Do angiotensin-converting enzyme inhibitors reduce the risk of symptomatic radiation pneumonitis in patients with non-small cell lung cancer after definitive radiation therapy? Analysis of a single-institution database

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.

Decreased risk of radiation pneumonitis with concurrent use of renin-angiotensin system inhibitors in thoracic radiation therapy of lung cancer

Background

Radiation pneumonitis (RP) is the primary dose-limiting toxicity associated with radiotherapy. This study aimed to observe the effects of renin-angiotensin system inhibitors in Chinese patients with lung cancer who received thoracic radiation.

Methods

Patients with lung cancer who received thoracic radiation at a total dose of ≥45 Gray between October 2017 and December 2022 were enrolled in this study. We retrospectively evaluated the factors influencing grade 2 or higher RP.

Results

A total of 320 patients were enrolled in this study; 62 patients were identified as angiotensin receptor blockers or angiotensin-converting enzyme inhibitor users. Additionally, 99 patients (30.9%) had grade 2 or higher RP, and the incidence in the renin-angiotensin system inhibitor group was 17.7% (11 out of 62 patients). Patients in the renin-angiotensin system inhibitors (RASi) group were older and had a higher percentage of males, lower percentage of ECOG score 0, higher percentage of hypertension, and higher percentage of adenocarcinoma than those in the non-RASi group. ECOG score [hazard ratio (HR) = 1.69, p = 0.009], history of smoking (HR = 1.76, p = 0.049), mean dose (HR = 3.63, p = 0.01), and RASi (HR = 0.3, p = 0.003) were independent predictive factors for RP. All subgroups benefited from RASi.

Conclusion

This study showed that oral RASi administration has the potential to mitigate the incidence of grade 2 or higher RP in patients with lung cancer undergoing thoracic radiotherapy. To validate and further substantiate these findings, additional prospective research is warranted.

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).

Angiotensin converting enzyme (ACE) inhibitors as radiation countermeasures for long-duration space flights

Angiotensin converting enzyme (ACE) inhibitors are effective countermeasures to chronic radiation injuries in rodent models, and there is evidence for similar effects in humans. In rodent models ACE inhibitors are effective mitigators of radiation injury to kidney, lung, central nervous system (CNS) and skin, even when started weeks after irradiation. In humans, the best data for their efficacy as radiation countermeasures comes from retrospective studies of injuries in radiotherapy patients. We propose that ACE inhibitors, at doses approved for human use for other indications, could be used to reduce the risk of chronic radiation injuries from deep-space exploration. Because of the potential interaction of ACE inhibitors and microgravity (due to effects of ACE inhibitors on fluid balance) use might be restricted to post-exposure when/if radiation exposures reached a danger level. A major unresolved issue for this approach is the sparse evidence for the efficacy of ACE inhibitors after low-dose-rate exposure and/or for high-LET radiations (as would occur on long-duration space flights). A second issue is that the lack of a clear mechanism of action of the ACE inhibitors as mitigators makes obtaining an appropriate label under the Food and Drug Administration Animal Rule difficult.

Imaging features of toxicities associated with immune checkpoint inhibitors

The past decade has witnessed a change in landscape of cancer management with the advent of precision oncology. Immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment and have played an important role in improving patient survival. While the patients are living longer, treatment with ICIs are sometimes associated with adverse effects, some of which could be fatal. Radiologists can play a crucial role by early identification of some of these adverse effects during restaging scans. Our paper focuses on the imaging features of commonly occurring ICI toxicities based on organ system.

Radiation-Induced Lung Injury-Current Perspectives and Management

Radiotherapy plays an important role in the treatment of localized primary malignancies involving the chest wall or intrathoracic malignancies. Secondary effects of radiotherapy on the lung result in radiation-induced lung disease. The phases of lung injury from radiation range from acute pneumonitis to chronic pulmonary fibrosis. Radiation pneumonitis is a clinical diagnosis based on the history of radiation, imaging findings, and the presence of classic symptoms after exclusion of infection, pulmonary embolism, heart failure, drug-induced pneumonitis, and progression of the primary tumor. Computed tomography (CT) is the preferred imaging modality as it provides a better picture of parenchymal changes. Lung biopsy is rarely required for the diagnosis. Treatment is necessary only for symptomatic patients. Mild symptoms can be treated with inhaled steroids while subacute to moderate symptoms with impaired lung function require oral corticosteroids. Patients who do not tolerate or are refractory to steroids can be considered for treatment with immunosuppressive agents such as azathioprine and cyclosporine. Improvements in radiation technique, as well as early diagnosis and appropriate treatment with high-dose steroids, will lead to lower rates of pneumonitis and an overall good prognosis.

Prevention and treatment of radiation-induced lung injury

Radiation-induced lung injury (RILI) is a common complication in cancer patients receiving local thoracic radiation and bone marrow transplantation conditioning. It is divided into early-stage radiation pneumonitis and advanced radiation fibrosis of the lung. This severely hampers the quality of life and survival of cancer patients. Meanwhile, RILI is a major factor limiting radiation doses in clinical practice, which affects the local control of cancer. Unfortunately, the mechanism of RILI is still not well defined, and there are no treatment options available for these patients. In this review we summarize the methods and agents used for the treatment and prevention of RILI, with the aim of increasing understanding of RILI.

Radiation recall pneumonitis induced by PD-1/PD-L1 blockades: mechanisms and therapeutic implications

BACKGROUND

The synergistic effect of radiotherapy (RT) in combination with immunotherapy has been shown in several clinical trials and case reports. The overlapping pulmonary toxicity induced by thoracic RT and programmed death 1/programmed death ligand-1 (PD-1/PD-L1) blockades is an important issue of clinical investigation in combination treatment. Thus far, the underlying mechanism of this toxicity remains largely unknown.

MAIN TEXT

In this review, we discuss the unique pattern of radiation recall pneumonitis (RRP) induced by PD-1 blockade. The clinical presentation is different from common radiation pneumonitis (RP) or RRP induced by cytotoxic drugs. The immune checkpoint inhibitors may evoke an inflammatory reaction in patients' previously irradiated fields, with infiltrating lymphocytes and potential involvement of related cytokines. All RRP patients have showed durable response to anti-PD-1/PD-L1. RRP is manageable; however, interruption of checkpoint blockades is necessary and immunosuppressive treatment should be started immediately. Further analyses of the predictive factors, including RT dosimetric parameters, tumor-infiltrating lymphocytes (TILs), and PD-L1 expression, are needed given the wide use of immune checkpoint inhibitors and high mortality from lung toxicity with the combination treatment.

CONCLUSION

Immune checkpoint inhibitors may evoke an RRP in the patients' previously irradiated fields. Interactions between immune checkpoint inhibitors and radiotherapy should be studied further.

Targets for protection and mitigation of radiation injury

Protection of normal tissues against toxic effects of ionizing radiation is a critical issue in clinical and environmental radiobiology. Investigations in recent decades have suggested potential targets that are involved in the protection against radiation-induced damages to normal tissues and can be proposed for mitigation of radiation injury. Emerging evidences have been shown to be in contrast to an old dogma in radiation biology; a major amount of reactive oxygen species (ROS) production and cell toxicity occur during some hours to years after exposure to ionizing radiation. This can be attributed to upregulation of inflammatory and fibrosis mediators, epigenetic changes and disruption of the normal metabolism of oxygen. In the current review, we explain the cellular and molecular changes following exposure of normal tissues to ionizing radiation. Furthermore, we review potential targets that can be proposed for protection and mitigation of radiation toxicity.

Decreased Risk of Radiation Pneumonitis With Coincident Concurrent Use of Angiotensin-converting Enzyme Inhibitors in Patients Receiving Lung Stereotactic Body Radiation Therapy

OBJECTIVES

Angiotensin-converting enzyme inhibitors (ACEi) have demonstrated decreased rates of radiation-induced lung injury in animal models and clinical reports have demonstrated decreased pneumonitis in the setting of conventionally fractionated radiation to the lung. We tested the role of ACEi in diminishing rates of symptomatic (grade ≥2) pneumonitis in the setting of lung stereotactic body radiation therapy (SBRT).

METHODS

We analyzed patients treated with thoracic SBRT to 48 to 60 Gy in 4 to 5 fractions from 2006 to 2014. We reviewed pretreatment and posttreatment medication profiles to document use of ACEi, angiotensin receptor blockers, bronchodilators, aspirin, PDE-5 inhibitors, nitrates, and endothelin receptor antagonists. Pneumonitis was graded posttreatment based on Common Terminology Criteria for Adverse Events Version 4.0. Univariate and multivariate analysis was performed and time to development of pneumonitis was evaluated by the Kaplan-Meier method.

RESULTS

A total of 189 patients were evaluated with a median follow-up of 24.8 months. The overall 1-year rate of symptomatic pneumonitis was 13.2%. The 1-year rate of symptomatic pneumonitis was 4.2% for ACEi users versus 16.3% in nonusers (P=0.03). On univariate analysis, the odds of developing grade 2 or greater pneumonitis were significantly lower for patients on ACEi (P=0.03). On multivariate analysis, after controlling for clinicopathologic characteristics and dosimetric endpoints, there was a significant association between ACEi use and decreased risk of clinical pneumonitis (P=0.04). Angiotensin receptor blockers or other bronchoactive medications did not show significant associations with development of pneumonitis.

CONCLUSIONS

Incidental concurrent use of ACEi demonstrated efficacy in diminishing rates of symptomatic pneumonitis in the setting of lung SBRT.

Daily Lisinopril vs Placebo for Prevention of Chemoradiation-Induced Pulmonary Distress in Patients With Lung Cancer (Alliance MC1221): A Pilot Double-Blind Randomized Trial

PURPOSE

Chemoradiation (CRT) is an integral treatment modality for patients with locally advanced lung cancer. It has been hypothesized that current use of an angiotensin-converting enzyme inhibitor during CRT may be protective for treatment-related lung damage and pneumonitis.

METHODS AND MATERIALS

We conducted a pilot, double-blind, placebo-controlled, randomized trial. Study-eligible patients receiving curative thoracic radiation therapy (RT) were randomly assigned to 20 mg of lisinopril or placebo once daily during and up to 3 months after RT. All patients received concurrent chemotherapy. The primary endpoint was adverse event profiling. Multiple patient-reported outcome (PRO) surveys, including the Lung Cancer Symptom Scale, Function Assessment of Cancer Therapy-Lung, and the European Organisation for Research and Treatment of Cancer Lung Cancer Questionnaire, were applied with a symptom experience questionnaire. Exploratory comparative statistics were used to detect differences between arms with χ² and Kruskal-Wallis testing.

RESULTS

Five institutions enrolled 23 patients. However, accrual was less than expected. Eleven and 12 patients were in the placebo and lisinopril arms, respectively (mean age, 63.5 years; male, 62%). Baseline characteristics were balanced. Eighteen patients (86%) were former or current smokers. The primary endpoint was met; neither arm had grade 3 or higher hypotension, acute kidney injury, allergic reaction (medication-induced cough), or anaphylaxis (medication-related angioedema). Few PRO measures suggested that compared with the placebo arm, patients receiving lisinopril had less cough, less shortness of breath, fewer symptoms from lung cancer, less dyspnea with both walking and climbing stairs, and better overall quality of life (for all, P < .05).

CONCLUSIONS

Although underpowered because of low accrual, our results suggest that there was a clinical signal for safety-and possibly beneficial by limited PRO measures-in concurrently administering lisinopril during thoracic CRT to mitigate or prevent RT-induced pulmonary distress. Our results showed that a definitive, larger-scale, randomized phase 3 trial is needed in the future.

Radiation Pneumonitis: Old Problem, New Tricks

Radiation therapy is a major treatment modality for management of non-small cell lung cancer. Radiation pneumonitis is a dose limiting toxicity of radiotherapy, affecting its therapeutic ratio. This review presents patient and treatment related factors associated with the development of radiation pneumonitis. Research focusing on reducing the incidence of radiation pneumonitis by using information about lung ventilation, imaging-based biomarkers as well as normal tissue complication models is discussed. Recent advances in our understanding of molecular mechanisms underlying lung injury has led to the development of several targeted interventions, which are also explored in this review.

Angiotensin-converting Enzyme Inhibitors Decrease the Incidence of Radiation-induced Pneumonitis Among Lung Cancer Patients: A Systematic Review and Meta-analysis

Background: Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) have been demonstrated to mitigate radiation-induced lung damage in animal models and preclinical studies. Our study aims to evaluate whether ACEIs or ARBs reduce the incidence of radiation-induced pneumonitis (RP) in lung cancer patients.

Methods: Publications were searched from EMBASE, PubMed and Web of Science databases. Seven studies published from April 2000 to August 2016 met inclusion criteria and included 1412 patients in total. Only patients with grade 2 and above pneumonitis within 12 months after radiotherapy were analyzed.

Results: Patients taking ACEIs had a lower risk of developing radiation pneumonitis compared with non-users (OR = 0.46, 95%CI = 0.31-0.67, p < 0.0001). While the use of ARBs couldn't reduce the incidence of RP (OR = 1.42, 95%CI = 0.94-2.14, p = 0.10). Elderly patients (age ≥ 70) benefited more from ACEIs (OR = 0.12, 95%CI = 0.02-0.67, p = 0.02). In addition, smokers were found to have a lower risk of developing RP than non-smokers (OR = 0.49, 95%CI = 0.30-0.81, p = 0.005), but sex and the use of statin or NSAID had no influence on the appearance of RP (p = 0.59, p = 0.70, p = 0.40, respectively).

Conclusions: ACE inhibitors could decrease the incidence of symptomatic RP among lung cancer patients. However, the use of ARBs has a slight trend to develop RP but not above statistical significance. Elderly patients (age ≥ 70) benefited the most from ACEIs.

Late respiratory effects of cancer treatment

PURPOSE OF REVIEW

The aim of this article is to examine significant advances in our understanding of the late respiratory effects of cancer treatment, including surgery, radiotherapy, chemotherapy, biological therapies and haematopoietic stem cell transplant, and to provide a framework for assessing such patients.

RECENT FINDINGS

Oncology therapies have advanced considerably over recent years but pulmonary toxicity remains a concern. Advances have been made in our understanding of the risk factors, including genetic ones that lead to toxicity from radiotherapy and chemotherapy and risk stratification models are being developed to aid treatment planning. Targeted biological treatments are continuously being developed and consequently the Pneumotox database of pulmonary toxicity continues to be an essential resource. Early detection of bronchiolitis obliterans in haematopoietic stem cell transplant patients has been found to be critical, with some positive results from intervention trials.

SUMMARY

Pulmonary toxicity is a common unwanted consequence of life enhancing or saving cancer treatments which remain difficult to treat. Developments in these fields are mainly in the areas of prevention, early detection and monitoring of unwanted side effects. We discuss some of these developments within this review.

Renin-Angiotensin System Inhibitors to Mitigate Cancer Treatment-Related Adverse Events

Treatment-related side effects are a major clinical problem in cancer treatment. They lead to reduced compliance to therapy as well as increased morbidity and mortality. Well-known are the sequelae of chemotherapy on the heart, especially in childhood cancer survivors. Therefore, measures to mitigate the adverse events of cancer therapy may improve health and quality of life in patients with cancer, both in the short and long term. The renin-angiotensin system (RAS) affects all hallmarks of cancer, and blockage of the RAS is associated with an improved outcome in several cancer types. There is also increasing evidence that inhibition of the RAS might be able to alleviate or even prevent certain types of cancer treatment-related adverse effects. In this review, we summarize the potential of RAS inhibitors to mitigate cancer treatment-related adverse events, with a special emphasis on chemotherapy-induced cardiotoxicity, radiation injury, and arterial hypertension. Clin Cancer Res; 24(16); 3803-12. ©2018 AACR.

Angiotensin receptor blockade: a novel approach for symptomatic radiation necrosis after stereotactic radiosurgery

Preclinical evidence suggests angiotensin blockade therapy (ABT) decreases late radiation toxicities. This study aims to investigate the association between ABT and symptomatic radiation necrosis (SRN) following stereotactic radiosurgery (SRS). Resected brain metastases (rBM) and arteriovenous malformation (AVM) patients treated with SRS from 2002 to 2015 were identified. Patients in the ABT cohort were on therapy during SRS and at 1-month follow up. Kaplan Meier method and cumulative incidence model were used to analyze overall survival (OS) and intracranial outcomes. 228 consecutive patients were treated with SRS: 111 with rBM and 117 with AVM. Overall, 51 (22.4%) patients were in the ABT group: 32 (28.8%) in the rBM and 19 (16.2%) in AVM cohorts. Baseline characteristics were similar, except for higher Graded Prognostic Analysis (3-4) in the rBM (ABT: 25.0% vs. non-ABT: 49.0%, p = 0.033) and median age in the AVM (ABT: 51.4 vs. non-ABT: 35.4, p < 0.001) cohorts. In both populations, OS and intracranial efficacy (rBM-local control; AVM-obliteration rates) were statistically similar between the cohorts. ABT was associated with lower 1-year SRN rates in both populations: rBM, 3.1 versus 25.3% (p = 0.003); AVM, 6.7 vs. 14.6% (p = 0.063). On multivariate analysis, ABT was a significant predictive factor for rBM (HR: 0.17; 95% CI 0.03-0.88, p = 0.035), but did not reach statistical significance for AVM (HR: 0.36; 95% CI 0.09-1.52, p = 0.165). ABT use appears to be associated with a reduced risk of SRN following SRS, without detriment to OS or intracranial efficacy. A prospective trial to validate these findings is warranted.

Effect of captopril on radiation-induced TGF-β1 secretion in EA.Hy926 human umbilical vein endothelial cells

The pathophysiological mechanism involved in the sustained endothelial secretion of cytokines that leads to fibrosis 6–16 months after radiotherapy remains unclear. Angiotensin II (Ang II) is produced by the endothelium in response to stressing stimuli, like radiation, and may induce the synthesis of TGF-β, a profibrotic cytokine. In this study we tested the hypothesis that captopril, an angiotensin-converting enzyme (ACE) inhibitor, inhibits or attenuates radiation-induced endothelial TGF-β1 secretion. The human endothelial hybrid cell line EA.HY926 was irradiated with split doses of x-rays (28 Gy delivered in 14 fractions of 2 Gy). TGF-β1 mRNA, TNF-α mRNA and TGF-β1 protein levels were evaluated by RT-PCR and western blotting each month until the fifth month post radiation. Ang II was detected using radioimmunoassays, NF-κB activity was examined using EMSA, and western blotting was used to detect the expression of Iκ-Bα. To explore the role of Ang II on radiation-induced TGF-β1 release and Iκ-Bα expression, captopril was added to cultured cells before, during, or after irradiation. Sustained strong expression of TGF-β1 was observed after conventional fractionated irradiation. TNF-α, Ang II, and NF-κB activity were also increased in EA.Hy926 cells after radiation. Captopril decreased Ang II expression, inhibited the NF-κB pathway and reduced TGF-β1 expression. These data suggest that captopril might protect the endothelium from radiation-induced injury.

Novel Indications for Commonly Used Medications as Radiation Protectants in Spaceflight

BACKGROUND

In the space environment, the traditional radioprotective principles of time, distance, and shielding become difficult to implement. Additionally, the complex radiation environment inherent in space, the chronic exposure timeframe, and the presence of numerous confounding variables complicate the process of creating appropriate risk models for astronaut exposure. Pharmaceutical options hold tremendous promise to attenuate acute and late effects of radiation exposure in the astronaut population. Pharmaceuticals currently approved for other indications may also offer radiation protection, modulation, or mitigation properties along with a well-established safety profile. Currently there are only three agents which have been clinically approved to be employed for radiation exposure, and these only for very narrow indications. This review identifies a number of agents currently approved by the U.S. Food and Drug Administration (FDA) which could warrant further investigation for use in astronauts. Specifically, we examine preclinical and clinical evidence for statins, nonsteroidal anti-inflammatory drugs (NSAIDs), angiotensin converting enzyme inhibitors (ACEIs), angiotensin II receptor blockers (ARBs), metformin, calcium channel blockers, β adrenergic receptor blockers, fingolimod, N-acetylcysteine, and pentoxifylline as potential radiation countermeasures.McLaughlin MF, Donoviel DB, Jones JA. Novel indications for commonly used medications as radiation protectants in spaceflight. Aerosp Med Hum Perform. 2017; 88(7):665-676.

Pulmonary toxicity generated from radiotherapeutic treatment of thoracic malignancies

Radiation-induced lung injury (RILI) remains a major obstacle for thoracic radiotherapy for the treatment of lung cancer, esophageal cancer and lymphoma. It is the principal dose-limiting complication, and can markedly impair the therapeutic ratio as well as a patient's quality of life. The current review presents the relevant concepts associated with RILI, including the pathogenic mechanisms and the potential treatment strategies, so as to achieve a general understanding of this issue. RILI comprises an acute radiation pneumonitis phase and subsequent late lung fibrosis. The established assessment criteria are clinical manifestations, imaging changes and the necessity for medical assistance. Risk factors are also considered in order to optimize treatment planning. Due to the underlying molecular mechanisms of RILI, the present review also discusses several targeted pharmacological approaches for its treatment, as well as corticosteroid therapy.

Immunological Aspect of Radiation-Induced Pneumonitis, Current Treatment Strategies, and Future Prospects

Delivery of high doses of radiation to thoracic region, particularly with non-small cell lung cancer patients, becomes difficult due to subsequent complications arising in the lungs of the patient. Radiation-induced pneumonitis is an early event evident in most radiation exposed patients observed within 2-4 months of treatment and leading to fibrosis later. Several cytokines and inflammatory molecules interplay in the vicinity of the tissue developing radiation injury leading to pneumonitis and fibrosis. While certain cytokines may be exploited as biomarkers, they also appear to be a potent target of intervention at transcriptional level. Initiation and progression of pneumonitis and fibrosis thus are dynamic processes arising after few months to year after irradiation of the lung tissue. Currently, available treatment strategies are challenged by the major dose limiting complications that curtails success of the treatment as well as well being of the patient's future life. Several approaches have been in practice while many other are still being explored to overcome such complications. The current review gives a brief account of the immunological aspects, existing management practices, and suggests possible futuristic approaches.

Current Status of Targeted Radioprotection and Radiation Injury Mitigation and Treatment Agents: A Critical Review of the Literature

As more cancer patients survive their disease, concerns about radiation therapy-induced side effects have increased. The concept of radioprotection and radiation injury mitigation and treatment offers the possibility to enhance the therapeutic ratio of radiation therapy by limiting radiation therapy-induced normal tissue injury without compromising its antitumor effect. Advances in the understanding of the underlying mechanisms of radiation toxicity have stimulated radiation oncologists to target these pathways across different organ systems. These generalized radiation injury mechanisms include production of free radicals such as superoxides, activation of inflammatory pathways, and vascular endothelial dysfunction leading to tissue hypoxia. There is a significant body of literature evaluating the effectiveness of various treatments in preventing, mitigating, or treating radiation-induced normal tissue injury. Whereas some reviews have focused on a specific disease site or agent, this critical review focuses on a mechanistic classification of activity and assesses multiple agents across different disease sites. The classification of agents used herein further offers a useful framework to organize the multitude of treatments that have been studied. Many commonly available treatments have demonstrated benefit in prevention, mitigation, and/or treatment of radiation toxicity and warrant further investigation. These drug-based approaches to radioprotection and radiation injury mitigation and treatment represent an important method of making radiation therapy safer.

The Role of Lymphocytes in Radiotherapy-Induced Adverse Late Effects in the Lung

Radiation-induced pneumonitis and fibrosis are dose-limiting side effects of thoracic irradiation. Thoracic irradiation triggers acute and chronic environmental lung changes that are shaped by the damage response of resident cells, by the resulting reaction of the immune system, and by repair processes. Although considerable progress has been made during the last decade in defining involved effector cells and soluble mediators, the network of pathophysiological events and the cellular cross talk linking acute tissue damage to chronic inflammation and fibrosis still require further definition. Infiltration of cells from the innate and adaptive immune systems is a common response of normal tissues to ionizing radiation. Herein, lymphocytes represent a versatile and wide-ranged group of cells of the immune system that can react under specific conditions in various ways and participate in modulating the lung environment by adopting pro-inflammatory, anti-inflammatory, or even pro- or anti-fibrotic phenotypes. The present review provides an overview on published data about the role of lymphocytes in radiation-induced lung disease and related damage-associated pulmonary diseases with a focus on T lymphocytes and B lymphocytes. We also discuss the suspected dual role of specific lymphocyte subsets during the pneumonitic phase and fibrotic phase that is shaped by the environmental conditions as well as the interaction and the intercellular cross talk between cells from the innate and adaptive immune systems and (damaged) resident epithelial cells and stromal cells (e.g., endothelial cells, mesenchymal stem cells, and fibroblasts). Finally, we highlight potential therapeutic targets suited to counteract pathological lymphocyte responses to prevent or treat radiation-induced lung disease.

Radiotherapy for soft tissue sarcoma: 50 years of change and improvement

Radiotherapy for soft tissue sarcoma (STS) has advanced significantly over the past 50 years. This review focuses briefly on the period from 1964 to 1999 and more substantially on the changes of the past 15 years, such as IMRT and image-guided radiotherapy (IG-RT), especially when brought together (IG-IMRT) in the same planning and delivery process to treat localized STS. In particular, the introduction of IG-RT, target volume definitions for IG-RT, and review of recent clinical trials using IG-RT to treat localized STS in extremity will be reviewed. Finally, potential investigational agents combined with IG-RT to improve outcomes in patients with localized STS are discussed.

Can Angiotensin-Converting Enzyme Inhibitors Reduce the Incidence, Severity, and Duration of Radiation Proctitis?

PURPOSE

To determine whether participants taking angiotensin-converting enzyme inhibitors (ACEIs) and treated with radical radiation therapy with neoadjuvant/adjuvant hormone therapy have less incidence, severity, and duration of radiation proctitis.

METHODS AND MATERIALS

A propensity score analysis of 817 patients who underwent radical radiation therapy with neoadjuvant or adjuvant hormone therapy as primary line management in a cohort study during 2009 to 2013 was conducted. Patients were stratified as follows: group 1, hypertensive patients taking ACEIs (as a study group); group 2, nonhypertensive patients not taking ACEIs; and group 3, hypertensive patients not taking ACEIs (both as control groups). The incidence, severity, and duration of proctitis were the main outcome. χ(2) tests, Mann-Whitney U tests, analysis of variance, risk ratio (RR), confidence interval (CI), Kaplan-Meier plots, and log-rank tests were used.

RESULTS

The mean age of the participants was 68.91 years, with a follow-up time of 3.38 years. Based on disease and age-matched comparison, there was a statistically significant difference of proctitis grading between the 3 groups: χ(2) (8, n=308) = 72.52, P<.001. The Mann-Whitney U test indicated that grades of proctitis were significantly lower in hypertensive patients taking ACEIs than in nonhypertensive patients not taking ACEIs and hypertensive patients not taking ACEIs (P<.001). The risk ratio (RR) of proctitis in hypertensive patients taking ACEIs was significantly lower than in hypertensive patients not taking ACEIs (RR 0.40, 95% CI 0.30-0.53, P<.001) and in nonhypertensive patients not taking ACEIs (RR 0.58, 95% CI 0.44-0.77, P<.001). Time to event analysis revealed that hypertensive patients taking ACEIs were significantly different from the control groups (P<.0001). Furthermore, hypertensive patients taking ACEIs had significantly faster resolution of proctitis (P<.0001).

CONCLUSION

Patients who were taking ACEIs were significantly less likely to have high-grade proctitis after radical radiation therapy with neoadjuvant or adjuvant hormone therapy (P<.001). The intake of ACEIs was significantly associated with a reduced risk of radiation-induced proctitis and also with acceleration of its resolution.

Renin-Angiotensin System Inhibitors Might Help to Reduce the Development of Symptomatic Radiation Pneumonitis After Stereotactic Body Radiotherapy for Lung Cancer

INTRODUCTION

The purpose of the present study was to evaluate the role of renin-angiotensin system (RAS) inhibitors in preventing symptomatic radiation pneumonitis (RP) after stereotactic body radiotherapy (SBRT).

MATERIALS AND METHODS

The data from 158 patients with a solitary lung lesion treated with 1 to 3 fractions of SBRT from December 2008 to July 2014 were retrospectively analyzed. The incidence of RP was evaluated according to the Common Toxicity Criteria for Adverse Events, version 4. The use of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) was analyzed to assess for possible correlations with the development of grade ≥ 2 RP. The patient and dosimetric variables were also assessed.

RESULTS

After a median follow-up period of 13.8 months (range, 3.2-55.0 months), 22 patients had developed grade ≥ 2 RP. Patients with peripheral lesions, favorable dosimetric data, and ACEI and/or ARB use had a reduced risk of symptomatic RP. In unadjusted and adjusted multivariate analyses, ACEI and/or ARB intake and the dosimetric variables were statistically significant factors. In a secondary analysis, the use of ACEIs and ARBs among patients with a greater planning target volume and higher dosimetric values correlated with a reduced risk of symptomatic RP.

CONCLUSION

The use of a RAS inhibitor was associated with a decreased incidence of symptomatic RP among patients undergoing SBRT for lung lesions. Patients with higher dosimetric values had a reduced risk of grade ≥ 2 RP with ACEI and ARB use.

Radioprotective agents for radiation therapy: future trends

Only two radioprotective compounds, amifostine and palifermin, currently have the US FDA approval for use in radiation therapy. However, several agents have been reported that show therapeutic promise. Many of these agents are free radical scavengers/antioxidants. Superoxide dismutase and superoxide dismutase mimetics, nitroxides and dietary antioxidants are all being investigated. Recently, alternative strategies of drug development have been evolving, which focus on targeting the series of cellular insult recognition/repair responses initiated following radiation. These agents, which include cytokines/growth factors, angiotensin-converting enzyme inhibitors and apoptotic modulators, show promise of having significant impact on the mitigation of radiation injury. Herein, we review current literature on the development of radioprotectors with emphasis on compounds with proven or potential usefulness in radiation therapy.

Angiotensin-converting enzyme inhibitors decrease the risk of radiation pneumonitis after stereotactic body radiation therapy

PURPOSE

Although angiotensin-converting enzyme (ACE) inhibitor use during conventionally fractionated radiation therapy has been associated with a decreased risk of radiation pneumonitis (RP), a similar effect has not been demonstrated in stereotactic body radiation therapy (SBRT). The purpose of this study was to examine the impact of ACE inhibitor use during SBRT on the risk of symptomatic (grade ≥2) RP.

METHODS AND MATERIALS

Patients with at least 1 follow-up treated with SBRT for primary lung cancer were included. ACE inhibitors, angiotensin receptor blockers, statins, nonsteroidal anti-inflammatory drugs, and glucocorticoids were examined. RP was determined from all available medical records, including follow-up appointments with radiation oncology, pulmonology, medical oncology, and hospitalizations. It was scored with the Common Terminology Criteria for Adverse Events, version 4.0. Analysis was performed with Kaplan-Meier and Cox proportional hazards modeling.

RESULTS

A total of 257 patients met inclusion criteria. Seventy (27.2%) used an ACE inhibitor during SBRT. The overall rates of grade ≥2 and ≥3 RP were 19.1% (n = 49) and 7.0% (n = 18), respectively. ACE inhibitor users experienced greater freedom from symptomatic RP on univariate (vs nonusers, 89.8% vs 76.3% at 12 months, P = .029) and multivariate analysis (hazard ratio 0.373, 95% confidence interval 0.156-0.891, P =.026). The volume of normal lung tissue receiving ≥5 Gy, %, ≥10 Gy, ≥20 Gy, and mean lung dose were also significantly associated with RP on univariate and multivariate analysis. ACE inhibitor use was not associated with overall survival. Angiotensin receptor blockers, nonsteroidal anti-inflammatory drugs, glucocorticoids, and statin administration were not associated with symptomatic RP or survival.

CONCLUSIONS

ACE inhibitor use during SBRT was associated with significantly greater freedom from grade ≥2 RP, even after adjusting for pulmonary dose. Given the data on their protective effect in human and animal models, a prospective evaluation is warranted.

Targeting the Renin-angiotensin system combined with an antioxidant is highly effective in mitigating radiation-induced lung damage

PURPOSE

To investigate the outcome of suppression of the renin angiotensin system using captopril combined with an antioxidant (Eukarion [EUK]-207) for mitigation of radiation-induced lung damage in rats.

METHODS AND MATERIALS

The thoracic cavity of female Sprague-Dawley rats was irradiated with a single dose of 11 Gy. Treatment with captopril at a dose of 40 mg/kg/d in drinking water and EUK-207 given by subcutaneous injection (8 mg/kg daily) was started 1 week after irradiation (PI) and continuing until 14 weeks PI. Breathing rate was monitored until the rats were killed at 32 weeks PI, when lung fibrosis was assessed by lung hydroxyproline content. Lung levels of the cytokine transforming growth factor-β1 and macrophage activation were analyzed by immunohistochemistry. Oxidative DNA damage was assessed by 8-hydroxy-2-deoxyguanosine levels, and lipid peroxidation was measured by a T-BARS assay.

RESULTS

The increase in breathing rate in the irradiated rats was significantly reduced by the drug treatments. The drug treatment also significantly decreased the hydroxyproline content, 8-hydroxy-2-deoxyguanosine and malondialdehyde levels, and levels of activated macrophages and the cytokine transforming growth factor-β1 at 32 weeks. Almost complete mitigation of these radiation effects was observed by combining captopril and EUK-207.

CONCLUSION

Captopril and EUK-207 can provide mitigation of radiation-induced lung damage out to at least 32 weeks PI after treatment given 1-14 weeks PI. Overall the combination of captopril and EUK-207 was more effective than the individual drugs used alone.