Radiation Therapy and the In Situ Vaccination Approach

Prodrugs of paclitaxel improve in situ photo-vaccination

Photodynamic therapy (PDT) effectively kills cancer cells and initiates immune responses that promote anticancer effects locally and systemically. Primarily developed for local and regional cancers, the potential of PDT for systemic antitumor effects [in situ photo-vaccination (ISPV)] remains underexplored. This study investigates: (1) the comparative effectiveness of paclitaxel (PTX) prodrug [Pc-(L-PTX)2] for PDT and site-specific PTX effects versus its pseudo-prodrug [Pc-(NCL-PTX)2] for PDT combined with checkpoint inhibitors; (2) mechanisms driving systemic antitumor effects; and (3) the prophylactic impact on preventing cancer recurrence. A bilateral tumor model was established in BALB/c mice through subcutaneous injection of CT26 cells. Mice received the PTX prodrug (0.5 μmole kg-1, i.v.), and tumors were treated with a 690-nm laser (75 mW cm-2 for 30 min, drug-light interval 0.5 h, light does 135 J cm-1), followed by anti-CTLA-4 (100 μg dose-1, i.p.) on days 1, 4, and 7. Notable enhancement in both local and systemic antitumor effectiveness was observed with [Pc-(L-PTX)2] compared to [Pc-(NCL-PTX)2] with checkpoint inhibitor. Immune cell depletion and immunohistochemistry confirmed neutrophils and CD8+ T cells are effectors for systemic antitumor effects. Treatment-induced immune memory resisted newly rechallenged CT26, showcasing prophylactic benefits. ISPV with a PTX prodrug and anti-CTLA-4 is a promising approach for treating metastatic cancers and preventing recurrence.

Immunological signatures from irradiated cancer-associated fibroblasts

Introduction

Cancer-associated fibroblasts (CAFs) are abundant and influential elements of the tumor microenvironment (TME), giving support to tumor development in multiple ways. Among other mechanisms, CAFs are important regulators of immunological processes occurring in tumors. However, CAF-mediated tumor immunomodulation in the context of radiotherapy remains poorly understood. In this study, we explore effects of radiation on CAF-derived immunoregulatory signals to the TME.

Methods

Primary CAF cultures were established from freshly collected human NSCLC lung tumors. CAFs were exposed to single-high or fractionated radiation regimens (1x18Gy or 3x6Gy), and the expression of different immunoregulatory cell-associated and secreted signaling molecules was analyzed 48h and 6 days after initiation of treatment. Analyses included quantitative measurements of released damage-associated molecular patterns (DAMPs), interferon (IFN) type I responses, expression of immune regulatory receptors, and secretion of soluble cytokines, chemokines, and growth factors. CAFs are able to survive ablative radiation regimens, however they enter into a stage of premature cell senescence.

Results

Our data show that CAFs avoid apoptosis and do not contribute by release of DAMPs or IFN-I secretion to radiation-mediated tumor immunoregulation. Furthermore, the secretion of relevant immunoregulatory cytokines and growth factors including TGF-β, IL-6, IL-10, TNFα, IL-1β, VEGF, CXCL12, and CXCL10 remain comparable between non-irradiated and radiation-induced senescent CAFs. Importantly, radiation exposure modifies the cell surface expression of some key immunoregulatory receptors, including upregulation of CD73 and CD276.

Discussion

Our data suggest that CAFs do not participate in the release of danger signals or IFN-I secretion following radiotherapy. The immune phenotype of CAFs and radiation-induced senescent CAFs is similar, however, the observed elevation of some cell surface immunological receptors on irradiated CAFs could contribute to the establishment of an enhanced immunosuppressive TME after radiotherapy.

Near-infrared photoimmunotherapy as a complementary modality to in situ vaccine in a preclinical pancreatic cancer model

Pancreatic cancer is one of the most refractory malignancies. In situ vaccines (ISV), in which intratumorally injected immunostimulatory adjuvants activate innate immunity at the tumor site, utilize tumor-derived patient-specific antigens, thereby allowing for the development of vaccines in patients themselves. Near-infrared photoimmunotherapy (NIR-PIT) is a novel therapy that selectively kills cancer cells exclusively in the NIR-irradiated region. Extending our previous research showing that ISV using the unique nanoparticulate Toll-like receptor 9 (TLR9) ligand K3-SPG induced effective antitumor immunity, here we incorporated NIR-PIT into K3-SPG-ISV so that local tumor destruction by NIR-PIT augments the antitumor effect of ISV. In the mouse model of pancreatic cancer, the combination of K3-SPG-ISV and CD44-targeting NIR-PIT showed synergistic systemic antitumor effects and enhanced anti-programmed cell death-1 (PD-1) blockade. Mechanistically, strong intratumoral upregulation of interferon-related genes and dependency on CD8+ T cells were observed, suggesting the possible role of interferon and cytotoxic T cell responses in the induction of antitumor immunity. Importantly, this combination induced immunological memory in therapeutic and neoadjuvant settings. This study represents the first attempt to integrate NIR-PIT with ISV, offering a promising new direction for cancer immunotherapy, particularly for pancreatic cancer.

Advances in breast cancer treatment: a systematic review of preoperative stereotactic body radiotherapy (SBRT) for breast cancer

Breast conserving treatment typically involves surgical excision of tumor and adjuvant radiotherapy targeting the breast area or tumor bed. Accurately defining the tumor bed is challenging and lead to irradiation of greater volume of healthy tissues. Preoperative stereotactic body radiotherapy (SBRT) which target tumor may solves that issues. We conducted a systematic literature review to evaluates the early toxicity and cosmetic outcomes of this promising treatment approach. Secondary we reviewed pathological complete response (pCR) rates, late toxicity, patient selection criteria and radiotherapy protocols. We retrieved literature from PubMed, Scopus, Web of Science, Cochrane, ScienceDirect, and ClinicalTrials.gov. The study adhered to the PRISMA 2020 guidelines. Ten prospective clinical trials (7 phase II, 3 phase I), encompassing 188 patients (aged 18-75 years, cT1-T3 cN0-N3 cM0, primarily with ER/PgR-positive, HER2-negative status,), were analyzed. Median follow-up was 15 months (range 3-30). Treatment involved single-fraction SBRT (15-21Gy) in five studies and fractionated (19.5-31.5Gy in 3 fractions) in the rest. Time interval from SBRT to surgery was 9.5 weeks (range 1-28). Acute and late G2 toxicity occurred in 0-17% and 0-19% of patients, respectively, G3 toxicity was rarely observed. The cosmetic outcome was excellent in 85-100%, fair in 0-10% and poor in only 1 patient. pCR varied, showing higher rates (up to 42%) with longer intervals between SBRT and surgery and when combined with neoadjuvant systemic therapy (up to 90%). Preoperative SBRT significantly reduce overall treatment time, enabling to minimalize volumes. Early results indicate excellent cosmetic effects and low toxicity.

An investigator-initiated clinical study in patients with refractory or recurrent solid tumors: 'R-ISV-FOLactis' trial

Aim: In situ vaccination, a kind of therapeutic cancer vaccine, can be realized by radiotherapy and intratumoral immune injection. This study combines intratumoral injection, radiotherapy and PD-1 blockade for synergistic antitumor effect.Materials & methods: Patients with advanced solid tumors who are unresponsive or intolerant to standard treatment will be treated with hypofractionated radiotherapy, intratumoral injection of FOLactis, PD-1 blockade. The primary end point is to observe the efficacy and safety, with the secondary end point to evaluate abscopal effects and the correlation between the immunological rationale and efficacy.Discussion: The combined regimen will be utilized to trigger antitumor immunity and is expected to be feasible and effective and provide a novel option for the comprehensive treatment of cancer.Clinical Trial Registration: ChiCTR2200060660 (ChiCTR.gov.cn).

Radioactive Hydroxyapatite Microspheres Empower Sustainable In Situ Tumor Vaccination

Tumor in situ vaccination (ISV) strategies have emerged in clinical trials as promising approaches, involving the release of tumor antigens through local radiotherapy and intratumorally adjuvant injections. However, the current fabrication strategy for achieving a sustainable immune response to ISV remains a pressing challenge. In this study, we present an empowered sustainable ISV method for antitumor therapy using 177Lu-labeled manganese-doped mesoporous hydroxyapatite (177Lu/Mn-HAP) microspheres. The ISV enables the sustained utilization of tumor antigens, leading to the activation of dendritic cells and polarization of macrophages toward the M1 subtype. Consequently, it facilitates the generation of potent CD8+ T-cell responses, enhancing the antitumor effects of internal radiation in both primary and distant tumors. Importantly, this approach achieves complete remission in all tumor-bearing mice and stimulates immune memory to prevent tumor recurrence. Our study highlights a universal and safe ISV strategy capable of inducing potent tumor-specific and sustainable immune response.

Bridging clinical radiotherapy and space radiation therapeutics through reactive oxygen species (ROS)-triggered delivery

This review explores the convergence of clinical radiotherapy and space radiation therapeutics, focusing on ionizing radiation (IR)-generated reactive oxygen species (ROS). IR, with high-energy particles, induces precise cellular damage, particularly in cancer treatments. The paper discusses parallels between clinical and space IR, highlighting unique characteristics of high-charge and energy particles in space and potential health risks for astronauts. Emphasizing the parallel occurrence of ROS generation in both clinical and space contexts, the review identifies ROS as a crucial factor with dual roles in cellular responses and potential disease initiation. The analysis covers ROS generation mechanisms, variations, and similarities in terrestrial and extraterrestrial environments leading to innovative ROS-responsive delivery systems adaptable for both clinical and space applications. The paper concludes by discussing applications of personalized ROS-triggered therapeutic approaches and discussing the challenges and prospects of implementing these strategies in clinical radiotherapy and extraterrestrial missions. Overall, it underscores the potential of ROS-targeted delivery for advancing therapeutic strategies in terrestrial clinical settings and space exploration, contributing to human health improvement on Earth and beyond.

Antitumor efficacy and potential mechanism of FAP-targeted radioligand therapy combined with immune checkpoint blockade

Radiotherapy combined with immune checkpoint blockade holds great promise for synergistic antitumor efficacy. Targeted radionuclide therapy delivers radiation directly to tumor sites. LNC1004 is a fibroblast activation protein (FAP)-targeting radiopharmaceutical, conjugated with the albumin binder Evans Blue, which has demonstrated enhanced tumor uptake and retention in previous preclinical and clinical studies. Herein, we demonstrate that 68Ga/177Lu-labeled LNC1004 exhibits increased uptake and prolonged retention in MC38/NIH3T3-FAP and CT26/NIH3T3-FAP tumor xenografts. Radionuclide therapy with 177Lu-LNC1004 induced a transient upregulation of PD-L1 expression in tumor cells. The combination of 177Lu-LNC1004 and anti-PD-L1 immunotherapy led to complete eradication of all tumors in MC38/NIH3T3-FAP tumor-bearing mice, with mice showing 100% tumor rejection upon rechallenge. Immunohistochemistry, single-cell RNA sequencing (scRNA-seq), and TCR sequencing revealed that combination therapy reprogrammed the tumor microenvironment in mice to foster antitumor immunity by suppressing malignant progression and increasing cell-to-cell communication, CD8+ T-cell activation and expansion, M1 macrophage counts, antitumor activity of neutrophils, and T-cell receptor diversity. A preliminary clinical study demonstrated that 177Lu-LNC1004 was well-tolerated and effective in patients with refractory cancers. Further, scRNA-seq of peripheral blood mononuclear cells underscored the importance of addressing immune evasion through immune checkpoint blockade treatment. This was emphasized by the observed increase in antigen processing and presentation juxtaposed with T cell inactivation. In conclusion, our data supported the efficacy of immunotherapy combined with 177Lu-LNC1004 for cancer patients with FAP-positive tumors.

Design of a single-center, phase II trial to explore the efficacy and safety of 'R-ISV-RO' treatment in advanced tumors

Background: The authors' preclinical study has confirmed that RO adjuvant (composed of TLR 7 agonists [imiquimod/R837] and OX40 agonists) injected into local lesions induces the regression of both primary tumor and distant metastasis. The authors propose to realize local control and exert abscopal effect through an 'R-ISV-RO' in situ strategy plus anti-PD-1 monoclonal antibody in advanced tumors. Methods: This study is a single-center, exploratory, phase II trial to evaluate the efficacy and safety of R-ISV-RO plus anti-PD-1 monoclonal antibody in advanced tumors. 30 patients with one or more measurable extracerebral lesions that are accessible for radiation or injection will be enrolled. The primary endpoint is the objective response rate of target lesions. Discussion/Conclusion: The efficacy and safety of the novel strategy will be further validated through this clinical trial.Clinical trial registration: ChiCTR2100053870 (www.chictr.org.cn/).

Radiotherapy-Triggered In Situ Tumor Vaccination Boosts Checkpoint Blockaded Immune Response via Antigen-Capturing Nanoadjuvants

In situ vaccination (ISV) formed with the aid of intratumorally injected adjuvants has shed bright light on enhancing the abscopal therapeutic effects of radiotherapy. However, the limited availability of antigens resulting from the radiotherapy-induced immunogenic cell death largely hampers the clinical outcome of ISV. To maximally utilize the radiotherapy-induced antigen, we herein developed a strategy by capturing the radiotherapy-induced antigen in situ with a nanoadjuvant comprised of CpG-loaded Fe3O4 nanoparticles. The highly efficient click reaction between the maleimide residue on the nanoadjuvant and sulfhydryl group on the antigen maximized the bioavailability of autoantigens and CpG adjuvant in vivo. Importantly, combined immune checkpoint blockade can reverse T cell exhaustion after treatment with radiotherapy-induced ISV, thereby largely suppressing the treated and distant tumor. Mechanistically, metabolomics reveals the intratumorally injected nanoadjuvants disrupt redox homeostasis in the tumor microenvironment, further inducing tumor ferroptosis after radiotherapy. Overall, the current study highlights the immense potential of the innovative antigen-capturing nanoadjuvants for synergistically enhancing the antitumor effect.

Implications of Rectal Cancer Radiotherapy on the Immune Microenvironment: Allies and Foes to Therapy Resistance and Patients' Outcome

Aside from surgical resection, locally advanced rectal cancer is regularly treated with neoadjuvant chemoradiotherapy. Since the concept of cancer treatment has shifted from only focusing on tumor cells as drivers of disease progression towards a broader understanding including the dynamic tumor microenvironment (TME), the impact of radiotherapy on the TME and specifically the tumor immune microenvironment (TIME) is increasingly recognized. Both promoting as well as suppressing effects on anti-tumor immunity have been reported in response to rectal cancer (chemo-)radiotherapy and various targets for combination therapies are under investigation. A literature review was conducted searching the PubMed database for evidence regarding the pleiotropic effects of (chemo-)radiotherapy on the rectal cancer TIME, including alterations in cytokine levels, immune cell populations and activity as well as changes in immune checkpoint proteins. Radiotherapy can induce immune-stimulating and -suppressive alterations, potentially mediating radioresistance. The response is influenced by treatment modalities, including the dosage administered and the highly individual intrinsic pre-treatment immune status. Directly addressing the main immune cells of the TME, this review aims to highlight therapeutical implications since efficient rectal cancer treatment relies on personalized strategies combining conventional therapies with immune-modulating approaches, such as immune checkpoint inhibitors.

Toxicity and outcomes of melanoma brain metastases treated with stereotactic radiosurgery: the risk of subsequent symptomatic intralesional hemorrhage exceeds that of radiation necrosis

PURPOSE

We aimed to assess the outcomes and patterns of toxicity in patients with melanoma brain metastases (MBM) treated with stereotactic radiosurgery (SRS) with or without immunotherapy (IO).

METHODS

From a prospective registry, we reviewed MBM patients treated with single fraction Gamma Knife SRS between 2008 and 2021 at our center. We recorded all systemic therapies (chemotherapy, targeted therapy, or immunotherapy) administered before, during, or after SRS. Patients with prior brain surgery were excluded. We captured adverse events following SRS, including intralesional hemorrhage (IH), radiation necrosis (RN) and local failure (LF), as well as extracranial disease status. Distant brain failure (DBF), extracranial progression-free survival (PFS) and overall survival (OS) were determined using a cumulative Incidence function and the Kaplan-Meier method.

RESULTS

Our analysis included 165 patients with 570 SRS-treated MBM. Median OS for patients who received IO was 1.41 years versus 0.79 years in patients who did not (p = 0.04). Ipilimumab monotherapy was the most frequent IO regimen (30%). In the absence of IO, the cumulative incidence of symptomatic (grade 2 +) RN was 3% at 24 months and remained unchanged with respect to the type or timing of IO. The incidence of post-SRS g2 + IH in patients who did not receive systemic therapy was 19% at 1- and 2 years compared to 7% at 1- and 2 years among patients who did (HR: 0.33, 95% CI 0.11-0.98; p = 0.046). Overall, neither timing nor type of IO correlated to rates of DBF, OS, or LF. Among patients treated with IO, the median time to extracranial PFS was 5.4 months (95% IC 3.2 - 9.1).

CONCLUSION

The risk of g2 + IH exceeds that of g2 + RN in MBM patients undergoing SRS, with or without IO. IH should be considered a critical adverse event following MBM treatments.

Updates on radiotherapy-immunotherapy combinations: Proceedings of 6th annual ImmunoRad conference

Focal radiation therapy (RT) has attracted considerable attention as a combinatorial partner for immunotherapy (IT), largely reflecting a well-defined, predictable safety profile and at least some potential for immunostimulation. However, only a few RT-IT combinations have been tested successfully in patients with cancer, highlighting the urgent need for an improved understanding of the interaction between RT and IT in both preclinical and clinical scenarios. Every year since 2016, ImmunoRad gathers experts working at the interface between RT and IT to provide a forum for education and discussion, with the ultimate goal of fostering progress in the field at both preclinical and clinical levels. Here, we summarize the key concepts and findings presented at the Sixth Annual ImmunoRad conference.

Emerging evidence for adapting radiotherapy to immunotherapy

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

Combining radiation therapy with immune checkpoint blockade for the treatment of small cell lung cancer

The addition of immune checkpoint blockade (ICB) therapy to standard chemotherapy has been shown to improve survival in patients with metastatic small cell lung cancer. However, the benefit is modest and there remains an unmet need for novel therapeutic approaches to enhance the effectiveness of immunotherapy in this disease, both in the early and late stages. Ionizing radiation, which is a standard treatment for small cell lung cancer, is known to trigger immunogenic cell death in tumor cells, making it an attractive partner for ICB therapies in multiple solid tumor types. However, the optimal radiation dosage and fractionation scheme, target sites for radiation, and sequencing of radiation in relation to ICB treatment are still unclear. In this review we discuss the molecular biology underlying radiation-induced tumor immunity as well as pre-clinical and clinical studies combining radiation with ICB treatments, with a focus on translational and clinical trials in small cell lung cancer.

The current understanding of the immune landscape relative to radiotherapy across tumor types

Radiotherapy is part of the standard of care treatment for a great majority of cancer patients. As a result of radiation, both tumor cells and the environment around them are affected directly by radiation, which mainly primes but also might limit the immune response. Multiple immune factors play a role in cancer progression and response to radiotherapy, including the immune tumor microenvironment and systemic immunity referred to as the immune landscape. A heterogeneous tumor microenvironment and the varying patient characteristics complicate the dynamic relationship between radiotherapy and this immune landscape. In this review, we will present the current overview of the immunological landscape in relation to radiotherapy in order to provide insight and encourage research to further improve cancer treatment. An investigation into the impact of radiation therapy on the immune landscape showed in several cancers a common pattern of immunological responses after radiation. Radiation leads to an upsurge in infiltrating T lymphocytes and the expression of programmed death ligand 1 (PD-L1) which can hint at a benefit for the patient when combined with immunotherapy. In spite of this, lymphopenia in the tumor microenvironment of 'cold' tumors or caused by radiation is considered to be an important obstacle to the patient's survival. In several cancers, a rise in the immunosuppressive populations is seen after radiation, mainly pro-tumoral M2 macrophages and myeloid-derived suppressor cells (MDSCs). As a final point, we will highlight how the radiation parameters themselves can influence the immune system and, therefore, be exploited to the advantage of the patient.

Neoadjuvant chemoradiotherapy plus tislelizumab followed by surgery for esophageal carcinoma (CRISEC study): the protocol of a prospective, single-arm, phase II trial

BACKGROUND

The failure rate after neoadjuvant chemoradiotherapy followed by surgery is approximately 34.6%-48% for resectable esophageal carcinoma. Pathologic complete response after neoadjuvant chemoradiotherapy is an important factor in predicting lower recurrence and better survival. Whether the sequential addition of immunotherapy to neoadjuvant chemoradiotherapy will be beneficial to improving the pathologic complete response rate is unknown.

METHODS

Patients with pathologically confirmed thoracic esophageal squamous cell carcinoma and at clinical T1-2N1-3M0 or T3-4aN0-3M0 (stage II-IVA) according to the eighth edition of American Joint Committee on Cancer staging will be allocated to receive neoadjuvant radiotherapy (41.4 Gy with 23 fractions to planning target volume) with concurrent chemotherapy (albumin-bound paclitaxel, 100 mg/m2, once weekly for five weeks; carboplatin, area under the curve of 2 mg/mL/min, once weekly for five weeks) plus tislelizumab monotherapy sequentially (200 mg every three weeks for three cycles, beginning from the first to the 14th day after the end of radiotherapy). Then, subtotal esophagectomy with two-field lymphadenectomy, including the whole mediastinum and abdomen, will be performed. The primary endpoint for this study is the pathologic complete response rate after neoadjuvant chemoradiotherapy plus tislelizumab.

DISCUSSION

The optimal timing of the combination of immunotherapy and neoadjuvant chemoradiotherapy in esophageal carcinoma is not determined. The results of this phase II trial will be helpful to clarify the safety and efficacy of the sequential addition of tislelizumab after neoadjuvant chemoradiotherapy for locally advanced resectable esophageal carcinoma.

TRIAL REGISTRATION

This study was approved on January 26, 2021 and retrospectively registered with ClinicalTrials.gov ( NCT04776590 ) on March 1, 2021.

Application of individualized multimodal radiotherapy combined with immunotherapy in metastatic tumors

Radiotherapy is one of the mainstays of cancer treatment. More than half of cancer patients receive radiation therapy. In addition to the well-known direct tumoricidal effect, radiotherapy has immunomodulatory properties. When combined with immunotherapy, radiotherapy, especially high-dose radiotherapy (HDRT), exert superior systemic effects on distal and unirradiated tumors, which is called abscopal effect. However, these effects are not always effective for cancer patients. Therefore, many studies have focused on exploring the optimized radiotherapy regimens to further enhance the antitumor immunity of HDRT and reduce its immunosuppressive effect. Several studies have shown that low-dose radiotherapy (LDRT) can effectively reprogram the tumor microenvironment, thereby potentially overcoming the immunosuppressive stroma induced by HDRT. However, bridging the gap between preclinical commitment and effective clinical delivery is challenging. In this review, we summarized the existing studies supporting the combined use of HDRT and LDRT to synergistically enhance antitumor immunity, and provided ideas for the individualized clinical application of multimodal radiotherapy (HDRT+LDRT) combined with immunotherapy.

Nanomedicine embraces cancer radio-immunotherapy: mechanism, design, recent advances, and clinical translation

Cancer radio-immunotherapy, integrating external/internal radiation therapy with immuno-oncology treatments, emerges in the current management of cancer. A growing number of pre-clinical studies and clinical trials have recently validated the synergistic antitumor effect of radio-immunotherapy, far beyond the "abscopal effect", but it suffers from a low response rate and toxicity issues. To this end, nanomedicines with an optimized design have been introduced to improve cancer radio-immunotherapy. Specifically, these nanomedicines are elegantly prepared by incorporating tumor antigens, immuno- or radio-regulators, or biomarker-specific imaging agents into the corresponding optimized nanoformulations. Moreover, they contribute to inducing various biological effects, such as generating in situ vaccination, promoting immunogenic cell death, overcoming radiation resistance, reversing immunosuppression, as well as pre-stratifying patients and assessing therapeutic response or therapy-induced toxicity. Overall, this review aims to provide a comprehensive landscape of nanomedicine-assisted radio-immunotherapy. The underlying working principles and the corresponding design strategies for these nanomedicines are elaborated by following the concept of "from bench to clinic". Their state-of-the-art applications, concerns over their clinical translation, along with perspectives are covered.

Anti-PD-1 immunotherapy combined with stereotactic body radiation therapy and GM-CSF for the treatment of advanced malignant PEComa: A case report

Background

Perivascular epithelioid cell neoplasm (PEComa) is a rare mesenchymal tumour. Due to its low incidence, a standard treatment regimen for PEComa has not yet been established. Radiotherapy has a synergistic effect with PD-1 inhibitors and GM-CSF. We treated advanced malignant PEComa with a triple regimen of PD-1 inhibitor, SBRT and GM-CSF to provide better therapeutic effect.

Case presentation

A 63-year-old woman was diagnosed with malignant PEComa after presenting with postmenopausal vaginal bleeding. Despite two surgeries, the neoplasm eventually metastasized throughout the body. We formulated triple therapy with SBRT, a PD-1 inhibitor, and GM-CSF for the patient. The patient's local symptoms were controlled at the radiotherapy site, and the lesions at the unirradiated sites were also relieved.

Conclusions

For the first time, a triple regimen of PD-1 inhibitor, SBRT and GM-CSF was used in the treatment of malignant PEComa and achieved good efficacy. Considering the lack of prospective clinical studies in PEComa, we believe that this triple therapy is a good-quality regimen for advanced malignant PEComa.

Combination of Pembrolizumab and Stereotactic Body Radiation Therapy in Recurrent Metastatic Penile Squamous Cell Carcinoma: A Case Study

The prognosis for patients with penile squamous cell carcinoma metastatic to regional lymph nodes or distant sites remains poor with limited treatment options, especially after the failure of first-line chemotherapy. Clinical trials evaluating the use of checkpoint inhibitor therapy, or the use of checkpoint inhibitor therapy with stereotactic body radiation therapy for the treatment of metastatic penile squamous cell carcinoma, are currently unavailable. In this case report, we present a patient with relapsed advanced penile squamous cell carcinoma and an unknown (human papilloma virus) HPV status and borderline programmed death-ligand 1 (PD-L)1 status who was treated with pembrolizumab and stereotactic body radiation therapy. This patient achieved a complete durable treatment response despite having genomic features of an immunologically "cold" tumor. This case highlights the importance of investigating more into the treatment of these tumors that lack genomic features that classically have been observed to be susceptible to treatment with immunotherapy or immunotherapy augmented with stereotactic body radiation therapy in solid tumors, particularly in metastatic penile squamous cell carcinoma.

NBTXR3 improves the efficacy of immunoradiotherapy combining nonfucosylated anti-CTLA4 in an anti-PD1 resistant lung cancer model

The efficacy of immunoradiotherapy consisting of radiation therapy and immune checkpoint blockade relies on effectively promoting the systemic antitumor immune response's activation while simultaneously reducing local factors favoring immune suppression. We previously demonstrated that NBTXR3, a nanoparticle radioenhancer, significantly improved immune responses in a murine anti-PD1-resistant metastatic lung cancer model. We hypothesize that radioactivated-NBTXR3 addition to anti-PD1 and a second-generation anti-CTLA4 could improve treatment effectiveness. To test this hypothesis, we inoculated mice with 344SQR cells in the right and left legs to establish primary and secondary tumors. The primary tumors were intratumorally injected with NBTXR3 nanoparticles on day 7, followed by three fractions of 12 Gy radiation on days 8, 9, and 10. The secondary tumors received two fractions of 1Gy radiation on days 13 and 14. Multiple rounds of anti-PD1, anti-CTLA4 or nonfucosylated anti-CTLA4 were given to the mice. Immune profiling of the tumors revealed that the combination of NBTXR3 with immunoradiotherapy significantly upregulated the activities of a wide range of antitumor immune pathways and reduced the abundance of regulatory suppressor T cells. This combination effectively eradicated the primary and secondary tumors and increased animal survival to 75%. Remarkably, previously treated with NBTXR3-containing treatment, the survivor mice exhibited a long-lasting antitumor memory immune response. This data provides compelling evidence of the efficacy of NBTXR3 to synergize with the immunoradiotherapy approach when combined with an anti-PD1 and multiple checkpoints such as a second generation anti-CTLA4 and show the potential for clinical uses of antitumor immunomodulatory effects of NBTXR3.

Radioimmunotherapy in HPV-Associated Head and Neck Squamous Cell Carcinoma

HPV-associated head and neck squamous cell carcinoma (HNSCC) is a cancer entity with unique biological and clinical characteristics that requires more personalized treatment strategies. As the backbone of conventional therapeutics, radiation is now harnessed to synergize with immunotherapy in multiple malignancies. Accumulating preclinical and clinical data have suggested the potential of radioimmunotherapy in eliciting local and systemic anti-tumor response via direct killing of tumor cells and immunogenic cell death. However, this effect remains uncertain in HPV-associated HNSCC. Owing to its intrinsic radiosensitivity and distinct tumor microenvironment, HPV-associated HNSCC may represent a good candidate for radioimmunotherapy. In this review, we provide a detailed illustration of the biology, the genomic features, and immune landscapes of HPV-associated HNSCC that support the synergism between radiation and immune agents. The interaction between radiotherapy and immunotherapy is described. We also highlight the present evidence as well as ongoing trials using different combination strategies in the recurrent/metastatic or definitive settings. In addition, we have summarized the challenges and outlook for future trial design, with special emphasis on radiotherapy optimization and novel therapeutic options to incorporate.

A phase II clinical trial of neoadjuvant sasanlimab and stereotactic body radiation therapy as an in situ vaccine for cisplatin-ineligible MIBC: the RAD VACCINE MIBC trial

The utilization of neoadjuvant immune checkpoint inhibitor therapy, specifically anti-PD-1/L1 agents, prior to radical cystectomy is an emerging paradigm in muscle-invasive bladder cancer (MIBC). In situ vaccination represents a strategy to manipulate the tumor in order to augment the immune response toward improved local and distant cancer control. The authors describe the study rationale, design and objectives for RAD VACCINE MIBC, a single-arm, single-institution, phase II trial evaluating the efficacy and safety of combination neoadjuvant sasanlimab (humanized IgG monoclonal antibody that targets PD-1) with stereotactic body radiotherapy as an in situ vaccine in cisplatin-ineligible patients with MIBC. The results from this trial will establish the safety profile of this combination strategy and evaluate pathologic complete response rates.

PD-1 Inhibitor Combined With Radiotherapy and GM-CSF (PRaG) in Patients With Metastatic Solid Tumors: An Open-Label Phase II Study

Patients with metastatic cancer refractory to standard systemic therapies have a poor prognosis and few therapeutic options. Radiotherapy can shape the tumor microenvironment (TME) by inducing immunogenic cell death and promoting tumor recognition by natural killer cells and T lymphocytes. Granulocyte macrophage-colony stimulating factor (GM-CSF) was known to promote dendric cell maturation and function, and might also induce the macrophage polarization with anti-tumor capabilities. A phase II trial (ChiCTR1900026175) was conducted to assess the clinical efficacy and safety of radiotherapy, PD-1 inhibitor and GM-CSF (PRaG regimen). This trial was registered at http://www.chictr.org.cn/index.aspx. A PRaG cycle consisted of 3 fractions of 5 or 8 Gy delivered for one metastatic lesion from day 1, followed by 200 μg subcutaneous injection of GM-CSF once daily for 2 weeks, and intravenous infusion of PD-1 inhibitor once within one week after completion of radiotherapy. The PRaG regimen was repeated every 21 days for at least two cycles. Once the PRaG therapy was completed, the patient continued PD-1 inhibitor monotherapy until confirmed disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR). A total of 54 patients were enrolled with a median follow-up time of 16.4 months. The ORR was 16.7%, and the disease control rate was 46.3% in intent-to-treat patients. Median progression-free survival was 4.0 months (95% confidence interval [CI], 3.3 to 4.8), and median overall survival was 10.5 months (95% CI, 8.7 to 12.2). Grade 3 treatment-related adverse events occurred in five patients (10.0%) and grade 4 in one patient (2.0%). Therefore, the PRaG regimen was well tolerated with acceptable toxicity and may represent a promising salvage treatment for patients with chemotherapy-refractory solid tumors. It is likely that PRaG acts via heating upthe TME with radiotherapy and GM-CSF, which was further boosted by PD-1 inhibitors.

Innate and Adaptive Responses of Intratumoral Immunotherapy with Endosomal Toll-Like Receptor Agonists

Toll-like receptors (TLRs) are natural initial triggers of innate and adaptive immune responses. With the advent of cancer immunotherapy, nucleic acids engineered as ligands of endosomal TLRs have been investigated for the treatment of solid tumors. Despite promising results, their systemic administration, similarly to other immunotherapies, raises safety issues. To overcome these problems, recent studies have applied the direct injection of endosomal TLR agonists in the tumor and/or draining lymph nodes, achieving high local drug exposure and strong antitumor response. Importantly, intratumoral delivery of TLR agonists showed powerful effects not only against the injected tumors but also often against uninjected lesions (abscopal effects), resulting in some cases in cure and antitumoral immunological memory. Herein, we describe the structure and function of TLRs and their role in the tumor microenvironment. Then, we provide our vision on the potential of intratumor versus systemic delivery or vaccination approaches using TLR agonists, also considering the use of nanoparticles to improve their targeting properties. Finally, we collect the preclinical and clinical studies applying intratumoral injection of TLR agonists as monotherapies or in combination with: (a) other TLR or STING agonists; (b) other immunotherapies; (c) radiotherapy or chemotherapy; (d) targeted therapies.

ATR-mediated CD47 and PD-L1 up-regulation restricts radiotherapy-induced immune priming and abscopal responses in colorectal cancer

Radiotherapy (RT) of colorectal cancer (CRC) can prime adaptive immunity against tumor-associated antigen (TAA)-expressing CRC cells systemically. However, abscopal tumor remissions are extremely rare, and the postirradiation immune escape mechanisms in CRC remain elusive. Here, we found that irradiated CRC cells used ATR-mediated DNA repair signaling pathway to up-regulate both CD47 and PD-L1, which through engagement of SIRPα and PD-1, respectively, prevented phagocytosis by antigen-presenting cells and thereby limited TAA cross-presentation and innate immune activation. This postirradiation CD47 and PD-L1 up-regulation was observed across various human solid tumor cells. Concordantly, rectal cancer patients with poor responses to neoadjuvant RT exhibited significantly elevated postirradiation CD47 levels. The combination of RT, anti-SIRPα, and anti-PD-1 reversed adaptive immune resistance and drove efficient TAA cross-presentation, resulting in robust TAA-specific CD8 T cell priming, functional activation of T effectors, and increased T cell clonality and clonal diversity. We observed significantly higher complete response rates to RT/anti-SIRPα/anti-PD-1 in both irradiated and abscopal tumors and prolonged survival in three distinct murine CRC models, including a cecal orthotopic model. The efficacy of triple combination therapy was STING dependent as knockout animals lost most benefit of adding anti-SIRPα and anti-PD-1 to RT. Despite activation across the myeloid stroma, the enhanced dendritic cell function accounts for most improvements in CD8 T cell priming. These data suggest ATR-mediated CD47 and PD-L1 up-regulation as a key mechanism restraining radiation-induced immune priming. RT combined with SIRPα and PD-1 blockade promotes robust antitumor immune priming, leading to systemic tumor regressions.

Neoadjuvant Therapy Induces a Potent Immune Response to Sarcoma, Dominated by Myeloid and B Cells

PURPOSE

To characterize changes in the soft-tissue sarcoma (STS) tumor immune microenvironment induced by standard neoadjuvant therapy with the goal of informing neoadjuvant immunotherapy trial design.

EXPERIMENTAL DESIGN

Paired pre- and postneoadjuvant therapy specimens were retrospectively identified for 32 patients with STSs and analyzed by three modalities: multiplexed IHC, NanoString, and RNA sequencing with ImmunoPrism analysis.

RESULTS

All 32 patients, representing a variety of STS histologic subtypes, received neoadjuvant radiotherapy and 21 (66%) received chemotherapy prior to radiotherapy. The most prevalent immune cells in the tumor before neoadjuvant therapy were myeloid cells (45% of all immune cells) and B cells (37%), with T (13%) and natural killer (NK) cells (5%) also present. Neoadjuvant therapy significantly increased the total immune cells infiltrating the tumors across all histologic subtypes for patients receiving neoadjuvant radiotherapy with or without chemotherapy. An increase in the percentage of monocytes and macrophages, particularly M2 macrophages, B cells, and CD4+ T cells was observed postneoadjuvant therapy. Upregulation of genes and cytokines associated with antigen presentation was also observed, and a favorable pathologic response (≥90% necrosis postneoadjuvant therapy) was associated with an increase in monocytic infiltrate. Upregulation of the T-cell checkpoint TIM3 and downregulation of OX40 were observed posttreatment.

CONCLUSIONS

Standard neoadjuvant therapy induces both immunostimulatory and immunosuppressive effects within a complex sarcoma microenvironment dominated by myeloid and B cells. This work informs ongoing efforts to incorporate immune checkpoint inhibitors and novel immunotherapies into the neoadjuvant setting for STSs.

PI3Kδ/γ inhibitor BR101801 extrinsically potentiates effector CD8+ T cell-dependent antitumor immunity and abscopal effect after local irradiation

BACKGROUND

Radiotherapy enhances antitumor immunity. However, it also induces immunosuppressive responses, which are major hurdles for an effective treatment. Thus, targeting the immunosuppressive tumor microenvironment is essential for enhancing the antitumor immunity after radiotherapy. Retrospective studies show that a blockade of PI3Kδ and/or γ, which are abundant in leukocytes, exhibits antitumor immune response by attenuating activity of immune suppressive cells, however, the single blockade of PI3Kδ or γ is not sufficient to completely eliminate solid tumor.

METHODS

We used BR101801, PI3Kδ/γ inhibitor in the CT-26 syngeneic mouse model with a subcutaneously implanted tumor. BR101801 was administered daily, and the target tumor site was locally irradiated. We monitored the tumor growth regularly and evaluated the immunological changes using flow cytometry, ELISpot, and transcriptional analysis.

RESULTS

This study showed that BR101801 combined with irradiation promotes systemic antitumor immunity and abscopal response by attenuating the activity of immune suppressive cells in the CT-26 tumor model. BR101801 combined with irradiation systemically reduced the proliferation of regulatory T cells (Tregs) and enhanced the number of tumor-specific CD8α⁺ T cells in the tumor microenvironment, thereby leading to tumor regression. Furthermore, the high ratio of CD8α⁺ T cells to Tregs was maintained for 14 days after irradiation, resulting in remote tumor regression in metastatic lesions, the so-called abscopal effect. Moreover, our transcriptomic analysis showed that BR101801 combined with irradiation promoted the immune-stimulatory tumor microenvironment, suggesting that the combined therapy converts immunologically cold tumors into hot one.

CONCLUSIONS

Our data suggest the first evidence that PI3Kδ/γ inhibition combined with irradiation promotes systemic antitumor immunity against solid tumors, providing the preclinical result of the potential use of PI3Kδ/γ inhibitor as an immune-regulatory radiosensitizer.

Brain metastases: increasingly precision medicine-a narrative review

Objective

To broadly review the modern management of brain metastases.

Background

Brain metastases are the commonest neurological manifestation of cancer and a major cause of morbidity in cancer patients. Brain metastases are increasing in frequency, as a result of longer life expectancy of cancer patients, more sensitive methods for brain metastasis detection and an ageing population. The proportional incidence of brain metastases according to cancer of origin, from greatest to least, is lung cancer, melanoma, renal, breast and colorectal cancers. Patients with lung cancer and melanoma are most likely to have brain metastases at diagnosis. Brain metastases cause a variety of symptoms, depending on their size and location, whether they cause mass effect and oedema, compression of the brain parenchyma, or focal neurological deficits. The major differential diagnoses of brain metastases include primary tumours and vascular/inflammatory lesions. Prognosis is dependent on the site, number and volume of lesions, the patients’ performance status, age and the activity and extent of extracranial disease.

Methods

English literature articles in PubMed from 1950 to June 2021 were reviewed. Article bibliographies provided further references.

Conclusions

Treatment of brain metastasis patients has moved from considering them as a homogenous population of patients, to individualised treatment. In those brain metastases patients of satisfactory performance status with a solitary lesion, especially one in a non-eloquent/accessible area causing significant mass effect and/or raised intracranial pressure or for whom the diagnosis is in doubt (histology needed), surgical resection is usually the treatment of choice. For multiple brain metastases, radiotherapy with or without systemic therapies are usually employed. For relatively fit patients with limited numbers of brain metastases (e.g., 4 or less), stereotactic radiosurgery is standard of care. Current clinical trials are testing the efficacy of stereotactic treatment alone for >4 brain metastases (although it is increasingly used for such patients in many centres) as well as integration of local therapies with targeted and immunological therapies in appropriately selected cases. In certain circumstances, cranial irradiation can be omitted.

High-LET Carbon and Iron Ions Elicit a Prolonged and Amplified p53 Signaling and Inflammatory Response Compared to low-LET X-Rays in Human Peripheral Blood Mononuclear Cells

Understanding the differences in biological response to photon and particle radiation is important for optimal exploitation of particle therapy for cancer patients, as well as for the adequate application of radiation protection measures for astronauts. To address this need, we compared the transcriptional profiles of isolated peripheral blood mononuclear cells 8 h after exposure to 1 Gy of X-rays, carbon ions or iron ions with those of non-irradiated cells using microarray technology. All genes that were found differentially expressed in response to either radiation type were up-regulated and predominantly controlled by p53. Quantitative PCR of selected genes revealed a significantly higher up-regulation 24 h after exposure to heavy ions as compared to X-rays, indicating their prolonged activation. This coincided with increased residual DNA damage as evidenced by quantitative γH2AX foci analysis. Furthermore, despite the converging p53 signature between radiation types, specific gene sets related to the immune response were significantly enriched in up-regulated genes following irradiation with heavy ions. In addition, irradiation, and in particular exposure to carbon ions, promoted transcript variation. Differences in basal and iron ion exposure-induced expression of DNA repair genes allowed the identification of a donor with distinct DNA repair profile. This suggests that gene signatures may serve as a sensitive indicator of individual DNA damage repair capacity. In conclusion, we have shown that photon and particle irradiation induce similar transcriptional pathways, albeit with variable amplitude and timing, but also elicit radiation type-specific responses that may have implications for cancer progression and treatment

Anti-PD-1 Immunotherapy Combined With Stereotactic Body Radiation Therapy and GM-CSF as Salvage Therapy in a PD-L1-Positive Patient With Refractory Metastatic Thyroid Hürthle Cell Carcinoma: A Case Report and Literature Review

Thyroid Hürthle cell carcinoma, known as thyroid eosinophilic carcinoma, is a rare pathological type of differentiated thyroid cancer (DTC), representing 3-4% of all thyroid cancers. However, given the high risk of invasion and metastasis, thyroid Hürthle cell carcinoma has a relatively poor prognosis. Traditional treatment methods have limited effects on patients with metastatic thyroid cancers. Developing a valuable therapy for advanced thyroid carcinomas is an unfilled need, and immunotherapy could represent another choice for these tumors. We herein reported the case of a patient with recurrent advanced thyroid Hürthle cell cancer and positive programmed death-ligand 1 (PD-L1) expression, who suffered tumor progression after re-surgery, radiotherapy, and targeted therapy. It is encouraging that PD-1 inhibitors in combination with GM-CSF and stereotactic body irradiation (SBRT) on metastatic disease have a significant anti-tumor effect.

Radiotherapy in the Treatment of Subcutaneous Melanoma

Simple Summary

The non-surgical treatment of cutaneous and/or subcutaneous melanoma lesions involves a multitude of local treatments, including radiotherapy. This is often used when other local methods fail, and there are currently no clear guidelines or evidence-based recommendations to support its use in this setting. This review, collecting the retrospective and prospective experiences on radiotherapy alone or in combination with other methods, aims to provide a scenario of the possible advantages and disadvantages related to its use in the treatment of skin/subcutaneous melanoma lesions.

Abstract

Malignant melanoma frequently develops cutaneous and/or subcutaneous metastases during the course of the disease. These may present as non-nodal locoregional metastases (microsatellite, satellite, or in-transit) included in stage III or as distant metastases in stage IV. Their presentation is heterogeneous and associated with significant morbidity resulting from both disease-related functional damage and treatment side effects. The standard treatment is surgical excision, whereas local therapies or systemic therapies have a role when surgery is not indicated. Radiotherapy can be used in the local management of ITM, subcutaneous relapses, or distant metastases to provide symptom relief and prolong regional disease control. To increase the local response without increasing toxicity, the addition of hyperthermia and intralesional therapies to radiotherapy appear to be very promising. Boron neutron capture therapy, based on nuclear neutron capture and boron isotope fission reaction, could be an alternative to standard treatments, but its use in clinical practice is still limited. The potential benefit of combining radiotherapy with targeted therapies and immunotherapy has yet to be explored in this lesion setting. This review explores the role of radiotherapy in the treatment of cutaneous and subcutaneous lesions, its impact on outcomes, and its association with other treatment modalities.

Targeting of the tumor microenvironment by curcumin

The tumor microenvironment (TME) is made up of several cells and molecules that affect the survival of cancer cells. Indeed, certain (immunosuppressive) cells which promote tumors can promote the growth of tumors by stimulating the proliferation of cancer cells and promoting angiogenesis. During tumor growth, antitumoral immunity includes natural killer cells and CD8+ T cells cannot overcome immunosuppressive responses and cancer cell proliferation. In order to achieve the appropriate therapeutic response, we must kill cancer cells and suppress the release of immunosuppressive molecules. The balance between anti-tumor immunity and immunosuppressive cells, such as regulatory T cells (Tregs), cancer-associated fibroblasts, tumor-associated macrophages, and myeloid-derived suppressor cells plays a key role in the suppression or promotion of cancer cells. Curcumin is a plant-derived agent that has shown interesting properties for cancer therapy. It has shown that not only directly inhibit the growth of cancer cells, but can also modulate the growth and activity of immunosuppressant and tumor-promoting cells. In this review, we explain how curcumin modulates interactions within TME in favor of tumor treatment. The potential modulating effects of curcumin on the responses of cancer cells to treatment modalities such as immunotherapy will also be discussed.

A Rational Approach to Unilateral Neck RT for Head and Neck Cancers in the Era of Immunotherapy

Radiotherapy plays an important role in the definitive and adjuvant treatment of head and neck squamous cell carcinoma (HNSCC). However, standard courses of radiation therapy may contribute to the depletion of circulating lymphocytes and potentially attenuate optimal tumor antigen presentation that may be detrimental to the efficacy of novel immunotherapeutic agents. This review explores the advantages of restricting radiation to the primary tumor/tumor bed and ipsilateral elective neck as it pertains to the evolving field of immunotherapy.

Abscopal Effect and Drug-Induced Xenogenization: A Strategic Alliance in Cancer Treatment?

The current state of cancer treatment is still far from being satisfactory considering the strong impairment of patients' quality of life and the high lethality of malignant diseases. Therefore, it is critical for innovative approaches to be tested in the near future. In view of the crucial role that is played by tumor immunity, the present review provides essential information on the immune-mediated effects potentially generated by the interplay between ionizing radiation and cytotoxic antitumor agents when interacting with target malignant cells. Therefore, the radiation-dependent abscopal effect (i.e., a biological effect of ionizing radiation that occurs outside the irradiated field), the influence of cancer chemotherapy on the antigenic pattern of target neoplastic cells, and the immunogenic cell death (ICD) caused by anticancer agents are the main topics of this presentation. It is widely accepted that tumor immunity plays a fundamental role in generating an abscopal effect and that anticancer drugs can profoundly influence not only the host immune responses, but also the immunogenic pattern of malignant cells. Remarkably, several anticancer drugs impact both the abscopal effect and ICD. In addition, certain classes of anticancer agents are able to amplify already expressed tumor-associated antigens (TAA). More importantly, other drugs, especially triazenes, induce the appearance of new tumor neoantigens (TNA), a phenomenon that we termed drug-induced xenogenization (DIX). The adoption of the abscopal effect is proposed as a potential therapeutic modality when properly applied concomitantly with drug-induced increase in tumor cell immunogenicity and ICD. Although little to no preclinical or clinical studies are presently available on this subject, we discuss this issue in terms of potential mechanisms and therapeutic benefits. Upcoming investigations are aimed at evaluating how chemical anticancer drugs, radiation, and immunotherapies are interacting and cooperate in evoking the abscopal effect, tumor xenogenization and ICD, paving the way for new and possibly successful approaches in cancer therapy.

[Abscopal effect: Myth or reality?]

The abscopal effect has been mentioned since 1953. The increase in knowledge about the immune system and the development of immunotherapies support its potential therapeutic interest. While it is accepted that radiotherapy induces an immune response, demonstrating its systemic impact is not easy. The preclinical basis is solid but its clinical validation pending. Radiotherapy rarely induces tumor reduction at a distance from the beams, probably due to its immunosuppressive effect. This is why a synergy between radiotherapy and systemic treatments targeting these immunosuppressive mechanisms was observed. Several parameters can modulate the induction of the abscopal effect. Among these, the fractionation of the dose seems to be determining with currently a pre-eminence of hypofractionated stereotaxis. On the other hand, even if the choice of more immunogenic targets (liver, lung) should be favoured, the optimal number of lesions to be irradiated remains to be defined as well as the minimum volume allowing sufficient release of tumor antigens. The impact of radiation-induced lymphopenia on radiotherapy/immunotherapy efficacy needs to be assessed more precisely, as does the effect of radiotherapy techniques on them. Finally, the choice of immunotherapy(ies) and the combination regimen with radiotherapy remain under discussion. A sequential scheme appears to provide less toxicities but the concomitant would lead to a better response. The study of these different parameters should allow us to deliver optimized radiotherapy/immunotherapy(ies) combinations to our metastatic patients in order to benefit as many people as possible from this abscopal effect.

Radiation Therapy Enhanced by NBTXR3 Nanoparticles Overcomes Anti-PD1 Resistance and Evokes Abscopal Effects

PURPOSE

Radiation combined with PD1 blockade offers significant treatment benefits in several tumor types; however, anti-PD1 resistance precludes such benefits in many cases. Here we attempted to overcome anti-PD1 resistance by combining localized radiation with a radioenhancing nanoparticle (NBTXR3) and systemic anti-PD1 treatment to achieve abscopal effects in an anti-PD1-resistant mouse model of lung cancer.

METHODS AND MATERIALS

Female 129Sv/Ev mice were inoculated with 344SQ anti-PD1-resistant (344SQR) or anti-PD1-sensitive (344SQP) metastatic lung cancer cells in the right leg on day 0 ("primary" tumor) and the left leg on day 4 ("secondary" tumor). Primary tumors were injected intratumorally with NBTXR3 on day 7 and were irradiated with 12 Gy on days 8, 9, and 10. Mice were given 6 intraperitoneal injections of anti-PD1. T cell receptor repertoire was analyzed in tumor samples with RNA sequencing, infiltration of CD8 T cells with immunohistochemical staining, and activities of various immune pathways with NanoString analysis.

RESULTS

The triple combination of NBTXR3 with localized radiation and systemic anti-PD1 significantly delayed the growth of both irradiated and unirradiated tumors in both 344SQP and 344SQR tumor models. NBTXR3 remodeled the immune microenvironment of unirradiated tumors by triggering the activation of various immune pathways, increasing the number of CD8⁺ T cells, and modifying the T cell receptor repertoire in the 344SQR tumor model.

CONCLUSIONS

The ability of NBTXR3 to evoke significant abscopal effects in both anti-PD1-sensitive and anti-PD1-resistant lung cancers could open the possibility of its use for treating patients with metastatic lung cancer regardless of sensitivity (or resistance) to immunotherapies.

Perspectives on metals-based radioimmunotherapy (RIT): moving forward

Radioimmunotherapy (RIT) is FDA-approved for the clinical management of liquid malignancies, however, its use for solid malignancies remains a challenge. The putative benefit of RIT lies in selective targeting of antigens expressed on the tumor surface using monoclonal antibodies, to systemically deliver cytotoxic radionuclides. The past several decades yielded dramatic improvements in the quality, quantity, recent commercial availability of alpha-, beta- and Auger Electron-emitting therapeutic radiometals. Investigators have created new or improved existing bifunctional chelators. These bifunctional chelators bind radiometals and can be coupled to antigen-specific antibodies. In this review, we discuss approaches to develop radiometal-based RITs, including the selection of radiometals, chelators and antibody platforms (i.e. full-length, F(ab')2, Fab, minibodies, diabodies, scFv-Fc and nanobodies). We cite examples of the performance of RIT in the clinic, describe challenges to its implementation, and offer insights to address gaps toward translation.

Optimizing the Treatment Schedule of Radiotherapy Combined With Anti-PD-1/PD-L1 Immunotherapy in Metastatic Cancers

Immune checkpoint inhibitors (ICIs) targeting programmed cell death protein-1 (PD-1), and programmed cell death ligand-1 (PD-L1) have been approved for a variety of malignant tumors and are widely used to treat patients with metastatic disease. However, the efficacy of PD-1 inhibitors is limited due to tumor heterogeneity, high tumor burden, and "cold" tumor microenvironment. Radiotherapy can improve the anti-tumor effects of PD-1/PD-L1 inhibitors in various ways. As a new radiotherapy method, stereotactic body radiotherapy (SBRT) or hypofractionated radiotherapy (HFRT) provides higher doses per fraction to the target lesions, thus achieving immune activation effects and overcoming tumor resistance to anti-PD-1/PD-L1 treatment, which significantly improves the local and distant control of tumors. However, for different metastatic situations, radiotherapy plays different roles in the combination therapy. In oligometastatic status, radiotherapy can be used as a local radical treatment aiming to eliminate cancers in cooperation with systemic PD-1 inhibitors. In other circumstances, like bulky metastasis or multiple metastatic tumors, radiotherapy can be used as adjuvant to systemic immunotherapy. This review focuses on the underlying mechanisms and optimization strategies for the combination of radiotherapy and anti-PD-1/PD-L1 therapy in metastatic disease.

Biological factors of the tumour response to electrochemotherapy: Review of the evidence and a research roadmap

The beneficial effects of electrochemotherapy (ECT) for superficial tumours and, more recently, deep-seated malignancies in terms of local control and quality of life are widely accepted. However, the variability in responses across histotypes needs to be explored. Currently, patient selection for ECT is based on clinical factors (tumour size, histotype, and exposure to previous oncological treatments), whereas there are no biomarkers to predict the response to treatment. In this field, two major areas of investigation can be identified, i.e., tumour cell characteristics and the tumour microenvironment (vasculature, extracellular matrix, and immune infiltrate). For each of these areas, we describe the current knowledge and discuss how to foster further investigation. This review aims to provide a summary of the currently used guiding clinical factors and delineates a research roadmap for future studies to identify putative biomarkers of response to ECT. These biomarkers may allow researchers to improve ECT practice by customising treatment parameters, manipulating the tumour and its microenvironment, and exploring novel therapeutic combinations.

Ablative Radiotherapy Reprograms the Tumor Microenvironment of a Pancreatic Tumor in Favoring the Immune Checkpoint Blockade Therapy

The low overall survival rate of patients with pancreatic cancer has driven research to seek a new therapeutic protocol. Radiotherapy (RT) is frequently an option in the neoadjuvant or palliative settings for pancreatic cancer treatment. This study explored the effect of RT protocols on the tumor microenvironment (TME) and their consequent impact on anti-programmed cell death ligand-1 (PD-L1) therapy. Using a murine orthotopic pancreatic tumor model, UN-KC-6141, RT-disturbed TME was examined by immunohistochemical staining. The results showed that ablative RT is more effective than fractionated RT at recruiting T cells. On the other hand, fractionated RT induces more myeloid-derived suppressor cell infiltration than ablative RT. The RT-disturbed TME presents a higher perfusion rate per vessel. The increase in vessel perfusion is associated with a higher amount of anti-PD-L1 antibody being delivered to the tumor. Animal survival is increased by anti-PD-L1 therapy after ablative RT, with 67% of treated animals surviving more than 30 days after tumor inoculation compared to a median survival time of 16.5 days for the control group. Splenocytes isolated from surviving animals were specifically cytotoxic for UN-KC-6141 cells. We conclude that the ablative RT-induced TME is more suited than conventional RT-induced TME to combination therapy with immune checkpoint blockade.

Radiotherapy Delivered before CDK4/6 Inhibitors Mediates Superior Therapeutic Effects in ER+ Breast Cancer

PURPOSE

Recent preclinical data suggest that cyclin-dependent kinase 4/6 (CDK4/6) inhibition may be harnessed to sensitize estrogen receptor-positive (ER⁺) breast cancer to radiotherapy. However, these findings were obtained in human ER⁺ breast cancer cell lines exposed to subclinical doses of CDK4/6 inhibitors with limited attention to treatment schedule. We investigated the activity of radiotherapy combined with the prototypic CDK4/6 inhibitor palbociclib placing emphasis on therapeutic schedule.

EXPERIMENTAL DESIGN

We combined radiotherapy and palbociclib in various doses and therapeutic schedules in human and mouse models of ER⁺ and ER-negative (ER^-) breast cancer, including an immunocompetent mouse model that recapitulates key features of human luminal B breast cancer in women. We assessed proliferation, cell death, cell-cycle control, and clonogenic survival in vitro, as well as tumor growth, overall survival, and metastatic dissemination in vivo.

RESULTS

Radiotherapy and palbociclib employed as standalone agents had partial cytostatic effects in vitro, correlating with suboptimal tumor control in vivo. However, while palbociclib delivered before focal radiotherapy provided minimal benefits as compared with either treatment alone, delivering focal radiotherapy before palbociclib mediated superior therapeutic effects, even in the absence of p53. Such superiority manifested in vitro with enhanced cytostasis and loss of clonogenic potential, as well as in vivo with improved local and systemic tumor control.

CONCLUSIONS

Our preclinical findings demonstrate that radiotherapy delivered before CDK4/6 inhibitors mediates superior antineoplastic effects compared with alternative treatment schedules, calling into question the design of clinical trials administering CDK4/6 inhibitors before radiotherapy in women with ER⁺ breast cancer.

Therapy-Induced Modulation of the Tumor Microenvironment: New Opportunities for Cancer Therapies

Advances in immunotherapy have achieved remarkable clinical outcomes in tumors with low curability, but their effects are limited, and increasing evidence has implicated tumoral and non-tumoral components of the tumor microenvironment as critical mediators of cancer progression. At the same time, the clinical successes achieved with minimally invasive and optically-guided surgery and image-guided and ablative radiation strategies have been successfully implemented in clinical care. More effective, localized and safer treatments have fueled strong research interest in radioimmunotherapy, which has shown the potential immunomodulatory effects of ionizing radiation. However, increasingly more observations suggest that immunosuppressive changes, metabolic remodeling, and angiogenic responses in the local tumor microenvironment play a central role in tumor recurrence. In this review, we address challenges to identify responders vs. non-responders to the immune checkpoint blockade, discuss recent developments in combinations of immunotherapy and radiotherapy for clinical evaluation, and consider the clinical impact of immunosuppressive changes in the tumor microenvironment in the context of surgery and radiation. Since the therapy-induced modulation of the tumor microenvironment presents a multiplicity of forms, we propose that overcoming microenvironment related resistance can become clinically relevant and represents a novel strategy to optimize treatment immunogenicity and improve patient outcome.