Decreased Survival After Combining Thoracic Irradiation and an Anti-PD-1 Antibody Correlated With Increased T-cell Infiltration Into Cardiac and Lung Tissues

Effects of confounding and effect-modifying lifestyle, environmental and medical factors on risk of radiation-associated cardiovascular disease

BACKGROUND

Cardiovascular disease (CVD) is the leading cause of death worldwide. It has been known for some considerable time that radiation is associated with excess risk of CVD. A recent systematic review of radiation and CVD highlighted substantial inter-study heterogeneity in effect, possibly a result of confounding or modifications of radiation effect by non-radiation factors, in particular by the major lifestyle/environmental/medical risk factors and latent period.

METHODS

We assessed effects of confounding by lifestyle/environmental/medical risk factors on radiation-associated CVD and investigated evidence for modifying effects of these variables on CVD radiation dose-response, using data assembled for a recent systematic review.

RESULTS

There are 43 epidemiologic studies which are informative on effects of adjustment for confounding or risk modifying factors on radiation-associated CVD. Of these 22 were studies of groups exposed to substantial doses of medical radiation for therapy or diagnosis. The remaining 21 studies were of groups exposed at much lower levels of dose and/or dose rate. Only four studies suggest substantial effects of adjustment for lifestyle/environmental/medical risk factors on radiation risk of CVD; however, there were also substantial uncertainties in the estimates in all of these studies. There are fewer suggestions of effects that modify the radiation dose response; only two studies, both at lower levels of dose, report the most serious level of modifying effect.

CONCLUSIONS

There are still large uncertainties about confounding factors or lifestyle/environmental/medical variables that may influence radiation-associated CVD, although indications are that there are not many studies in which there are substantial confounding effects of these risk factors.

Immune checkpoint inhibitor-associated cardiovascular toxicities: A review

Immune checkpoint inhibitors (ICIs) have revolutionary effects on therapeutic strategies for multiple malignancies. Their efficacy depends on their ability to reactivate the host immune system to fight cancer cells. However, adverse reactions to ICIs are common and involve several organs, limiting their use in clinical practice. Although the incidence of cardiovascular toxicity is relatively low, it is associated with serious consequences and high mortality rates. The primary cardiovascular toxicities include myocarditis, pericarditis, Takotsubo syndrome, arrhythmia, vasculitis, acute coronary syndrome, and venous thromboembolism. Currently, the mechanism underlying ICI-associated cardiovascular toxicity remains unclear and underexplored. The diagnosis and monitoring of ICI-associated cardiovascular toxicities mainly include the following indicators: symptoms, signs, laboratory examination, electrocardiography, imaging, and pathology. Treatments are based on the grade of cardiovascular toxicity and mainly include drug withdrawal, corticosteroid therapy, immunosuppressants, and conventional cardiac treatment. This review focuses on the incidence, underlying mechanisms, clinical manifestations, diagnoses, and treatment strategies.

ATP protects anti-PD-1/radiation-induced cardiac dysfunction by inhibiting anti-PD-1 exacerbated cardiomyocyte apoptosis, and improving autophagic flux

The synergy between radiotherapy and immunotherapy in treating thoracic cancers presents a potent therapeutic advantage, yet it also carries potential risks. The extent and nature of cumulative cardiac toxicity remain uncertain, prompting the need to discern its mechanisms and devise effective mitigation strategies. Radiation alone or in combination with an anti- Programmed cell death protein1 (PD-1) antibody significantly reduced cardiac function in C57BL/6J mice, and this pathologic effect was aggravated by anti-PD-1 (anti-PD-1 + radiation). To examine the cellular mechanism that causes the detrimental effect of anti-PD-1 upon cardiac function after radiation, AC16 human cardiomyocytes were used to study cardiac apoptosis and cardiac autophagy. Radiation-induced cardiomyocyte apoptosis was significantly promoted by anti-PD-1 treatment, while anti-PD-1 combined radiation administration blocked the cardiac autophagic flux. Adenosine 5'-triphosphate (ATP) (a molecule that promotes lysosomal acidification) not only improved autophagic flux in AC16 human cardiomyocytes, but also attenuated apoptosis induced by radiation and anti-PD-1 treatment. Finally, ATP administration in vivo significantly reduced radiation-induced and anti-PD-1-exacerbated cardiac dysfunction. We demonstrated for the first time that anti-PD-1 can aggravate radiation-induced cardiac dysfunction via promoting cardiomyocyte apoptosis without affecting radiation-arrested autophagic flux. ATP enhanced cardiomyocyte autophagic flux and inhibited apoptosis, improving cardiac function in anti-PD-1/radiation combination-treated animals.

Risk Factors for Immune Checkpoint Inhibitor-Mediated Cardiovascular Toxicities

PURPOSE OF REVIEW

Immune checkpoint inhibitors (ICIs) have improved the field of cancer, especially in patients with advanced malignancies. Nevertheless, cardiovascular immune-related adverse events (irAEs) with high mortality and morbidity have been observed, including myocarditis, pericarditis, and vasculitis. To date, only a few clinical risk factors have been described and are currently being investigated.

RECENT FINDINGS

In this review, we address the four most prevailing risk factors for cardiovascular irAEs. ICI combination therapy is a predominant risk factor for developing ICI-mediated myocarditis. Additionally, ICI combined with other anti-cancer treatments (e.g., tyrosine kinase inhibitors, radiation, chemotherapy) seems to increase the risk of developing cardiovascular irAEs. Other risk factors include female sex, pre-existing cardiovascular disease, and specific tumors, on which we will further elaborate in this review. An a priori risk strategy to determine who is at risk to develop these cardiovascular irAEs is needed. Insights into the impact of risk factors are therefore warranted to help clinicians improve care and disease management in these patients.

Emerging evidence for adapting radiotherapy to immunotherapy

Immunotherapy has revolutionized the clinical management of many malignancies but is infrequently associated with durable objective responses when used as a standalone treatment approach, calling for the development of combinatorial regimens with superior efficacy and acceptable toxicity. Radiotherapy, the most commonly used oncological treatment, has attracted considerable attention as a combination partner for immunotherapy owing to its well-known and predictable safety profile, widespread clinical availability, and potential for immunostimulatory effects. However, numerous randomized clinical trials investigating radiotherapy-immunotherapy combinations have failed to demonstrate a therapeutic benefit compared with either modality alone. Such a lack of interaction might reflect suboptimal study design, choice of end points and/or administration of radiotherapy according to standard schedules and target volumes. Indeed, radiotherapy has empirically evolved towards radiation doses and fields that enable maximal cancer cell killing with manageable toxicity to healthy tissues, without much consideration of potential radiation-induced immunostimulatory effects. Herein, we propose the concept that successful radiotherapy-immunotherapy combinations might require modifications of standard radiotherapy regimens and target volumes to optimally sustain immune fitness and enhance the antitumour immune response in support of meaningful clinical benefits.

Cellular Atlas of Senescent Lineages in Radiation- or Immunotherapy-Induced Lung Injury by Single-Cell RNA-Sequencing Analysis

PURPOSE

Although the combination of immunotherapy and radiation therapy to treat various malignancies is rapidly expanding, concerns regarding increased pulmonary toxicities remain. The mechanisms of immunotherapy- and irradiation-induced lung injury involve a complex interplay of cell types and signaling pathways, much of which remains to be elucidated.

METHODS AND MATERIALS

C57/BL6 mice were treated with a single fraction (20 Gy) of radiation therapy to the right lung or 200 μg anti-Programmed cell death protein 1 antibody twice a week. At 7, 30, and 60 days after treatment, the lung tissues were obtained for unbiased single-cell RNA sequencing or histologic staining. The Seurat analysis pipeline, Cellchat, Monocol, and Single-Cell rEgulatory Network Inference and Clustering were used to define cell types, mechanisms, and mediators driving pathologic remodeling in response to this lung injury. Reverse transcription polymerase chain reaction, immunofluorescent staining, and multiplex immunohistochemistry were applied to validate the key results.

RESULTS

Thirty distinct cell subsets encompassing 75,396 cells were identified. A comprehensive investigation of cell-cell crosstalk revealed that monokine signals derived from senescent fibroblasts were substantially elevated after lung injury. Independent analytical strategies revealed that senescence-like subtypes of fibroblasts, alveolar epithelial cells, B cells, and myeloid immune cells were functionally pathologic, with high expression of senescence-signature proteins, especially Apolipoprotein E, during injury response. Senescence markers were also elevated in irradiated human cell lines, mouse cell lines (B3T3 and L929), and the publicly available human pulmonary fibrosis data set.

CONCLUSIONS

These findings demonstrate that the accumulation of senescence-like fibroblasts, macrophages, and alveolar epithelial cells is the primary common pathologic mechanism of immunotherapy- and irradiation-induced lung injury. These high-resolution transcriptomic data provide novel insights into therapeutic opportunities to predict or prevent therapy-induced lung injury.

Preclinical models of radiation-induced cardiac toxicity: Potential mechanisms and biomarkers

Radiation therapy (RT) is an important modality in cancer treatment with >50% of cancer patients undergoing RT for curative or palliative intent. In patients with breast, lung, and esophageal cancer, as well as mediastinal malignancies, incidental RT dose to heart or vascular structures has been linked to the development of Radiation-Induced Heart Disease (RIHD) which manifests as ischemic heart disease, cardiomyopathy, cardiac dysfunction, and heart failure. Despite the remarkable progress in the delivery of radiotherapy treatment, off-target cardiac toxicities are unavoidable. One of the best-studied pathological consequences of incidental exposure of the heart to RT is collagen deposition and fibrosis, leading to the development of radiation-induced myocardial fibrosis (RIMF). However, the pathogenesis of RIMF is still largely unknown. Moreover, there are no available clinical approaches to reverse RIMF once it occurs and it continues to impair the quality of life of long-term cancer survivors. Hence, there is an increasing need for more clinically relevant preclinical models to elucidate the molecular and cellular mechanisms involved in the development of RIMF. This review offers an insight into the existing preclinical models to study RIHD and the suggested mechanisms of RIMF, as well as available multi-modality treatments and outcomes. Moreover, we summarize the valuable detection methods of RIHD/RIMF, and the clinical use of sensitive radiographic and circulating biomarkers.

Experimental investigation of skin toxicity after immune checkpoint inhibition in combination with radiation therapy

Immune checkpoint inhibitors (ICIs) have revolutionized cancer therapy. However, structured knowledge to mitigate a patient's specific risk of developing adverse events are limited. Nevertheless, there is an exponential growth of clinical studies combining conventional therapies such as radiation therapy (RT) with ICIs. Cutaneous reactions are amongst the most common adverse events after monotherapy with either ICIs or RT. So far, little is known about inter-individual differences in the risk of developing severe tissue toxicity after the combination of RT with ICIs, and the underlying biological mechanisms are ill defined. We used experimental models of RT-induced skin injury to analyze skin toxicity after simultaneous application of ICIs. We compared different RT regimens such as fractionated or stereotactic RT with varying dose intensity. Strikingly, we found that simultaneous application of RT and ICIs did not significantly aggravate acute skin injury in two different mouse strains. Detailed examination of long-term tissue damage of the skin revealed similar signs of epidermal hyperplasia, dermal fibrosis, and adnexal atrophy. In summary, we here present the first experimental study demonstrating excellent safety profiles of concurrent treatment with RT and ICIs. These findings will help to interpret the development of adverse events of the skin after radioimmunotherapy and guide the design of new clinical trials and clinical decision making in individual cases. This article is protected by copyright. All rights reserved.

Radiation-Induced Cardiac Dysfunction: Optimizing Radiation Delivery and Postradiation Care

Radiation therapy (RT) is part of standard-of-care treatment of many thoracic cancers. More than 60% of patients receiving thoracic RT may eventually develop radiation-induced cardiac dysfunction (RICD) secondary to collateral heart dose. This article reviews factors contributing to a thoracic cancer patient's risk for RICD, including RT dose to the heart and/or cardiac substructures, other anticancer treatments, and a patient's cardiometabolic health. It is also discussed how automated tracking of these factors within electronic medical record environments may aid radiation oncologists and other treating physicians in their ability to prevent, detect, and/or treat RICD in this expanding patient population.

Checkpoint Inhibitor Pneumonitis Induced by Anti-PD-1/PD-L1 Therapy in Non-Small-Cell Lung Cancer: Occurrence and Mechanism

Immune checkpointty inhibitors (ICIs), particularly those targeting programmed death 1 (PD-1) and anti-programmed death ligand 1 (PD-L1), enhance the antitumor effect by restoring the function of the inhibited effector T cells and produce durable responses in a large variety of metastatic and late patients with non-small-cell lung cancer. Although often well tolerated, the activation of the immune system results in side effects known as immune-related adverse events (irAEs), which can affect multiple organ systems, including the lungs. The occurrence of severe pulmonary irAEs, especially checkpoint inhibitor pneumonitis (CIP), is rare but has extremely high mortality and often overlaps with the respiratory symptoms and imaging of primary tumors. The development of CIP may be accompanied by radiation pneumonia and infectious pneumonia, leading to the simultaneous occurrence of a mixture of several types of inflammation in the lungs. However, there is a lack of authoritative diagnosis, grading criteria and clarified mechanisms of CIP. In this article, we review the incidence and median time to onset of CIP in patients with non-small-cell lung cancer treated with PD-1/PD-L1 blockade in clinical studies. We also summarize the clinical features, potential mechanisms, management and predictive biomarkers of CIP caused by PD-1/PD-L1 blockade in non-small-cell lung cancer treatment.

Small animal models of localized heart irradiation

A subset of cancer patients treated with radiation therapy may experience radiation-induced heart disease (RIHD) that develops within weeks to several years after cancer treatment. Rodent models are most commonly used to examine the biological effects of local X-rays in the heart and test potential strategies to reduce RIHD. While developments in technology over the last decades have changed the procedures for local heart irradiation in animal models, the X-ray settings and radiation doses have remained quite consistent in time and between different research laboratories. This chapter provides a protocol for whole heart irradiation in rodent models, using an X-ray machine with cone beam computed tomography (CBCT) capabilities. Some methods for the quantification of common histological changes after whole heart irradiation in the rodent are also described.

Gut Microbiota-Derived l-Histidine/Imidazole Propionate Axis Fights against the Radiation-Induced Cardiopulmonary Injury

Radiation-induced cardiopulmonary injuries are the most common and intractable side effects that are entwined with radiotherapy for thorax cancers. However, the therapeutic options for such complications have yielded disappointing results in clinical applications. Here, we reported that gut microbiota-derived l-Histidine and its secondary metabolite imidazole propionate (ImP) fought against radiation-induced cardiopulmonary injury in an entiric flora-dependent manner in mouse models. Local chest irradiation decreased the level of l-Histidine in fecal pellets, which was increased following fecal microbiota transplantation. l-Histidine replenishment via an oral route retarded the pathological process of lung and heart tissues and improved lung respiratory and heart systolic function following radiation exposure. l-Histidine preserved the gut bacterial taxonomic proportions shifted by total chest irradiation but failed to perform radioprotection in gut microbiota-deleted mice. ImP, the downstream metabolite of l-Histidine, accumulated in peripheral blood and lung tissues following l-Histidine replenishment and protected against radiation-induced lung and heart toxicity. Orally gavaged ImP could not enter into the circulatory system in mice through an antibiotic cocktail treatment. Importantly, ImP inhibited pyroptosis to nudge lung cell proliferation after radiation challenge. Together, our findings pave a novel method of protection against cardiopulmonary complications intertwined with radiotherapy in pre-clinical settings and underpin the idea that gut microbiota-produced l-Histidine and ImP are promising radioprotective agents.

Immune Checkpoint Inhibitors: Cardiotoxicity in Pre-clinical Models and Clinical Studies

Since the approval of the first immune checkpoint inhibitor (ICI) 9 years ago, ICI-therapy have revolutionized cancer treatment. Lately, antibodies blocking the interaction of programmed cell death protein (PD-1) and ligand (PD-L1) are gaining momentum as a cancer treatment, with multiple agents and cancer types being recently approved for treatment by the US Food and Drug Administration (FDA). Unfortunately, immunotherapy often leads to a wide range of immune related adverse events (IRAEs), including several severe cardiac effects and most notably myocarditis. While increased attention has been drawn to these side effects, including publication of multiple clinical observational data, the underlying mechanisms are unknown. In the event of IRAEs, the most widely utilized clinical solution is administration of high dose corticosteroids and in severe cases, discontinuation of these ICIs. This is detrimental as these therapies are often the last line of treatment options for many types of advanced cancer. In this review, we have systematically described the pathophysiology of the PD-1/PD-L1 axis (including a historical perspective) and cardiac effects in pre-clinical models, clinical trials, autoimmune mechanisms, and immunotherapy in combination with other cancer treatments. We have also reviewed the current challenges in the diagnosis of cardiac events and future directions in the field. In conclusion, this review will delve into this expanding field of cancer immunotherapy and the emerging adverse effects that should be quickly detected and prevented.

PD-1 restrains IL-17A production from γδ T cells to modulate acute radiation-induced lung injury

Background

Combining radiotherapy (RT) with programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1) inhibitors has been shown to enhance anti-tumor effects in the treatment of non-small cell lung carcinoma (NSCLC). Pulmonary toxicity is a major adverse effect of thoracic RT in NSCLC patients, whether it is administered alone or in combination with PD-1/PD-L1 inhibitors. This study aimed to evaluate the potential pulmonary toxicity of RT combined with concurrent PD-1 inhibitor and to clarify the underlying mechanisms.

Methods

Radiation-induced lung injury (RILI) was induced in C57BL/6 mice by given 24 Gy in three fractions on consecutive days, with or without concurrent injection of anti-PD-1 antibody. On days 3, 7, 14, and 28 after the first exposure to irradiation, lung tissue and peripheral blood samples were collected from the mice. Histological injury was analyzed, and inflammatory cell infiltration and interleukin (IL)-17A production in the lung tissues were quantified.

Results

Mice that received irradiation with concurrent administration of anti-PD-1 antibody had the highest histological score for RILI. In the murine lung tissues, the levels of PD-1 and IL-17A expression were increased in γδ T cells but not in the other CD3⁺ T cells after irradiation. Concurrent blockade of PD-1 enhanced IL-17A production from γδ T cells in the lung tissues after irradiation. In the mice with acute RILI, concurrent administration of anti-PD-1 antibody exaggerated pulmonary inflammation, with significantly increased levels of neutrophilic infiltration and IL-17A detected in both the lung and blood.

Conclusions

PD-1 could restrain IL-17A production from γδ T cells to modulate acute RILI. The concurrent administration of anti-PD-1 antibody aggravates the severity of acute RILI. More attention should be paid to pulmonary toxicity in patients undergoing thoracic RT with concurrent anti-PD-1 immunotherapy.

Radiotherapy for unresectable locally advanced non-small cell lung cancer: a narrative review of the current landscape and future prospects in the era of immunotherapy

Significant recent advances have occurred in the use of radiation therapy for locally advanced non-small cell lung cancer (LA-NSCLC). In fact, the past few decades have seen both therapeutic gains and setbacks in the evolution of radiotherapy for LA-NSCLC. The PACIFIC trial has heralded a new era of immunotherapy and has raised important questions for future study, such as the future directions of radiation therapy for LA-NSCLC in the era of immunotherapy. Modern radiotherapy techniques such as three-dimensional (3D) conformal radiotherapy and intensity-modulated radiotherapy (IMRT) provide opportunities for improved target conformity and reduced normal-tissue exposure. However, the low-dose radiation volume brought by IMRT and its effects on the immune system deserve particular attention when combing radiotherapy and immunotherapy. Particle radiotherapy offers dosimetric advantages and exhibits great immunoregulatory potential. With the ongoing improvement in particle radiotherapy techniques and knowledge, the combination of immunotherapy and particle radiotherapy has tremendous potential to improve treatment outcomes. Of particular importance are questions on the optimal radiation schedule in the settings of radio-immunotherapy. Strategies for the reduction of the irradiated field such as involved-field irradiation (IFI) and omission of clinical target volume (CTV) hold promise for better preservation of immune function while not compromising locoregional and distant control. In addition, different dose-fractionation regimens can have diverse effects on the immune system. Thus, prospective trials are urgently needed to establish the optimal dose fractionation regimen. Moreover, personalized radiotherapy which allows the tailoring of radiation dose to each individual's genetic background and immune state is of critical importance in maximizing the benefit of radiation to patients with LA-NSCLC.

A narrative review of synergistic drug administration in unresectable locally advanced non-small cell lung cancer: current landscape and future prospects in the era of immunotherapy

Based on the PACIFIC study, the standard care of unresectable locally advanced non-small cell lung cancer (LA-NSCLC) shifted from concurrent chemo-radiotherapy (CCRT) alone to CCRT followed by durvalumab consolidation in 2017. In the era of immunotherapy, two kinds of therapeutic drugs are involved in the management of LA-NSCLC: chemotherapeutics and anti-PD-1/PD-L1 agents. However, the best choices of systematic chemotherapy, immunotherapy, and treatment schedule remain controversial. The immune modulation effects of chemotherapy, as well as the potential immunosuppressive impact of pretreatment medications, should be taken into consideration. Indeed, chemotherapeutics are double-edged swords to immunotherapy, with both stimulatory and suppressive effects on the immune system. Moreover, low-dose chemotherapy is reported to enhance anti-tumor immune responses with reduced toxicities. As for glucocorticoids, there is no consensus about its exact impact on the efficacy of immunotherapy. In addition, the timing of anti-PD-1/PD-L1 agent related to CCRT has three modes: induction, concurrent, and consolidation therapy. Although CCRT followed by durvalumab consolidation is the standard of care, the best sequence of immunotherapy and chemo-radiotherapy is still under debate. Furthermore, the efficacy and toxicity of various PD-1/PD-L1 inhibitors should be compared, especially in the background of CCRT. In this review, we will summarize the detailed knowledge about chemotherapeutics and anti-PD-1/PD-L1 axis agents, and discuss the potential implications in designing novel, effective treatment strategies for LA-NSCLC.

Is clinical target volume necessary?-a failure pattern analysis in patients with locally advanced non-small cell lung cancer treated with concurrent chemoradiotherapy using intensity-modulated radiotherapy technique

Background

Our previous dosimetric study showed that for locally advanced non-small cell lung cancer (LA-NSCLC), radiotherapy with intensity-modulated radiotherapy (IMRT) technique could deliver sufficient dose coverage to subclinical regions and reduce the dose to normal tissues with the omission of clinical target volume (CTV). To further clinically validate this strategy, we conducted the current study to analyze the failure pattern for patients with LA-NSCLC treated with concurrent chemotherapy and CTV-omitted IMRT. We also investigated the effects of target volumes on lymphopenia during radiotherapy to further test the potential benefits of CTV omission in anti-tumor immunotherapy.

Methods

A total of 63 patients with LA-NSCLC treated with CTV-omitted IMRT with concurrent chemotherapy were enrolled in this study. Their planning target volume (PTV) (also PTV-g) was expanded directly from gross tumor volume (GTV). A virtual CTV was expanded from GTV, and the PTV generated from virtual CTV was named planning target volume with CTV expansion (PTV-c). Treatment failures were divided into local, regional, and distant failures, and local–regional recurrences were classified into inside PTV-g (IN-PTV-g), between PTV-g and PTV-c (PTV-g-c), and outside PTV-c (OUT-PTV-c). The relationship between lymphopenia during radiotherapy and the target volumes was also evaluated using Spearman’s correlation analysis.

Results

Among the 60 patients with detailed follow-up data for recurrences, 46 (76.7%) experienced recurrences, with 18 (30.0%) being local recurrence, 5 (8.4%) being regional failure, and 33 (55.0%) being distant failure. For the 21 patients with local–regional recurrences, 16, 6, and 1 were IN-PTV-g, OUT-PTV-c, and PTV-g-c recurrences, respectively. Lymphopenia during radiotherapy was associated with both GTV and PTV, with larger volumes linked to severe lymphopenia.

Conclusions

CTV omission is feasible for LA-NSCLC treated with concurrent chemoradiotherapy and does not compromise failure inside the subclinical region. The radiation volumes were associated with lymphopenia during radiotherapy, with larger volumes related to severe lymphopenia. This finding supports the further exploration of CTV omission for immunotherapy.

Acquired Immunity Is Not Essential for Radiation-Induced Heart Dysfunction but Exerts a Complex Impact on Injury

While radiation therapy (RT) can improve cancer outcomes, it can lead to radiation-induced heart dysfunction (RIHD) in patients with thoracic tumors. This study examines the role of adaptive immune cells in RIHD. In Salt-Sensitive (SS) rats, image-guided whole-heart RT increased cardiac T-cell infiltration. We analyzed the functional requirement for these cells in RIHD using a genetic model of T- and B-cell deficiency (interleukin-2 receptor gamma chain knockout (IL2RG-/-)) and observed a complex role for these cells. Surprisingly, while IL2RG deficiency conferred protection from cardiac hypertrophy, it worsened heart function via echocardiogram three months after a large single RT dose, including increased end-systolic volume (ESV) and reduced ejection fraction (EF) and fractional shortening (FS) (p < 0.05). Fractionated RT, however, did not yield similarly increased injury. Our results indicate that T cells are not uniformly required for RIHD in this model, nor do they account for our previously reported differences in cardiac RT sensitivity between SS and SS.BN3 rats. The increasing use of immunotherapies in conjunction with traditional cancer treatments demands better models to study the interactions between immunity and RT for effective therapy. We present a model that reveals complex roles for adaptive immune cells in cardiac injury that vary depending on clinically relevant factors, including RT dose/fractionation, sex, and genetic background.

Advances in Preclinical Research Models of Radiation-Induced Cardiac Toxicity

Radiation therapy (RT) is an important component of cancer therapy, with >50% of cancer patients receiving RT. As the number of cancer survivors increases, the short- and long-term side effects of cancer therapy are of growing concern. Side effects of RT for thoracic tumors, notably cardiac and pulmonary toxicities, can cause morbidity and mortality in long-term cancer survivors. An understanding of the biological pathways and mechanisms involved in normal tissue toxicity from RT will improve future cancer treatments by reducing the risk of long-term side effects. Many of these mechanistic studies are performed in animal models of radiation exposure. In this area of research, the use of small animal image-guided RT with treatment planning systems that allow more accurate dose determination has the potential to revolutionize knowledge of clinically relevant tumor and normal tissue radiobiology. However, there are still a number of challenges to overcome to optimize such radiation delivery, including dose verification and calibration, determination of doses received by adjacent normal tissues that can affect outcomes, and motion management and identifying variation in doses due to animal heterogeneity. In addition, recent studies have begun to determine how animal strain and sex affect normal tissue radiation injuries. This review article discusses the known and potential benefits and caveats of newer technologies and methods used for small animal radiation delivery, as well as how the choice of animal models, including variables such as species, strain, and age, can alter the severity of cardiac radiation toxicities and impact their clinical relevance.

Radiotherapy toxicity

Radiotherapy is used in >50% of patients with cancer, both for curative and palliative purposes. Radiotherapy uses ionizing radiation to target and kill tumour tissue, but normal tissue can also be damaged, leading to toxicity. Modern and precise radiotherapy techniques, such as intensity-modulated radiotherapy, may prevent toxicity, but some patients still experience adverse effects. The physiopathology of toxicity is dependent on many parameters, such as the location of irradiation or the functional status of organs at risk. Knowledge of the mechanisms leads to a more rational approach for controlling radiotherapy toxicity, which may result in improved symptom control and quality of life for patients. This improved quality of life is particularly important in paediatric patients, who may live for many years with the long-term effects of radiotherapy. Notably, signs and symptoms occurring after radiotherapy may not be due to the treatment but to an exacerbation of existing conditions or to the development of new diseases. Although differential diagnosis may be difficult, it has important consequences for patients.

Safety of combined PD-1 pathway inhibition and radiation therapy for non-small-cell lung cancer: A multicentric retrospective study from the GFPC

INTRODUCTION

Randomized prospective studies on patients with metastatic non-small-cell lung cancers (NSCLCs) showed that anti-programmed death-1 (PD-1) agents notably improved 2-year overall survival (OS) rates, compared to docetaxel. NSCLC patients now receive nivolumab and irradiation, concurrently or not. However, little is known about the safety of this combination, even though the preclinical model suggested a possible synergic effect. We analyzed NSCLC patients treated with radiotherapy and nivolumab according to former's timing.

METHODS

We retrospectively reviewed records of a large series of metastatic NSCLC patients from three French centers, irradiated during the 6 months preceding, concomitantly, or 3 months after nivolumab administration to assess nivolumab tolerance and outcomes.

RESULTS

Among 104 patients included (37 women; 67 men; median age 60.3 years; 67% with performance status <2; 93.2% were current or past smokers) and their 144 intra- or extracranial irradiation courses, any-grade adverse events (AEs) were observed in 62 (59.6%), with 10 (9.6%) experiencing at least one grade 3/4 toxicity and 9 (8.7%) at least one grade 3/4 immune-related AE (IRAE). Respective 1- and 2-year OS rates were 48.8% and 29.1%, while 1- and 2-year progression-free survival (PFS) rates were 20.9% and 10.1%. PFS was significantly better for patients with IRAE(s) (P = 0.038) than those without and a trend toward better OS (P = 0.06). Delivering radiation before or during/after nivolumab administration was not associated with better OS or PFS.

CONCLUSION

Radiotherapy delivered during the 6 months before, during, or the three months following nivolumab for NSCLCs was not associated with an increased risk of severe or unexpected toxicities.

Radiation therapy and PD-1/PD-L1 blockade: the clinical development of an evolving anticancer combination

Several inhibitors of programmed cell death-1 (PD-1) and programmed death ligand-1 (PD-L1) have been approved as a form of immunotherapy for multiple cancers. Ionizing radiation therapy (RT) has been shown to enhance the priming and effector phases of the antitumor T-cell response rendering it an attractive therapy to combine with PD-1/PD-L1 inhibitors. Preclinical data support the rational combination of the 2 modalities and has paved way for the clinical development of the combination across a spectrum of cancers. In this review, we highlight the preclinical and clinical development of combined RT and PD-1/PD-L1 blockade to date. In addition to a comprehensive evaluation of available safety and efficacy data, we discuss important points of consideration in clinical trial design for this promising combination.

Local Radiotherapy Affects Drug Pharmacokinetics-Exploration of a Neglected but Significant Uncertainty of Cancer Therapy

Purpose:

Concurrent chemoradiation therapy is the mainstay of treatment for many types of malignancies. However, concurrent chemoradiation therapy is associated with a greater number of systemic adverse effects than radiotherapy or chemotherapy alone.

Summary:

Pharmacokinetics is the study of a drug and/or its metabolite kinetics in the body, including absorption, distribution, metabolism, and elimination. The incidences of adverse effects are markedly higher in patients who receive concurrent chemoradiation therapy than in those who receive either radiotherapy or chemotherapy alone. This phenomenon implies that irradiation affects the pharmacokinetics of cytotoxic agents, namely the radiotherapy–pharmacokinetic phenomenon. Experimental animal studies have shown that local irradiation affects the systemic pharmacokinetics of 5-fluorouracil and cisplatin at both low dose (simulating generous dose distributed to normal tissues) and daily practice dose (mimicking therapeutic dose to target volumes). These effects are significant in the circulation of blood and lymphatic system as well as in the hepatobiliary excretion. Furthermore, recent studies have demonstrated that matrix metalloproteinase-8 plays an important role in the radiotherapy–pharmacokinetic phenomenon.

Conclusion:

In the present review, we provide a general overview of the radiotherapy–pharmacokinetic phenomenon and discuss the possible mechanisms governing the phenomenon.