.4 to 99.9 Gy). The NTCP model gave good fit with an area under the curve (AUC) of 0.75 (OR 7.3, 95% CI: 0.8-68.3) for BP Dmax (EQD2_{3 Gy}) threshold of 20 Gy.

CONCLUSION

Significant variation exists in the dose delivered to the brachial plexus for patients treated by SBRT for apical lung tumors. The incidence of neuropathic symptoms in the post-SBRT setting was appreciable and prospective clinical correlation with dosimetric information should be utilized in order to develop evidence-based dose constraints.

Percutaneous Image-Guided Ablation of Lung Tumors

Tumors of the lung, including primary cancer and metastases, are notoriously common and difficult to treat. Although surgical resection of lung lesions is often indicated, many conditions disqualify patients from being surgical candidates. Percutaneous image-guided lung ablation is a relatively new set of techniques that offers a promising treatment option for a variety of lung tumors. Although there have been no clinical trials to definitively compare its efficacy to those of traditional treatments, lung ablation is widely practiced and generally accepted to be safe and effective. Especially encouraging results have recently emerged for cryoablation, one of the newer ablative techniques. This article reviews the indications, techniques, contraindications, and complications of percutaneous image-guided ablation of lung tumors with special attention to cryoablation and its recent developments in protocol optimization.

Preclinical Risk Evaluation of Normal Tissue Injury With Novel Radiosensitizers

Genotoxic damage induced by radiation triggers a highly coordinated DNA damage response, and molecular inhibitors of key nodes within this complex response network can profoundly enhance the antitumor efficacy of radiation. This is especially true for drugs targeting the catalytic subunit of DNA-dependent protein kinase, which is a core component of the nonhomologous end-joining DNA repair pathway, and ataxia telangiectasia mutated, which coordinates cell cycle arrest, apoptosis, and DNA repair functionalities after radiation exposure. Unlike the more modest in vitro radiosensitizing effects seen with classic sensitizing agents such as cisplatin, 5-fluorouracil, or taxanes, DNA-dependent protein kinase or ataxia telangiectasia mutated inhibitors provide much more robust sensitizing effects in vitro, as might be anticipated from targeting these key DNA repair modulators. However, patients with homozygous inactivating mutations of ataxia telangiectasia mutated or mice with homozygous defects in DNA-dependent protein kinase (severe combined immunodeficiency) have profoundly enhanced acute normal tissue radiation reactions. Therefore, there is significant potential that the combination of small molecule inhibitors of these kinases with radiation could cause similar dose-limiting acute normal tissue toxicities. Similarly, although less understood, inhibition of these DNA repair response pathways could markedly increase the risk of late radiation toxicities. Because these potent radiosensitizers could be highly useful to improve local control of otherwise radiation-resistant tumors, understanding the potential for elevated risks of radiation injury is essential for optimizing therapeutic ratio and developing safe and informative clinical trials. In this review, we will discuss 2 straightforward models to assess the potential for enhanced mucosal toxicity in the oral cavity and small intestine established in our laboratories. We also will discuss similar strategies for evaluating potential drug-radiation interactions with regard to increased risks of debilitating late effects.

Potential Morbidity Reduction for Lung Stereotactic Body Radiation Therapy Using Respiratory Gating

Simple Summary

Lung stereotactic body radiotherapy (SBRT) is the standard of care for early-stage lung cancer and oligometastases. For SBRT, motion has to be considered to avoid misdosage. Respiratory phase gating, meaning to irradiate the target volume only in a predefined gating motion phase window, can be applied to mitigate motion-induced effects. The aim of this study was to exploit the clinical benefit of gating for lung SBRT. For the majority of 14 lung tumor patients and various gating windows, we could prove a reduced dose to normal tissue by gating simulation. A normal tissue complication probability (NTCP) model analysis revealed a major reduction of normal tissue toxicity for moderate gating window sizes. The most beneficial effect of gating was found for those patients with the highest prior toxicity risk. The presented results are useful for personalized risk assessment prior to treatment and may help to select patients and optimal gating windows.

Abstract

We investigated the potential of respiratory gating to mitigate the motion-caused misdosage in lung stereotactic body radiotherapy (SBRT). For fourteen patients with lung tumors, we investigated treatment plans for a gating window (GW) including three breathing phases around the maximum exhalation phase, GW40–60. For a subset of six patients, we also assessed a preceding three-phase GW20–40 and six-phase GW20–70. We analyzed the target volume, lung, esophagus, and heart doses. Using normal tissue complication probability (NTCP) models, we estimated radiation pneumonitis and esophagitis risks. Compared to plans without gating, GW40–60 significantly reduced doses to organs at risk without impairing the tumor doses. On average, the mean lung dose decreased by 0.6 Gy (p < 0.001), treated lung V20Gy by 2.4% (p = 0.003), esophageal dose to 5cc by 2.0 Gy (p = 0.003), and maximum heart dose by 3.2 Gy (p = 0.009). The model-estimated mean risks of 11% for pneumonitis and 12% for esophagitis without gating decreased upon GW40–60 to 7% and 9%, respectively. For the highest-risk patient, gating reduced the pneumonitis risk from 43% to 32%. Gating is most beneficial for patients with high-toxicity risks. Pre-treatment toxicity risk assessment may help optimize patient selection for gating, as well as GW selection for individual patients.

Brachial Plexus Tolerance to Single-Session SAbR in a Pig Model

PURPOSE

The single-session dose tolerance of the spinal nerves has been observed to be similar to that of the spinal cord in pigs, counter to the perception that peripheral nerves are more tolerant to radiation. This pilot study aims to obtain a first impression of the single-session dose-response of the brachial plexus using pigs as a model.

METHODS AND MATERIALS

Ten Yucatan minipigs underwent computed tomography and magnetic resonance imaging for treatment planning, followed by single-session stereotactic ablative radiotherapy. A 2.5-cm length of the left-sided brachial plexus cords was irradiated. Pigs were distributed in 3 groups with prescription doses of 16 (n = 3), 19 (n = 4), and 22 Gy (n = 3). Neurologic status was assessed by observation for changes in gait and electrodiagnostic examination. Histopathologic examination was performed with light microscopy of paraffin-embedded sections stained with Luxol fast blue/periodic acid-Schiff and Masson's trichrome.

RESULTS

Seven of the 10 pigs developed motor deficit to the front limb of the irradiated side, with a latency from 5 to 8 weeks after irradiation. Probit analysis of the maximum nerve dose yields an estimated ED₅₀ of 19.3 Gy for neurologic deficit, but the number of animals was insufficient to estimate 95% confidence intervals. No motor deficits were observed at a maximum dose of 17.6 Gy for any pig. Nerve conduction studies showed an absence of sensory response in all responders and absent or low motor response in most of the responders (71%). All symptomatic pigs showed histologic lesions to the left-sided plexus consistent with radiation-induced neuropathy.

CONCLUSIONS

The single-session ED₅₀ for symptomatic plexopathy in Yucatan minipigs after irradiation of a 2.5-cm length of the brachial plexus cords was determined to be 19.3 Gy. The dose-response curve overlaps that of the spinal nerves and the spinal cord in the same animal model. The relationship between the brachial plexus tolerance in pigs and humans is unknown, and caution is warranted when extrapolating for clinical use.

American Radium Society Appropriate Use Criteria for Radiation Therapy in Oligometastatic or Oligoprogressive Non-Small Cell Lung Cancer

PURPOSE

Recent randomized studies have suggested improvements in progression-free and overall survival with the addition of stereotactic body radiation therapy (SBRT, also known as SABR) in patients with oligometastatic non-small cell lung cancer. Given the novelty and complexity of incorporating SBRT in the oligometastatic setting, the multidisciplinary American Radium Society Lung Cancer Panel was assigned to create appropriate use criteria on SBRT as part of consolidative local therapy for patients with oligometastatic and oligoprogressive non-small cell lung cancer.

METHODS AND MATERIALS

A review of the current literature was conducted from January 1, 2008, to December 25, 2020, using the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines to systematically search the PubMed database to retrieve a comprehensive set of relevant articles.

RESULTS

Based on representation in existing randomized trials, the panel defined the term "oligometastasis" as ≤3 metastatic deposits (not including the primary tumor) in the previously untreated setting or after first-line systemic therapy after the initial diagnosis. "Oligoprogression" also referred to ≤3 discrete areas of progression in the setting of prior or ongoing receipt of systemic therapy. In all appropriate patients, the panel strongly recommends enrollment in a clinical trial whenever available. For oligometastatic disease, administering first-line systemic therapy followed by consolidative radiation therapy (to all sites plus the primary/nodal disease) is preferred over up-front radiation therapy. Owing to a dearth of data, the panel recommended that consolidative radiation therapy be considered on a case-by-case basis for 4 to 5 sites of oligometastatic disease, driver mutation-positive oligometastatic disease without progression on up-front targeted therapy, and oligoprogressive cases.

CONCLUSIONS

Although SBRT/SABR appears to be both safe and effective in treating patients with limited metastatic sites of disease, many clinical circumstances require individualized management and strong multidisciplinary discussion on account of the limited existing data.

Strategies to develop radiomics and machine learning models for lung cancer stage and histology prediction using small data samples

Predictive models based on radiomics and machine-learning (ML) need large and annotated datasets for training, often difficult to collect. We designed an operative pipeline for model training to exploit data already available to the scientific community. The aim of this work was to explore the capability of radiomic features in predicting tumor histology and stage in patients with non-small cell lung cancer (NSCLC). We analyzed the radiotherapy planning thoracic CT scans of a proprietary sample of 47 subjects (L-RT) and integrated this dataset with a publicly available set of 130 patients from the MAASTRO NSCLC collection (Lung1). We implemented intra- and inter-sample cross-validation strategies (CV) for evaluating the ML predictive model performances with not so large datasets. We carried out two classification tasks: histology classification (3 classes) and overall stage classification (two classes: stage I and II). In the first task, the best performance was obtained by a Random Forest classifier, once the analysis has been restricted to stage I and II tumors of the Lung1 and L-RT merged dataset (AUC = 0.72 ± 0.11). For the overall stage classification, the best results were obtained when training on Lung1 and testing of L-RT dataset (AUC = 0.72 ± 0.04 for Random Forest and AUC = 0.84 ± 0.03 for linear-kernel Support Vector Machine). According to the classification task to be accomplished and to the heterogeneity of the available dataset(s), different CV strategies have to be explored and compared to make a robust assessment of the potential of a predictive model based on radiomics and ML.

Influence of target dose heterogeneity on dose sparing of normal tissue in peripheral lung tumor stereotactic body radiation therapy

OBJECTIVE

To evaluate the influence of target dose heterogeneity on normal tissue dose sparing for peripheral lung tumor stereotactic body radiation therapy (SBRT).

METHODS

Based on the volumetric-modulated arc therapy (VMAT) technique, three SBRT plans with homogeneous, moderate heterogeneous, and heterogeneous (HO, MHE, and HE) target doses were compared in 30 peripheral lung tumor patients. The prescription dose was 48 Gy in 4 fractions. Ten rings outside the PTV were created to limit normal tissue dosage and evaluate dose falloff.

RESULTS

When MHE and HE plans were compared to HO plans, the conformity index of the PTV was increased by approximately 0.08. The median mean lung dose (MLD), V₅, V₁₀, V₂₀ of whole lung, D_2%, D_1cc, D_2cc of the rib, V₃₀ of the rib, D_2% and the maximum dose (D_max) of the skin, and D_2% and D_max of most mediastinal organs at risk (OARs) and spinal cord were reduced by up to 4.51 Gy or 2.8%. Analogously, the median D_max, D_2% and mean dose of rings were reduced by 0.71 to 8.46 Gy; and the median R_50% and D_2cm were reduced by 2.1 to 2.3 and 7.4% to 8.0%, respectively. Between MHE and HE plans there was little to no difference in OARs dose and dose falloff beyond the target. Furthermore, the dose sparing of rib V₃₀ and the mean dose of rings were negatively correlated with the rib and rings distance from tumor, respectively.

CONCLUSIONS

For peripheral lung tumor SBRT, target conformity, normal tissue dose, and dose falloff around the target could be improved by loosening or abandoning homogeneity. While there was negligible further dose benefit for the maximum target dose above 125% of the prescription, dose sparing of normal tissue derived from a heterogeneous target decreased as the distance from the tumor increased.

Treatment outcomes of passive scattering proton beam therapy for stage I non-small cell lung cancer

INTRODUCTION

To investigate the treatment outcomes of passive scattering proton beam therapy using stereotactic ablative radiotherapy (SABR) or hypofractionated radiation therapy (RT) for inoperable patients or those who refused surgery for stage I non-small cell lung cancer (NSCLC).

METHODS

From January 2016 to December 2019, we retrospectively analyzed 42 patients with stage I NSCLC treated with proton beam therapy. The initially intended dose regimen was 60 cobalt Gray equivalents (CGE) in 4 fractions; however, sequentially modified dose regimens were used when the dose-volume constraints could not be met. The median total dose was 50 CGE (range 50-70 CGE), while the corresponding median biologically effective dose using [Formula: see text]= 10 (BED₁₀) was 112.5 CGE (range 96-150 CGE).

RESULTS

The median follow-up time was 40 months (interquartile range 32-48 months). Among the 42 treated patients, 33 had pathologically proven cancers of which most were adenocarcinoma (n = 21, 64%). The 3-year overall survival rate was 71.8%. The estimated rates of local control and progression free survival at 3 years were 91.5% and 66.9%, respectively. Thirteen patients experienced disease progression consisting of three local, six regional, and nine distant failures. No grade 4 or 5 toxicities were observed.

CONCLUSION

Passive scattering proton beam therapy for stage I NSCLC using SABR or hypofractionated RT was safe and showed high LC rates.

Radiation-Induced Dyspnea in Lung Cancer Patients Treated with Stereotactic Body Radiation Therapy

Simple Summary

Dyspnea is a common symptomatic side-effect of thoracic radiation therapy. The aim of this study is to build a predictive model of any-grade radiation-induced dyspnea within six months after stereotactic body radiation therapy in patients treated for non-small cell lung cancer. The occurrence of pre-treatment chronic obstructive pulmonary disease and higher relative lungs volume receiving more than 15 Gy as well as heart volume were shown to be risk factors for dyspnea. The obtained results encourage further studies on the topic, which could validate the present organ-based findings and explore the voxel-based landscape of radiation dose sensitivity in the development of dyspnea.

Abstract

In this study, we investigated the prognostic factors for radiation-induced dyspnea after hypo-fractionated radiation therapy (RT) in 106 patients treated with Stereotactic Body RT for Non-Small-Cell Lung Cancer (NSCLC). The median prescription dose was 50 Gy (range: 40–54 Gy), delivered in a median of four fractions (range: 3–12). Dyspnea within six months after SBRT was scored according to CTCAE v.4.0. Biologically Effective Dose (α/β = 3 Gy) volume histograms for lungs and heart were extracted. Dosimetric parameters along with patient-specific and treatment-related factors were analyzed, multivariable logistic regression method with Leave-One-Out (LOO) internal validation applied. Model performance was evaluated by the area under the receiver operating characteristic (ROC) curve (AUC) and calibration plot parameters. Fifty-seven patients (53.8%) out of 106 developed dyspnea of any grade after SBRT (25/57 grade ≥ 2 cases). A three-variable predictive model including patient comorbidity (COPD), heart volume and the relative lungs volume receiving more than 15 Gy was selected. The model displays an encouraging performance given by a training ROC-AUC = 0.71 [95%CI 0.61–0.80] and a LOO-ROC-AUC = 0.64 [95%CI 0.53–0.74]. Further modeling efforts are needed for dyspnea prediction in hypo-fractionated treatments in order to identify patients at high risk for developing lung toxicity more accurately.