Possible Misinterpretation of Demarcated Solid Patterns of Radiation Fibrosis on CT Scans as Tumor Recurrence in Patients Receiving Hypofractionated Stereotactic Radiotherapy for Lung Cancer

Evaluation of chest CT-scans following lung stereotactic ablative radiotherapy: Challenges and new insights

Stereotactic ablative radiotherapy (SABR) is increasingly used for the treatment of early-stage non-small cell lung cancer (ES-NSCLC) and for pulmonary metastases. In patients with ES-NSCLC, SABR is highly successful with reported 5-year local control rates of approximately 90%. However, the assessment of local control following lung SABR can be challenging as radiological changes arising from radiation-induced lung injury (RILI) can be observed in up to 90% of patients. These so-called 'benign' radiological changes evolve with time and are often asymptomatic. Several radiological and metabolic features have been explored to help distinguish RILI from local recurrences (LR). These include the Response Evaluation Criteria for Solid Tumors (RECIST), high-risk features (HRF's) and maximum standardized uptake value (SUVmax) on FDG-PET-CT. However, use of some of these approaches have poor predictive values and low specificity for recurrence. A proposed new workflow for the evaluation of post-lung SABR radiological changes will be reviewed which uses the presence of so-called 'actionable radiological features' to trigger changes to imaging schedules and identifies the need for a multidisciplinary board review. Furthermore, this critical review of post-lung SABR imaging will highlight current challenges, new insights, and unknowns in this field.

Radiation Therapy for Lung Cancer: Imaging Appearances and Pitfalls

Radiation therapy is part of a multimodality treatment approach to lung cancer. The radiologist must be aware of both the expected and the unexpected imaging findings of the post-radiation therapy patient, including the time course for development of post- radiation therapy pneumonitis and fibrosis. In this review, a brief discussion of radiation therapy techniques and indications is presented, followed by an image-heavy differential diagnostic approach. The review focuses on computed tomography imaging examples to help distinguish normal postradiation pneumonitis and fibrosis from alternative complications, such as infection, local recurrence, or radiation-induced malignancy.

Noninvasive Quantification of Radiation-Induced Lung Injury Using a Targeted Molecular Imaging Probe

PURPOSE

Radiation-induced lung injury (RILI) is a progressive inflammatory process seen after irradiation for lung cancer. The disease can be insidious, often characterized by acute pneumonitis followed by chronic fibrosis with significant associated morbidity. No therapies are approved for RILI, and accurate disease quantification is a major barrier to improved management. Here, we sought to noninvasively quantify RILI using a molecular imaging probe that specifically targets type 1 collagen in mouse models and patients with confirmed RILI.

METHODS AND MATERIALS

Using a murine model of lung radiation, mice were imaged with EP-3533, a type 1 collagen probe, to characterize the development of RILI and to assess disease mitigation after losartan treatment. The human analog probe 68Ga-CBP8, targeting type 1 collagen, was tested on excised human lung tissue containing RILI and was quantified via autoradiography. 68Ga-CBP8 positron emission tomography was used to assess RILI in vivo in 6 human subjects.

RESULTS

Murine models demonstrated that probe signal correlated with progressive RILI severity over 6 months. The probe was sensitive to mitigation of RILI by losartan. Excised human lung tissue with RILI had increased binding versus unirradiated control tissue, and 68Ga-CBP8 uptake correlated with collagen proportional area. Human imaging revealed significant 68Ga-CBP8 uptake in areas of RILI and minimal background uptake.

CONCLUSIONS

These findings support the ability of a molecular imaging probe targeted at type 1 collagen to detect RILI in preclinical models and human disease, suggesting a role for targeted molecular imaging of collagen in the assessment of RILI.

Noninvasive Quantification of Radiation-Induced Lung Injury using a Targeted Molecular Imaging Probe

Rationale

Radiation-induced lung injury (RILI) is a progressive inflammatory process commonly seen following irradiation for lung cancer. The disease can be insidious, often characterized by acute pneumonitis followed by chronic fibrosis with significant associated morbidity. No therapies are approved for RILI, and accurate disease quantification is a major barrier to improved management.

Objective

To noninvasively quantify RILI, utilizing a molecular imaging probe that specifically targets type 1 collagen in mouse models and patients with confirmed RILI.

Methods

Using a murine model of lung radiation, mice were imaged with EP-3533, a type 1 collagen probe to characterize the development of RILI and to assess disease mitigation following losartan treatment. The human analog probe targeted against type 1 collagen, 68Ga-CBP8, was tested on excised human lung tissue containing RILI and quantified via autoradiography. Finally, 68Ga-CBP8 PET was used to assess RILI in vivo in six human subjects.

Results

Murine models demonstrated that probe signal correlated with progressive RILI severity over six-months. The probe was sensitive to mitigation of RILI by losartan. Excised human lung tissue with RILI had increased binding vs unirradiated control tissue and 68Ga-CBP8 uptake correlated with collagen proportional area. Human imaging revealed significant 68Ga-CBP8 uptake in areas of RILI and minimal background uptake.

Conclusions

These findings support the ability of a molecular imaging probe targeted at type 1 collagen to detect RILI in preclinical models and human disease, suggesting a role for targeted molecular imaging of collagen in the assessment of RILI.Clinical trial registered with www.clinicaltrials.gov (NCT04485286, NCT03535545).

Radiomic analysis for early differentiation of lung cancer recurrence from fibrosis in patients treated with lung stereotactic ablative radiotherapy

Objective. The development of radiation-induced fibrosis after stereotactic ablative radiotherapy (SABR) can obscure follow-up images and delay detection of a local recurrence in early-stage lung cancer patients. The objective of this study was to develop a radiomics model for computer-assisted detection of local recurrence and fibrosis for an earlier timepoint (<1 year) after the SABR treatment.Approach. This retrospective clinical study included CT images (n= 107) of 66 patients treated with SABR. A z-score normalization technique was used for radiomic feature standardization across scanner protocols. The training set for the radiomics model consisted of CT images (66 patients; 22 recurrences and 44 fibrosis) obtained at 24 months (median) follow-up. The test set included CT-images of 41 patients acquired at 5-12 months follow-up. Combinations of four widely used machine learning techniques (support vector machines, gradient boosting, random forests (RF), and logistic regression) and feature selection methods (Relief feature scoring, maximum relevance minimum redundancy, mutual information maximization, forward feature selection, and LASSO) were investigated. Pyradiomics was used to extract 106 radiomic features from the CT-images for feature selection and classification.Main results. An RF + LASSO model scored the highest in terms of AUC (0.87) and obtained a sensitivity of 75% and a specificity of 88% in identifying a local recurrence in the test set. In the training set, 86% accuracy was achieved using five-fold cross-validation. Delong's test indicated that AUC achieved by the RF+LASSO is significantly better than 11 other machine learning models presented here. The top three radiomic features: interquartile range (first order), Cluster Prominence (GLCM), and Autocorrelation (GLCM), were revealed as differentiating a recurrence from fibrosis with this model.Significance. The radiomics model selected, out of multiple machine learning and feature selection algorithms, was able to differentiate a recurrence from fibrosis in earlier follow-up CT-images with a high specificity rate and satisfactory sensitivity performance.

Response Evaluation Following Radiation Therapy With 18F-FDG PET/CT: Common Variants of Radiation-Induced Changes and Potential Pitfalls

Radiation therapy (RT) is one of the cornerstones in cancer treatment and approximately half of all patients will receive some form of RT during the course of their cancer management. Response evaluation after RT and follow-up imaging with ¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) can be complicated by RT-induced acute, chronic or consequential effects. There is a general consensus that ¹⁸F-FDG PET/CT for response evaluation should be delayed for 12 weeks after completing RT to minimize the risk of false-positive findings. Radiation-induced late side effects in normal tissue can take years to develop and eventually cause symptoms that on imaging can potentially mimic recurrent disease. Imaging findings in radiation induced injuries depend on the normal tissue included in the irradiated volume and the radiation therapy regime including the total dose delivered, dose per fraction and treatment schedule. The intent for radiation therapy should be taken in consideration when evaluating the response on imaging, that is palliative vs curative or neoadjuvant vs adjuvant RT. Imaging findings can further be distorted by altered anatomy and sequelae following surgery within the radiation field. An awareness of common PET/CT-induced changes/injuries is essential when interpreting ¹⁸F-FDG PET/CT as well as obtaining a complete medical history, as patients are occasionally scanned for an unrelated cause to previously RT treated malignancy. In addition, secondary malignancies due to carcinogenic effects of radiation exposure in long-term cancer survivors should not be overlooked. ¹⁸F-FDG PET/CT can be very useful in response evaluation and follow-up in patients treated with RT, however, variants and pitfalls are common and it is important to remember that radiation-induced injury is often a diagnosis of exclusion.

A pictorial essay on radiological changes after stereotactic body radiation therapy for lung tumors

Stereotactic body radiation therapy (SBRT) is a frequently used modality for the treatment of early stage non-small cell lung cancer and oligometastatic disease of the lung. The radiological changes observed in the lung after SBRT are likely to differ from those observed after conventional thoracic radiation therapy, primarily due to the small size of the target volume and highly conformal dose distributions with steep dose gradients from the target to surrounding normal lung tissues used in SBRT. Knowledge of the radiological changes that can occur after SBRT is required to correctly diagnose local failure. Herein, I report several radiological changes specific to SBRT that have been observed.

Moderne Tumortherapien und ihre pulmonalen Nebenwirkungen

Die Strahlentherapie und in jüngerer Zeit insbesondere die medikamentöse molekulare Therapie sind zentrale Bestandteile der modernen Onkologie. Beide Therapieformen eignen sich dazu, Tumoren bei vergleichsweise geringen systemischen Nebenwirkungen effektiv zu behandeln. Dennoch haben auch diese Behandlungsansätze Nebenwirkungen, die zum einen durch die Toxizität der Strahlung, zum anderen durch immunmodulatorische Effekte der verabreichten Medikamente ausgelöst werden. Das pneumotoxische Potenzial dieser Therapieformen spiegelt sich unter anderem in der Entstehung von interstitiellen Pneumonitiden wider, die in fibrotische Lungengerüstveränderungen übergehen können. Erschwert wird die klinische Diagnose der Erkrankung durch die unspezifischen Symptome. Die Computertomographie (CT) stellt ein ausgezeichnetes Mittel dar, um korrespondierende Verdichtungen zu diagnostizieren und im zeitlichen Verlauf zu monitoren. Damit wird dem Radiologen im interdisziplinären Kontext eine wichtige Rolle bei der Diagnostik dieses Krankheitsbildes zuteil.

A systematic review into the radiological features predicting local recurrence after stereotactic ablative body radiotherapy (SABR) in patients with non-small cell lung cancer (NSCLC): Local recurrence features of NSCLC post-SABR

BACKGROUND AND PURPOSE

Post-treatment surveillance for local recurrence (LR) following SABR can include both fluorodeoxyglucose-positron emission tomography (FDG-PET) and computed tomography (CT). Radiation-induced lung injury (RILI) shares a similar appearance to LR after treatment making the detection of LR on imaging difficult for clinicians. We aimed to summarise radiological features of CT and FDG-PET predicting LR, and to evaluate radiomics as another tool for detecting LR.

METHODS AND MATERIALS

We searched MEDLINE, EMBASE and PubMed databases for published studies and Web of Science, Wiley Online and Science Direct databases for conference abstracts that had patient populations with NSCLC and reported post-SABR radiological features of FDG-PET or CT and radiomics from either FDG-PET or CT. Studies for inclusion were independently reviewed by two authors.

RESULTS

Across 32 relevant studies, the incidence of LR was 13% (222/1726). On CT, certain gross radiological appearances, and kinetic features of changes in size, diameter, volume or 3 consecutive rises in volume of mass-like consolidation are suggestive of LR. Particular regard should be made for the presence of any ≥3 high-risk features (HRF) on CT or the individual HRF of enlarging opacity at ≥12 month's post-SABR as being highly suspicious of LR. On FDG-PET a relative reduction of <5% of SUV_max from baseline in the first 12 months or cut-offs of SUV_max >5 and SUV_mean >3.44 after 12 months can indicate LR. There is limited evidence available to corroborate radiomic features suggestive of LR.

CONCLUSION

This research has identified common features of LR compared to RILI which may aid in early and accurate detection of LR post-SABR; further research is required to validate these findings.

[Modern tumor therapy and its pulmonary side effects]

Die Strahlentherapie und in jüngerer Zeit insbesondere die medikamentöse molekulare Therapie sind zentrale Bestandteile der modernen Onkologie. Beide Therapieformen eignen sich dazu, Tumoren bei vergleichsweise geringen systemischen Nebenwirkungen effektiv zu behandeln. Dennoch haben auch diese Behandlungsansätze Nebenwirkungen, die zum einen durch die Toxizität der Strahlung, zum anderen durch immunmodulatorische Effekte der verabreichten Medikamente ausgelöst werden. Das pneumotoxische Potenzial dieser Therapieformen spiegelt sich unter anderem in der Entstehung von interstitiellen Pneumonitiden wider, die in fibrotische Lungengerüstveränderungen übergehen können. Erschwert wird die klinische Diagnose der Erkrankung durch die unspezifischen Symptome. Die Computertomographie (CT) stellt ein ausgezeichnetes Mittel dar, um korrespondierende Verdichtungen zu diagnostizieren und im zeitlichen Verlauf zu monitoren. Damit wird dem Radiologen im interdisziplinären Kontext eine wichtige Rolle bei der Diagnostik dieses Krankheitsbildes zuteil.

Stereotactic body radiotherapy for adenoid cystic carcinoma metastatic to the lung: a case report

Background

Adenoid cystic carcinoma (ACC) is a rare malignant tumor involving mostly the head and neck region, and frequently the salivary glands. The development of lung metastasis after treatment of the primary tumor is a common occurrence in ACC. Although lung metastases show a slow rate of growth, approximately 10% of patients die from distant metastases. The radioresistance of ACC limits the efficacy of conventional radiotherapy for lung metastases, and the optimal dose remains to be determined. Stereotactic body radiotherapy (SBRT) using CyberKnife can deliver a high dose to the lung tumor, while sparing the surrounding normal lung tissues, leading to favorable local control in non-squamous cell lung cancer and metastatic lung tumors. We report a case of lung metastases from ACC treated successfully with SBRT using CyberKnife.

Case presentation

A 76-year-old Japanese man with ACC who was treated with carbon ion radiotherapy for a primary oropharynx tumor presented with three metastatic lesions in the lung. The tumor masses were located in the right upper, right lower, and left lower lobes of the lungs. Surgical resection was not indicated because of the presence of multiple tumors. The patient underwent SBRT at 60 Gy in 10 sequential fractions for each tumor. The biologically effective dose based on an alpha/beta ratio of 2 Gy was 240 Gy per tumor. The percentage of the total lung volume irradiated with >20 Gy was 4.9%, 3.2%, and 2.6% for each tumor. The patient developed acute radiation pneumonitis during the initial therapy, which resolved at 6 months after the CyberKnife treatment. At 21 months after the first CyberKnife treatment, three tumors showed no signs of recurrence. No late toxicity was observed.

Conclusions

SBRT using CyberKnife is an effective and feasible approach to the management of multiple lung metastases of ACC.

Safety and utility of performing CT-guided biopsies of pulmonary lesions that arise after radiotherapy

This study aimed to evaluate the feasibility, safety and usefulness of performing computed tomography (CT)-guided biopsies of pulmonary lesions that arise after radiotherapy. Seventeen patients (14 males and 3 females; median age: 69 years, range: 48-84 years) underwent CT-guided biopsies of pulmonary lesions that occurred in lung regions that had previously been treated with radiotherapy. Three patients underwent CT-guided biopsies twice, and thus, the total number of procedures was 20. We reviewed the subjects' medical records and images, and evaluated the rate for obtaining pathological diagnosis with the biopsy sample, subsequent clinical course, and complications associated with the procedure. In 19 of 20 procedures (95%), the CT-guided biopsy resulted in a pathological diagnosis being obtained. In 14 procedures, the pathological results were consistent with the patients' clinical courses. In the remaining 5 procedures, the lesions were pathologically diagnosed as benign, but they increased in size thereafter; so the lesions were considered to be clinically malignant. The results were considered to represent sampling errors. There were 3 minor complications (slight pneumothorax which did not require drainage) (3/20, 15%), and there were no major complications. In conclusion, performing CT-guided biopsies of pulmonary lesions that arise after radiotherapy appears to be feasible, safe and useful.

Predicting pathological complete response (pCR) after stereotactic ablative radiation therapy (SABR) of lung cancer using quantitative dynamic [18F]FDG PET and CT perfusion: a prospective exploratory clinical study

BACKGROUND

Stereotactic ablative radiation therapy (SABR) is effective in treating inoperable stage I non-small cell lung cancer (NSCLC), but imaging assessment of response after SABR is difficult. This prospective study aimed to develop a predictive model for true pathologic complete response (pCR) to SABR using imaging-based biomarkers from dynamic [¹⁸F]FDG-PET and CT Perfusion (CTP).

METHODS

Twenty-six patients with early-stage NSCLC treated with SABR followed by surgical resection were included, as a pre-specified secondary analysis of a larger study. Dynamic [¹⁸F]FDG-PET and CTP were performed pre-SABR and 8-week post. Dynamic [¹⁸F]FDG-PET provided maximum and mean standardized uptake value (SUV) and kinetic parameters estimated using a previously developed flow-modified two-tissue compartment model while CTP measured blood flow, blood volume and vessel permeability surface product. Recursive partitioning analysis (RPA) was used to establish a predictive model with the measured PET and CTP imaging biomarkers for predicting pCR. The model was compared to current RECIST (Response Evaluation Criteria in Solid Tumours version 1.1) and PERCIST (PET Response Criteria in Solid Tumours version 1.0) criteria.

RESULTS

RPA identified three response groups based on tumour blood volume before SABR (BV_pre-SABR) and change in SUV_max (ΔSUV_max), the thresholds being BV_pre-SABR = 9.3 mL/100 g and ΔSUV_max = - 48.9%. The highest true pCR rate of 92% was observed in the group with BV_pre-SABR < 9.3 mL/100 g and ΔSUV_max < - 48.9% after SABR while the worst was observed in the group with BV_pre-SABR ≥ 9.3 mL/100 g (0%). RPA model achieved excellent pCR prediction (Concordance: 0.92; P = 0.03). RECIST and PERCIST showed poor pCR prediction (Concordance: 0.54 and 0.58, respectively).

CONCLUSIONS

In this study, we developed a predictive model based on dynamic [¹⁸F]FDG-PET and CT Perfusion imaging that was significantly better than RECIST and PERCIST criteria to predict pCR of NSCLC to SABR. The model used BV_pre-SABR and ΔSUV_max which correlates to tumour microvessel density and cell proliferation, respectively and warrants validation with larger sample size studies.

TRIAL REGISTRATION

MISSILE-NSCLC, NCT02136355 (ClinicalTrials.gov). Registered May 8, 2014, https://clinicaltrials.gov/ct2/show/NCT02136355.

Regulatory T Cells: An Emerging Player in Radiation-Induced Lung Injury

Regulatory T cells (Tregs), which have long been recognized as essential regulators of both inflammation and autoimmunity, also impede effective antitumor immune response due to their immunosuppressive properties. Combined radiotherapy and immunotherapeutic interventions focusing on the removal of Tregs have recently garnered interest as a promising strategy to reverse immunosuppression. Meanwhile, Tregs are emerging as a key player in the pathogenesis of radiation-induced lung injury (RILI), a frequent and potentially life-threatening complication of thoracic radiotherapy. Recognition of the critical role of Tregs in RILI raises the important question of whether radiotherapy combined with Treg-targeting immunotherapy offers any beneficial effects in the protection of normal lung tissue. This present review focuses on the contributions of Tregs to RILI, with particular emphasis on the suspected differential role of Tregs in the pneumonitic phase and fibrotic phase of RILI. We also introduce recent progress on the potential mechanisms by which Tregs modulate RILI and the crosstalk among Tregs, other infiltrating T cells, fibrocytes, and resident epithelial cells driving disease pathogenesis. Finally, we discuss whether Tregs also hold promise as a potential target for immunotherapeutic interventions for RILI.

Modern evidence and future prospects of external body radiation therapy for lung oligometastases of breast cancer

After Hellman and Weichselbaum defined "Oligometastasis" in 1995, several local therapies for lung oligometastases including surgical resection and external body radiation therapy were reported that improved local control (LC) and progression-free survival, overall survival, and quality of life. This suggests that oligometastases is a potentially curable state. Modern advances in radiation therapy such as stereotactic body radiation therapy (SBRT) in which high dose coverage of target lesion without exposure of normal organ is possible, and are widely used to treat solitary or a limited number of primary lung cancer and metastases. Several reports showed that SBRT was a useful treatment method for lung oligometastases, and the LC rate of SBRT was 80-90% in 2 years and less invasive than surgical resection. SBRT is a safe and effective especially for small and peripheral lung metastases. However, if the metastatic lesion is big or centrally located, careful treatment is necessary to prevent radiation pneumonitis. After SBRT, it is sometimes difficult to differentiate local recurrence and pulmonary injury, especially in the early phase. However, it is important to detect local recurrence especially in patients who require further local therapy such as surgical resection and re-irradiation or systemic therapy. The diagnosis can be improved by determining the natural course after SBRT and local recurrence with computed tomography imaging and ¹⁸F-fluorodeoxyglucose positron emission tomography, respectively. Moreover, radiation therapy may have both local and systemic effects that are related to the enhancement of immune-response after radiation. Currently, several trials evaluating the benefits of SBRT for oligometastatic breast cancer are underway. However, the adaption of SBRT for lung metastases including other treatment strategies should be carefully discussed by the radiation oncologist and a multi-disciplinary team comprising a breast surgeon, medical oncologist, diagnostic radiologist, and radiation oncologist, among others.

Artificial Intelligence in Lung Cancer: Bridging the Gap Between Computational Power and Clinical Decision-Making

Lung cancer remains the most common cause of cancer death worldwide. Recent advances in lung cancer screening, radiotherapy, surgical techniques, and systemic therapy have led to increasing complexity in diagnosis, treatment decision-making, and assessment of recurrence. Artificial intelligence (AI)-based prediction models are being developed to address these issues and may have a future role in screening, diagnosis, treatment selection, and decision-making around salvage therapy. Imaging plays an essential role in all components of lung cancer management and has the potential to play a key role in AI applications. Artificial intelligence has demonstrated value in prognostic biomarker discovery in lung cancer diagnosis, treatment, and response assessment, putting it at the forefront of the next phase of personalized medicine. However, although exploratory studies demonstrate potential utility, there is a need for rigorous validation and standardization before AI can be utilized in clinical decision-making. In this review, we will provide a summary of the current literature implementing AI for outcome prediction in lung cancer. We will describe the anticipated impact of AI on the management of patients with lung cancer and discuss the challenges of clinical implementation of these techniques.

Radiation-Induced Lung Fibrosis: Preclinical Animal Models and Therapeutic Strategies

Radiation-induced lung injury (RILI), including acute radiation pneumonitis and chronic radiation-induced lung fibrosis, is the most common side effect of radiation therapy. RILI is a complicated process that causes the accumulation, proliferation, and differentiation of fibroblasts and, finally, results in excessive extracellular matrix deposition. Currently, there are no approved treatment options for patients with radiation-induced pulmonary fibrosis (RIPF) partly due to the absence of effective targets. Current research advances include the development of small animal models reflecting modern radiotherapy, an understanding of the molecular basis of RIPF, and the identification of candidate drugs for prevention and treatment. Insights provided by this research have resulted in increased interest in disease progression and prognosis, the development of novel anti-fibrotic agents, and a more targeted approach to the treatment of RIPF.

Can high-risk CT features suggest local recurrence after stereotactic body radiation therapy for lung cancer? A systematic review and meta-analysis

PURPOSE

To perform a systematic review and meta-analysis evaluating usefulness of high-risk CT features (HRFs) on follow-up CT in detecting local recurrence after stereotactic body radiation therapy (SBRT) in lung cancer patients.

METHODS

Pubmed and EMBASE were searched up to January 11th, 2019. We included studies that differentiated local recurrence from post-SBRT changes after SBRT on follow-up CT in lung cancer patients. Methodological quality was assessed using QUADAS-2. The association between HRFs and local recurrence were pooled in the form of odds ratio (OR) using the random effects model. Heterogeneity was examined by the Inconsistency index (I²).

RESULTS

Eight studies were included, consisting of 356 lung cancer patients. The overall prevalence of patients with local recurrence was 18.8 % (67/356). Compared with post-SBRT changes, local recurrence after SBRT more frequently demonstrated air-bronchogram disappearance (OR = 7.15), bulging margin (OR = 24.12), craniocaudal growth (OR = 26.07), enlargement after 12 months (OR = 28.11), enlarging opacity (OR = 7.92), linear margin disappearance (OR = 29.24), and sequential enlargement (OR = 83.23) (p ≤ 0.02). Pleural effusion appearance was not related with local recurrence (p = 0.82). Heterogeneity varied among HRFs (I² = 0-91 %). The quality of the studies was considered moderate.

CONCLUSIONS

Several HRFs on follow-up CT after SBRT were useful in suggesting local recurrence. These HRFs may help raise clinical suspicion of local recurrence, initiate prompt additional test for confirmation and perform subsequent proper personalized salvage treatment.

Concise Review: Therapeutic Potential of the Mesenchymal Stem Cell Derived Secretome and Extracellular Vesicles for Radiation-Induced Lung Injury: Progress and Hypotheses

Radiation-induced lung injury (RILI) is a common complication in radiotherapy of thoracic tumors and limits the therapeutic dose of radiation that can be given to effectively control tumors. RILI develops through a complex pathological process, resulting in induction and activation of various cytokines, infiltration by inflammatory cells, cytokine-induced activation of fibroblasts, and subsequent tissue remodeling by activated fibroblasts, ultimately leading to impaired lung function and respiratory failure. Increasing evidence shows that mesenchymal stem cells (MSCs) may play a main role in modulating inflammation and immune responses, promoting survival and repair of damaged resident cells and enhancing regeneration of damaged tissue through soluble paracrine factors and therapeutic extracellular vesicles. Therefore, the use of the MSC-derived secretome and exosomes holds promising potential for RILI therapy. Here, we review recent progress on the potential mechanisms of MSC therapy for RILI, with an emphasis on soluble paracrine factors of MSCs. Hypotheses on how MSC derived exosomes or MSC-released exosomal miRNAs could attenuate RILI are also proposed. Problems and translational challenges of the therapies based on the MSC-derived secretome and exosomes are further summarized and underline the need for caution on rapid clinical translation. Stem Cells Translational Medicine 2019;8:344-354.

Assessment of tumour response after stereotactic ablative radiation therapy for lung cancer: A prospective quantitative hybrid 18 F-fluorodeoxyglucose-positron emission tomography and CT perfusion study

INTRODUCTION

Stereotactic ablative radiotherapy (SABR) is a guideline-recommended treatment for inoperable stage I non-small cell lung cancer (NSCLC), but imaging assessment of response after SABR is difficult. The goal of this study was to evaluate imaging-based biomarkers of tumour response using dynamic ¹⁸ F-FDG-PET and CT perfusion (CTP).

METHODS

Thirty-one patients with early-stage NSCLC participated in this prospective correlative study. Each underwent dynamic ¹⁸ F-FDG-PET/CTP studies on a PET/CT scanner pre- and 8 weeks post-SABR. The dynamic ¹⁸ F-FDG-PET measured the tumour SUV_max , SUV_mean and the following parameters: K₁ , k₂ , k₃ , k₄ and K_i , all using the Johnson-Wilson-Lee kinetic model. CTP quantitatively mapped BF, BV, MTT and PS in tumours and measured largest tumour diameter. Since free-breathing was allowed during CTP scanning, non-rigid image registration of CT images was applied to minimize misregistration before generating the CTP functional maps. Differences between pre- and post-SABR imaging-based parameters were compared.

RESULTS

Tumour size changed only slightly after SABR (median 26 mm pre-SABR vs. 23 mm post-SABR; P = 0.01). However, dynamic ¹⁸ F-FDG-PET and CTP study showed substantial and significant changes in SUV_max , SUV_mean , k₃ , k₄ and K_i . Significant decreases were evident in SUV_max (median 6.1 vs. 2.6; P < 0.001), SUV_mean (median 2.5 vs. 1.5; P < 0.001), k₃ (relative decrease of 52%; P = 0.002), K_i (relative decrease of 27%; P = 0.03), whereas there was an increase in k₄ (+367%; P < 0.001).

CONCLUSIONS

Hybrid ¹⁸ F-FDG-PET/CTP allowed the response of NSCLC to SABR to be assessed regarding metabolic and functional parameters. Future studies are needed, with correlation with long-term outcomes, to evaluate these findings as potential imaging biomarkers of response.

Nebulisation of synthetic lamellar lipids mitigates radiation-induced lung injury in a large animal model

Methods to protect against radiation-induced lung injury (RILI) will facilitate the development of more effective radio-therapeutic protocols for lung cancer and may provide the means to protect the wider population in the event of a deliberate or accidental nuclear or radiological event. We hypothesised that supplementing lipid membranes through nebulization of synthetic lamellar lipids would mitigate RILI. Following pre-treatment with either nebulised lamellar lipids or saline, anaesthetised sheep were prescribed fractionated radiotherapy (30 Gray (Gy) total dose in five 6 Gy fractions at 3–4 days intervals) to a defined unilateral lung volume. Gross pathology in radio-exposed lung 37 days after the first radiation treatment was consistent between treatment groups and consisted of deep red congestion evident on the pleural surface and firmness on palpation. Consistent histopathological features in radio-exposed lung were subpleural, periarteriolar and peribronchial intra-alveolar oedema, alveolar fibrosis, interstitial pneumonia and type II pneumocyte hyperplasia. The synthetic lamellar lipids abrogated radiation-induced alveolar fibrosis and reduced alpha-smooth muscle actin (ASMA) expression in radio-exposed lung compared to saline treated sheep. Administration of synthetic lamellar lipids was also associated with an increased number of cells expressing dendritic cell-lysosomal associated membrane protein throughout the lung.

Circulating Tumor Cell Assessment in Presumed Early Stage Non-Small Cell Lung Cancer Patients Treated with Stereotactic Body Radiation Therapy: A Prospective Pilot Study

PURPOSE

In patients treated with stereotactic body radiation therapy (SBRT) for presumed early stage non-small cell lung cancer (NSCLC), detection and monitoring of circulating tumor cells (CTCs) may be useful for assessing treatment response safely and noninvasively. No published reports of CTC trends in this patient population exist to date.

METHODS AND MATERIALS

Patients with clinically diagnosed stage I NSCLC treated with SBRT were eligible for this institutional review board-approved prospective clinical trial. Peripheral blood samples were assayed for CTCs via a green fluorescent protein-expressing adenoviral probe. CTC positivity was defined as 1.3 green fluorescent protein-positive cells/mL of collected blood. Samples were obtained before (pre-radiation therapy [RT]), during, and after SBRT (post-RT; months 1, 3, 6, 12, 18, and 24). SBRT was delivered in ≤5 fractions (median dose of 50 Gy in 12.5 Gy fractions) to a biological equivalent dose of ≥100 Gy in all cases.

RESULTS

Forty-eight consecutive patients (T1a [73%], T1b [21%], and T2a [6%]) were enrolled. Median follow-up was 14.2 months. Twenty patients (42%) had a positive CTC level pre-RT, with a median CTC count of 4.2 CTCs per mL (interquartile range [IQR], 2.2-18.7). Of these 20 patients, 17 had evaluable post-RT CTC evaluations showing reduced CTC counts at 1 month (median, 0.2; IQR, 0.1-0.8) and 3 months (median, 0.6; IQR, 0-1.1). Three of these 17 patients experienced disease progression at a median of 19.9 months; all 3 experienced ≥1 positive post-RT CTC test predating clinical progression by a median of 16 months (range, 2-17 months). In contrast, among patients presenting with CTC-detectable disease and for whom all post-RT CTC tests were negative, none experienced recurrence or progression.

CONCLUSIONS

CTC monitoring after SBRT for presumed early stage NSCLC may give lead-time notice of disease recurrence or progression. Conversely, negative CTC counts after treatment may provide reassurance of disease control. CTC analysis is thus potentially useful in enhancing clinical diagnosis and follow-up in this population.

FoxM1-dependent RAD51 and BRCA2 signaling protects idiopathic pulmonary fibrosis fibroblasts from radiation-induced cell death

Radiation therapy is critical for the control of many tumors and lung is an important dose-limiting organ that impacts radiation dose prescribed to avoid irreversible pulmonary fibrosis in cancer survivors. Idiopathic pulmonary fibrosis (IPF) is a chronic, irreversible lung disease caused by aberrantly activated lung (myo)fibroblasts. The presence of pro-fibrotic, apoptosis-resistant fibroblasts in IPF promotes progressive fibrosis and may have a role in other diseases, if these resistant cells are selected for as a consequence of treatment. However, the pathological response of IPF fibroblasts to radiation compared to non-IPF lung fibroblasts is not known. To address this, we examined fibroblast viability following radiation in lung fibroblasts from IPF and non-IPF patients and the underlying mechanism that protects IPF fibroblasts from radiation-induced death. IPF fibroblasts are significantly more resistant to apoptosis compared to non-IPF lung fibroblasts, suggesting that resistance to radiation-induced cell death is a predominant mechanism leading to lung fibrosis. Analysis of γH2AX induction demonstrated that radiation-induced DNA damage is reduced in IPF fibroblasts and correlates to the activation of the transcription factor forkhead box M1 (FoxM1) and subsequent upregulation of DNA repair proteins RAD51 and BRCA2. FoxM1 activation occurs secondary to FoxO3a suppression in IPF fibroblasts while restoration of FoxO3a function sensitizes IPF fibroblasts to radiation-induced cell death and downregulates FoxM1, RAD51, and BRCA2. Our findings support that increased FoxO3a/FoxM1-dependent DNA repair may be integral to the preservation of death-resistant fibrotic fibroblasts after radiation and that selective targeting of radioresistant fibroblasts may mitigate fibrosis.

Lung density change after SABR: A comparative study between tri-Co-60 magnetic resonance-guided system and linear accelerator

Radiation-induced lung damage is an important treatment-related toxicity after lung stereotactic ablative radiotherapy (SABR). After implementing a tri-⁶⁰Co magnetic-resonance image guided system, ViewRay^TM, we compared the associated early radiological lung density changes to those associated with a linear accelerator (LINAC). Eight patients treated with the tri-⁶⁰Co system were matched 1:1 with patients treated with LINAC. Prescription doses were 52 Gy or 60 Gy in four fractions, and lung dose-volumetric parameters were calculated from each planning system. The first two follow-up computed tomography (CT) were co-registered with the planning CT through deformable registration software, and lung density was measured by isodose levels. Tumor size was matched between the two groups, but the planning target volume of LINAC was larger than that of the tri-⁶⁰Co system (p = 0.036). With regard to clinically relevant dose-volumetric parameters in the lungs, the ipsilateral lung mean dose, V_10Gy and V_20Gy were significantly poorer in tri-⁶⁰Co plans compared to LINAC plans (p = 0.012, 0.036, and 0.017, respectively). Increased lung density was not observed in the first follow-up scan compared to the planning scan. A significant change of lung density was shown in the second follow-up scan and there was no meaningful difference between the tri-⁶⁰Co system and LINAC for all dose regions. In addition, no patient developed clinical radiation pneumonitis until the second follow-up scan. Therefore, there was no significant difference in the early radiological lung damage between the tri-⁶⁰Co system and LINAC for lung SABR despite of the inferior plan quality of the tri-⁶⁰Co system compared to that of LINAC. Further studies with a longer follow-up period are needed to confirm our findings.

Is heterogeneity in stage 3 non-small cell lung cancer obscuring the potential benefits of dose-escalated concurrent chemo-radiotherapy in clinical trials?

The current standard of care for the management of inoperable stage 3 non-small cell lung cancer (NSCLC) is concurrent chemoradiotherapy (cCRT) using radiotherapy dose-fractionation and chemotherapy regimens that were established 3 decades ago. In an attempt to improve the chances of long-term control from cCRT, dose-escalation of the radiotherapy dose was assessed in the RTOG 0617 randomised control study comparing the standard 60 Gy in 30 fractions with a high-dose arm receiving 74 Gy in 37 fractions. Following the publication of this trial the thoracic oncology community were surprised to learn that there was worse survival in the dose-escalated arm and that for now the standard of care must remain with the lower dose. In this article we review the RTOG 0617 paper with subsequent analyses and studies to explore why the use of dose-escalated cCRT in stage 3 NSCLC has not shown the benefits that were expected. The overarching theme of this opinion piece is how heterogeneity between stage 3 NSCLC cases in terms of patient, tumour, and clinical factors may obscure the potential benefits of dose-escalation by causing imbalances in the arms of studies such as RTOG 0617. We also examine recent advances in the staging, management, and technological delivery of radiotherapy in NSCLC and how these may be employed to optimise cCRT trials in the future and ensure that any potential benefits of dose-escalation can be detected.

The Role of the Mammalian Target of Rapamycin (mTOR) in Pulmonary Fibrosis

The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR)-dependent pathway is one of the most integral pathways linked to cell metabolism, proliferation, differentiation, and survival. This pathway is dysregulated in a variety of diseases, including neoplasia, immune-mediated diseases, and fibroproliferative diseases such as pulmonary fibrosis. The mTOR kinase is frequently referred to as the master regulator of this pathway. Alterations in mTOR signaling are closely associated with dysregulation of autophagy, inflammation, and cell growth and survival, leading to the development of lung fibrosis. Inhibitors of mTOR have been widely studied in cancer therapy, as they may sensitize cancer cells to radiation therapy. Studies also suggest that mTOR inhibitors are promising modulators of fibroproliferative diseases such as idiopathic pulmonary fibrosis (IPF) and radiation-induced pulmonary fibrosis (RIPF). Therefore, mTOR represents an attractive and unique therapeutic target in pulmonary fibrosis. In this review, we discuss the pathological role of mTOR kinase in pulmonary fibrosis and examine how mTOR inhibitors may mitigate fibrotic progression.

Early PET-CT After Stereotactic Radiotherapy for Stage 1 Non-small Cell Lung Carcinoma Is Predictive of Local Control

BACKGROUND/AIM

Radiological evaluation after stereotactic-body-radiotherapy (SBRT) for non-small-cell lung carcinoma (NSCLC) is often difficult due to lung radiation-induced image modifications on computed tomographic (CT) scan. The aim of this study was to evaluate positron-emission tomography-computed tomography (PET-CT) using fluorodeoxyglucose after SBRT in primary lung cancer.

PATIENTS AND METHODS

Eighteen patients with histologically proven NSCLC were treated with SBRT. All had PET-CT evaluations before treatment, at 2 to 3 months and at 1 year post SBRT during the follow-up.

RESULTS

Early PET-CT in 12/18 patients who did not experience local failure did not show any progression. No conclusion could be drawn in four cases because early PET-CT was disturbed by inflammatory reaction. Early PET-CT was not predictive of late outcome for two patients, as it showed a significant response followed by disease progression on late evaluation.

CONCLUSION

Early PET response appears to correlate with local control at 1 year post SBRT.

Radiological differential diagnosis between fibrosis and recurrence after stereotactic body radiation therapy (SBRT) in early stage non-small cell lung cancer (NSCLC)

Background

Parenchymal changes after stereotactic body radiation therapy (SBRT) make differential diagnosis between treatment outcomes and disease recurrence often difficult. The purpose of our study was to identify the radiographic features detectable at computed tomography (CT) scan [high-risk features (HRFs)] that allow enough specificity and sensitivity for early detection of recurrence.

Methods

We retrospectively evaluated patients who underwent SBRT for inoperable early stage non-small cell lung cancer (NSCLC). The median delivered dose performed was 50 Gy in 5 fractions prescribed to 80% isodose. All patients underwent chest CT scan before SBRT and at 3, 6, 12, 18, 24 months after, and then annually. Each CT scan was evaluated and benign and HRFs were recorded. ¹⁸F-fluorodeoxyglucose-CT was not used routinely.

Results

Forty-five patients were included (34 males, 11 females; median age: 77 years; stage IA: 77.8%, stage IB: 22.2%; median follow-up: 21.7 months). Two year and actuarial local control was 77%. HRFs were identified in 20 patients. The most significant predictor of relapse was an enlarging opacity at 12 months (P<0.001) with 84.6% sensitivity and 71.8% specificity. The presence of ≥2 HRFs demonstrated a high sensibility (92.3%) and specificity (71.9%) (P<0.0001).

Conclusions

Detection of HRFs is predictive of relapse with a sensibility that increases with the number of HRFs observed. This observation may allow to better define the diagnostic follow algorithm up suggesting to performing further exams only in patients with >2 HRFs.

Surveillance imaging following definitive radiotherapy for non-small cell lung cancer: What is the clinical impact?

Lung cancer is the leading cause of cancer death worldwide. Recurrence rates at all stages are high, but evidence-based post-treatment surveillance imaging strategies to detect recurrence are poorly defined, and salvage options are frequently limited. A number of national and international oncology guidelines address post-treatment imaging, but are largely based on low-level, retrospective evidence because of a paucity of high-quality data, particularly in regard to cost-effectiveness and quality-of-life endpoints. Given the lack of randomized data addressing appropriate surveillance imaging modality and interval following definitive treatment of lung cancer, there remains an unmet clinical need. Meaningful surveillance endpoints should include the financial impact, patient quality-of-life outcomes, and access-to-care issues associated with intensive follow-up to ensure that guidelines reflect quality and sustainability. A need for prospective randomized data on the subject of imaging surveillance after definitive local therapy remains an unmet need, and an opportunity for collaboration and further research.

Retrospective analysis of stereotactic ablative radiotherapy (SABR) for metastatic lung lesions (MLLs) in comparison with a contemporaneous cohort of primary lung lesions (PLLs)

BACKGROUND

The net benefit from local ablative therapy for pulmonary oligometastases remains unknown. The outcomes of stereotactic ablative radiotherapy (SABR) for metastatic lung lesions (MLLs) were analyzed retrospectively and compared with those of SABR for primary lung lesions (PLLs).

METHODS

Medical records of patients treated with lung SABR between 2011 and 2014 were retrospectively reviewed. Basic patient, lesion and treatment characteristics were compared using the Pearson chi-square test for categorical and Mann-Whitney U test for continuous variables. To estimate the rates of local control (LC), progression-free survival (PFS), survival after the first progression post-SABR (SAPF) and overall survival (OS), the Kaplan-Meier method was used, and the differences between groups were assessed by means of the log rank test. The uni- and multivariate Cox proportional hazards regression model was used to identify predictive factors for these endpoints.

RESULTS

Twenty-nine MLLs in 18 consecutive patients and 51 PLLs in 42 patients were treated stereotactically and included in the study. Median follow-up was 14 months (range, 4-40 months). Although patients with MLLs had a significantly better cardiopulmonary function (P=0.0001), more conservative dose-fractionation schedules were prescribed (P=0.0001), but this did not result in a significant difference in LC (P=0.98), PFS (P=0.06) and OS (P=0.14). Multivariate analysis revealed that the dose per fraction (≥ or <12 Gy) was an independent predictor for LC (P=0.02) and PFS (P=0.01) for the whole population, and for PFS (P=0.02) in the PLLs group. Late toxicities ≥ G2 occurred in six patients with PLLs, compared with none in the metastatic group.

CONCLUSIONS

SABR for MLLs was as successful as for PLLs with respect to LC and OS with lower long-term toxicity in patients with MLLs. Dose per fraction ≥12 Gy turned out to be an independent, favorable prognostic factor.

Salvage surgery for local failures after stereotactic ablative radiotherapy for early stage non-small cell lung cancer

Introduction

The literature on surgical salvage, i.e. lung resections in patients who develop a local recurrence following stereotactic ablative radiotherapy (SABR), is limited. We describe our experience with salvage surgery in nine patients who developed a local recurrence following SABR for early stage non-small cell lung cancer (NSCLC).

Methods

Patients who underwent surgical salvage for a local recurrence following SABR for NSCLC were identified from two Dutch institutional databases. Complications were scored using the Dindo-Clavien-classification.

Results

Nine patients who underwent surgery for a local recurrence were identified. Median time to local recurrence was 22 months. Recurrences were diagnosed with CT- and/or 18FDG-PET-imaging, with four patients also having a pre-surgical pathological diagnosis. Extensive adhesions were observed during two resections, requiring conversion from a thoracoscopic procedure to thoracotomy during one of these procedures. Three patients experienced complications post-surgery; grade 2 (N = 2) and grade 3a (N = 1), respectively. All resection specimens showed viable tumor cells. Median length of hospital stay was 8 days (range 5–15 days) and 30-day mortality was 0 %. Lymph node dissection revealed mediastinal metastases in 3 patients, all of whom received adjuvant therapy.

Conclusions

Our experience with nine surgical procedures for local recurrences post-SABR revealed two grade IIIa complications, and a 30-day mortality of 0 %, suggesting that salvage surgery can be safely performed after SABR.

Stereotactic Body Radiation Therapy Boost After Concurrent Chemoradiation for Locally Advanced Non-Small Cell Lung Cancer: A Phase 1 Dose Escalation Study

PURPOSE

Stereotactic body radiation therapy (SBRT) boost to primary and nodal disease after chemoradiation has potential to improve outcomes for advanced non-small cell lung cancer (NSCLC). A dose escalation study was initiated to evaluate the maximum tolerated dose (MTD).

METHODS AND MATERIALS

Eligible patients received chemoradiation to a dose of 50.4 Gy in 28 fractions and had primary and nodal volumes appropriate for SBRT boost (<120 cc and <60 cc, respectively). SBRT was delivered in 2 fractions after chemoradiation. Dose was escalated from 16 to 28 Gy in 2 Gy/fraction increments, resulting in 4 dose cohorts. MTD was defined when ≥2 of 6 patients per cohort experienced any treatment-related grade 3 to 5 toxicity within 4 weeks of treatment or the maximum dose was reached. Late toxicity, disease control, and survival were also evaluated.

RESULTS

Twelve patients (3 per dose level) underwent treatment. All treatment plans met predetermined dose-volume constraints. The mean age was 64 years. Most patients had stage III disease (92%) and were medically inoperable (92%). The maximum dose level was reached with no grade 3 to 5 acute toxicities. At a median follow-up time of 16 months, 1-year local-regional control (LRC) was 78%. LRC was 50% at <24 Gy and 100% at ≥24 Gy (P=.02). Overall survival at 1 year was 67%. Late toxicity (grade 3-5) was seen in only 1 patient who experienced fatal bronchopulmonary hemorrhage (grade 5). There were no predetermined dose constraints for the proximal bronchial-vascular tree (PBV) in this study. This patient's 4-cc PBV dose was substantially higher than that received by other patients in all 4 cohorts and was associated with the toxicity observed: 20.3 Gy (P<.05) and 73.5 Gy (P=.07) for SBRT boost and total treatment, respectively.

CONCLUSIONS

SBRT boost to both primary and nodal disease after chemoradiation is feasible and well tolerated. Local control rates are encouraging, especially at doses ≥24 Gy in 2 fractions. Toxicity at the PBV is a concern but potentially can be avoided with strict dose-volume constraints.

Imaging after radiation therapy of thoracic tumors

Radiation-induced lung disease (RILD) is frequent after therapeutic irradiation of thoracic malignancies. Many technique-, treatment-, tumor- and patient-related factors influence the degree of injury sustained by the lung after irradiation. Based on the time interval after the completion of the treatment RILD presents as early and late features characterized by inflammatory and fibrotic changes, respectively. They are usually confined to the radiation port. Though the typical pattern of RILD is easily recognized after conventional two-dimensional radiation therapy (RT), RILD may present with atypical patterns after more recent types of three- or four-dimensional RT treatment. Three atypical patterns are reported: the modified conventional, the mass-like and the scar-like patterns. Knowledge of the various features and patterns of RILD is important for correct diagnosis and appropriate treatment. RILD should be differentiated from recurrent tumoral disease, infection and radiation-induced tumors. Due to RILD, the follow-up after RT may be difficult as response evaluation criteria in solid tumours (RECIST) criteria may be unreliable to assess tumor control particularly after stereotactic ablation RT (SABR). Long-term follow-up should be based on clinical examination and morphological and/or functional investigations including CT, PET-CT, pulmonary functional tests, MRI and PET-MRI.

A Study of Pseudoprogression After Spine Stereotactic Body Radiation Therapy

PURPOSE

To determine the incidence of pseudoprogression (PP) after spine stereotactic body radiation therapy based on a detailed and quantitative assessment of magnetic resonance imaging (MRI) morphologic tumor alterations, and to identify predictive factors distinguishing PP from local recurrence (LR).

METHODS AND MATERIALS

A retrospective analysis of 35 patients with 49 spinal segments treated with spine stereotactic body radiation therapy, from 2009 to 2014, was conducted. The median number of follow-up MRI studies was 4 (range, 2-7). The gross tumor volumes (GTVs) within each of the 49 spinal segments were contoured on the pretreatment and each subsequent follow-up T1- and T2-weighted MRI sagittal sequence. T2 signal intensity was reported as the mean intensity of voxels constituting each volume. LR was defined as persistent GTV enlargement on ≥2 serial MRI studies for ≥6 months or on pathologic confirmation. PP was defined as a GTV enlargement followed by stability or regression on subsequent imaging within 6 months. Kaplan-Meier analysis was used for estimation of actuarial local control, disease-free survival, and overall survival.

RESULTS

The median follow-up was 23 months (range, 1-39 months). PP was identified in 18% of treated segments (9 of 49) and LR in 29% (14 of 49). Earlier volume enlargement (5 months for PP vs 15 months for LR, P=.005), greater GTV to reference nonirradiated vertebral body T2 intensity ratio (+30% for PP vs -10% for LR, P=.005), and growth confined to 80% of the prescription isodose line (80% IDL) (8 of 9 PP cases vs 1 of 14 LR cases, P=.002) were associated with PP on univariate analysis. Multivariate analysis confirmed an earlier time to volume enlargement and growth within the 80% IDL as significant predictors of PP. LR involved the epidural space in all but 1 lesion, whereas PP was confined to the vertebral body in 7 of 9 cases.

CONCLUSIONS

PP was observed in 18% of treated spinal segments. Tumor growth confined to the 80% IDL and earlier time to tumor enlargement were predictive for PP.

Pulmonary imaging after stereotactic radiotherapy-does RECIST still apply?

The use of stereotactic ablative radiotherapy (SABR) for the treatment of primary lung cancer and metastatic disease is rapidly increasing. However, the presence of benign fibrotic changes on CT imaging makes response assessment following SABR a challenge, as these changes develop with an appearance similar to tumour recurrence. Misclassification of benign fibrosis as local recurrence has resulted in unnecessary interventions, including biopsy and surgical resection. Response evaluation criteria in solid tumours (RECIST) are widely used as a universal set of guidelines to assess tumour response following treatment. However, in the context of non-spherical and irregular post-SABR fibrotic changes, the RECIST criteria can have several limitations. Positron emission tomography can also play a role in response assessment following SABR; however, false-positive results in regions of inflammatory lung post-SABR can be a major clinical issue and optimal standardized uptake values to distinguish fibrosis and recurrence have not been determined. Although validated CT high-risk features show a high sensitivity and specificity for predicting recurrence, most recurrences are not detected until more than 1-year post-treatment. Advanced quantitative radiomic analysis on CT imaging has demonstrated promise in distinguishing benign fibrotic changes from local recurrence at earlier time points, and more accurately, than physician assessment. Overall, the use of RECIST alone may prove inferior to novel metrics of assessing response.

Simple Factors Associated With Radiation-Induced Lung Toxicity After Stereotactic Body Radiation Therapy of the Thorax: A Pooled Analysis of 88 Studies

PURPOSE

To study the risk factors for radiation-induced lung toxicity (RILT) after stereotactic body radiation therapy (SBRT) of the thorax.

METHODS AND MATERIALS

Published studies on lung toxicity in patients with early-stage non-small cell lung cancer (NSCLC) or metastatic lung tumors treated with SBRT were pooled and analyzed. The primary endpoint was RILT, including pneumonitis and fibrosis. Data of RILT and risk factors were extracted from each study, and rates of grade 2 to 5 (G2+) and grade 3 to 5 (G3+) RILT were computed. Patient, tumor, and dosimetric factors were analyzed for their correlation with RILT.

RESULTS

Eighty-eight studies (7752 patients) that reported RILT incidence were eligible. The pooled rates of G2+ and G3+ RILT from all 88 studies were 9.1% (95% confidence interval [CI]: 7.15-11.4) and 1.8% (95% CI: 1.3-2.5), respectively. The median of median tumor sizes was 2.3 (range, 1.4-4.1) cm. Among the factors analyzed, older patient age (P=.044) and larger tumor size (the greatest diameter) were significantly correlated with higher rates of G2+ (P=.049) and G3+ RILT (P=.001). Patients with stage IA versus stage IB NSCLC had significantly lower risks of G2+ RILT (8.3% vs 17.1%, odds ratio = 0.43, 95% CI: 0.29-0.64, P<.0001). Among studies that provided detailed dosimetric data, the pooled analysis demonstrated a significantly higher mean lung dose (MLD) (P=.027) and V20 (P=.019) in patients with G2+ RILT than in those with grade 0 to 1 RILT.

CONCLUSIONS

The overall rate of RILT is relatively low after thoracic SBRT. Older age and larger tumor size are significant adverse risk factors for RILT. Lung dosimetry, specifically lung V20 and MLD, also significantly affect RILT risk.

The use of isodose levels to interpret radiation induced lung injury: a quantitative analysis of computed tomography changes

BACKGROUND

Patients treated with stereotactic body radiation therapy (SBRT) for lung cancer are often found to have radiation-induced lung injury (RILI) surrounding the treated tumor. We investigated whether treatment isodose levels could predict RILI.

METHODS

Thirty-seven lung lesions in 32 patients were treated with SBRT and received post-treatment follow up (FU) computed tomography (CT). Each CT was fused with the original simulation CT and treatment isodose levels were overlaid. The RILI surrounding the treated lesion was contoured. The RILI extension index [fibrosis extension index (FEI)] was defined as the volume of RILI extending outside a given isodose level relative to the total volume of RILI and was expressed as a percentage.

RESULTS

Univariate analysis revealed that the planning target volume (PTV) was positively correlated with RILI volume at FU: correlation coefficient (CC) =0.628 and P<0.0001 at 1(st) FU; CE =0.401 and P=0.021 at 2(nd) FU; CE =0.265 and P=0.306 at 3(rd) FU. FEI -40 Gy at 1(st) FU was significantly positively correlated with FEI -40 Gy at subsequent FU's (CC =0.689 and P=6.5×10(-5) comparing 1(st) and 2(nd) FU; 0.901 and P=0.020 comparing 2(nd) and 3(rd) FU. Ninety-six percent of the RILI was found within the 20 Gy isodose line. Sixty-five percent of patients were found to have a decrease in RILI on the second 2(nd) CT.

CONCLUSIONS

We have shown that RILI evolves over time and 1(st) CT correlates well with subsequent CTs. Ninety-six percent of the RILI can be found to occur within the 20 Gy isodose lines, which may prove beneficial to radiologists attempting to distinguish recurrence vs. RILI.

Follow-up of patients after stereotactic radiation for lung cancer: a primer for the nonradiation oncologist

BACKGROUND

The use of stereotactic ablative radiotherapy (SABR) as primary treatment for early stage non-small-cell lung cancer, or for ablation of metastases, has increased rapidly in the past decade. With local recurrence rates reported at approximately 10%, and a patient population that is becoming increasingly fit and amenable to salvage treatment, appropriate multidisciplinary follow-up care is critical. Appropriate follow-up will allow for detection and management of radiation-related toxicity, early detection of recurrent disease and differentiation of recurrence from radiation-induced lung injury.

METHODS

This narrative review summarizes issues surrounding follow-up of patients treated with SABR in the context of a multidisciplinary perspective. We summarize treatment-related toxicities including radiation pneumonitis, chest wall pain, rib fracture, and fatal toxicity, and highlight the challenges of early and accurate detection of local recurrence, while avoiding unnecessary biopsy or treatment of benign radiation-induced fibrotic lung damage.

RESULTS

Follow-up recommendations based on the current evidence and available guidelines are summarized. Imaging follow-up recommendations include serial computed tomography (CT) imaging at 3-6 months posttreatment for the initial year, then every 6-12 months for an additional 3 years, and annually thereafter. With suspicion of progressive disease, recommendations include a multidisciplinary team discussion, the use of high-risk CT features for accurate detection of local recurrence, and positron emission tomography/CT SUV max cutoffs to prompt further investigation. Biopsy and/or surgical or nonsurgical salvage therapy can be considered if safe and when investigations are nonreassuring.

CONCLUSIONS

The appropriate follow-up of patients after SABR requires collaborative input from nearly all members of the thoracic multidisciplinary team, and evidence is available to guide treatment decisions. Further research is required to develop better predictors of toxicity and recurrence.

Lungtech, a phase II EORTC trial of SBRT for centrally located lung tumours - a clinical physics perspective

Background

The EORTC has launched a phase II trial to assess safety and efficacy of SBRT for centrally located NSCLC: The EORTC 22113-08113—Lungtech trial. Due to neighbouring critical structures, these tumours remain challenging to treat. To guarantee accordance to protocol and treatment safety, an RTQA procedure has been implemented within the frame of the EORTC RTQA levels. These levels are here expanded to include innovative tools beyond protocol compliance verification: the actual dose delivered to each patient will be estimated and linked to trial outcomes to enable better understanding of dose related response and toxicity.

Method

For trial participation, institutions must provide a completed facility questionnaire and beam output audit results. To insure ability to comply with protocol specifications a benchmark case is sent to all centres. After approval, institutions are allowed to recruit patients. Nonetheless, each treatment plan will be prospectively reviewed insuring trial compliance consistency over time. As new features, patient’s CBCT images and applied positioning corrections will be saved for dose recalculation on patient’s daily geometry. To assess RTQA along the treatment chain, institutions will be visited once during the time of the trial. Over the course of this visit, end-to-end tests will be performed using the 008ACIRS-breathing platform with two separate bodies. The first body carries EBT3 films and an ionization chamber. The other body newly developed for PET- CT evaluation is fillable with a solution of high activity. 3D or 4D PET-CT and 4D-CT scanning techniques will be evaluated to assess the impact of motion artefacts on target volume accuracy. Finally, a dosimetric evaluation in static and dynamic conditions will be performed.

Discussion

Previous data on mediastinal toxicity are scarce and source of cautiousness for setting-up SBRT treatments for centrally located NSCLC. Thanks to the combination of documented patient related outcomes and CBCT based dose recalculation we expect to provide improved models for dose response and dose related toxicity.

Conclusion

We have developed a comprehensive RTQA model for trials involving modern radiotherapy. These procedures could also serve as examples of extended RTQA for future radiotherapy trials involving quantitative use of PET and tumour motion.

Computed Tomography Assessment of Ablation Zone Enhancement in Patients With Early-Stage Lung Cancer After Stereotactic Ablative Radiotherapy

INTRODUCTION

Stereotactic ablative radiotherapy (SABR) offers a curative treatment for lung cancer in patients who are marginal surgical candidates. However, unlike traditional surgery the lung cancer remains in place after treatment. Thus, imaging follow-up for evaluation of recurrence is of paramount importance.

MATERIALS AND METHODS

In this retrospective designed Institutional Review Board-approved study, follow-up contrast-enhanced computed tomography (CT) exams were performed on sixty one patients to evaluate enhancement pattern in the ablation zone at 1, 3, 6, and 12 months after SABR.

RESULTS

Eleven patients had recurrence within the ablation zone after SABR. The postcontrast enhancement in the recurrence group showed a washin and washout phenomenon, whereas the radiation-induced lung injury group showed continuous enhancement suggesting an inflammatory process.

CONCLUSIONS

The textural feature of the ablation zone of enhancement and perfusion as demonstrated in computed tomography nodule enhancement may allow early differentiation of recurrence from radiation-induced lung injury in patients' status after SABR or primary lung cancer.

Stereotactic radiotherapy for early lung cancer: Evidence-based approach and future directions

AIM

To review key studies evaluating stereotactic radiotherapy in the setting of early-stage non-small cell lung cancer (NSCLC) for inoperable or high-risk patients, and discuss areas of ongoing research and clinical trials.

BACKGROUND

The use of stereotactic radiotherapy for the treatment of early stage non-small cell lung cancer (NSCLC) has increased rapidly over the past decade. Numerous studies have reported outcomes for patients treated with SBRT who are unfit for surgical resection, or at high risk of surgical complications.

MATERIALS AND METHODS

A narrative review.

RESULTS

The preponderance of evidence suggests that SBRT is associated with excellent local control (∼90% at 3 years) and a favorable toxicity profile. In patients with higher operative risks, such as the elderly and patients with severe COPD, SBRT may provide a less-toxic treatment than surgery with similar oncologic outcomes. Ongoing studies are evaluating the use of SBRT for locally advanced or oligometastatic NSCLC.

CONCLUSIONS

A large body of evidence now exists to support the use of SBRT for early-stage NSCLC. Decisions regarding the optimal choice of treatment should be individualized, and made in the context of a multidisciplinary team.

LungTech, an EORTC Phase II trial of stereotactic body radiotherapy for centrally located lung tumours: a clinical perspective

Evidence supports stereotactic body radiotherapy (SBRT) as a curative treatment option for inoperable early stage non-small-cell lung cancer (NSCLC) resulting in high rates of tumour control and low risk of toxicity. However, promising results are mainly derived from SBRT of peripheral pulmonary lesions, whereas SBRT for the central tumours can lead to severe radiation sequelae owing to the spatial proximity to the serial organs at risk. Robust data on the tolerance of mediastinal structures to high-dose hypofractionated radiation are limited; furthermore, there are many open questions regarding the efficiency, safety and response assessment of SBRT in inoperable, centrally located early stage NSCLC, which are addressed in a prospective multicentre study [sponsored by the European Organization for Research and Treatment of Cancer (EORTC 22113-08113-LungTech)]. In this review, we summarize the current status regarding SBRT for centrally located early stage NSCLC that leads to the rationale of the LungTech trial. Outline and some essential features of the study with focus on a summary of current experiences in dose/fraction-toxicity coherences after SBRT to the mediastinal structures that lead to LungTech normal tissue constraints are provided.

The role of stereotactic body radiation therapy in the management of oligometastatic lung cancer

A growing body of evidence has surfaced over the past 20 years that supports the use of surgery for metastasis limited in number termed ‘oligometastases’. Local therapy for oligometastases results in long progression free survival in the absence of systemic therapy, including non-small-cell lung cancer (NSCLC). Stereotactic body radiation therapy (SBRT) allows for the delivery of anatomically precise, ablative doses of radiation therapy able to achieve local control rates of approximately 80% with minimal toxicity. In NSCLC, SBRT is emerging as an effective therapy in the management of sites resistant to targeted therapy. This review summarizes the published evidence for the use of local therapy in the management of oligometsatic cancer, with a focus on SBRT and NSCLC.

Bronchoscopy-Guided Cooled Radiofrequency Ablation as a Novel Intervention Therapy for Peripheral Lung Cancer

BACKGROUND

Our previous animal and preliminary human studies indicated that bronchoscopy-guided cooled radiofrequency ablation (RFA) for the lung is a safe and feasible procedure without major complications.

OBJECTIVES

The present study was performed to evaluate the safety, effectiveness and feasibility of computed tomography (CT)-guided bronchoscopy cooled RFA in patients with medically inoperable non-small-cell lung cancer (NSCLC).

METHODS

Patients with pathologically diagnosed NSCLC, who had no lymph node involvement or distant metastases (T1-2aN0M0) but were not surgical candidates because of comorbidities (e.g., synchronous multiple nodules, advanced age, cardiovascular disease, poor pulmonary function, etc.) were enrolled in the present study. The diagnosis and location between the nearest bronchus and target tumor were made by CT-guided bronchoscopy before the treatment. A total of 28 bronchoscopy-guided cooled RFA procedures were performed in 20 patients. After treatment, serial CT imaging was performed as follow-up.

RESULTS

Eleven lesions showed significant reductions in tumor size and 8 lesions showed stability, resulting in a local control rate of 82.6%. The median progression-free survival was 35 months (95% confidence interval: 22-45 months), and the 5-year overall survival was 61.5% (95% confidence interval: 36-87%). Three patients developed an acute ablation-related reaction (fever, chest pain) and required hospitalization but improved with conservative treatment. There were no other adverse events in the present study.

CONCLUSIONS

CT-guided bronchoscopy cooled RFA is applicable for only highly selected subjects; however, our trial may be an alternative strategy, especially for disease local control in medically inoperable patients with stage I NSCLC.