Recent Developments in Radiotherapy

[Brachytherapy in France in 2020: State of the art and perspectives from the Groupe curiethérapie de la SFRO]

Because of its principle and its high proof level clinical results, brachytherapy represents a specific irradiation technique for the treatment of primary tumors as well as some local relapses in pre-irradiated area. After a glory period between the 80's and 90's, brachytherapy has progressively lost its attractiveness. In order to provide a practical solution to this deleterious situation, it is important that guardianships, health care payers, patient associations, specialist doctors and radiation oncologists understand the reasons leading to this harmful state as well as the risks concerned. A teaching judged insufficient, non-adapted value and an aging image of brachytherapy represent the three main reasons of this degradation and constitute the three most important challenges conditioning its maintain in the anticancer treatment arsenal. An adapted communication with radiation oncologists themselves but also with the other scientific societies remains crucial as well as with guardianship and patient associations. It is central that brachytherapy could be recognized in order to make it stronger and accessible for all the patients who could need it.

Machine Learning-Based Models for Prediction of Toxicity Outcomes in Radiotherapy

In order to limit radiotherapy (RT)-related side effects, effective toxicity prediction and assessment schemes are essential. In recent years, the growing interest toward artificial intelligence and machine learning (ML) within the science community has led to the implementation of innovative tools in RT. Several researchers have demonstrated the high performance of ML-based models in predicting toxicity, but the application of these approaches in clinics is still lagging, partly due to their low interpretability. Therefore, an overview of contemporary research is needed in order to familiarize practitioners with common methods and strategies. Here, we present a review of ML-based models for predicting and classifying RT-induced complications from both a methodological and a clinical standpoint, focusing on the type of features considered, the ML methods used, and the main results achieved. Our work overviews published research in multiple cancer sites, including brain, breast, esophagus, gynecological, head and neck, liver, lung, and prostate cancers. The aim is to define the current state of the art and main achievements within the field for both researchers and clinicians.

Metabolic Fingerprinting on Synthetic Alloys for Medulloblastoma Diagnosis and Radiotherapy Evaluation

Diagnostics is the key in screening and treatment of cancer. As an emerging tool in precision medicine, metabolic analysis detects end products of pathways, and thus is more distal than proteomic/genetic analysis. However, metabolic analysis is far from ideal in clinical diagnosis due to the sample complexity and metabolite abundance in patient specimens. A further challenge is real-time and accurate tracking of treatment effect, e.g., radiotherapy. Here, Pd-Au synthetic alloys are reported for mass-spectrometry-based metabolic fingerprinting and analysis, toward medulloblastoma diagnosis and radiotherapy evaluation. A core-shell structure is designed using magnetic core particles to support Pd-Au alloys on the surface. Optimized synthetic alloys enhance the laser desorption/ionization efficacy and achieve direct detection of 100 nL of biofluids in seconds. Medulloblastoma patients are differentiated from healthy controls with average diagnostic sensitivity of 94.0%, specificity of 85.7%, and accuracy of 89.9%, by machine learning of metabolic fingerprinting. Furthermore, the radiotherapy process of patients is monitored and a preliminary panel of serum metabolite biomarkers is identified with gradual changes. This work will lead to the application-driven development of novel materials with tailored structural design and establishment of new protocols for precision medicine in near future.

Infiltrating immune cells are associated with radiosensitivity and favorable survival in head and neck cancer treated with definitive radiotherapy

OBJECTIVES

The aim of this study was to investigate the influence of CD4⁺, CD8⁺ and Forkhead box protein 3 (FoxP3⁺) tumor-infiltrating lymphocytes, as well as CD1a⁺ tumor-infiltrating dendritic cells on the radiosensitivity and survival of primarily chemoirradiated advanced head and neck squamous cell carcinomas.

STUDY DESIGN

Immunohistochemical staining for CD4, CD8, FoxP3 and CD1a was performed in 82 primarily chemoirradiated head and neck squamous cell carcinomas. Associations with clinicopathologic data, programmed cell death protein-1 (PD-1), programmed cell death ligand-1 (PD-L1), p16, radiation response, and survival were examined.

RESULTS

High CD4 expression was associated with complete response after radiation (P = .006) and high CD1a expression (P = .024). High CD8⁺ tumor-infiltrating lymphocyte counts were associated with absence of tumor relapse (P = .032) and better disease-free survival (P = .051). Strong overall T-cell infiltration was found more often in tumors with high-grade differentiation (P = .004), complete response after radiation (P = .022), and better overall survival and disease-specific survival (each P = .052). Tumors with high FoxP3⁺ T regulatory (T_reg) infiltration more often showed high-grade tumor differentiation (P = .017), advanced patient age (P = .02), high PD-1 (P = .007), high CD4 (P = .002), and high CD8 expression (P = .002), as well as better disease-free survival (P = .019).

CONCLUSIONS

T-cell activation (high CD4, CD8 and FoxP3 expression) is associated with radio response and favorable survival in advanced head and neck cancer treated with definitive chemoradiation.

Impact of adjuvant radiotherapy on the survival of women with optimally resected stage III endometrial cancer in the era of modern radiotherapy: a retrospective study

Background

The optimal adjuvant treatment for stage III endometrial cancer in the era of modern radiotherapy remains undefined. We investigated the benefit of adjuvant radiotherapy for women who underwent optimal resection for stage III endometrial cancer in the era of modern radiotherapy.

Methods

We retrospectively reviewed patients with endometrial cancer who were treated between 2010 and 2018. Adjuvant treatment included radiotherapy by modern radiotherapy techniques (intensity-modulated or volumetric modulated arc radiotherapy), chemotherapy, or both. Recurrence-free survival (RFS) and overall survival (OS) were calculated using the Kaplan-Meier method and analyzed via multivariate Cox proportional hazards models.

Results

One hundred sixty-one patients were initially included (52, 9, and 100 with stages IIIA, IIIB, and IIIC cancer, respectively); 154 patients (96%) received adjuvant therapy. Such adjuvant treatment was associated with improved RFS (p = 0.014) and OS (p = 0.044) over surgery alone. Adjuvant radiotherapy by modern radiotherapy techniques led to low incidence of acute (25%) and chronic (7%) grade ≥ 2 gastrointestinal toxicity. On univariate analysis, non-endometrioid histology and grade 3 status were associated with higher risks of tumor recurrence and death, whereas adjuvant radiotherapy alone or in combination chemotherapy reduced their risks. On multivariate analysis, non-endometrioid histology was associated with increased recurrence (hazard ratio [HR], 2.95; p = 0.009), whereas adjuvant radiotherapy alone or with chemotherapy was associated with lower recurrence (HR, 0.62; p = 0.042). Patients > 60 years of age (p = 0.038) as well as those with endometrioid histology (p = 0.045), lymphovascular space invasion (p = 0.031), and ≥ 2 positive lymph nodes (p = 0.044) benefited most from adjuvant radiotherapy.

Conclusions

Modern adjuvant radiotherapy (intensity-modulated or volumetric modulated arc radiotherapy) alone or with chemotherapy should be considered for women with optimally resected stage III endometrial cancer.

Trial registration

ClinicalTrials.gov, NCT04251676. Registered 24 January 2020. Retrospectively registered.

DNA Strand Break Properties of Protoporphyrin IX by X-Ray Irradiation against Melanoma

Recent reports have suggested that 5-aminolevulinic acid (5-ALA), which is a precursor to protoporphyrin IX (PpIX), leads to selective accumulation of PpIX in tumor cells and acts as a radiation sensitizer in vitro and in vivo in mouse models of melanoma, glioma, and colon cancer. In this study, we investigated the effect of PpIX under X-ray irradiation through ROS generation and DNA damage. ROS generation by the interaction between PpIX and X-ray was evaluated by two kinds of probes, 3′-(p-aminophenyl) fluorescein (APF) for hydroxyl radical (•OH) detection and dihydroethidium (DHE) for superoxide (O₂^•-). •OH showed an increase, regardless of the dissolved oxygen. Meanwhile, the increase in O₂^•- was proportional to the dissolved oxygen. Strand breaks (SBs) of DNA molecule were evaluated by gel electrophoresis, and the enhancement of SBs was observed by PpIX treatment. We also studied the effect of PpIX for DNA damage in cells by X-ray irradiation using a B16 melanoma culture. X-ray irradiation induced γH2AX, DNA double-strand breaks (DSBs) in the context of chromatin, and affected cell survival. Since PpIX can enhance ROS generation even in a hypoxic state and induce DNA damage, combined radiotherapy treatment with 5-ALA is expected to improve therapeutic efficacy for radioresistant tumors.

Platelet-Activating Factor as an Effector for Environmental Stressors

Environmental stressors exert a profound effect on humans. Many environmental stressors have in common the ability to induce reactive oxygen species. The goal of this chapter is to present evidence that the potent lipid mediator platelet-activating factor (PAF) is involved in the effects of many stressors ranging from cigarette smoke to ultraviolet B radiation. These environmental stressors can generate PAF enzymatically as well as PAF-like lipids produced by free radical-mediated attack of glycerophosphocholines. Inasmuch as PAF exerts both acute inflammation and delayed immunosuppressive effects, involvement of the PAF system can provide an explanation for many consequences of environmental stressor exposures.

Exploring the Molecular Mechanisms Underlying the in vitro Anticancer Effects of Multitarget-Directed Hydrazone Ruthenium(II)-Arene Complexes

The molecular targets and the modes of action behind the cytotoxicity of two structurally established N,O- or N,N-hydrazone ruthenium(II)-arene complexes were explored in human breast adenocarcinoma cells (MCF-7) and paralleled in non-cancerous and cisplatin-resistant counterparts (MCF-10A and MCF-7CR respectively). Both complexes, [Ru(hmb)(L1)Cl] (1, L1=4-((2-(2,4-dinitrophenyl)hydrazono)(phenyl)methyl)-3-methyl-1-phenyl-1H-pyrazol-5-olate) and [Ru(cym)(L2)Cl] (2, L2=1-((3-methyl-5-oxo-1-phenyl-1H-pyrazol-4(5H)-ylidene)(phenyl)methyl)-2-(pyridin-2-yl)hydrazin-1-ide), reversibly interact with moderate-to-high affinity with a number of molecular targets in cell-free assays, namely serum albumin, DNA, the 20S proteasome and hydroxymethylglutaryl-CoA reductase. Most interestingly, only 2 readily crosses the cell membrane and preserves its binding/modulatory ability toward the targets of interest upon rapid cellular internalization. The resulting action at multiple levels of the cancer cascade is likely the cause for the selective sensitization of tumour cells to p27-mediated apoptotic death, and for the ability of 2 to overcome the drug resistance problem.

N-Dihydrogalactochitosan Potentiates the Radiosensitivity of Liver Metastatic Tumor Cells Originated from Murine Breast Tumors

Radiation is a widely used therapeutic method for treating breast cancer. N-dihydrogalactochitosan (GC), a biocompatible immunostimulant, is known to enhance the effects of various treatment modalities in different tumor types. However, whether GC can enhance the radiosensitivity of cancer cells remains to be explored. In this study, triple-negative murine 4T1 breast cancer cells transduced with multi-reporter genes were implanted in immunocompetent Balb/C mice to track, dissect, and identify liver-metastatic 4T1 cells. These cells expressed cancer stem cell (CSC) -related characteristics, including the ability to form spheroids, the expression of the CD44 marker, and the increase of protein stability. We then ex vivo investigated the potential effect of GC on the radiosensitivity of the liver-metastatic 4T1 breast cancer cells and compared the results to those of parental 4T1 cells subjected to the same treatment. The cells were irradiated with increased doses of X-rays with or without GC treatment. Colony formation assays were then performed to determine the survival fractions and radiosensitivity of these cells. We found that GC preferably increased the radiosensitivity of liver-metastatic 4T1 breast cancer cells rather than that of the parental cells. Additionally, the single-cell DNA electrophoresis assay (SCDEA) and γ-H2AX foci assay were performed to assess the level of double-stranded DNA breaks (DSBs). Compared to the parental cells, DNA damage was significantly increased in liver-metastatic 4T1 cells after they were treated with GC plus radiation. Further studies on apoptosis showed that this combination treatment increased the sub-G1 population of cells, but not caspase-3 cleavage, in liver-metastatic breast cancer cells. Taken together, the current data suggest that the synergistic effects of GC and irradiation might be used to enhance the efficacy of radiotherapy in treating metastatic tumors.

Quantum-inspired algorithm for radiotherapy planning optimization

PURPOSE

Modern inverse radiotherapy treatment planning requires nonconvex, large-scale optimizations that must be solved within a clinically feasible timeframe. We have developed and tested a quantum-inspired, stochastic algorithm for intensity-modulated radiotherapy (IMRT): quantum tunnel annealing (QTA). By modeling the likelihood probability of accepting a higher energy solution after a particle tunneling through a potential energy barrier, QTA features an additional degree of freedom (the barrier width, w) not shared by traditional stochastic optimization methods such as Simulated Annealing (SA). This additional degree of freedom can improve convergence rates and achieve a more efficient and, potentially, effective treatment planning process.

METHODS

To analyze the character of the proposed QTA algorithm, we chose two stereotactic body radiation therapy (SBRT) liver cases of variable complexity. The "easy" first case was used to confirm functionality, while the second case, with a more challenging geometry, was used to characterize and evaluate the QTA algorithm performance. Plan quality was assessed using dose-volume histogram-based objectives and dose distributions. Due to the stochastic nature of the solution search space, extensive tests were also conducted to determine the optimal smoothing technique, ensuring balance between plan deliverability and the resulting plan quality. QTA convergence rates were investigated in relation to the chosen barrier width function, and QTA and SA performances were compared regarding sensitivity to the choice of solution initializations, annealing schedules, and complexity of the dose-volume constraints. Finally, we investigated the extension from beamlet intensity optimization to direct aperture optimization (DAO). Influence matrices were calculated using the Eclipse scripting application program interface (API), and the optimizations were run on the University of Michigan's high-performance computing cluster, Flux.

RESULTS

Our results indicate that QTA's barrier-width function can be tuned to achieve faster convergence rates. The QTA algorithm reached convergence up to 46.6% faster than SA for beamlet intensity optimization and up to 26.8% faster for DAO. QTA and SA were ultimately found to be equally insensitive to the initialization process, but the convergence rate of QTA was found to be more sensitive to the complexity of the dose-volume constraints. The optimal smoothing technique was found to be a combination of a Laplace-of-Gaussian (LOG) edge-finding filter implemented as a penalty within the objective function and a two-dimensional Savitzky-Golay filter applied to the final iteration; this achieved total monitor units more than 20% smaller than plans optimized by commercial treatment planning software.

CONCLUSIONS

We have characterized the performance of a stochastic, quantum-inspired optimization algorithm, QTA, for radiotherapy treatment planning. This proof of concept study suggests that QTA can be tuned to achieve faster convergence than SA; therefore, QTA may be a good candidate for future knowledge-based or adaptive radiation therapy applications.

Apatinib potentiates irradiation effect via suppressing PI3K/AKT signaling pathway in hepatocellular carcinoma

Background

Limited effective intervention for advanced hepatocellular carcinoma (HCC) is available. This study aimed to investigate the potential clinical utility of apatinib, a highly selective inhibitor of the vascular endothelial growth factor receptor-2 (VEGFR2) tyrosine kinase, as a radiosensitizer in the treatment of HCC.

Methods

Four human HCC cell lines SMMC-7721, MHCC-97H, HCCLM3 and Hep-3B were treated with apatinib, irradiation or combination treatment. Colony formation assay, flow cytometry and nuclear γ-H2AX foci immunofluorescence staining were performed to evaluate the efficacy of combination treatment. RNA sequencing was conducted to explore the potential mechanism. The impact of combination treatment on tumor growth was assessed by xenograft mice models.

Results

Colony formation assay revealed that apatinib enhanced the radiosensitivity of HCC cell lines. Apatinib suppressed repair of radiation-induced DNA double-strand breaks. Flow cytometry analysis showed that apatinib increased radiation-induced apoptosis. Apatinib radiosensitized HCC via suppression of radiation-induced PI3K/AKT pathway. Moreover, an in vivo study indicated apatinib combined with irradiation significantly decreased xenograft tumor growth.

Conclusions

Our results indicate that apatinib has therapeutic potential as a radiosensitizer in HCC, and PI3K/AKT signaling pathway plays a critical role in mediating radiosensitization of apatinib.

Molecular imaging and radionuclide therapy of pheochromocytoma and paraganglioma in the era of genomic characterization of disease subgroups

In recent years, advancement in genetics has profoundly helped to gain a more comprehensive molecular, pathogenic, and prognostic picture of pheochromocytomas and paragangliomas (PPGLs). Newly discovered molecular targets, particularly those that target cell membranes or signaling pathways have helped move nuclear medicine in the forefront of PPGL precision medicine. This is mainly based on the introduction and increasing experience of various PET radiopharmaceuticals across PPGL genotypes quickly followed by implementation of novel radiotherapies and revised imaging algorithms. Particularly, 68Ga-labeled-SSAs have shown excellent results in the diagnosis and staging of PPGLs and in selecting patients for PRRT as a potential alternative to 123/131I-MIBG theranostics. PRRT using 90Y/177Lu-DOTA-SSAs has shown promise for treatment of PPGLs with improvement of clinical symptoms and/or disease control. However, more well-designed prospective studies are required to confirm these findings, in order to fully exploit PRRT's antitumoral properties to obtain the final FDA approval. Such an approval has recently been obtained for high-specific-activity 131I-MIBG for inoperable/metastatic PPGL. The increasing experience and encouraging preliminary results of these radiotherapeutic approaches in PPGLs now raises an important question of how to further integrate them into PPGL management (e.g. monotherapy or in combination with other systemic therapies), carefully taking into account the PPGLs locations, genotypes, and growth rate. Thus, targeted radionuclide therapy (TRT) should preferably be performed at specialized centers with an experienced interdisciplinary team. Future perspectives include the introduction of dosimetry and biomarkers for therapeutic responses for more individualized treatment plans, α-emitting isotopes, and the combination of TRT with other systemic therapies.

Identification and characterization of Cardiac Glycosides as senolytic compounds

Compounds with specific cytotoxic activity in senescent cells, or senolytics, support the causal involvement of senescence in aging and offer therapeutic interventions. Here we report the identification of Cardiac Glycosides (CGs) as a family of compounds with senolytic activity. CGs, by targeting the Na+/K+ATPase pump, cause a disbalanced electrochemical gradient within the cell causing depolarization and acidification. Senescent cells present a slightly depolarized plasma membrane and higher concentrations of H+, making them more susceptible to the action of CGs. These vulnerabilities can be exploited for therapeutic purposes as evidenced by the in vivo eradication of tumors xenografted in mice after treatment with the combination of a senogenic and a senolytic drug. The senolytic effect of CGs is also effective in the elimination of senescence-induced lung fibrosis. This experimental approach allows the identification of compounds with senolytic activity that could potentially be used to develop effective treatments against age-related diseases.

Senolytic compounds have the ability to eliminate senescent cells from tissues and have been shown to be beneficial in various animal models of age-related diseases. Here the authors show that cardiac glycosides commonly used for heart diseases have senolytic properties in humanized mouse models of tumorigenesis and lung fibrosis.

Characteristics of Radiotherapy Trials Compared With Other Oncological Clinical Trials in the Past 10 Years

Importance

Modern precision radiotherapy is an innovative and effective treatment of cancer, yet it is unclear how radiotherapy trials are affected by expanding targeted and immune therapies and declining National Institutes of Health funding.

Objective

To analyze and compare the characteristics of radiotherapy trials with other oncological trials registered on ClinicalTrials.gov.

Design, Setting, and Participants

This is a cross-sectional analysis of trials registered on ClinicalTrials.gov between June 1, 2007, and May 8, 2017. Records of all 243 758 clinical studies registered by May 8, 2017, were downloaded, but only 25 907 interventional oncological trials registered between June 1, 2007, and May 8, 2017, and whose primary purpose was "treatment" were included in the final analysis. Trials were categorized according to cancer type and other registration information.

Main Outcomes and Measures

Characteristics of radiotherapy trials were compared with characteristics of other oncological trials. Chronological shifts in radiotherapy trials were also analyzed.

Results

Of the 25 907 trials selected, 1378 (5.3%) were radiotherapy trials and 24 529 (94.7%) were other oncological studies. The number of radiotherapy trials increased gradually from 94 (June 1, 2007, through May 31, 2008) to 192 (June 1, 2015, through May 31, 2016). Radiotherapy trials were less likely than other oncological studies to be registered before participant enrollment (763 of 1370 [55.7%] vs 16 105 of 24 434 [65.9%]; P < .001), to be blinded (45 of 1378 [3.3%] vs 2784 of 24 529 [11.3%]; P < .001), or to involve multiple geographic regions (2.4% vs 9.5%; P < .001), but they were more likely to be phase 2 to 3 (773 of 1124 [68.8%] vs 12 910 of 22 300 [57.9%]; P < .001) and to have a data-monitoring committee (839 of 1264 [66.4%] vs 11 728 of 21 060 [55.7%]; P < .001). Only a minority of radiotherapy trials were industry sponsored, which was significantly lower than for other oncological trials (80 of 1378 [5.8%] vs 10 651 of 24 529 [43.4%]; P < .001; adjusted odds ratio, 0.08; 95% CI, 0.06-0.10). The number of National Institutes of Health-sponsored radiotherapy trials decreased from 80 of 544 trials (14.7%) from 2007 to 2012 to 72 of 834 trials (8.6%) from 2012 to 2017 (P < .001). Radiotherapy trials with a sample size of more than 100 patients decreased from 155 of 543 trials (28.5%) from 2007 to 2012 to 157 of 833 trials (18.8%) from 2012 to 2017 (P < .001).

Conclusions and Relevance

The limited number of and the scarcity of funding for radiotherapy trials is concerning given the integral role of radiotherapy in the clinical management of patients with cancer worldwide. A multidisciplinary collaboration to promote and fund more radiotherapy research is warranted.

Efficacy and Safety of Transarterial Chemoembolization Plus External Beam Radiotherapy vs Sorafenib in Hepatocellular Carcinoma With Macroscopic Vascular Invasion: A Randomized Clinical Trial

Importance

Patients with hepatocellular carcinoma showing macroscopic vascular invasion have a poor prognosis. Sorafenib is the sole treatment option for these patients, with unsatisfactory response and survival benefit. Combined treatment with transarterial chemoembolization (TACE) plus external beam radiotherapy (RT) has shown promising results for these patients in observational studies.

Objective

To evaluate the efficacy and safety of TACE plus RT compared with sorafenib for patients with hepatocellular carcinoma and macroscopic vascular invasion.

Design, Setting, and Participants

In this randomized, open-label clinical trial conducted at an academic tertiary care center between July 1, 2013, and October 31, 2016, 90 treatment-naive patients with liver-confined hepatocellular carcinoma showing macroscopic vascular invasion were randomly assigned to receive sorafenib (400 mg twice daily; 45 participants [the sorafenib group]) or TACE (every 6 weeks) plus RT (within 3 weeks after the first TACE, maximum 45 Gy with the fraction size of 2.5 to 3 Gy; 45 participants [the TACE-RT group]).

Main Outcomes and Measures

The primary end point was the 12-week progression-free survival rate by intention-to-treat analysis. Radiologic response was assessed by independent review according to the Response Evaluation Criteria in Solid Tumors (RECIST; version 1.1). Treatment crossover was permitted after confirming disease progression.

Results

Of the 90 patients (median age, 55 years; range, 33-82 years), 77 were men and 13 were women. All patients had portal vein invasion of hepatocellular carcinoma and Child-Pugh class A liver function. The median maximal tumor diameter was 9.7 cm. Most patients (71 [78.9%]) had multiple lesions. At week 12, the progression-free survival rate was significantly higher in the TACE-RT group than the sorafenib group (86.7% vs 34.3%; P < .001). The TACE-RT group showed a significantly higher radiologic response rate than the sorafenib group at 24 weeks (15 [33.3%] vs 1 [2.2%]; P < .001), a significantly longer median time to progression (31.0 vs 11.7 weeks; P < .001), and significantly longer overall survival (55.0 vs 43.0 weeks; P = .04). Curative surgical resection was conducted for 5 patients (11.1%) in the TACE-RT group owing to downstaging. No patients in the TACE-RT group discontinued treatment owing to hepatic decompensation.

Conclusions and Relevance

For patients with advanced hepatocellular carcinoma showing macroscopic vascular invasion, first-line treatment with TACE plus RT was well tolerated and provided an improved progression-free survival, objective response rate, time to progression, and overall survival compared with sorafenib treatment.

Trial Registration

clinicaltrials.gov Identifier: NCT01901692.

Efficacy of combined modality therapy with sorafenib following hepatic arterial injection chemotherapy and three-dimensional conformal radiotherapy for advanced hepatocellular carcinoma with major vascular invasion

The prognosis of hepatocellular carcinoma (HCC) patients exhibiting macroscopic vascular invasion (MVI) is poor, and the most appropriate treatment approach remains unclear. The current study aimed to investigate the efficacy and safety of sorafenib treatment following chemoradiotherapy for advanced HCC exhibiting MVI. A newly reported regimen, including 5-fluorouracil and cisplatin therapy (NewFP), plus three-dimensional conformal radiotherapy (3D-CRT) for MVI was used as the initial treatment. Additionally, sorafenib, as a secondary treatment, was administered after NewFP plus 3D-CRT for MVI. The present retrospective study enrolled patients with unresectable advanced HCC that was treated with NewFP plus 3D-CRT for MVI between January 2009 and December 2017. In total, 32 HCC patients with MVI were registered. Of these 32 patients, 18 were treated with NewFP plus 3D-CRT for MVI (NewFP + 3D-CRT group) and 14 were treated with sorafenib following NewFP plus 3D-CRT for MVI (sorafenib after NewFP + 3D-CRT group). The study endpoints were overall survival, overall response rate and disease control rate. Clinical factors influencing overall survival were identified using univariate and multivariate analyses. The median survival time in the NewFP + 3D-CRT group and sorafenib following NewFP + 3D-CRT group was 6.7 and 49.2 months, respectively (P=0.0003). For patients with advanced HCC exhibiting MVI, the initial treatment with NewFP plus 3D-CRT for MVI was well tolerated. The administration of sorafenib as the secondary treatment following NewFP plus 3D-CRT for MVI was associated with a significantly higher overall response rate, disease control rate and increased overall survival as compared with the NewFP plus 3D-CRT treatment.

Development of an anatomically correct mouse phantom for dosimetry measurement in small animal radiotherapy research

Significant improvements in radiotherapy are likely to come from biological rather than technical optimization, for example increasing tumour radiosensitivity via combination with targeted therapies. Such paradigms must first be evaluated in preclinical models for efficacy, and recent advances in small animal radiotherapy research platforms allow advanced irradiation protocols, similar to those used clinically, to be carried out in orthotopic models. Dose assessment in such systems is complex however, and a lack of established tools and methodologies for traceable and accurate dosimetry is currently limiting the capabilities of such platforms and slowing the clinical uptake of new approaches. Here we report the creation of an anatomically correct phantom, fabricated from materials with tissue-equivalent electron density, into which dosimetry detectors can be incorporated for measurement as part of quality control (QC). The phantom also allows training in preclinical radiotherapy planning and cross-institution validation of dose delivery protocols for small animal radiotherapy platforms without the need to sacrifice animals, with high reproducibility. Mouse CT data was acquired and segmented into soft tissue, bone and lung. The skeleton was fabricated using 3D printing, whilst lung was created using computer numerical control (CNC) milling. Skeleton and lung were then set into a surface-rendered mould and soft tissue material added to create a whole-body phantom. Materials for fabrication were characterized for atomic composition and attenuation for x-ray energies typically found in small animal irradiators. Finally cores were CNC milled to allow intracranial incorporation of bespoke detectors (alanine pellets) for dosimetry measurement.

Radiation induces apoptosis primarily through the intrinsic pathway in mammalian cells

Radiation-induced tumor cells death is the theoretical basis of tumor radiotherapy. Death signaling disorder is the most important factor for radioresistance. However, the signaling pathway(s) leading to radiation-triggered cell death is (are) still not completely known. To better understand the cell death signaling induced by radiation, the immortalized mouse embryonic fibroblast (MEF) deficient in "initiator" caspases, "effector" caspases or different Bcl-2 family proteins together with human colon carcinoma cell HCT116 were used. Our data indicated that radiation selectively induced the activation of caspase-9 and caspase-3/7 but not caspase-8 by triggering mitochondrial outer membrane permeabilization (MOMP). Importantly, the role of radiation in MOMP is independent of the activation of both "initiator" and "effector" caspases. Furthermore, both proapoptotic and antiapoptotic Bcl-2 family proteins were involved in radiation-induced apoptotic signaling. Overall, our study indicated that radiation specifically triggered the intrinsic apoptotic signaling pathway through Bcl-2 family protein-dependent mitochondrial permeabilization, which indicates targeting mitochondria is a promising strategy for cancer radiotherapy.

Safety of combining radiotherapy with immune-checkpoint inhibition

Immune-checkpoint inhibitors targeting cytotoxic T- lymphocyte antigen 4 (CTLA-4), programmed cell death protein 1 (PD-1), or programmed cell death 1 ligand 1 (PD-L1) have transformed the care of patients with a wide range of advanced-stage malignancies. More than half of these patients will also have an indication for treatment with radiotherapy. The effects of both radiotherapy and immune-checkpoint inhibition (ICI) involve a complex interplay with the innate and adaptive immune systems, and accumulating evidence suggests that, under certain circumstances, the effects of radiotherapy synergize with those of ICI to augment the antitumour responses typically observed with either modality alone and thus improve clinical outcomes. However, the mechanisms by which radiotherapy and immune-checkpoint inhibitors synergistically modulate the immune response might also affect both the type and severity of treatment-related toxicities. Moreover, in patients receiving immune-checkpoint inhibitors, the development of immune-related adverse events has been linked with superior treatment responses and patient survival durations, suggesting a relationship between the antitumour and adverse autoimmune effects of these agents. In this Review, we discuss the emerging data on toxicity profiles related to immune-checkpoint inhibitors and radiotherapy, both separately and in combination, their potential mechanisms, and the approaches to managing these toxicities.

Modeling long-term tumor growth and kill after combinations of radiation and radiosensitizing agents

PURPOSE

Radiation therapy, whether given alone or in combination with chemical agents, is one of the cornerstones of oncology. We develop a quantitative model that describes tumor growth during and after treatment with radiation and radiosensitizing agents. The model also describes long-term treatment effects including tumor regrowth and eradication.

METHODS

We challenge the model with data from a xenograft study using a clinically relevant administration schedule and use a mixed-effects approach for model-fitting. We use the calibrated model to predict exposure combinations that result in tumor eradication using Tumor Static Exposure (TSE).

RESULTS

The model is able to adequately describe data from all treatment groups, with the parameter estimates taking biologically reasonable values. Using TSE, we predict the total radiation dose necessary for tumor eradication to be 110 Gy, which is reduced to 80 or 30 Gy with co-administration of 25 or 100 mg kg^-1 of a radiosensitizer. TSE is also explored via a heat map of different growth and shrinkage rates. Finally, we discuss the translational potential of the model and TSE concept to humans.

CONCLUSIONS

The new model is capable of describing different tumor dynamics including tumor eradication and tumor regrowth with different rates, and can be calibrated using data from standard xenograft experiments. TSE and related concepts can be used to predict tumor shrinkage and eradication, and have the potential to guide new experiments and support translations from animals to humans.

How rapid advances in imaging are defining the future of precision radiation oncology

Imaging has an essential role in the planning and delivery of radiotherapy. Recent advances in imaging have led to the development of advanced radiotherapy techniques—including image-guided radiotherapy, intensity-modulated radiotherapy, stereotactic body radiotherapy and proton beam therapy. The optimal use of imaging might enable higher doses of radiation to be delivered to the tumour, while sparing normal surrounding tissues. In this article, we review how the integration of existing and novel forms of computed tomography, magnetic resonance imaging and positron emission tomography have transformed tumour delineation in the radiotherapy planning process, and how these advances have the potential to allow a more individualised approach to the cancer therapy. Recent data suggest that imaging biomarkers that assess underlying tumour heterogeneity can identify areas within a tumour that are at higher risk of radio-resistance, and therefore potentially allow for biologically focussed dose escalation. The rapidly evolving concept of adaptive radiotherapy, including artificial intelligence, requires imaging during treatment to be used to modify radiotherapy on a daily basis. These advances have the potential to improve clinical outcomes and reduce radiation-related long-term toxicities. We outline how recent technological advances in both imaging and radiotherapy delivery can be combined to shape the future of precision radiation oncology.

Biological effects in normal cells exposed to FLASH dose rate protons

BACKGROUND

Radiotherapy outcomes are limited by toxicity in the healthy tissues surrounding the irradiated tumor. Recent pre-clinical studies have shown that irradiations with electrons or photons delivered at so called FLASH dose rates (i.e. >40 Gy/s) dramatically reduce adverse side effects in the normal tissues while being equally efficient for tumor control as irradiations at conventional dose rates (3-5 cGy/s). In the case of protons however, FLASH effects have not been investigated partially because of the limited availability of facilities that can achieve such high dose rates.

METHODS

Using a novel irradiation platform, we measured acute and long-term biological effects in normal human lung fibroblasts (IMR90) exposed to therapeutically relevant doses of 4.5 MeV protons (LET = 10 keV/µm) delivered at dose rates spanning four orders of magnitude. Endpoints included clonogenic cell survival, γH2AX foci formation, induction of premature senescence (β-gal), and the expression of the pro-inflammatory marker TGFβ.

RESULTS

Proton dose rate had no influence on the cell survival, but for the highest dose rate used (i.e. 1000 Gy/s) foci formation saturated beyond 10 Gy. In the progeny of irradiated cells, an increase in dose (20 Gy vs. 10 Gy) and dose rate (1000 Gy/s vs. 0.05 Gy/s) positively affected the number of senescence cells and the expression of TGFβ1.

CONCLUSIONS

In normal lung fibroblasts proton dose rate had little impact on acute effects, but significantly influenced the expression of long-term biological responses in vitro. Compared to conventional dose rates, protons delivered at FLASH dose rates mitigated such delayed detrimental effects.

Radiotherapy toxicity

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

Late effects of total body irradiation on hematopoietic recovery and immune function in rhesus macaques

While exposure to radiation can be lifesaving in certain settings, it can also potentially result in long-lasting adverse effects, particularly to hematopoietic and immune cells. This study investigated hematopoietic recovery and immune function in rhesus macaques Cross-sectionally (at a single time point) 2 to 5 years after exposure to a single large dose (6.5 to 8.4 Gray) of total body radiation (TBI) derived from linear accelerator-derived photons (2 MeV, 80 cGy/minute) or Cobalt 60-derived gamma irradiation (60 cGy/min). Hematopoietic recovery was assessed through measurement of complete blood counts, lymphocyte subpopulation analysis, and thymus function assessment. Capacity to mount specific antibody responses against rabies, Streptococcus pneumoniae, and tetanus antigens was determined 2 years after TBI. Irradiated macaques showed increased white blood cells, decreased platelets, and decreased frequencies of peripheral blood T cells. Effects of prior radiation on production and export of new T cells by the thymus was dependent on age at the time of analysis, with evidence of interaction with radiation dose for CD8+ T cells. Irradiated and control animals mounted similar mean antibody responses to proteins from tetanus and rabies and to 10 of 11 serotype-specific pneumococcal polysaccharides. However, irradiated animals uniformly failed to make antibodies against polysaccharides from serotype 5 pneumococci, in contrast to the robust responses of non-irradiated controls. Trends toward decreased serum levels of anti-tetanus IgM and slower peak antibody responses to rabies were also observed. Taken together, these data show that dose-related changes in peripheral blood cells and immune responses to both novel and recall antigens can be detected 2 to 5 years after exposure to whole body radiation. Longer term follow-up data on this cohort and independent validation will be helpful to determine whether these changes persist or whether additional changes become evident with increasing time since radiation, particularly as animals begin to develop aging-related changes in immune function.

Proton therapy for prostate cancer: A review of the rationale, evidence, and current state

Men diagnosed with localized prostate cancer have many curative treatment options including several different radiotherapeutic approaches. Proton radiation is one such radiation treatment modality and, due to its unique physical properties, offers the appealing potential of reduced side effects without sacrificing cancer control. In this review, we examine the intriguing dosimetric rationale and theoretical benefit of proton radiation for prostate cancer and highlight the results of preclinical modeling studies. We then discuss the current state of the clinical evidence for proton efficacy and toxicity, derived from both large claim-based datasets and prospective patient-reported data. The result is that the data are mixed, and clinical equipoise persists in this area. We place these studies into context by summarizing the economics of proton therapy and the changing practice patterns of prostate proton irradiation. Finally, we await the results of a large prospective randomized clinical trial currently accruing and also a large prospective pragmatic comparative study which will provide more rigorous evidence regarding the clinical and comparative effectiveness of proton therapy for prostate cancer.

Role and future of MRI in radiation oncology

Technical innovations and developments in areas such as disease localization, dose calculation algorithms, motion management and dose delivery technologies have revolutionized radiation therapy resulting in improved patient care with superior outcomes. A consequence of the ability to design and accurately deliver complex radiation fields is the need for improved target visualization through imaging. While CT imaging has been the standard of care for more than three decades, the superior soft tissue contrast afforded by MR has resulted in the adoption of this technology in radiation therapy. With the development of real time MR imaging techniques, the problem of real time motion management is enticing. Currently, the integration of an MR imaging and megavoltage radiation therapy treatment delivery system (MR-linac or MRL) is a reality that has the potential to provide improved target localization and real time motion management during treatment. Higher magnetic field strengths provide improved image quality potentially providing the backbone for future work related to image texture analysis-a field known as Radiomics-thereby providing meaningful information on the selection of future patients for radiation dose escalation, motion-managed treatment techniques and ultimately better patient care. On-going advances in MRL technologies promise improved real time soft tissue visualization, treatment margin reductions, beam optimization, inhomogeneity corrected dose calculation, fast multileaf collimators and volumetric arc radiation therapy. This review article provides rationale, advantages and disadvantages as well as ideas for future research in MRI related to radiation therapy mainly in adoption of MRL.

Velocity-based Adaptive Registration and Fusion for Fractionated Stereotactic Radiosurgery Using the Small Animal Radiation Research Platform

PURPOSE

To implement Velocity-based image fusion and adaptive deformable registration to enable treatment planning for preclinical murine models of fractionated stereotactic radiosurgery (fSRS) using the small animal radiation research platform (SARRP).

METHODS AND MATERIALS

C57BL6 mice underwent 3 unique cone beam computed tomography (CBCT) scans: 2 in the prone position and a third supine. A single T1-weighted post-contrast magnetic resonance imaging (MRI) series of a murine metastatic brain tumor model was selected for MRI-to-CBCT registration and gross tumor volume (GTV) identification. Two arms were compared: Arm 1, where we performed 3 individual MRI-to-CBCT fusions using rigid registration, contouring GTVs on each, and Arm 2, where the authors performed MRI-to-CBCT fusion and contoured GTV on the first CBCT followed by Velocity-based adaptive registration. The first CBCT and associated GTV were exported from MuriPlan (Xstrahl Life Sciences) into Velocity (Varian Medical Systems, Inc, Palo Alto, CA). In Arm 1, the second and third CBCTs were exported similarly along with associated GTVs (Arm 1), while in Arm 2, the first (prone) CBCT was fused separately to the second (prone) and third (supine) CBCTs, performing deformable registrations on initial CBCTs and applying resulting matrices to the contoured GTV. Resulting GTVs were compared between Arms 1 and 2.

RESULTS

Comparing GTV overlays using repeated MRI fusion and GTV delineation (Arm 1) versus those of Velocity-based CBCT and GTV adaptive fusion (Arm 2), mean deviations ± standard deviation in the axial, sagittal, and coronal planes were 0.46 ± 0.16, 0.46 ± 0.22, and 0.37 ± 0.22 mm for prone-to-prone and 0.52 ± 0.27, 0.52 ± 0.36, and 0.68 ± 0.31 mm for prone-to-supine adaptive fusions, respectively.

CONCLUSIONS

Velocity-based adaptive fusion of CBCTs and contoured volumes allows for efficient fSRS planning using a single MRI-to-CBCT fusion. This technique is immediately implementable on current SARRP systems, facilitating advanced preclinical treatment paradigms using existing clinical treatment planning software.

Novel biological strategies to enhance the radiation therapeutic ratio

Successful anticancer strategies require a differential response between tumor and normal tissue (i.e., a therapeutic ratio). In fact, improving the effectiveness of a cancer therapeutic is of no clinical value in the absence of a significant increase in the differential response between tumor and normal tissue. Although radiation dose escalation with the use of intensity modulated radiation therapy has permitted the maximum tolerable dose for most locally advanced cancers, improvements in tumor control without damaging normal adjacent tissues are needed. As a means of increasing the therapeutic ratio, several new approaches are under development. Drugs targeting signal transduction pathways in cancer progression and more recently, immunotherapeutics targeting specific immune cell subsets have entered the clinic with promising early results. Radiobiological research is underway to address pressing questions as to the dose per fraction, irradiated tumor volume and time sequence of the drug administration. To exploit these exciting novel strategies, a better understanding is needed of the cellular and molecular pathways responsible for both cancer and normal tissue and organ response, including the role of radiation-induced accelerated senescence. This review will highlight the current understanding of promising biologically targeted therapies to enhance the radiation therapeutic ratio.

Impact of early life exposure to ionizing radiation on influenza vaccine response in an elderly Japanese cohort

The objective of this study was to evaluate effects of whole body radiation exposure early in life on influenza vaccination immune responses much later in life. A total of 292 volunteers recruited from the cohort members of ongoing Adult Health Study (AHS) of Japanese atomic bomb (A-bomb) survivors completed this observational study spanning two influenza seasons (2011-2012 and 2012-2013). Peripheral blood samples were collected prior to and three weeks after vaccination. Serum hemagglutination inhibition (HAI) antibody titers were measured as well as concentrations of 25 cytokines and chemokines in culture supernatant from peripheral blood mononuclear cells, with and without in vitro stimulation with influenza vaccine. We found that influenza vaccination modestly enhanced serum HAI titers in this unique cohort of elderly subjects, with seroprotection ranging from 18 to 48% for specific antigen/season combinations. Twelve percent of subjects were seroprotected against all three vaccine antigens post-vaccination. Males were generally more likely to be seroprotected for one or more antigens post-vaccination, with no differences in vaccine responses based on age at vaccination or radiation exposure in early life. These results show that early life exposure to ionizing radiation does not prevent responses of elderly A-bomb survivors to seasonal influenza vaccine.

Emerging role of MRI in radiation therapy

Advances in multimodality imaging, providing accurate information of the irradiated target volume and the adjacent critical structures or organs at risk (OAR), has made significant improvements in delivery of the external beam radiation dose. Radiation therapy conventionally has used computed tomography (CT) imaging for treatment planning and dose delivery. However, magnetic resonance imaging (MRI) provides unique advantages: added contrast information that can improve segmentation of the areas of interest, motion information that can help to better target and deliver radiation therapy, and posttreatment outcome analysis to better understand the biologic effect of radiation. To take advantage of these and other potential advantages of MRI in radiation therapy, radiologists and MRI physicists will need to understand the current radiation therapy workflow and speak the same language as our radiation therapy colleagues. This review article highlights the emerging role of MRI in radiation dose planning and delivery, but more so for MR-only treatment planning and delivery. Some of the areas of interest and challenges in implementing MRI in radiation therapy workflow are also briefly discussed. Level of Evidence: 5 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2018;48:1468-1478.

Combined external beam radiotherapy with carbon ions and tumor targeting endoradiotherapy

External beam radiotherapy (EBRT) with carbon ions and endoradiotherapy using radiolabeled tumor targeting agents are emerging concepts in precision cancer therapy. We report on combination effects of these two promising strategies.

Tumor targeting ¹³¹I-labelled anti-EGFR-antibody (Cetuximab) was used in the prototypic EGFR-expressing A431 human squamous cell carcinoma xenograft model. A ¹³¹I-labelled melanin-binding benzamide derivative was utilized targeting B16F10 melanoma in an orthotopic syngeneic C57bl6 model. Fractionated EBRT was performed using carbon ions in direct comparison with conventional photon irradiation.

Tumor uptake of ¹³¹I-Cetuximab and ¹³¹I-Benzamide was enhanced by fractionated EBRT as determined by biodistribution studies. This effect was independent of radiation quality and significant for the small molecule ¹³¹I-Benzamide, i.e., >30% more uptake in irradiated vs. non-irradiated melanoma was found (p<0.05). Compared to each monotherapy, dual combination with ¹³¹I-Cetuximab and EBRT was most effective in inhibiting A431 tumor growth. A similar trend was seen for ¹³¹I-Benzamide and EBRT in B16F10 melanoma model. Addition of ¹³¹I-Benzamide endoradiotherapy to EBRT altered expression of genes related to DNA-repair, cell cycle and cell death. In contrast, immune-response related pathways such as type 1 interferon response genes (ISG15, MX1) were predominantly upregulated after combined ¹³¹I-Cetuximab and EBRT. The beneficial effects of combined 131I-Cetuximab and EBRT was further attributed to a reduced microvascular density (CD31) and decreased proliferation index (Ki-67).

Fractionated EBRT could be favorably combined with endoradiotherapy. ¹³¹I-Benzamide endoradiotherapy accelerated EBRT induced cytotoxic effects. Activation of immune-response by carbon ions markedly enhanced anti-EGFR based endoradiotherapy suggesting further evaluation of this novel and promising radioimmunotherapy concept.

Rapid expansion in the WAVE bioreactor of clinical scale cells for tumor immunotherapy

Cell-based immunotherapy using natural killer (NK) cells, cytokine-induced killer (CIK) cells and dendritic cells (DCs) is emerging as a potential novel approach in the auxiliary treatment of a tumor. However, non-standard operation procedure, small-scale cell number, or human error may limit the clinical development of cell-based immunotherapy. To simplify clinical scale NK cells, CIK cells and DCs expansions, we investigated the use of the WAVE bioreactor, a closed system bioreactor that utilizes active perfusion to generate high cell numbers in minimal volumes. We developed an optimized rapid expansion protocol for the WAVE bioreactor that produces clinically relevant number of cells for our adoptive cell transfer clinical protocols. The high proliferative rate, surface phenotypes, and cytotoxicity of these immune cells, as well as the safety of cultivation were analyzed to illuminate the effect of WAVE bioreactor. The results demonstrated that the benefit of utilizing modern WAVE bioreactors in cancer immunotherapy was simple, safe, and flexible production.