The impact of radiation therapy on the antitumor immunity: local effects and systemic consequences

Respiratory adverse effects in patients treated with immune checkpoint inhibitors in combination with radiotherapy: a systematic review and meta-analysis

BACKGROUND

We conducted a systematic review and meta-analysis to assess the risk of respiratory adverse effects in patients with solid tumors treated with immune checkpoint inhibitors (PD-1, PD-L1 and CTLA-4 inhibitors) in combination with radiation therapy.

METHODS

We selected eligible studies through the following databases: PubMed, Embase, Cochrane Library, and Clinicaltrials ( https://clinicaltrials.gov/ ). The data was analyzed by using Rstudio.

RESULTS

Among 3737 studies, 26 clinical trials, including 2670 patients, were qualified for the meta-analysis. We evaluated the incidence rates of adverse respiratory events, including cough, pneumonia, upper respiratory tract infections, and others: grades 1-5 cough, 0.176 (95%CI: 0.113-0.274, I2 = 92.36%); grades 1-5 pneumonitis, 0.118 (95%CI: 0.067-0.198, I2 = 88.64%); grades 1-5 upper respiratory tract infection, 0.064 (95%CI: 0.049-0.080, I2 = 0.98%); grades 3-5 cough, 0.050 (95%CI: 0.012-0.204, I2 = 8.90%); grades 3-5 pneumonitis, 0.052 (95%CI: 0.031-0.078, I2 = 83.86%); grades 3-5 upper respiratory tract infection, 0.040 (95%CI: 0.007-0.249, I2 = 45.31%).

CONCLUSIONS

Our meta-analysis demonstrated that ICI combined with radiotherapy for solid tumors can produce respiratory adverse effects. ICIs combination treatment, a tumor located in the chest, is more likely to cause adverse reactions, and SBRT treatment and synchronous treatment will bring less incidence of adverse reactions. This study provide insights for clinicians to balance the risks of radiotherapy in the course of treating oncology patients.

Spatially fractionated radiation therapy: a critical review on current status of clinical and preclinical studies and knowledge gaps

Spatially fractionated radiation therapy (SFRT) is a therapeutic approach with the potential to disrupt the classical paradigms of conventional radiation therapy. The high spatial dose modulation in SFRT activates distinct radiobiological mechanisms which lead to a remarkable increase in normal tissue tolerances. Several decades of clinical use and numerous preclinical experiments suggest that SFRT has the potential to increase the therapeutic index, especially in bulky and radioresistant tumors. To unleash the full potential of SFRT a deeper understanding of the underlying biology and its relationship with the complex dosimetry of SFRT is needed. This review provides a critical analysis of the field, discussing not only the main clinical and preclinical findings but also analyzing the main knowledge gaps in a holistic way.

Antitumor Effect by Either FLASH or Conventional Dose Rate Irradiation Involves Equivalent Immune Responses

PURPOSE

The capability of ultrahigh dose rate FLASH radiation therapy to generate the FLASH effect has opened the possibility to enhance the therapeutic index of radiation therapy. The contribution of the immune response has frequently been hypothesized to account for a certain fraction of the antitumor efficacy and tumor kill of FLASH but has yet to be rigorously evaluated.

METHODS AND MATERIALS

To investigate the immune response as a potentially important mechanism of the antitumor effect of FLASH, various murine tumor models were grafted either subcutaneously or orthotopically into immunocompetent mice or in moderately and severely immunocompromised mice. Mice were locally irradiated with single dose (20 Gy) or hypofractionated regimens (3 × 8 or 2 × 6 Gy) using FLASH (≥2000 Gy/s) and conventional (CONV) dose rates (0.1 Gy/s), with/without anti-CTLA-4. Tumor growth was monitored over time and immune profiling performed.

RESULTS

FLASH and CONV 20 Gy were isoeffective in delaying tumor growth in immunocompetent and moderately immunodeficient hosts and increased tumor doubling time to >14 days versus >7 days in control animals. Similar observations were obtained with a hypofractionated scheme, regardless of the microenvironment (subcutaneous flank vs ortho lungs). Interestingly, in profoundly immunocompromised mice, 20 Gy FLASH retained antitumor activity and significantly increased tumor doubling time to >14 days versus >8 days in control animals, suggesting a possible antitumor mechanism independent of the immune response. Analysis of the tumor microenvironment showed similar immune profiles after both irradiation modalities with significant decrease of lymphoid cells by ∼40% and a corresponding increase of myeloid cells. In addition, FLASH and CONV did not increase transforming growth factor-β1 levels in tumors compared with unirradiated control animals. Furthermore, when a complete and long-lasting antitumor response was obtained (>140 days), both modalities of irradiation were able to generate a long-term immunologic memory response.

CONCLUSIONS

The present results clearly document that the tumor responses across multiple immunocompetent and immunodeficient mouse models are largely dose rate independent and simultaneously contradict a major role of the immune response in the antitumor efficacy of FLASH. Therefore, our study indicates that FLASH is as potent as CONV in modulating antitumor immune response and can be used as an immunomodulatory agent.

Combining spatially fractionated radiation therapy (SFRT) and immunotherapy opens new rays of hope for enhancing therapeutic ratio

Spatially Fractionated Radiation Therapy (SFRT) is a form of radiotherapy that delivers a single large dose of radiation within the target volume in a heterogeneous pattern with regions of peak dosage and regions of under dosage. SFRT types can be defined by how the heterogeneous pattern of radiation is obtained. Immune checkpoint inhibitors (ICIs) have been approved for various malignant tumors and are widely used to treat patients with metastatic cancer. The efficacy of ICI monotherapy is limited due to the "cold" tumor microenvironment. Fractionated radiotherapy can achieve higher doses per fraction to the target tumor, and induce immune activation (immodulate tumor immunogenicity and microenvironment). Therefore, coupling ICI therapy and fractionated radiation therapy could significantly improve the outcome of metastatic cancer. This review focuses on both preclinical and clinical studies that use a combination of radiotherapy and ICI therapy in cancer.

Immunotherapy combined with local therapy in the late-line treatment of repair-proficient (pMMR)/microsatellite stable (MSS) metastatic colorectal cancer

Colorectal cancer (CRC) is one of the most common malignancies, and at the initial visit, most patients are diagnosed with metastatic CRC (mCRC). However, immunotherapy is only and highly effective in a very small proportion of patients with mCRC having mismatch repair defect (dMMR)/high microsatellite instability, and the majority of the patients with mCRC having mismatch repair proficient (pMMR)/microsatellite stability (MSS) cannot benefit from it. At present, many clinical studies of immunotherapy combined with tyrosine kinase inhibitors (TKIs) are trying to regulate the immune microenvironment of pMMR/MSS mCRC, transforming a "cold tumor" into a "hot tumor," which has not only surprising effects but also certain limitations, i.e., the response could not be specific to metastasis. Therefore, regarding the bottleneck encountered by immunotherapy in patients with patients pMMR/MSS mCRC, this study summarized current research and possible mechanisms of immunotherapy combined with local therapy for metastasis, including radiotherapy, ablation, and transcatheter arterial chemoembolization.

Comparison of peripheral leukocyte parameters in patients receiving conventionally and hypofractionated radiotherapy schemes for the treatment of newly diagnosed glioblastoma

Introduction

Treatment for glioblastomas, aggressive and nearly uniformly fatal brain tumors, provide limited long-term success. Immunosuppression by myeloid cells in both the tumor microenvironment and systemic circulation are believed to contribute to this treatment resistance. Standard multi-modality therapy includes conventionally fractionated radiotherapy over 6 weeks; however, hypofractionated radiotherapy over 3 weeks or less may be appropriate for older patients or populations with poor performance status. Lymphocyte concentration changes have been reported in patients with glioblastoma; however, monocytes are likely a key cell type contributing to immunosuppression in glioblastoma. Peripheral monocyte concentration changes in patients receiving commonly employed radiation fractionation schemes are unknown.

Methods

To determine the effect of conventionally fractionated and hypofractionated radiotherapy on complete blood cell leukocyte parameters, retrospective longitudinal concentrations were compared prior to, during, and following standard chemoradiation treatment.

Results

This study is the first to report increased monocyte concentrations and decreased lymphocyte concentrations in patients treated with conventionally fractionated radiotherapy compared to hypofractionated radiotherapy.

Discussion

Understanding the impact of fractionation on peripheral blood leukocytes is important to inform selection of dose fractionation schemes for patients receiving radiotherapy.

Dual effects of radiotherapy on tumor microenvironment and its contribution towards the development of resistance to immunotherapy in gastrointestinal and thoracic cancers

Successful clinical methods for tumor elimination include a combination of surgical resection, radiotherapy, and chemotherapy. Radiotherapy is one of the crucial components of the cancer treatment regimens which allow to extend patient life expectancy. Current cutting-edge radiotherapy research is focused on the identification of methods that should increase cancer cell sensitivity to radiation and activate anti-cancer immunity mechanisms. Radiation treatment activates various cells of the tumor microenvironment (TME) and impacts tumor growth, angiogenesis, and anti-cancer immunity. Radiotherapy was shown to regulate signaling and anti-cancer functions of various TME immune and vasculature cell components, including tumor-associated macrophages, dendritic cells, endothelial cells, cancer-associated fibroblasts (CAFs), natural killers, and other T cell subsets. Dual effects of radiation, including metastasis-promoting effects and activation of oxidative stress, have been detected, suggesting that radiotherapy triggers heterogeneous targets. In this review, we critically discuss the activation of TME and angiogenesis during radiotherapy which is used to strengthen the effects of novel immunotherapy. Intracellular, genetic, and epigenetic mechanisms of signaling and clinical manipulations of immune responses and oxidative stress by radiotherapy are accented. Current findings indicate that radiotherapy should be considered as a supporting instrument for immunotherapy to limit the cancer-promoting effects of TME. To increase cancer-free survival rates, it is recommended to combine personalized radiation therapy methods with TME-targeting drugs, including immune checkpoint inhibitors.

IL-17 A correlates with disease progression in papillary thyroid carcinoma

BACKGROUND

Cancer progression can be promoted by chronic inflammation. Local immune response may be associated with favourable or unfavourable prognosis of Papillary Thyroid Carcinoma (PTC). Regulatory T (Treg) cells and T helper 17 (Th17) cells exert opposing function and their balance may have a vital role in promotion of tumor growth. Treg cells in tumor microenvironment (TME) may promote tumor progression and reduced survival of patients. Whereas, Th17 cells can promote or inhibit tumor progression depending on phenotypic characteristics of tumor. In this study, we aimed to analyse the kind of immune response developed and its prognostic impact in future therapeutics.

METHODS

Cytometric Bead Array (CBA) analysis of pro and anti-inflammatory cytokines (IFN-gamma, IL-2, IL-6, IL-17 A, TNF-alpha and IL-4, IL-10) was done in 15 PTC irrespective of Lymphocytic Thyroiditis (LT) and 16 Hashimoto's Thyroiditis (HT) cases. Immunohistochemical expression of FoxP3 and IL-17 A was studied in 27 cases of PTC with LT. Whereas, quantitative gene expression of both was analysed in 10 cases.

RESULTS

All the pro-inflammatory cytokines showed mild elevation in PTC with LT. On IHC, IL-17 A expression was observed in 74% PTC with LT. Whereas, FoxP3 was present in only 40% cases. Also, IL-17 A expression was significantly associated with age group (> 45 years), tumor size ≤ 1 cm and disease progression.

CONCLUSIONS

Increased expression of cytokines suggested correlation between inflammatory factors and progression of thyroid tumors. Along with this, the balance between IL-17 A and FoxP3 may play an important role in PTC development, prognosis and future management.

A Mathematical Model for Predicting Patient Responses to Combined Radiotherapy with CTLA-4 Immune Checkpoint Inhibitors

The purpose of this study was to develop a cell-cell interaction model that could predict a tumor's response to radiotherapy (RT) combined with CTLA-4 immune checkpoint inhibition (ICI) in patients with hepatocellular carcinoma (HCC). The previously developed model was extended by adding a new term representing tremelimumab, an inhibitor of CTLA-4. The distribution of the new immune activation term was derived from the results of a clinical trial for tremelimumab monotherapy (NCT01008358). The proposed model successfully reproduced longitudinal tumor diameter changes in HCC patients treated with tremelimumab (complete response = 0%, partial response = 17.6%, stable disease = 58.8%, and progressive disease = 23.6%). For the non-irradiated tumor control group, adding ICI to RT increased the clinical benefit rate from 8% to 32%. The simulation predicts that it is beneficial to start CTLA-4 blockade before RT in terms of treatment sequences. We developed a mathematical model that can predict the response of patients to the combined CTLA-4 blockade with radiation therapy. We anticipate that the developed model will be helpful for designing clinical trials with the ultimate aim of maximizing the efficacy of ICI-RT combination therapy.

Effect of Stereotactic Body Radiation Therapy on Diverse Organ Lesions in Advanced Non-Small Cell Lung Cancer Patients Receiving Immune Checkpoint Inhibitors

OBJECTIVE

The combination of stereotactic body radiation therapy (SBRT) and immune checkpoint inhibitors (ICIs) is actively being explored in advanced non-small-cell lung cancer (NSCLC) patients. However, little is known about the optimal fractionation and radiotherapy target lesions in this scenario. This study investigated the effect of SBRT on diverse organ lesions and radiotherapy dose fractionation regimens on the prognosis of advanced NSCLC patients receiving ICIs.

METHODS

The medical records of advanced NSCLC patients consecutively treated with ICIs and SBRT were retrospectively reviewed at our institution from Dec. 2015 to Sep. 2021. Patients were grouped according to radiation sites. Progression-free survival (PFS) and overall survival (OS) were recorded using the Kaplan-Meier method and compared between different treatment groups using the log-rank (Mantel-Cox) test.

RESULTS

A total of 124 advanced NSCLC patients receiving ICIs combined with SBRT were identified in this study. Radiation sites included lung lesions (lung group, n=43), bone metastases (bone group, n=24), and brain metastases (brain group, n=57). Compared with the brain group, the mean PFS (mPFS) in the lung group was significantly prolonged by 13.3 months (8.5 months vs. 21.8 months, HR=0.51, 95%CI: 0.28-0.92, P=0.0195), and that in the bone group prolonged by 9.5 months with a 43% reduction in the risk of disease progression (8.5 months vs. 18.0 months, HR=0.57, 95%CI: 0.29-1.13, P=0.1095). The mPFS in the lung group was prolonged by 3.8 months as compared with that in the bone group. The mean OS (mOS) in the lung and bone groups was longer than that of the brain group, and the risk of death decreased by up to 60% in the lung and bone groups as compared with that of the brain group. When SBRT was concurrently given with ICIs, the mPFS in the lung and brain groups were significantly longer than that of the bone group (29.6 months vs. 16.5 months vs. 12.1 months). When SBRT with 8-12 Gy per fraction was combined with ICIs, the mPFS in the lung group was significantly prolonged as compared with that of the bone and brain groups (25.4 months vs. 15.2 months vs. 12.0 months). Among patients receiving SBRT on lung lesions and brain metastases, the mPFS in the concurrent group was longer than that of the SBRT→ICIs group (29.6 months vs. 11.4 months, P=0.0003 and 12.1 months vs. 8.9 months, P=0.2559). Among patients receiving SBRT with <8 Gy and 8-12 Gy per fraction, the mPFS in the concurrent group was also longer than that of the SBRT→ICIs group (20.1 months vs. 5.3 months, P=0.0033 and 24.0 months vs. 13.4 months, P=0.1311). The disease control rates of the lung, bone, and brain groups were 90.7%, 83.3%, and 70.1%, respectively.

CONCLUSION

The study demonstrated that the addition of SBRT on lung lesions versus bone and brain metastases to ICIs improved the prognosis in advanced NSCLC patients. This improvement was related to the sequence of radiotherapy combined with ICIs and the radiotherapy fractionation regimens. Dose fractionation regimens of 8-12 Gy per fraction and lung lesions as radiotherapy targets might be the appropriate choice for advanced NSCLC patients receiving ICIs combined with SBRT.

Cardiovascular outcomes after curative prostate cancer treatment: A population-based cohort study

Objective

To investigate differences in cardiovascular disease (CVD) morbidity and mortality after radical prostatectomy or definitive radiotherapy with or without androgen deprivation therapy (ADT).

Materials and methods

We used population-based data from the Cancer Registry of Norway, the Norwegian Patient Registry and the Norwegian Cause of Death Registry including 19 289 men ≤80 years diagnosed with non-metastatic prostate cancer during 2010-2019. Patients were treated with radical prostatectomy or definitive radiotherapy. We used competing risk models to compare morbidity from overall CVD, acute myocardial infarction (AMI), cerebral infarction, thromboembolism, and CVD-specific mortality for the overall cohort and stratified by prognostic risk groups.

Results

After a median follow-up time of 5.4 years (IQR 4.6 years), there were no differences in adjusted rates of AMI, cerebral infarction, and CVD-specific death between radical prostatectomy and definitive radiotherapy in any of the prognostic risk groups. Rates of overall CVD (0.82; 95% CI 0.76-0.89) and thromboembolism (0.30; 95% CI 0.20-0.44) were lower for definitive radiotherapy than radical prostatectomy during the first year of follow-up. After this overall CVD rates (1.19; 95% CI 1.11-1.28) were consistently higher across all risk groups in patients treated with definitive radiotherapy, but there were no differences regarding thromboembolism.

Conclusions

During the first years after treatment, no differences were found in rates of AMI, cerebral infarction, and CVD-specific death between radiotherapy and radical prostatectomy in any of the prognostic risk groups. This suggests that ADT use in combination with radiotherapy may not increase the risks of these outcomes in a curative setting. The increased overall CVD rate for definitive radiotherapy after the first year indicates a possible relationship between definitive radiotherapy and other CVDs than AMI and cerebral infarction.

Effect of stereotactic body radiotherapy dose escalation plus pembrolizumab and trametinib versus stereotactic body radiotherapy dose escalation plus gemcitabine for locally recurrent pancreatic cancer after surgical resection on survival outcomes: A secondary analysis of an open-label, randomised, controlled, phase 2 trial

BACKGROUND

There are a lack of studies about whether radiation dose escalation synergizes with immunotherapy and targeted therapy in pancreatic cancer. In this study, we performed a secondary analysis to investigate whether a high radiation dose rather than a low dose plus pembrolizumab and trametinib provided improved survival compared with gemcitabine in post-operative locally recurrent pancreatic cancer.

METHODS

In this open-label, randomised, controlled, phase 2 trial, eligible patients with pancreatic ductal adenocarcinoma characterized by mutant KRAS and positive immunohistochemical staining of PD-L1 and documented post-operative local recurrence were randomly assigned using an interactive voice or web response system, without stratification, to receive stereotactic body radiation therapy (SBRT) with doses ranging from 35 to 40Gy in five fractions, pembrolizumab 200 mg every three weeks and oral trametinib 2 mg once daily (SBRT + K + M) or SBRT and gemcitabine (1000 mg/m²) on day 1 and 8 of each 21-day cycle (SBRT + G) until disease progression in our hospital in China. Those had radiotherapy, immunotherapy or targeted therapy were excluded. Patients and investigators were not masked to the assignment. In each arm, patients were stratified based on biologically effective dose (BED₁₀; α/β = 10) of 60-65Gy and BED₁₀ ≥65Gy. The primary endpoint was overall survival (OS) and the secondary endpoint was progression-free survival (PFS). All patients received their assigned treatment and were included in the efficacy and safety analyses. This study is registered with ClinicalTrials.gov, NCT02704156.

FINDINGS

Between Oct 10, 2016, and Oct 28, 2017, 147 of 170 randomly assigned participants were eligible for inclusion in this analysis. In BED₁₀ of 60-65Gy group, 34 and 29 patients had SBRT + G and SBRT + K + M, respectively. While there were 42 and 42 patients with SBRT + G and SBRT + K + M in BED₁₀ ≥65Gy group. Patients in the SBRT + K + M group had longer OS compared with the SBRT + G group, but this did not reach statistical significance (median: 15.1 vs. 12.4 months, HR 0.67 [95%CI 0.43-1.04]; p = 0.071). For BED₁₀ of 60-65Gy, OS was similar between patients in the SBRT + K + M and SBRT + G groups (median, 13.6 vs. 12.4 months; HR 0.69 [95% CI 0.41-1.16]; p = 0.16). For BED₁₀ of ≥65Gy, PFS was prolonged with SBRT + K + M versus SBRT + G (median: 8.6 vs. 5.0 months, HR 0.48 [95% CI 0.31-0.77]; p = 0.0021). For BED₁₀ of 60-65Gy, there was no significant difference in PFS between the two groups (PFS: median, 7.9 vs. 4.3 months; HR 0.69 [95% CI 0.42-1.15]; p = 0.16). In BED₁₀ of 60-65Gy group, 7 (20.6%) and 8 patients (27.6%) with SBRT + G and SBRT + K + M had grade 3 or 4 adverse events (p = 0.52). In BED₁₀ ≥65Gy group, 8 (19.0%) and 12 patients (28.6%) with SBRT + G and SBRT + K + M had grade 3 or 4 adverse events (p = 0.31). No treatment-related death occurred.

INTERPRETATION

Dose escalation of SBRT may improve PFS with pembrolizumab and trametnib versus gemcitabine for patients with post-operative locally recurrent pancreatic cancer. However, benefits of PFS did not translate into longer OS. This may be ascribed to small sample size and post-hoc analysis that was not powered to determine the significance. Therefore, synergy of high dose of SBRT with immunotherapy and targeted therapy required further investigations in phase 3 trials.

FUNDING

Shanghai Shenkang Centre and Changhai Hospital.

Targeted Radionuclide Therapy with Low and High-Dose Lutetium-177-Labeled Single Domain Antibodies Induces Distinct Immune Signatures in a Mouse Melanoma Model

Targeted radionuclide therapy (TRT) using probes labeled with Lutetium-177 (177Lu) represents a new and growing type of cancer therapy. We studied immunologic changes in response to TRT with 177Lu labeled anti-human CD20 camelid single domain antibodies (sdAb) in a B16-melanoma model transfected to express human CD20, the target antigen, and ovalbumin, a surrogate tumor antigen. High-dose TRT induced melanoma cell death, calreticulin exposure, and ATP-release in vitro. Melanoma-bearing mice received fractionated low and high-dose TRT via tumor targeting anti-human CD20 sdAbs, as opposed to control sdAbs. Tumor growth was delayed with both doses. Low- and high-dose TRT increased IL10 serum levels. Low-dose TRT also decreased CCL5 serum levels. At the tumor, high-dose TRT induced a type I IFN gene signature, while low-dose TRT induced a proinflammatory gene signature. Low- and high-dose TRT increased the percentage of PD-L1pos and PD-L2pos myeloid cells in tumors with a marked increase in alternatively activated macrophages after high-dose TRT. The percentage of tumor-infiltrating T cells was not changed, yet a modest increase in ovalbumin-specific CD8pos T-cells was observed after low-dose TRT. Contradictory, low and high-dose TRT decreased CD4pos Th1 cells in addition to double negative T cells. In conclusion, these data suggest that low and high-dose TRT induce distinct immunologic changes, which might serve as an anchoring point for combination therapy.

ASSESSMENT OF THE STATE OF IMMUNE SYSTEM IN PATIENTS WITH METASTATIC AND GLIAL BRAIN TUMORS AT THE PREPARATORY STAGE OF RADIOTHERAPY

OBJECTIVE

The aim: To assess the state of the immune system in patients before radiation therapy and radiosurgery and compare the features of immunity in metastatic and glial brain tumors.

PATIENTS AND METHODS

Materials and methods: Our study presents the results of immunograms of 41 patients. Of these: 18 patients with primary glial tumors and 23 patients with secondary metastatic tumors to the brain. The results of 20 conditionally healthy patients who did not have cancer are presented as a control group. The age of patients was 24-75 years. All patients have histological confirmation of the tumor diagnosis. Surgery was performed 1.0-3.0 years before the examination.

RESULTS

Results: When comparing the immune parameters of the number of T and B subpopulations of lymphocytes in patients with primary malignant brain tumors and secondary metastatic tumors, no statistically significant difference was found between these indicators. Glioblastomas show higher levels of IgG and IgA than other tumors, while the concentration of IgM is almost at the same level in all three groups of patients. There is a tendency to decrease the level of IgG and IgM in the blood of patients with metastatic tumors. In the study group of patients there is an inhibition of myeloperoxidase activity of neutrophils on the background of maintaining the function of NBT cell activity.

CONCLUSION

Conclusions: Both metastatic and primary malignant glial have partial changes in various parts of the immune system.

Novel Carbon Ion and Proton Partial Irradiation of Recurrent Unresectable Bulky Tumors (Particle-PATHY): Early Indication of Effectiveness and Safety

Background: We present the early results of a novel partial bulky-tumor irradiation using particles for patients with recurrent unresectable bulky tumors who failed previous state-of-the-art treatments. Methods: First, eleven consecutive patients were treated from March 2020 until December 2021. The targeted Bystander Tumor Volume (BTV) was created by subtracting 1 cm from Gross Tumor Volume (GTV) surface. It reflected approximately 30% of the central GTV volume and was irradiated with 30–45 Gy RBE (Relative Biological Effectiveness) in three consecutive fractions. The Peritumoral Immune Microenvironment (PIM) surrounding the GTV, containing nearby tissues, blood-lymphatic vessels and lymph nodes, was considered an organ at risk (OAR) and protected by highly conservative constraints. Results: With the median follow up of 6.3 months, overall survival was 64% with a median survival of 6.7 months; 46% of patients were progression-free. The average tumor volume regression was 61% from the initial size. The symptom control rate was 91%, with an average increase of the Karnofsky Index of 20%. The abscopal effect has been observed in 60% of patients. Conclusions: Partial bulky-tumor irradiation is an effective, safe and well tolerated treatment for patients with unresectable recurrent bulky disease. Abscopal effects elucidate an immunogenic pathway contribution. Extensive tumor shrinkage in some patients might permit definitive treatment—otherwise previously impossible.

Radiation-induced immune response in novel radiotherapy approaches FLASH and spatially fractionated radiotherapies

The last several years have revealed increasing evidence of the immunomodulatory role of radiation therapy. Radiotherapy reshapes the tumoral microenvironment can shift the balance toward a more immunostimulatory or immunosuppressive microenvironment. The immune response to radiation therapy appears to depend on the irradiation configuration (dose, particle, fractionation) and delivery modes (dose rate, spatial distributions). Although an optimal irradiation configuration (dose, temporal fractionation, spatial dose distribution, etc.) has not yet been determined, temporal schemes employing high doses per fraction appear to favor radiation-induced immune response through immunogenic cell death. Through the release of damage-associated molecular patterns and the sensing of double-stranded DNA and RNA breaks, immunogenic cell death activates the innate and adaptive immune response, leading to tumor infiltration by effector T cells and the abscopal effect. Novel radiotherapy approaches such as FLASH and spatially fractionated radiotherapies (SFRT) strongly modulate the dose delivery method. FLASH-RT and SFRT have the potential to trigger the immune system effectively while preserving healthy surrounding tissues. This manuscript reviews the current state of knowledge on the immunomodulation effects of these two new radiotherapy techniques in the tumor, healthy immune cells and non-targeted regions, as well as their therapeutic potential in combination with immunotherapy.

Predicting the effect of indirect cell kill in the treatment of multiple brain metastases via single-isocenter/multitarget volumetric modulated arc therapy stereotactic radiosurgery

Purpose

Due to spatial uncertainty, patient setup errors are of major concern for radiosurgery of multiple brain metastases (m‐bm) when using single‐isocenter/multitarget (SIMT) volumetric modulated arc therapy (VMAT) techniques. However, recent clinical outcome studies show high rates of tumor local control for SIMT‐VMAT. In addition to direct cell kill (DCK), another possible explanation includes the effects of indirect cell kill (ICK) via devascularization for a single dose of 15 Gy or more and by inducing a radiation immune intratumor response. This study quantifies the role of indirect cell death in dosimetric errors as a function of spatial patient setup uncertainty for stereotactic treatments of multiple lesions.

Material and Methods

Nine complex patients with 61 total tumors (2‐16 tumors/patient) were planned using SIMT‐VMAT with geometry similar to HyperArc with a 10MV‐FFF beam (2400 MU/min). Isocenter was placed at the geometric center of all tumors. Average gross tumor volume (GTV) and planning target volume (PTV) were 1.1 cc (0.02–11.5) and 1.9 cc (0.11–18.8) with an average distance to isocenter of 5.4 cm (2.2–8.9). The prescription was 20 Gy to each PTV. Plans were recalculated with induced clinically observable patient setup errors [±2 mm, ±2^o] in all six directions. Boolean structures were generated to calculate the effect of DCK via 20 Gy isodose volume (IDV) and ICK via 15 Gy IDV minus the 20 Gy IDV. Contributions of each IDV to the PTV coverage were analyzed along with normal brain toxicity due to the patient setup uncertainty. Induced uncertainty and minimum dose covering the entire PTV were analyzed to determine the maximum tolerable patient setup errors to utilize the ICK effect for radiosurgery of m‐bm via SIMT‐VMAT.

Results

Patient setup errors of 1.3 mm /1.3° in all six directions must be maintained to achieve PTV coverage of the 15 Gy IDV for ICK. Setup errors of ±2 mm/2° showed clinically unacceptable loss of PTV coverage of 29.4 ± 14.6% even accounting the ICK effect. However, no clinically significant effect on normal brain dosimetry was observed.

Conclusions

Radiosurgery of m‐bm using SIMT‐VMAT treatments have shown positive clinical outcomes even with small residual patient setup errors. These clinical outcomes, while largely due to DCK, may also potentially be due to the ICK. Potential mechanisms, such as devascularization and/or radiation‐induced intratumor immune enhancement, should be explored to provide a better understanding of the radiobiological response of stereotactic radiosurgery of m‐bm using a SIMT‐VMAT plan.

TNF-α May Exert Different Antitumor Effects in Response to Radioactive Iodine Therapy in Papillary Thyroid Cancer with/without Autoimmune Thyroiditis

Simple Summary

Recent evidence shows that autoimmune thyroiditis (AIT) may impair the uptake of radioiodine (¹³¹I), altering the success of attempted remnant ablation in papillary thyroid cancer (PTC), but the cause is not clear. Finding the mechanisms that govern immune cells during the ¹³¹I therapy of PTC with concomitant AIT (PTC + AIT) could provide a rationale for these reports. Our study was conducted on female patients admitted for ¹³¹I therapy. In the PTC group, ¹³¹I therapy modulates the production of cytokines in situ, increasing the antitumor immune response accordingly. On the contrary, in the presence of chronic inflammation due to AIT, ¹³¹I therapy amplifies innate immunity, leading to a weaker development of adaptive, specific immunity.

Abstract

Autoimmune thyroiditis (AIT) may impair radioiodine (¹³¹I) uptake in papillary thyroid cancer (PTC). Finding the mechanisms that govern immune cells during ¹³¹I therapy of PTC with concomitant AIT (PTC + AIT) could provide a rationale. Our study aimed to evaluate the effects of ¹³¹I on anti-thyroglobulin antibodies (TgAb), matrix metalloproteinase-9 (MMP-9) and its tissue inhibitor TIMP-1 and tumor necrosis factor-α (TNF-α) and its receptors TNFR1 and TNFR2, in PTC and PTC + AIT patients. Peripheral blood was collected from 56 female patients with PTC and 32 with PTC + AIT before and 4 days after ¹³¹I (3.7 GBq). The serum levels of TgAb, MMP-9, TIMP-1, TNF-α, TNFR1 and TNFR2 were measured by ELISA. The mean radioactivity of blood samples collected after ¹³¹I intake was higher in the PTC + AIT group than in PTC (p < 0.001). In the PTC + AIT group, TNF-α/TNFR1 and TNF-α/TNFR2 ratios decreased by 0.38-fold and 0.32-fold after ¹³¹I and were positively correlated with the MMP-9/TIMP-1 ratio (r = 0.48, p = 0.005, and r = 0.46, p = 0.007). In the PTC group, TNF-α/TNFR1 and TNF-α/TNFR2 ratios increased by 3.17-fold and 3.33-fold and were negatively correlated with the MMP-9/TIMP-1 ratio (r = −0.62, p < 0.001 and r = −0.58, p < 0.001). Our results demonstrate that TNF-α may exert different antitumor effects in response to ¹³¹I therapy depending on the patient’s immune profile.

Radiation dose and fraction in immunotherapy: one-size regimen does not fit all settings, so how does one choose?

Recent evidence indicates that ionizing radiation can enhance immune responses to tumors. Advances in radiation delivery techniques allow hypofractionated delivery of conformal radiotherapy. Hypofractionation or other modifications of standard fractionation may improve radiation’s ability to promote immune responses to tumors. Other novel delivery options may also affect immune responses, including T-cell activation and tumor-antigen presentation changes. However, there is limited understanding of the immunological impact of hypofractionated and unique multifractionated radiotherapy regimens, as these observations are relatively recent. Hence, these differences in radiotherapy fractionation result in distinct immune-modulatory effects. Radiation oncologists and immunologists convened a virtual consensus discussion to identify current deficiencies, challenges, pitfalls and critical gaps when combining radiotherapy with immunotherapy and making recommendations to the field and advise National Cancer Institute on new directions and initiatives that will help further development of these two fields.

This commentary aims to raise the awareness of this complexity so that the need to study radiation dose, fractionation, type and volume is understood and valued by the immuno-oncology research community. Divergence of approaches and findings between preclinical studies and clinical trials highlights the need for evaluating the design of future clinical studies with particular emphasis on radiation dose and fractionation, immune biomarkers and selecting appropriate end points for combination radiation/immune modulator trials, recognizing that direct effect on the tumor and potential abscopal effect may well be different. Similarly, preclinical studies should be designed as much as possible to model the intended clinical setting. This article describes a conceptual framework for testing different radiation therapy regimens as separate models of how radiation itself functions as an immunomodulatory ‘drug’ to provide alternatives to the widely adopted ‘one-size-fits-all’ strategy of frequently used 8 Gy×3 regimens immunomodulation.

Low dose ionizing radiation effects on the immune system

Ionizing radiation interacts with the immune system in many ways with a multiplicity that mirrors the complexity of the immune system itself: namely the need to maintain a delicate balance between different compartments, cells and soluble factors that work collectively to protect, maintain, and restore tissue function in the face of severe challenges including radiation damage. The cytotoxic effects of high dose radiation are less relevant after low dose exposure, where subtle quantitative and functional effects predominate that may go unnoticed until late after exposure or after a second challenge reveals or exacerbates the effects. For example, low doses may permanently alter immune fitness and therefore accelerate immune senescence and pave the way for a wide spectrum of possible pathophysiological events, including early-onset of age-related degenerative disorders and cancer. By contrast, the so called low dose radiation therapy displays beneficial, anti-inflammatory and pain relieving properties in chronic inflammatory and degenerative diseases. In this review, epidemiological, clinical and experimental data regarding the effects of low-dose radiation on the homeostasis and functional integrity of immune cells will be discussed, as will be the role of immune-mediated mechanisms in the systemic manifestation of localized exposures such as inflammatory reactions. The central conclusion is that ionizing radiation fundamentally and durably reshapes the immune system. Further, the importance of discovery of immunological pathways for modifying radiation resilience amongst other research directions in this field is implied.

Mechanistic Insights into Synergy between Melanin-Targeting Radioimmunotherapy and Immunotherapy in Experimental Melanoma

Melanoma incidence continues to rise, and while therapeutic approaches for early stage cases are effective, metastatic melanoma continues to be associated with high mortality. Immune checkpoint blockade (ICB) has demonstrated clinical success with approved drugs in cohorts of patients with metastatic melanoma and targeted radionuclide therapy strategies showed promise in several clinical trials against various cancers including metastatic melanoma. This led our group to investigate the combination of these two treatments which could be potentially offered to patients with metastatic melanoma not responsive to ICB alone. Previously, we have demonstrated that a combination of humanized anti-melanin antibody conjugated to 213Bismuth and anti-PD-1 ICB reduced tumor growth and increased survival in the Cloudman S91 murine melanoma DBA/2 mouse model. In the current study, we sought to improve the tumoricidal effect by using the long-lived radionuclides 177Lutetium and 225Actinium. Male Cloudman S91-bearing DBA/2 mice were treated intraperitoneally with PBS (Sham), unlabeled antibody to melanin, anti-PD-1 ICB, 177Lutetium or 225Actinium RIT, or a combination of ICB and RIT. Treatment with anti-PD-1 alone or low-dose 177Lutetium RIT alone resulted in modest tumor reduction, while their combination significantly reduced tumor growth and increased survival, suggesting synergy. 225Actinium RIT, alone or in combination with ICB, showed no therapeutic benefit, suggesting that the two radionuclides with different energetic properties work in distinct ways. We did not detect an increase in tumor-infiltrating T cells in the tumor microenvironment, which suggests the involvement of alternative mechanisms that improve the effect of combination therapy beyond that observed in the single therapies.

Modulation of Immuno-biome during Radio-sensitization of Tumors by Glycolytic Inhibitors

The Tumor Microenvironment (TME) comprising stromal cells, fibroblasts and various components of the immune system forms a pro-tumorigenic cocoon around the tumor cells with the reprogramming of the metabolism in the form of Warburg phenotype (enhanced aerobic glycolysis) in tumor as well as non-tumor cells. This reprogramming plays a significant role in suppressing the immune response leading to the survival and proliferation of tumor cells and resistance to therapies. Therefore, there is a considerable interest in developing strategies involving metabolic modifiers to improve the therapeutic efficacy that restores immune competence, besides enhancing the direct effects on tumor cells. Inhibitors of glycolysis like 2-deoxy-D-glucose (2-DG; a hexokinase inhibitor), dichloroacetate and small molecule inhibitors of lactate transport (MCT-1) are some of the metabolic modifiers investigated for their therapeutic as well as adjuvant potential. Among these, 2-DG has been widely investigated and established as an ideal adjuvant in the radio- and chemotherapy of tumors. Modulation of the immuno-biome in the form of cytokine shifts, differential transcriptional regulation, abrogation of immunosuppressive network and reduced accumulation of lactate are some of the contributing factors for immune stimulation linked to the radio- and chemosensitization by glycolytic inhibitors.

Functional response difference between diabetic/normal cancerous patients to inflammatory cytokines and oxidative stresses after radiotherapy

Diabetes, which is considered as a chronic metabolic disorder leads to an increase in inflammatory cytokines and oxidative stresses. Studies have shown several functional differences in the oxidative stress and inflammatory cytokines responses in diabetic/normal cancerous patients candidate for radiotherapy. Also, radiotherapy as a cancer treatment modality is known as a carcinogen due to oxidative damage via generation of reactive oxygen metabolites and also causing inflammation of the tissue by increasing the inflammatory cytokines. Therefore, the consequence of diabetes on oxidative stress and increased inflammatory factors and synergistic effects of radiotherapy on these factors cause complications in diabetics undergoing radiotherapy. It is considered as one of the most interesting objectives to control inflammation and oxidative stress in these patients. This review aims to concentrate on the influence of factors such as MPO, MDA, IL-1β, and TNF-α in diabetic patients by emphasizing the effects related to radiation-induced toxicity and inflammation by proposing therapeutic approaches which could be helpful in reduction of the complications.

Radiation Exposure-Induced Changes in the Immune Cells and Immune Factors of Mice With or Without Primary Lung Tumor

Recent studies have demonstrated that radiation activates in situ antitumor immunity and consequently induced a synergistic effect of radiotherapy and immunotherapy. However, studies related to radiation-induced changes in immune system of tumor-bearing mice are limited, which are of great significance to improve the efficacy of radioimmunotherapy. In this study, we first established a primary lung tumor mouse model using urethane. Then part of the right lung of the mouse was exposed to X-ray irradiation with a computed tomography-guided small animal irradiator and the changes of immune cells in both peripheral blood and spleen were determined by flow cytometry. Besides, the levels of both cytokines and immunoglobulins in mouse serum were detected by a protein chip. We found that B lymphocytes increased while CD8⁺ T lymphocytes reduced significantly. Interleukin-3 (IL-3), IL-6, regulated upon activation, normally T-expressed, and presumably secreted factor (RANTES), and vascular endothelial growth factor (VEGF) were found to be decreased after tumor formation, and the similar results have also been observed with kappa, IgG3, IgE, IgM, and IgG2a. After irradiation, lower concentrations of IgD, kappa, and IgM were found in the serum. Our findings indicate that localized tumor irradiation caused some obvious changes like inhibiting the ability of innate immunity, and these changes may be useful in predicting prognosis.

Radiation-Enhanced Expression of CCL22 in Nasopharyngeal Carcinoma is Associated With CCR4+ CD8 T Cell Recruitment

PURPOSE

Radiation therapy elicits profound alterations in gene expression in tumor cells. This study aims to determine the dynamic changes in the expression of immunity-associated genes in nasopharyngeal carcinoma (NPC) cells upon radiation therapy.

METHODS AND MATERIALS

The study was performed using NPC patient-derived tumor xenograft tumors, cell lines, CCR4⁺ CD8 T cells sorted from peripheral blood mononuclear cells of healthy volunteers, and TCGA-derived bulk RNA-seq or single-cell RNA-seq (scRNA-seq) data sets. Patient-derived tumor xenograft tumors or cell lines were irradiated and collected for bulk RNA sequencing or for CCL22 expression and release detection. Malignant phenotypes and radiosensitivity were assessed in cells with or without overexpression of CCL22 or recombinant CCL22 treatment in the presence or absence of irradiation. TCGA data sets were used for uncovering CCR4 status in subtypes of T cells. CCL22 in supernatants, cell lysates, or serum samples was measured with enzyme-linked immunosorbent assay.

RESULTS

CCL22 was significantly increased in the irradiated patient-derived tumor xenograft tumors, the supernatants and cell lysates collected from irradiated NPC cell lines, and the serum of patients who received radiation therapy. No alterations of malignant phenotypes were found in tumor cells with CCL22 overexpression or recombinant CCL22 treatment. Kaplan-Meier analysis revealed that CCL22 or its receptor CCR4 positively correlated with cytotoxic T lymphocyte signatures, and high expression of CCL22 or CCR4 was associated with better prognosis for patients with NPC. scRNA-seq data set-based analysis demonstrated that CCR4 was expressed in multiple subtypes of T cells, including effector CD8 T cells. Chemotaxis assay indicated that CCR4⁺ CD8 T cells could be recruited by CCL22 treatment.

CONCLUSION

The radiation-enhanced release of CCL22 from NPC cells promotes migration of CCR4 ⁺ effector CD8 T cells, which might partially be associated with radiation therapy-mediated antitumor immunity.

Adverse outcome pathways for ionizing radiation and breast cancer involve direct and indirect DNA damage, oxidative stress, inflammation, genomic instability, and interaction with hormonal regulation of the breast

Knowledge about established breast carcinogens can support improved and modernized toxicological testing methods by identifying key mechanistic events. Ionizing radiation (IR) increases the risk of breast cancer, especially for women and for exposure at younger ages, and evidence overall supports a linear dose-response relationship. We used the Adverse Outcome Pathway (AOP) framework to outline and evaluate the evidence linking ionizing radiation with breast cancer from molecular initiating events to the adverse outcome through intermediate key events, creating a qualitative AOP. We identified key events based on review articles, searched PubMed for recent literature on key events and IR, and identified additional papers using references. We manually curated publications and evaluated data quality. Ionizing radiation directly and indirectly causes DNA damage and increases production of reactive oxygen and nitrogen species (RONS). RONS lead to DNA damage and epigenetic changes leading to mutations and genomic instability (GI). Proliferation amplifies the effects of DNA damage and mutations leading to the AO of breast cancer. Separately, RONS and DNA damage also increase inflammation. Inflammation contributes to direct and indirect effects (effects in cells not directly reached by IR) via positive feedback to RONS and DNA damage, and separately increases proliferation and breast cancer through pro-carcinogenic effects on cells and tissue. For example, gene expression changes alter inflammatory mediators, resulting in improved survival and growth of cancer cells and a more hospitable tissue environment. All of these events overlap at multiple points with events characteristic of "background" induction of breast carcinogenesis, including hormone-responsive proliferation, oxidative activity, and DNA damage. These overlaps make the breast particularly susceptible to ionizing radiation and reinforce that these biological activities are important characteristics of carcinogens. Agents that increase these biological processes should be considered potential breast carcinogens, and predictive methods are needed to identify chemicals that increase these processes. Techniques are available to measure RONS, DNA damage and mutation, cell proliferation, and some inflammatory proteins or processes. Improved assays are needed to measure GI and chronic inflammation, as well as the interaction with hormonally driven development and proliferation. Several methods measure diverse epigenetic changes, but it is not clear which changes are relevant to breast cancer. In addition, most toxicological assays are not conducted in mammary tissue, and so it is a priority to evaluate if results from other tissues are generalizable to breast, or to conduct assays in breast tissue. Developing and applying these assays to identify exposures of concern will facilitate efforts to reduce subsequent breast cancer risk.

Adverse outcome pathways for ionizing radiation and breast cancer involve direct and indirect DNA damage, oxidative stress, inflammation, genomic instability, and interaction with hormonal regulation of the breast

Knowledge about established breast carcinogens can support improved and modernized toxicological testing methods by identifying key mechanistic events. Ionizing radiation (IR) increases the risk of breast cancer, especially for women and for exposure at younger ages, and evidence overall supports a linear dose-response relationship. We used the Adverse Outcome Pathway (AOP) framework to outline and evaluate the evidence linking ionizing radiation with breast cancer from molecular initiating events to the adverse outcome through intermediate key events, creating a qualitative AOP. We identified key events based on review articles, searched PubMed for recent literature on key events and IR, and identified additional papers using references. We manually curated publications and evaluated data quality. Ionizing radiation directly and indirectly causes DNA damage and increases production of reactive oxygen and nitrogen species (RONS). RONS lead to DNA damage and epigenetic changes leading to mutations and genomic instability (GI). Proliferation amplifies the effects of DNA damage and mutations leading to the AO of breast cancer. Separately, RONS and DNA damage also increase inflammation. Inflammation contributes to direct and indirect effects (effects in cells not directly reached by IR) via positive feedback to RONS and DNA damage, and separately increases proliferation and breast cancer through pro-carcinogenic effects on cells and tissue. For example, gene expression changes alter inflammatory mediators, resulting in improved survival and growth of cancer cells and a more hospitable tissue environment. All of these events overlap at multiple points with events characteristic of "background" induction of breast carcinogenesis, including hormone-responsive proliferation, oxidative activity, and DNA damage. These overlaps make the breast particularly susceptible to ionizing radiation and reinforce that these biological activities are important characteristics of carcinogens. Agents that increase these biological processes should be considered potential breast carcinogens, and predictive methods are needed to identify chemicals that increase these processes. Techniques are available to measure RONS, DNA damage and mutation, cell proliferation, and some inflammatory proteins or processes. Improved assays are needed to measure GI and chronic inflammation, as well as the interaction with hormonally driven development and proliferation. Several methods measure diverse epigenetic changes, but it is not clear which changes are relevant to breast cancer. In addition, most toxicological assays are not conducted in mammary tissue, and so it is a priority to evaluate if results from other tissues are generalizable to breast, or to conduct assays in breast tissue. Developing and applying these assays to identify exposures of concern will facilitate efforts to reduce subsequent breast cancer risk.

The resveratrol analogue, HS‑1793, enhances the effects of radiation therapy through the induction of anti‑tumor immunity in mammary tumor growth

Radiotherapy can induce the infiltration of immune suppressive cells which are involved in promoting tumor progression and recurrence. A number of natural products with immunomodulating abilities have been gaining attention as complementary cancer treatments. This attention is partly due to therapeutic strategies which have proven to be ineffective as a result of tumor-induced immunosuppressive cells found in the tumor microenvironment. The present study investigated whether HS-1793, a resveratrol analogue, can enhance the anti-tumor effects by inhibiting lymphocyte damage and immune suppression by regulatory T cells (Tregs) and tumor-associated macrophages (TAMs), during radiation therapy. FM3A cells were used to determine the role of HS-1793 in the radiation-induced tumor immunity of murine breast cancer. HS-1793 treatment with radiation significantly increased lymphocyte proliferation with concanavalin A (Con A) stimulation and reduced the DNA damage of lymphocytes in irradiated tumor-bearing mice. The administration of HS-1793 also decreased the number of Tregs, and reduced interleukin (IL)-10 and transforming growth factor (TGF)-β secretion in irradiated tumor-bearing mice. In addition, HS-1793 treatment inhibited CD206⁺ TAM infiltration in tumor tissue when compared to the controls or irradiation alone. Mechanistically, HS-1793 suppressed tumor growth via the activation of effector T cells in irradiated mice. On the whole, the findings of the present study reveal that HS-1793 treatment improves the outcome of radiation therapy by enhancing antitumor immunity. Indeed, HS-1793 appears to be a good therapeutic candidate for use in combination with radiotherapy in breast cancer.

Pure abscopal effect of radiotherapy in a salivary gland carcinoma: Case report, literature review, and a search for new approaches

We report the case of an 84-year-old woman with poorly differentiated non-small cell carcinoma of the right parotid who presented with headache, was found to have a primary right parotid gland cancer as well as metastatic disease, and underwent palliative radiotherapy to the primary site. The patient received no chemotherapy or immunotherapy, but both the primary site and several non-irradiated foci in the lungs regressed or completely resolved. The patient remained free of disease for about one year before progression. The case is a rare instance of abscopal regression of metastatic disease in the absence of pharmacologic immunomodulation. A literature review surveys the history of the abscopal effect of radiation therapy, attempts to understand the mechanisms of its successes and failures, and points to new approaches that can inform and improve the outcomes of radioimmunotherapy.

Impact of Sequencing Radiation Therapy and Immune Checkpoint Inhibitors in the Treatment of Melanoma Brain Metastases

PURPOSE

Melanoma brain metastases (MBM) occur in ∼50% of melanoma patients. Although both radiation therapy (RT) and immune checkpoint inhibitor (ICI) are used alone or in combination for MBM treatment, the role of this combination and how these treatments could best be sequenced remains unclear.

METHODS AND MATERIALS

We conducted a retrospective analysis of patients with resected MBM who underwent treatment with RT, ICI, or a combination of RT and ICI. Among the latter, we specifically investigated the differential gene expression via RNA-sequencing between patients who received RT first then ICI (RT → ICI) versus ICI first then RT (ICI → RT). We used a glycoprotein-transduced syngeneic melanoma mouse model for validation experiments.

RESULTS

We found that for patients with resected MBM, a combination of RT and ICI confers superior survival compared with RT alone. Specifically, we found that RT → ICI was superior compared with ICI → RT. Transcriptome analysis of resected MBM revealed that the RT → ICI cohort demonstrated deregulation of genes involved in apoptotic signaling and key modulators of inflammation that are most implicated in nuclear factor kappa-light-chain-enhancer of activated B cells signaling. In a preclinical model, we showed that RT followed by anti-programmed death-ligand 1 therapy was superior to the reverse sequence of therapy, supporting the observations we made in patients with MBM.

CONCLUSIONS

Our study provides initial insights into the optimal sequence of RT and ICI in the treatment of MBM after surgical resection. Prospective studies examining the best sequence of RT and ICI are necessary, and our study contributes to the rationale to pursue these.

Hadrontherapy Interactions in Molecular and Cellular Biology

The resistance of cancer cells to radiotherapy is a major issue in the curative treatment of cancer patients. This resistance can be intrinsic or acquired after irradiation and has various definitions, depending on the endpoint that is chosen in assessing the response to radiation. This phenomenon might be strengthened by the radiosensitivity of surrounding healthy tissues. Sensitive organs near the tumor that is to be treated can be affected by direct irradiation or experience nontargeted reactions, leading to early or late effects that disrupt the quality of life of patients. For several decades, new modalities of irradiation that involve accelerated particles have been available, such as proton therapy and carbon therapy, raising the possibility of specifically targeting the tumor volume. The goal of this review is to examine the up-to-date radiobiological and clinical aspects of hadrontherapy, a discipline that is maturing, with promising applications. We first describe the physical and biological advantages of particles and their application in cancer treatment. The contribution of the microenvironment and surrounding healthy tissues to tumor radioresistance is then discussed, in relation to imaging and accurate visualization of potentially resistant hypoxic areas using dedicated markers, to identify patients and tumors that could benefit from hadrontherapy over conventional irradiation. Finally, we consider combined treatment strategies to improve the particle therapy of radioresistant cancers.

Mono-institutional phase 2 study of innovative Stereotactic Body RadioTherapy targeting PArtial Tumor HYpoxic (SBRT-PATHY) clonogenic cells in unresectable bulky non-small cell lung cancer: profound non-targeted effects by sparing peri-tumoral immune microenvironment

BACKGROUND

Radiotherapy-induced lymphopenia may be limiting the success of therapy and could also negatively affect the ability of immune system in mediating the bystander (BE) and abscopal effects (AE). A novel SBRT-based PArtial Tumor irradiation of HYpoxic clonogenic cells (SBRT-PATHY) for induction of the tumoricidal BE and AE by sparing the peritumoral immune microenvironment and regional circulating lymphocytes has been developed to enhance the radiotherapy therapeutic ratio of advanced lung cancer. The aim of this retrospective review of prospectively collected mono-institutional phase 2 study was to compare the outcomes between unconventional SBRT-PATHY and standard of care in unresectable stage IIIB/IV bulky NSCLC.

MATERIALS AND METHODS

Sixty patients considered inoperable or unsuitable for radical radio-chemotherapy were enrolled and treated using the following 3 regimens: SBRT-PATHY (group I, n = 20 patients), recommended standard of care chemotherapy (group II, n = 20 patients), and institutional conventional palliative radiotherapy (group III, n = 20 patients).

RESULTS

Median follow-up was 13 months. The 1-year overall survival was 75, 60, and 20% in groups 1, 2 and 3, respectively (p = 0.099). The 1-year cancer specific survival was 90, 60, and 20% in groups 1, 2, and 3, respectively (p = 0.049). Bulky tumor control rate was 95% for SBRT-PATHY compared with 20% in the other two groups. BE and AE were seen by SBRT-PATHY in 95 and 45% of patients, respectively. Multi-variate analysis for cancer specific survival was significant for treatment effect with SBRT-PATHY (p < 0.001) independent of age, sex, performance status, histology, stage, treated bulky site and tumor diameter. SBRT-PATHY resulted in lower toxicity (p = 0.026), and improved symptom control (p = 0.018) when compared to other two treatment options.

CONCLUSION

SBRT-PATHY improved treatment outcomes in unresectable NSCLC and should be investigated in larger trials. Present study has been retrospectively registered on 8th of August 2019 by the ethic committee for Austrian region "Kärnten "in Klagenfurt (AUT), under study number A 31/19.

Radiation-Induced Skin Fibrosis: Pathogenesis, Current Treatment Options, and Emerging Therapeutics

Radiotherapy (RT) has become an indispensable part of oncologic treatment protocols for a range of malignancies. However, a serious adverse effect of RT is radiodermatitis; almost 95% of patients develop moderate to severe skin reactions following radiation treatment. In the acute setting, these can be erythema, desquamation, ulceration, and pain. Chronically, soft tissue atrophy, alopecia, and stiffness can be noted. Radiodermatitis can delay oncologic treatment protocols and significantly impair quality of life. There is currently a paucity of effective treatment options and prevention strategies for radiodermatitis. Importantly, recent preclinical and clinical studies have suggested that fat grafting may be of therapeutic benefit, reversing detrimental changes to soft tissue following RT. This review outlines the damaging effects of RT on the skin and soft tissue as well as discusses available treatment options for radiodermatitis. Emerging strategies to mitigate detrimental, chronic radiation-induced changes are also presented.

Association Between Circulating Lymphocyte Populations and Outcome After Stereotactic Body Radiation Therapy in Patients With Hepatocellular Carcinoma

Background and Objective: Radiation-induced lymphopenia has a tangible impact on overall survival (OS) in multiple solid tumors. We investigated the association between circulating lymphocyte populations (CLPs) before and after stereotactic body radiation therapy (SBRT) and OS in patients with hepatocellular carcinoma (HCC).

Materials and Methods: Seventy-eight HCC patients treated with SBRT between January 2013 and June 2017 were retrospectively analyzed. Baseline and post-treatment total peripheral lymphocyte counts (TPLCs) and values of different CLPs were obtained and analyzed for clinical outcomes. Univariate and multivariate Cox regression analyses were used to explore the independent prognostic factors for patient survival.

Results: The one-, two- and three-year OS rates were 94.8, 75.9, and 63.3%, respectively. The mean TPLCs before and 10 days after SBRT were 1.4 × 10⁹/L and 0.7 × 10⁹/L, respectively. The TPLC recovered to its baseline value 1 year after SBRT. Multivariate analysis results revealed that variables, including tumor necrosis factor-alpha (TNF-α) level <5.5 ng/mL and post-treatment TPLC <0.45 × 10⁹/L were independent factors for inferior OS. Further analysis showed that the values of CLPs, including CD3⁺, CD4⁺, CD8⁺, CD19⁺, and CD16⁺56⁺ cells dropped profoundly 10 days after SBRT, among which CD19⁺ B cell count was mostly depleted and gradually recovered after 2 months. Univariate analysis showed that both baseline and post-treatment TPLC and CLP (except post-treatment B cell) counts were significantly associated with patient OS (p < 0.05 for each). Further stratified analysis performed according to OS at 2 years demonstrated that the CD16⁺CD56⁺ NK cell counts remained significantly elevated in patients with better survival (OS > 2 years) compared to those in short-term survivors at 10 days, 1 month, and 2 months after SBRT (p < 0.05 for each). In addition, there were significant differences in TPLC and CD8⁺ T cell counts in patients with long-term and short-term OS at 2 months after SBRT (p < 0.05).

Conclusions: Peripheral lymphopenia after SBRT might be an independent prognostic factor for poorer outcome in HCC patients. Post-treatment lymphocyte subsets, including CD8⁺ T cell and NK cell counts were also associated with 2-year OS rates.

Radiotherapy-Induced Changes in the Systemic Immune and Inflammation Parameters of Head and Neck Cancer Patients

Though radiotherapy is a local therapy, it has systemic effects mainly influencing immune and inflammation processes. This has important consequences in the long-term prognosis and therapy individualization. Our objective was to investigate immune and inflammation-related changes in the peripheral blood of head and neck cancer patients treated with radiotherapy. Peripheral blood cells, plasma and blood cell-derived RNA were isolated from 23 patients before and at two time points after radiotherapy and cellular immune parameters, plasma protein changes and gene expression alterations were studied. Increased regulatory T cells and increased CTLA4 and PD-1 expression on CD4 cells indicated an immune suppression induced by the malignant condition, which was accentuated by radiotherapy. Circulating dendritic cells were strongly elevated before treatment and were not affected by radiotherapy. Decreased endoglin levels in the plasma of patients before treatment were further decreased by radiotherapy. Expression of the FXDR, SESN1, GADD45, DDB2 and MDM2 radiation-response genes were altered in the peripheral blood cells of patients after radiotherapy. All changes were long-lasting, detectable one month after radiotherapy. In conclusion we demonstrated radiotherapy-induced changes in systemic immune parameters of head and neck cancer patients and proposed markers suitable for patient stratification worth investigating in larger patient cohorts.

Radiation-Induced CXCL12 Upregulation via Histone Modification at the Promoter in the Tumor Microenvironment of Hepatocellular Carcinoma

Tumor cells can vary epigenetically during ionizing irradiation (IR) treatment. These epigenetic variegations can influence IR response and shape tumor aggressiveness. However, epigenetic disturbance of histones after IR, implicating in IR responsiveness, has been elusive. Here, we investigate whether altered histone modification after IR can influence radiation responsiveness. The oncogenic CXCL12 mRNA and protein were more highly expressed in residual cancer cells from a hepatoma heterotopic murine tumor microenvironment and coculture of human hepatoma Huh7 and normal IMR90 cells after radiation. H3K4 methylation was also enriched and H3K9 methylation was decreased at its promoter region. Accordingly, invasiveness and the subpopulation of aggressive CD133+/CD24- cells increased after IR. Histone demethylase inhibitor IOX1 attenuated CXCL12 expression and the malignant subpopulation, suggesting that responses to IR can be partially mediated via histone modifications. Taken together, radiation-induced histone alterations at the CXCL12 promoter in hepatoma cells are linked to CXCL12 upregulation and increased aggressiveness in the tumor microenvironment.

Gamma knife radiosurgery compared to whole brain radiation therapy enhances immunity via immunoregulatory molecules in patients with metastatic brain tumours

Background: There is lack of data on the effect of stereotactic radiosurgery in modulation of the immune system for cancer patients with metastatic brain tumours. Therefore, we investigated the change in levels of immunoregulatory molecules after Gamma Knife radiosurgery (GKR) and whole brain radiation therapy (WBRT) in patients with brain metastases.Methods: Peripheral blood samples were collected from 15 patients who received GKR, nine patients who received WBRT for brain metastases and 10 healthy controls. Samples were obtained at three time points such as before, 1h after and 1 week after the index procedure for patients treated with GKR or WBRT. All patients' demographic data and radiosurgical parameters were retrospectively reviewed. We analyzed the change in the levels of T-lymphocyte-associated antigen 4 (CTLA-4) and programmed cell death ligand-1 (PD-L1), and cytokines such as IL-2, IL-10, IFN-γ, TNF-α after GKR and WBRT using Enzyme-linked immunosorbent assays (ELISA).Results: Baseline level of IFN-γ was found to be lower and that of PD-L1 was higher in the GKR group compared to WBRT group and healthy controls (p < 0.05 and p < 0.01, respectively). Levels of IFN-γ and IL-2 were increased (p < 0.01 and p < 0.01, respectively), while CTLA-4 and PD-L1 were decreased (p = 0.05 and p = 0.01, respectively) after GKR compared to pre-GKR levels, while there was no change after WBRT.Conclusion: GKR regulates immunoregulatory molecules towards enhancing the immune system, while WBRT did not exert any effect. These findings suggested that treatment of metastatic brain lesion with GKR might stimulate a systemic immune response against the tumour.

Targeting the Immunomodulatory CD73/Adenosine System to Improve the Therapeutic Gain of Radiotherapy

Extracellular adenosine is a potent endogenous immunosuppressive mediator critical to the maintenance of homeostasis in various normal tissues including the lung. Adenosine is either released from stressed or injured cells or generated from extracellular adenine nucleotides by the concerted action of the ectoenzymes ectoapyrase (CD39) and 5′ ectonucleotidase (CD73) that catabolize ATP to adenosine. An acute CD73-dependent increase of adenosine in normal tissues mostly exerts tissue protective functions whereas chronically increased adenosine-levels in tissues exposed to DNA damaging chemotherapy or radiotherapy promote pathologic remodeling processes and fibrosis for example in the skin and the lung. Importantly, cancer cells also express CD73 and high CD73 expression in the tumor tissue has been linked to poor overall survival and recurrence free survival in patients suffering from breast and ovarian cancer. CD73 and adenosine support growth-promoting neovascularization, metastasis, and survival in cancer cells. In addition, adenosine can promote tumor intrinsic or therapy-induced immune escape by various mechanisms that dampen the immune system. Consequently, modulating CD73 or cancer-derived adenosine in the tumor microenvironment emerges as an attractive novel therapeutic strategy to limit tumor progression, improve antitumor immune responses, avoid therapy-induced immune deviation, and potentially limit normal tissue toxicity. However, the role of CD73/adenosine signaling in the tumor and normal tissue responses to radiotherapy and its use as therapeutic target to improve the outcome of radiotherapy approaches is less understood. The present review will highlight the dual role of CD73 and adenosine in tumor and tissue responses to radiotherapy with a special focus to the lung. It will also discuss the potential benefits and risks of pharmacologic modulation of the CD73/adenosine system to increase the therapeutic gain of radiotherapy or combined radioimmunotherapy in cancer treatment.

Biological Principles of Stereotactic Body Radiation Therapy (SBRT) and Stereotactic Radiation Surgery (SRS): Indirect Cell Death

PURPOSE

To review the radiobiological mechanisms of stereotactic body radiation therapy stereotactic body radiation therapy (SBRT) and stereotactic radiation surgery (SRS).

METHODS AND MATERIALS

We reviewed previous reports and recent observations on the effects of high-dose irradiation on tumor cell survival, tumor vasculature, and antitumor immunity. We then assessed the potential implications of these biological changes associated with SBRT and SRS.

RESULTS

Irradiation with doses higher than approximately 10 Gy/fraction causes significant vascular injury in tumors, leading to secondary tumor cell death. Irradiation of tumors with high doses has also been reported to increase the antitumor immunity, and various approaches are being investigated to further elevate antitumor immunity. The mechanism of normal tissue damage by high-dose irradiation needs to be further investigated.

CONCLUSIONS

In addition to directly killing tumor cells, high-dose irradiation used in SBRT and SRS induces indirect tumor cell death via vascular damage and antitumor immunity. Further studies are warranted to better understand the biological mechanisms underlying the high efficacy of clinical SBRT and SRS and to further improve the efficacy of SBRT and SRS.

Combining Radiotherapy and Immunotherapy in Lung Cancer: Can We Expect Limitations Due to Altered Normal Tissue Toxicity?

In recent decades, technical advances in surgery and radiotherapy, as well as breakthroughs in the knowledge on cancer biology, have helped to substantially improve the standard of cancer care with respect to overall response rates, progression-free survival, and the quality of life of cancer patients. In this context, immunotherapy is thought to have revolutionized the standard of care for cancer patients in the long term. For example, immunotherapy approaches such as immune checkpoint blockade are currently increasingly being used in cancer treatment, either alone or in combination with chemotherapy or radiotherapy, and there is hope from the first clinical trials that the appropriate integration of immunotherapy into standard care will raise the success rates of cancer therapy to a new level. Nevertheless, successful cancer therapy remains a major challenge, particularly in tumors with either pronounced resistance to chemotherapy and radiation treatment, a high risk of normal tissue complications, or both, as in lung cancer. Chemotherapy, radiotherapy and immunotherapy have the capacity to evoke adverse effects in normal tissues when administered alone. However, therapy concepts are usually highly complex, and it is still not clear if combining immunotherapy with radio(chemo)therapy will increase the risk of normal tissue complications, in particular since normal tissue toxicity induced by chemotherapy and radiotherapy can involve immunologic processes. Unfortunately, no reliable biomarkers are available so far that are suited to predict the unique normal tissue sensitivity of a given patient to a given treatment. Consequently, clinical trials combining radiotherapy and immunotherapy are attracting major attention, not only regarding efficacy, but also with regard to safety. In the present review, we summarize the current knowledge of radiation-induced and immunotherapy-induced effects in tumor and normal tissue of the lung, and discuss the potential limitations of combined radio-immunotherapy in lung cancer with a focus on the suspected risk for enhanced acute and chronic normal tissue toxicity.

In Vivo Irradiation of Mice Induces Activation of Dendritic Cells

It is becoming clear that ionizing radiation positively influences certain immune parameters, which opens the possibility for combining radio- and immunotherapies in cancer treatment. The presence of functionally competent dendritic cells (DCs) is crucial in mounting a successful antitumor immune response. While it has been shown that DCs are relatively radioresistant, few and contradictory data are available on how ionizing radiation alters the functional integrity of these cells. Therefore, our objective was to investigate the effect of whole-body irradiation on the function of splenic DCs. C57Bl/6 mice were irradiated with 0.1, 0.25, and 2 Gy X-rays and changes in the phenotype of splenic DCs were compared to unirradiated controls. An increase was seen in DC surface markers influencing DC-T cell interactions. In vivo cytokine production was determined by direct intracellular cytokine staining. Irradiation with 2 Gy induced a 1.6-fold increase in IL-1α production, while the combination of irradiation and lipopolysaccharide (LPS) treatment induced a 3.9-fold increase, indicating a strong synergism between irradiation and LPS stimulation. Interaction of DCs with effector and regulatory T cells was investigated in a mixed lymphocyte reaction. While DCs from control animals induced stronger proliferation of regulatory T cells, DCs from animals irradiated with 2 Gy induced stronger proliferation of effector T cells. Antigen uptake and presentation was investigated by measuring the capacity of DCs to internalize and present ovalbumine (OVA)-derived peptides on their major histocompatibility complex (MHCI) molecules. Irradiation with 2 Gy did not influence antigen uptake or presentation, while low doses stimulated antigen uptake and reduced the level of antigen presentation. In conclusion, high-dose in vivo irradiation induced increased expression of T cell costimulatory markers, enhanced production of proinflammatory cytokines and a stronger stimulation of effector T cell proliferation than that of regulatory T cells. However, it did not influence DC antigen uptake or presentation. On the other hand, low-dose irradiation increased antigen uptake and lowered antigen presentation of DCs, indicating that low- and high-dose irradiation act on different pathways in DCs.

Long-term survival of locally advanced stage III non-small cell lung cancer patients treated with chemoradiotherapy and perspectives for the treatment with immunotherapy

Background Standard treatment for patients with inoperable locally advanced non-small cell lung cancer (NSCLC) is concurrent chemoradiotherapy (CCRT). Five-year overall survival rates range between 15 and 25%, while long term survival data are rarely reported. Patients and methods A total of 102 patients with stage III NSCLC treated between September 2005 and November 2010 with induction chemotherapy and CCRT were included in this long term survival analysis. All patients were tested for PD-L1 status and expression of PD-L1 was correlated with overall survival (OS), progression free survival (PFS) and toxicities. Results The median OS of all patients was 24.8 months (95% CI 18.7 to 31.0) with 10 year-survival rate of 11.2%. The median OS of patients with PD-L1 expression was 12.1 months (95% CI 0.1 to 26.2), while in patients with negative or unknown PD-L1 status was significantly longer, 25.2 months (95% CI 18.9 to 31.6), p = 0.005. The median PFS of all patients was 16.4 months (95% CI 13.0 to 19.9). PFS of patients with PD-L1 expression was 10.1 months (95% CI 0.1 to 20.4) and in patients with negative or unknown PD-L1 status was 17.9 months (95% CI 14.2 to 21.7), p = 0.003. Conclusions 10-year overall survival of stage III NSCLC patients after CCRT is 11.2%. PFS and OS differ with regard to PD-L1 status and are significantly shorter for patients with PD-L1 expression. New treatment with check-point inhibitors combined with RT therefore seems reasonable strategy to improve these results.

The role of macrophage phenotype in regulating the response to radiation therapy

Increasing experimental and clinical evidence has revealed a critical role for myeloid cells in the development and progression of cancer. The ability of monocytes and macrophages to regulate inflammation allows them to manipulate the tumor microenvironment to support the growth and development of malignant cells. Recent studies have shown that macrophages can exist in several functional states depending on the microenvironment they encounter in the tissue. These functional phenotypes influence not only the genesis and propagation of tumors, but also the efficacy of cancer therapies, particularly radiation. Early classification of the macrophage phenotypes, or "polarization states," identified 2 major states, M1 and M2, that have cytotoxic and wound repair capacity, respectively. In the context of tumors, classically activated or M1 macrophages driven by interferon-gamma support antitumor immunity while alternatively activated or M2 macrophages generated in part from interleukin-4 exposure hinder antitumor immunity by suppressing cytotoxic responses against a tumor. In this review, we discuss the role that the functional phenotype of a macrophage population plays in tumor development. We will then focus specifically on how macrophages and myeloid cells regulate the tumor response to radiation therapy.

Improving the clinical impact of biomaterials in cancer immunotherapy

Immunotherapies for cancer have progressed enormously over the past few decades, and hold great promise for the future. The successes of these therapies, with some patients showing durable and complete remission, demonstrate the power of harnessing the immune system to eradicate tumors. However, the effectiveness of current immunotherapies is limited by hurdles ranging from immunosuppressive strategies employed by tumors, to inadequate specificity of existing therapies, to heterogeneity of disease. Further, the vast majority of approved immunotherapies employ systemic delivery of immunomodulators or cells that make addressing some of these challenges more difficult. Natural and synthetic biomaterials–such as biocompatible polymers, self-assembled lipid particles, and implantable biodegradable devices–offer unique potential to address these hurdles by harnessing the benefits of therapeutic targeting, tissue engineering, co-delivery, controlled release, and sensing. However, despite the enormous investment in new materials and nanotechnology, translation of these ideas to the clinic is still an uncommon outcome. Here we review the major challenges facing immunotherapies and discuss how the newest biomaterials and nanotechnologies could help overcome these challenges to create new clinical options for patients.

Neurocognitive sparing of desktop microbeam irradiation

BACKGROUND

Normal tissue toxicity is the dose-limiting side effect of radiotherapy. Spatial fractionation irradiation techniques, like microbeam radiotherapy (MRT), have shown promising results in sparing the normal brain tissue. Most MRT studies have been conducted at synchrotron facilities. With the aim to make this promising treatment more available, we have built the first desktop image-guided MRT device based on carbon nanotube x-ray technology. In the current study, our purpose was to evaluate the effects of MRT on the rodent normal brain tissue using our device and compare it with the effect of the integrated equivalent homogenous dose.

METHODS

Twenty-four, 8-week-old male C57BL/6 J mice were randomly assigned to three groups: MRT, broad-beam (BB) and sham. The hippocampal region was irradiated with two parallel microbeams in the MRT group (beam width = 300 μm, center-to-center = 900 μm, 160 kVp). The BB group received the equivalent integral dose in the same area of their brain. Rotarod, marble burying and open-field activity tests were done pre- and every month post-irradiation up until 8 months to evaluate the cognitive changes and potential irradiation side effects on normal brain tissue. The open-field activity test was substituted by Barnes maze test at 8th month. A multilevel model, random coefficients approach was used to evaluate the longitudinal and temporal differences among treatment groups.

RESULTS

We found significant differences between BB group as compared to the microbeam-treated and sham mice in the number of buried marble and duration of the locomotion around the open-field arena than shams. Barnes maze revealed that BB mice had a lower capacity for spatial learning than MRT and shams. Mice in the BB group tend to gain weight at the slower pace than shams. No meaningful differences were found between MRT and sham up until 8-month follow-up using our measurements.

CONCLUSIONS

Applying MRT with our newly developed prototype compact CNT-based image-guided MRT system utilizing the current irradiation protocol can better preserve the integrity of normal brain tissue. Consequently, it enables applying higher irradiation dose that promises better tumor control. Further studies are required to evaluate the full extent effects of this novel modality.

Neoadjuvant chemoradiotherapy of pancreatic cancer induces a favorable immunogenic tumor microenvironment associated with increased major histocompatibility complex class I-related chain A/B expression

BACKGROUND

Damage-associated molecular patterns (DAMPs) are related to immune responses in malignant tumors including tumor-infiltrating lymphocytes (TILs). The aim of the present study was to determine the relationship between expression of components of DAMPs and TILs in pancreatic cancer patients who underwent neoadjuvant chemoradiotherapy (NACRT) versus those who did not.

METHODS

NACRT was administered to 51 patients with borderline-resectable pancreatic cancer and not to 33 patients with resectable pancreatic cancer. Resected specimens were analyzed for the presence of DAMPs, major histocompatibility complex class I-related chain A/B (MICA/B), and CD8⁺ TILs, CD4⁺ TILs, and forkhead box P3 positive (Foxp3⁺ ) TILs. The Treg/TIL ratio was obtained by dividing the number of Foxp3⁺ TILs, a surrogate for regulatory T cells, by the sum of CD8⁺ and CD4⁺ TILs.

RESULTS

Overexpression of calreticulin, Hsp70, and MICA/B were all significantly correlated with NACRT administration. In the NACRT group, high MICA/B expression was associated with a low Treg/TIL ratio, indicating a favorable immunogenic tumor microenvironment. Patients with a lower Treg/TIL ratio had longer survival.

CONCLUSIONS

Overexpression of MICA/B, a component of DAMPs induced by NACRT, may play an important role in acquiring a favorable immune response for pancreatic cancer which contributes to longer survival, suggesting the potential of immunotherapy of this recalcitrant disease, especially for patients with overexpression of DAMPs.