The interplay between radiation and the immune system in the field of post-radical pneumonitis and fibrosis and why it is important to understand it

Pyroptotic cell death: an emerging therapeutic opportunity for radiotherapy

Pyroptotic cell death, an inflammatory form of programmed cell death (PCD), is emerging as a potential therapeutic opportunity for radiotherapy (RT). RT is commonly used for cancer treatment, but its effectiveness can be limited by tumor resistance and adverse effects on healthy tissues. Pyroptosis, characterized by cell swelling, membrane rupture, and release of pro-inflammatory cytokines, has been shown to enhance the immune response against cancer cells. By inducing pyroptotic cell death in tumor cells, RT has the potential to enhance treatment outcomes by stimulating anti-tumor immune responses and improving the overall efficacy of RT. Furthermore, the release of danger signals from pyroptotic cells can promote the recruitment and activation of immune cells, leading to a systemic immune response that may target distant metastases. Although further research is needed to fully understand the mechanisms and optimize the use of pyroptotic cell death in RT, it holds promise as a novel therapeutic strategy for improving cancer treatment outcomes. This review aims to synthesize recent research on the regulatory mechanisms underlying radiation-induced pyroptosis and to elucidate the potential significance of this process in RT. The insights gained from this analysis may inform strategies to enhance the efficacy of RT for tumors.

Tolerogenic dendritic cells in radiation-induced lung injury

Radiation-induced lung injury is a common complication associated with radiotherapy. It is characterized by early-stage radiation pneumonia and subsequent radiation pulmonary fibrosis. However, there is currently a lack of effective therapeutic strategies for radiation-induced lung injury. Recent studies have shown that tolerogenic dendritic cells interact with regulatory T cells and/or regulatory B cells to stimulate the production of immunosuppressive molecules, control inflammation, and prevent overimmunity. This highlights a potential new therapeutic activity of tolerogenic dendritic cells in managing radiation-induced lung injury. In this review, we aim to provide a comprehensive overview of tolerogenic dendritic cells in the context of radiation-induced lung injury, which will be valuable for researchers in this field.

MiR-223-3p attenuates radiation-induced inflammatory response and inhibits the activation of NLRP3 inflammasome in macrophages

Macrophage pyroptosis plays an important role in the development of radiation-induced cell and tissue damage, leading to acute lung injury. However, the underlying mechanisms of NOD-like receptor thermal protein domain-associated protein 3 (NLRP3)-mediated macrophage pyroptosis and the regulatory factors involved in radiation-induced pyroptosis are unclear. In this study, the expression of the NLRP3 inflammasome and pyroptosis-associated factors in murine macrophage cell lines was investigated after ionizing radiation. High-throughput RNA sequencing was performed to identify and characterize miRNAs and mRNA transcripts associated with NLRP3-mediated cell death. Our results demonstrated that cleaved-caspase-1 (p10) and N-terminal domain of gasdermin-D (GSDMD-N) were upregulated, and the number of NLRP3 inflammasomes and pyroptotic cells increased in murine macrophage cell lines after irradiation (8 Gy). Comparativeprofiling of 300miRNAs revealed that 41 miRNAsexhibited significantly different expression after 8 Gy of irradiation. Granulocyte-specific microRNA-223-3p (miR-223-3p) is a negative regulator of NLRP3. In vitro experiments revealed that the expression of miR-223-3p was significantly altered by irradiation. Moreover, miR-223-3p decreased the expression of NLRP3 and proinflammatory factors, resulting in reduced pyroptosis in irradiated murine macrophages. Subsequently, in vivo experiments revealed the efficacy of miR-223-3p supplementation in ameliorating alveolar macrophage (AM) pyroptosis, attenuating the infiltration of inflammatory monocytes, and significantly alleviating the severity of acute radiation-induced lung injury (ARILI). Our findings suggest that the miR-223-3p/NLRP3/caspase-1 axis is involved in radiation-induced AM pyroptosis and ARILI.

The occurrence and development of radiation-induced lung injury after interstitial brachytherapy and stereotactic radiotherapy in SD rats

BACKGROUND

To compare the severity of radiation-induced lung injury (RILI) after the right lung of SD rats received interstitial brachytherapy and stereotactic radiotherapy (SBRT).

METHODS

RILI rat model was established using interstitial brachytherapy and SBRT methods, respectively. CT scan was performed to analyze the lung volume and the CT value difference between the left and right lungs in rats. Then the lung tissues were analyzed through H&E staining, peripheral blood was extracted to detect the expression levels of serum inflammatory cytokines, pro-fibrotic cytokines, and fibrotic-inhibiting cytokines by ELISA.

RESULTS

The difference between right and left lung CT values was significantly elevated in the SBRT group when compared with the control group and the interstitial brachytherapy group (P < 0.05). The IFN-γ expression in the interstitial brachytherapy group was significantly different from that in the SBRT group at week 1, 4, 8 and 16. Besides, the expressions of IL-2, IL-6 and IL-10 in SBRT group were significantly higher than that of interstitial brachytherapy group (P < 0.05). The TGF-β expression in interstitial brachytherapy group reached its peak with the increase of time from week 1 to week 16, and it was significantly lower than SBRT group (P < 0.05). The mortality rate in the SBRT group was 16.7%, which was significantly higher than that in the interstitial brachytherapy group.

CONCLUSION

The treatment method of interstitial brachytherapy is considered as an effective and safe tool by reducing the side effects of radiotherapy and increasing the radiation dose of radiotherapy.

Effects of diabetes on the development of radiation pneumonitis

Radiation pneumonia (RP) is a common adverse reaction to radiation therapy in patients with chest tumors. Recent studies have shown that diabetes mellitus (DM), which can cause systemic multisystem damage, specifically targets lungs, and the incidence of RP in patients with a history of diabetes is higher than that in other patients with tumors who have undergone radiotherapy. DM is an important risk factor for RP in tumor patients undergoing RT, and patients with DM should be treated with caution. This article reviews research on the clinical aspects, as well as the mechanism, of the effects of diabetes on RP and suggests future research needed to reduce RP.

Investigating the SPECT Dose-Function Metrics Associated With Radiation-Induced Lung Toxicity Risk in Patients With Non-small Cell Lung Cancer Undergoing Radiation Therapy

Purpose

Dose to normal lung has commonly been linked with radiation-induced lung toxicity (RILT) risk, but incorporating functional lung metrics in treatment planning may help further optimize dose delivery and reduce RILT incidence. The purpose of this study was to investigate the impact of the dose delivered to functional lung regions by analyzing perfusion (Q), ventilation (V), and combined V/Q single-photon-emission computed tomography (SPECT) dose-function metrics with regard to RILT risk in patients with non-small cell lung cancer (NSCLC) patients who received radiation therapy (RT).

Methods and Materials

SPECT images acquired from 88 patients with locally advanced NSCLC before undergoing conventionally fractionated RT were retrospectively analyzed. Dose was converted to the nominal dose equivalent per 2 Gy fraction, and SPECT intensities were normalized. Regional lung segments were defined, and the average dose delivered to each lung region was quantified. Three functional categorizations were defined to represent low-, normal-, and high-functioning lungs. The percent of functional lung category receiving ≥20 Gy and mean functional intensity receiving ≥20 Gy (iV₂₀) were calculated. RILT was defined as grade 2+ radiation pneumonitis and/or clinical radiation fibrosis. A logistic regression was used to evaluate the association between dose-function metrics and risk of RILT.

Results

By analyzing V/Q normalized intensities and functional distributions across the population, a wide range in functional capability (especially in the ipsilateral lung) was observed in patients with NSCLC before RT. Through multivariable regression models, global lung average dose to the lower lung was found to be significantly associated with RILT, and Q and V iV₂₀ were correlated with RILT when using ipsilateral lung metrics. Through a receiver operating characteristic analysis, combined V/Q low-function receiving ≥20 Gy (low-functioning V/Q₂₀) in the ipsilateral lung was found to be the best predictor (area under the curce: 0.79) of RILT risk.

Conclusions

Irradiation of the inferior lung appears to be a locational sensitivity for RILT risk. The multivariable correlation between ipsilateral lung iV₂₀ and RILT, as well as the association of low-functioning V/Q₂₀ and RILT, suggest that irradiating low-functioning regions in the lung may lead to higher toxicity rates.

Naringenin Ameliorates Radiation-Induced Lung Injury by Lowering IL-1β Level

Radiation-induced lung injury (RILI) is the main complication of radiotherapy for thoracic malignancies. Since naringenin, a potent immune-modulator, has been found to relieve bleomycin-induced lung fibrosis by restoring the balance of disordered cytokines, we sought to determine whether naringenin would mitigate RILI and to investigate the underlying mechanism. Animals received fractionated irradiation in the thoracic area to induce RILI. Enzyme-linked immunosorbent assay and MILLIPLEX assays were used for serum and bronchoalveolar lavage fluid for cytokine analyses, hematoxylin and eosin staining for pathologic changes, and Masson trichrome staining for determination of lung fibrosis. Interleukin (IL)-1β was found significantly elevated after thoracic irradiation and it triggered production of profibrotic tumor growth factor β both in vivo and in vitro, suggesting the vital role of in IL-1β in the development of RILI. Furthermore, we found that naringenin was able to ameliorate RILI through downregulation of IL-1β and restoration of the homeostasis of inflammatory factors. Our results demonstrated that naringenin could serve as a potent immune-modulator to ameliorate RILI. More importantly, we suggest that a new complementary strategy of maintaining the homeostasis of inflammatory factors combined with radiation could improve the efficacy of thoracic radiotherapy.

Protective efficacy of inhaled quercetin for radiation pneumonitis

Radiation pneumonitis is a clinical problem with a high incidence. Once the onset of radiation pneumonitis has occurred, the administration of antioxidants and anti-inflammatory agents is the most commonly used method of clinical treatment. Quercetin (Que) is a common flavonoid, with potent anti-inflammatory and anti-oxidant activities. In the present study, the therapeutic effect of inhaled Que on radiation-induced radiation pneumonitis in rats was investigated. Treatment with Que via inhalation was shown to increase the number of leukocytes and erythrocytes in the blood, and reduce the number of inflammatory cells in bronchoalveolar lavage fluid. Histological examination of lung tissue indicated that inhaled Que reduced hemorrhaging and the infiltration of inflammatory cells, and suppressed the expression of the proinflammatory cytokines transforming growth factor-β₁ and interleukin-6. These results indicated that treatment with Que via inhalation ameliorates radiation pneumonitis by reducing the number of inflammatory cells, and attenuating the inflammatory response and pathological changes. This suggests that administration of Que via inhalation has the potential to become a novel treatment for radiation pneumonitis.

Temporal and spatial dose distribution of radiation pneumonitis after concurrent radiochemotherapy in stage III non-small cell cancer patients

Background and purpose

Radiation pneumonitis (RP) is the most common subacute side effect after concurrent chemoradiotherapy (CRT) for locally advanced non-small cell lung cancer. Several clinical and dose-volume (DV) parameters are associated with a distinct risk of symptomatic RP. The aim of this study was to assess the spatial dose distribution of the RP volume from first occurence to maximum volume expansion of RP.

Material and methods

Between 2007 and 2015, 732 patients with lung cancer were treated in an institution. Thirty-three patients met the following inclusion criteria: an RP grade II after CRT and a radiation dose ≥60 Gy and no prior medical history of cardiopulmonary comorbidities. The images of the first chest computed tomography (CT) confirming the diagnosis of RP and the CT images showing the maximum expansion of RP were merged with the treatment plan. The RP volume was delineated within the treatment plan, and a DV analysis was performed to evaluate the lung dose volume areas in which the RP manifested over time and whether dose volume changes within the RP volume occurred.

Results

A change from clinical diagnosis to maximum expansion of RP was observed as the RP at clinical appearance mainly manifested in the lower dose areas of the lung, whereas the RP volume at maximum expansion manifested in the higher dose areas, resulting in a significant shift of the assessed relative mean dose volume proportions within the RP volume. The mean relative dose volume proportion 0- ≤ 20 Gy decreased from 30.2% (range, 0–100) to 21.9% (range, 0–100; p = 0.04) at the expense of the dose volume > 40 Gy which increased from 39.2% (range, 0–100) to 49.8% (range, 0–100; p = 0.02), whereas the dose relative volume proportion > 20- ≤ 40 Gy showed no relevant change and slightly decreased from 30.6% (range, 0–85.7) to 28.3%, (range, 0–85.7; p = 0.34).

Conclusion

We observed a considerable increase in the relative dose proportions within the RP volume from diagnosis to maximum volume extent from low dose zones below 20 Gy to zones above 40 Gy. Although the clinical impact on RP remains unknown, a reduction of healthy healthy lung tissue receiving >40 Gy (V40) might be an additional parameter for irradiation planning in lung cancer patients.

Irradiation enhanced risks of hospitalised pneumonopathy in lung cancer patients: a population-based surgical cohort study

OBJECTIVE

Pulmonary radiotherapy has been reported to increase a risk of pneumonopathy, including pneumonitis and secondary pneumonia, however evidence from population-based studies is lacking. The present study intended to explore whether postoperative irradiation increases occurrence of severe pneumonopathy in lung cancer patients.

DESIGN, SETTING AND PARTICIPANTS

The nationwide population-based study analysed the Taiwan National Health Insurance Research Database (covered >99% of Taiwanese) in a real-world setting. From 2000 to 2010, 4335 newly diagnosed lung cancer patients were allocated into two groups: surgery-RT (n=867) and surgery-alone (n=3468). With a ratio of 1:4, propensity score was used to match 11 baseline factors to balance groups.

INTERVENTIONS/EXPOSURES

Irradiation was delivered to bronchial stump and mediastinum according to peer-audited guidelines.

OUTCOMES/MEASURES

Hospitalised pneumonia/pneumonitis-free survival was the primary end point. Risk factors and hazard effects were secondary measures.

RESULTS

Multivariable analysis identified five independent risk factors for hospitalised pneumonopathy: elderly (>65 years), male, irradiation, chronic obstructive pulmonary disease (COPD) and chronic kidney disease (CKD). Compared with surgery-alone, a higher risk of hospitalised pneumonopathy was found in surgery-RT patients (HR, 2.20; 95% CI, 1.93-2.51; 2-year hospitalised pneumonia/pneumonitis-free survival, 85.2% vs 69.0%; both p<0.0001), especially in elderly males with COPD and CKD (HR, 13.74; 95% CI, 6.61-28.53; p<0.0001). Unexpectedly, we observed a higher risk of hospitalised pneumonopathy in younger irradiated-CKD patients (HR, 13.07; 95% CI, 5.71-29.94; p<0.0001) than that of elderly irradiated-CKD patients (HR, 4.82; 95% CI, 2.88-8.08; p<0.0001).

CONCLUSIONS

A high risk of hospitalised pneumonopathy is observed in irradiated patients, especially in elderly males with COPD and CKD. For these patients, close clinical surveillance and aggressive pneumonia/pneumonitis prevention should be considered. Further investigations are required to define underlying biological mechanisms, especially for younger CKD patients.

Plasma Levels of IL-8 and TGF-β1 Predict Radiation-Induced Lung Toxicity in Non-Small Cell Lung Cancer: A Validation Study

PURPOSE AND OBJECTIVES

We previously reported that the combination of mean lung dose (MLD) and inflammatory cytokines interleukin-8 (IL-8) and transforming growth factor-β1 (TGF-β1) may provide a more accurate model for radiation-induced lung toxicity (RILT) prediction in 58 patients with non-small cell lung cancer (NSCLC). This study is to validate the previous findings with new patients and to explore new models with more cytokines.

METHODS AND MATERIALS

One hundred forty-two patients with stage I-III NSCLC treated with definitive radiation therapy (RT) from prospective studies were included. Sixty-five new patients were used to validate previous findings, and all 142 patients were used to explore new models. Thirty inflammatory cytokines were measured in plasma samples before RT and 2 weeks and 4 weeks during RT (pre, 2w, 4w). Grade ≥2 RILT was defined as grade 2, and higher radiation pneumonitis or symptomatic pulmonary fibrosis was the primary endpoint. Logistic regression was performed to evaluate the risk factors of RILT. The area under the curve (AUC) for the receiver operating characteristic curves was used for model assessment.

RESULTS

Sixteen of 65 patients (24.6%) experienced RILT2. Lower pre IL-8 and higher TGF-β1 2w/pre ratio were associated with higher risk of RILT2. The AUC increased to 0.73 by combining MLD, pre IL-8, and TGF-β1 2w/pre ratio compared with 0.61 by MLD alone to predict RILT. In all 142 patients, 29 patients (20.4%) experienced grade ≥2 RILT. Among the 30 cytokines measured, only IL-8 and TGF-β1 were significantly associated with the risk of RILT2. MLD, pre IL-8 level, and TGF-β1 2w/pre ratio were included in the final predictive model. The AUC increased to 0.76 by combining MLD, pre IL-8, and TGF-β1 2w/pre ratio compared with 0.62 by MLD alone.

CONCLUSIONS

We validated that a combination of mean lung dose, pre IL-8 level, and TGF-β1 2w/pre ratio provided a more accurate model to predict the risk of RILT2 compared with MLD alone.

Inhalative steroids as an individual treatment in symptomatic lung cancer patients with radiation pneumonitis grade II after radiotherapy - a single-centre experience

Purpose

To assess efficacy of our single-centre experience with inhalative steroids (IS) in lung cancer patients with symptomatic radiation pneumonitis (RP) grade II.

Material and methods

Between 05/09 and 07/10, 24 patients (female, n = 8; male, n = 16) with lung cancer (non-small cell lung carcinoma [NSCLC]: n = 19; small cell lung cancer [SCLC]: n = 3; unknown histology: n = 2) and good performance status (ECOG ≤1) received definitive radiotherapy to the primary tumour site and involved lymph nodes with concurrent chemotherapy (n = 18), sequential chemotherapy (n = 2) or radiation only (n = 4) and developed symptomatic RP grade II during follow-up. No patient presented with oxygen requiring RP grade III. The mean age at diagnosis was 66 years (range: 50–82 years). Nine patients suffered from chronic obstructive pulmonary disease (COPD) before treatment, and 18 patients had a smoking history (median pack years: 48). The mean lung dose was 15.5 Gy (range: 3.0–23.1 Gy). All patients were treated with IS. If a patient’s clinical symptoms did not significantly improve within two weeks of IS therapy initiation, their treatment was switched to oral prednisolone.

Results

All 24 patients were initially treated with a high dose IS (budesonide 800 μg 1-0-1) for 14 days. Of the patients, 18 showed a significant improvement of clinical symptoms and 6 patients did not show significant improvement of clinical symptoms and were classified as non-responders to IS. Their treatment was switched to oral steroids after two weeks (starting with oral prednisolone, 0.5 mg/kg bodyweight; at least 50 mg per day). All of these patients responded to the prednisolone. None of non-responders presented with increased symptoms of RP and required oxygen and / or hospitalization (RP grade III). The median follow-up after IS treatment initiation was 18 months (range: 4–66 months). The median duration of IS treatment and prednisolone treatment was 8.2 months (range: 3.0–48.3 months) and 11.4 months (range: 5.0–44.0 months), respectively. Of the 18 IS treatment responders, 2 (11.1 %) patients with pre-existing grade 2 COPD still required IS (400 μg twice a day) 45.0 and 48.3 months after radiotherapy, respectively. For the remaining 16 responders (88.9 %), IS therapy was stopped after 7.7 months (range: 3.0–18.2 months). None of the patients treated with IS developed any specific IS-related side effects such as oral candidiasis.

Conclusion

This single-centre experience shows that high-dose IS is an individual treatment option for radiation-induced pneumonitis grade II in patients with a good performance status.

Pretreatment Immune Parameters Predict for Overall Survival and Toxicity in Early-Stage Non-Small-Cell Lung Cancer Patients Treated With Stereotactic Body Radiation Therapy

INTRODUCTION

We determined whether pretreatment immunologic parameters could predict the outcomes and toxicity in early-stage non-small-cell lung cancer (NSCLC) patients treated with stereotactic body radiation therapy (SBRT).

PATIENTS AND METHODS

The pretreatment leukocyte, lymphocyte, and neutrophil counts, serum albumin levels, neutrophil-to-lymphocyte ratio (NLR,) and platelet-to-lymphocyte ratio (PLR) were evaluated to determine the association with locoregional control, distant metastasis-free survival (DMFS), disease-specific survival (DSS), overall survival (OS), and treatment-related toxicity. The survival rates were estimated with Kaplan-Meier analysis and multivariate analysis using the Cox proportional hazards model.

RESULTS

The data from 118 patients with a median follow-up period of 28.9 months were assessed. The 3-year local control, regional control, and DMFS rates were 97%, 87%, and 92%, respectively. The 3-year OS and DSS rates were 77% and 85%, respectively. On univariate analysis, none of the pretreatment immune parameters predicted for disease control. A higher NLR (P = .008), PLR (P = .002), neutrophil count (P = .059), and the presence of lymphocytopenia (P = .032) independently prognosticated for poor OS. Receiver operating characteristic curve analysis found NLRs > 2.18 and PLRs > 187.27 optimally predicted for poor 3-year OS (P = .0262 and P = .0089, respectively). A higher NLR predicted against the development of any symptomatic toxicity and against the development of symptomatic (grade ≥ 2) radiation pneumonitis on univariate analysis, and a higher serum albumin level independently predicted for the development of symptomatic radiation pneumonitis (P = .0491).

CONCLUSION

In the setting of SBRT, an elevated pretreatment NLR, PLR, and neutrophil count and the presence of lymphocytopenia independently predicted for poor OS. Patients who presented with higher NLRs and lower serum albumin levels experienced less treatment-related symptomatic toxicity.