Evofosfamide sensitizes esophageal carcinomas to radiation without increasing normal tissue toxicity

18F-Fluoroazomycin Arabinoside (FAZA) PET/MR as a Biomarker of Hypoxia in Rectal Cancer: A Pilot Study

Tumor hypoxia is a negative prognostic factor in many tumors and is predictive of metastatic spread and poor responsiveness to both chemotherapy and radiotherapy. Purpose: To assess the feasibility of using 18F-Fluoroazomycin arabinoside (FAZA) PET/MR to image tumor hypoxia in patients with locally advanced rectal cancer (LARC) prior to and following neoadjuvant chemoradiotherapy (nCRT). The secondary objective was to compare different reference tissues and thresholds for tumor hypoxia quantification. Patients and Methods: Eight patients with histologically proven LARC were included. All patients underwent 18F-FAZA PET/MR prior to initiation of nCRT, four of whom also had a second scan following completion of nCRT and prior to surgery. Tumors were segmented using T2-weighted MR. Each voxel within the segmented tumor was defined as hypoxic or oxic using thresholds derived from various references: ×1.0 or ×1.2 SUVmean of blood pool [BP] or left ventricle [LV] and SUVmean +3SD for gluteus maximus. Correlation coefficient (CoC) between HF and tumor SUVmax/reference SUVmean TRR for the various thresholds was calculated. Hypoxic fraction (HF), defined as the % hypoxic voxels within the tumor volume was calculated for each reference/threshold. Results: For all cases, baseline and follow-up, the CoCs for gluteus maximus and for BP and LV (×1.0) were 0.241, 0.344, and 0.499, respectively, and HFs were (median; range) 16.6% (2.4-33.8), 36.8% (0.3-72.9), and 30.7% (0.8-55.5), respectively. For a threshold of ×1.2, the CoCs for BP and LV as references were 0.611 and 0.838, respectively, and HFs were (median; range) 10.4% (0-47.6), and 4.3% (0-20.1%), respectively. The change in HF following nCRT ranged from (-18.9%) to (+54%). Conclusions: Imaging of hypoxia in LARC with 18F-FAZA PET/MR is feasible. Blood pool as measured in the LV appears to be the most reliable reference for calculating the HF. There is a wide range of HF and variable change in HF before and after nCRT.

Characterisation of quantitative imaging biomarkers for inflammatory and fibrotic radiation-induced lung injuries using preclinical radiomics

BACKGROUND AND PURPOSE

Radiomics is a rapidly evolving area of research that uses medical images to develop prognostic and predictive imaging biomarkers. In this study, we aimed to identify radiomics features correlated with longitudinal biomarkers in preclinical models of acute inflammatory and late fibrotic phenotypes following irradiation.

MATERIALS AND METHODS

Female C3H/HeN and C57BL6 mice were irradiated with 20 Gy targeting the upper lobe of the right lung under cone-beam computed tomography (CBCT) image-guidance. Blood samples and lung tissue were collected at baseline, weeks 1, 10 & 30 to assess changes in serum cytokines and histological biomarkers. The right lung was segmented on longitudinal CBCT scans using ITK-SNAP. Unfiltered and filtered (wavelet) radiomics features (n = 842) were extracted using PyRadiomics. Longitudinal changes were assessed by delta analysis and principal component analysis (PCA) was used to remove redundancy and identify clustering. Prediction of acute (week 1) and late responses (weeks 20 & 30) was performed through deep learning using the Random Forest Classifier (RFC) model.

RESULTS

Radiomics features were identified that correlated with inflammatory and fibrotic phenotypes. Predictive features for fibrosis were detected from PCA at 10 weeks yet overt tissue density was not detectable until 30 weeks. RFC prediction models trained on 5 features were created for inflammation (AUC 0.88), early-detection of fibrosis (AUC 0.79) and established fibrosis (AUC 0.96).

CONCLUSIONS

This study demonstrates the application of deep learning radiomics to establish predictive models of acute and late lung injury. This approach supports the wider application of radiomics as a non-invasive tool for detection of radiation-induced lung complications.

Predicting response to combination evofosfamide and immunotherapy under hypoxic conditions in murine models of colon cancer

The goal of this study is to develop a mathematical model that captures the interaction between evofosfamide, immunotherapy, and the hypoxic landscape of the tumor in the treatment of tumors. Recently, we showed that evofosfamide, a hypoxia-activated prodrug, can synergistically improve treatment outcomes when combined with immunotherapy, while evofosfamide alone showed no effects in an in vivo syngeneic model of colorectal cancer. However, the mechanisms behind the interaction between the tumor microenvironment in the context of oxygenation (hypoxic, normoxic), immunotherapy, and tumor cells are not fully understood. To begin to understand this issue, we develop a system of ordinary differential equations to simulate the growth and decline of tumors and their vascularization (oxygenation) in response to treatment with evofosfamide and immunotherapy (6 combinations of scenarios). The model is calibrated to data from in vivo experiments on mice implanted with colon adenocarcinoma cells and longitudinally imaged with [18F]-fluoromisonidazole ([18F]FMISO) positron emission tomography (PET) to quantify hypoxia. The results show that evofosfamide is able to rescue the immune response and sensitize hypoxic tumors to immunotherapy. In the hypoxic scenario, evofosfamide reduces tumor burden by $ 45.07 \pm 2.55 $%, compared to immunotherapy alone, as measured by tumor volume. The model accurately predicts the temporal evolution of five different treatment scenarios, including control, hypoxic tumors that received immunotherapy, normoxic tumors that received immunotherapy, evofosfamide alone, and hypoxic tumors that received combination immunotherapy and evofosfamide. The average concordance correlation coefficient (CCC) between predicted and observed tumor volume is $ 0.86 \pm 0.05 $. Interestingly, the model values to fit those five treatment arms was unable to accurately predict the response of normoxic tumors to combination evofosfamide and immunotherapy (CCC = $ -0.064 \pm 0.003 $). However, guided by the sensitivity analysis to rank the most influential parameters on the tumor volume, we found that increasing the tumor death rate due to immunotherapy by a factor of $ 18.6 \pm 9.3 $ increases CCC of $ 0.981 \pm 0.001 $. To the best of our knowledge, this is the first study to mathematically predict and describe the increased efficacy of immunotherapy following evofosfamide.

Overcoming radioresistance with the hypoxia-activated prodrug CP-506: A pre-clinical study of local tumour control probability

BACKGROUND AND PURPOSE

Tumour hypoxia is an established radioresistance factor. A novel hypoxia-activated prodrug CP-506 has been proven to selectively target hypoxic tumour cells and to cause anti-tumour activity. The current study investigates whether CP-506 improves outcome of radiotherapy in vivo.

MATERIALS AND METHODS

Mice bearing FaDu and UT-SCC-5 xenografts were randomized to receive 5 daily injections of CP-506/vehicle followed by single dose (SD) irradiation. In addition, CP-506 was combined once per week with fractionated irradiation (30 fractions/6 weeks). Animals were followed-up to score all recurrences. In parallel, tumours were harvested to evaluate pimonidazole hypoxia, DNA damage (γH2AX), expression of oxidoreductases.

RESULTS

CP-506 treatment significantly increased local control rate after SD in FaDu, 62% vs. 27% (p = 0.024). In UT-SCC-5, this effect was not curative and only marginally significant. CP-506 induced significant DNA damage in FaDu (p = 0.009) but not in UT- SCC-5. Hypoxic volume (HV) was significantly smaller (p = 0.038) after pretreatment with CP-506 as compared to vehicle in FaDu but not in less responsive UT-SCC-5. Adding CP-506 to fractionated radiotherapy in FaDu did not result in significant benefit.

CONCLUSION

The results support the use of CP-506 in combination with radiation in particular using hypofractionation schedules in hypoxic tumours. The magnitude of effect depends on the tumour model, therefore it is expected that applying appropriate patient stratification strategy will further enhance the benefit of CP-506 treatment for cancer patients. A phase I-IIA clinical trial of CP-506 in monotherapy or in combination with carboplatin or a checkpoint inhibitor has been approved (NCT04954599).

How the histological structure of some lung cancers shaped almost 70 years of radiobiology

Pivotal research led by Louis Harold Gray in the 1950s suggested that oxygen plays a vital role during radiotherapy. By proving that tumours have large necrotic cores due to hypoxia and that hypoxic cells require significantly larger doses of ionising radiation to achieve the same cell kill, Thomlinson and Gray inspired the subsequent decades of research into better defining the mechanistic role of molecular oxygen at the time of radiation. Ultimately, the work pioneered by Thomlinson and Gray led to numerous elegant studies which demonstrated that tumour hypoxia predicts for poor patient outcomes. Furthermore, this subsequently resulted in investigations into markers and measurement of hypoxia, as well as modification strategies. However, despite an abundance of pre-clinical data supporting hypoxia-targeted treatments, there is limited widespread application of hypoxia-targeted therapies routinely used in clinical practice. Significant contributing factors underpinning disappointing clinical trial results include the use of model systems which are more hypoxic than human tumours and a failure to stratify patients based on levels of hypoxia. However, translating the original findings of Thomlinson and Gray remains a research priority with the potential to significantly improve patient outcomes and specifically those receiving radiotherapy.

In Vivo Identification of Adducts from the New Hypoxia-Activated Prodrug CP-506 Using DNA Adductomics

Many chemotherapeutic drugs exert their cytotoxicity through the formation of DNA modifications (adducts), which interfere with DNA replication, an overactive process in rapidly dividing cancer cells. Side effects from the therapy are common, however, because these drugs also affect rapidly dividing noncancerous cells. Hypoxia-activated prodrugs (HAPs) have been developed to reduce these side effects as they preferentially activate in hypoxic environments, a hallmark of solid tumors. CP-506 is a newly developed DNA-alkylating HAP designed to exert strong activity under hypoxia. The resulting CP-506-DNA adducts can be used to elucidate the cellular and molecular effects of CP-506 and its selectivity toward hypoxic conditions. In this study, we characterize the profile of adducts resulting from the reaction of CP-506 and its metabolites CP-506H and CP-506M with DNA. A total of 39 putative DNA adducts were detected in vitro using our high-resolution/accurate-mass (HRAM) liquid chromatography tandem mass spectrometry (LC-MS³) adductomics approach. Validation of these results was achieved using a novel strategy involving ¹⁵N-labeled DNA. A targeted MS/MS approach was then developed for the detection of the 39 DNA adducts in five cancer cell lines treated with CP-506 under normoxic and hypoxic conditions to evaluate the selectivity toward hypoxia. Out of the 39 DNA adducts initially identified, 15 were detected, with more adducts observed from the two reactive metabolites and in cancer cells treated under hypoxia. The presence of these adducts was then monitored in xenograft mouse models bearing MDA-MB-231, BT-474, or DMS114 tumors treated with CP-506, and a relative quantitation strategy was used to compare the adduct levels across samples. Eight adducts were detected in all xenograft models, and MDA-MB-231 showed the highest adduct levels. These results suggest that CP-506-DNA adducts can be used to better understand the mechanism of action and monitor the efficacy of CP-506 in vivo, as well as highlight a new role of DNA adductomics in supporting the clinical development of DNA-alkylating drugs.

Inter-observer variability of organ contouring for preclinical studies with cone beam Computed Tomography imaging

Background and purpose

In preclinical radiation studies, there is great interest in quantifying the radiation response of healthy tissues. Manual contouring has significant impact on the treatment-planning because of variation introduced by human interpretation. This results in inconsistencies when assessing normal tissue volumes. Evaluation of these discrepancies can provide a better understanding on the limitations of the current preclinical radiation workflow. In the present work, interobserver variability (IOV) in manual contouring of rodent normal tissues on cone-beam Computed Tomography, in head and thorax regions was evaluated.

Materials and methods

Two animal technicians performed manually (assisted) contouring of normal tissues located within the thorax and head regions of rodents, 20 cases per body site. Mean surface distance (MSD), displacement of center of mass (ΔCoM), DICE similarity coefficient (DSC) and the 95th percentile Hausdorff distance (HD₉₅) were calculated between the contours of the two observers to evaluate the IOV.

Results

For the thorax organs, right lung had the lowest IOV (ΔCoM: 0.08 ± 0.04 mm, DSC: 0.96 ± 0.01, MSD:0.07 ± 0.01 mm, HD₉₅:0.20 ± 0.03 mm) while spinal cord, the highest IOV (ΔCoM:0.5 ± 0.3 mm, DSC:0.81 ± 0.05, MSD:0.14 ± 0.03 mm, HD₉₅:0.8 ± 0.2 mm). Regarding head organs, right eye demonstrated the lowest IOV (ΔCoM:0.12 ± 0.08 mm, DSC: 0.93 ± 0.02, MSD: 0.15 ± 0.04 mm, HD₉₅: 0.29 ± 0.07 mm) while complete brain, the highest IOV (ΔCoM: 0.2 ± 0.1 mm, DSC: 0.94 ± 0.02, MSD: 0.3 ± 0.1 mm, HD₉₅: 0.5 ± 0.1 mm).

Conclusions

Our findings reveal small IOV, within the sub-mm range, for thorax and head normal tissues in rodents. The set of contours can serve as a basis for developing an automated delineation method for e.g., treatment planning.

Improving therapeutic resistance: beginning with targeting the tumor microenvironment

Cancer is a serious threat to human health and life. The tumor microenvironment (TME) not only plays a key role in the occurrence, development and metastasis of cancer, but also has a profound impact on treatment resistance. To improve and solve this problem, an increasing number of strategies targeting the TME have been proposed, and great progress has been made in recent years. This article reviews the characteristics and functions of the main matrix components of the TME and the mechanisms by which each component affects drug resistance. Furthermore, this article elaborates on targeting the TME as a strategy to treat acquired drug resistance, reduce tumor metastasis, recurrence, and improve efficacy.

Antitumor effect of radiation therapy on orthotopic PDX models of human esophageal adenocarcinoma

As a rule, esophageal adenocarcinoma develops in the lower esophagus. Life expectancy and survival rates depend on the cancer stage and the general health of the patient. Chemoradiotherapy is the most successful treatment approach to this type of cancer. The choice of optimal radiation doses for achieving the best possible therapeutic effect is still a challenge. The aim of this paper was to study effective radiation doses and assess response of human esophageal adenocarcinoma to radiation using a PDX model. The study was conducted in female Balb/c nude mice (n = 25). Fragments of the donor tumor were implanted into the cervical esophagus of immunodeficient mice. Effects of radiation on the obtained orthotopic xenografts were studied after each of 3 irradiation sessions (4, 6, 8, and 10 Gy in each of the experimental groups, respectively). First-passage xenografts reproduced the morphology of the donor tumor. The mean tumor volume differed significantly between the control group and the experimental groups exposed to 6, 8 or 10 Gy (р ≤ 0.01) after each irradiation session. Tumor growth delay was significant after exposure to the total dose of 18 Gy. The further radiation dose increase was ineffective. The reduction of tumor volume in the xenografts was correlated to the increase in the one-time radiation dose. The total dose over 18 Gy produced a detrimental effect on the hematopoietic system and blood biochemistry of the experimental mice.

Hypoxia-activated KDAC inhibitor: Taking a breath from untargeted therapy

Use of hypoxia-activated prodrugs has emerged as a strategy for selectively targeting tumors in hypoxic conditions harboring reductive environments. In this issue of Cell Chemical Biology, Skwarska et al. (2021) report a hypoxia-activated prodrug targeting histone deacetylases (lysine deacetylases, KDACs) selectively over normoxic cells with activity in an animal model.

Targeting Hypoxia: Hypoxia-Activated Prodrugs in Cancer Therapy

Hypoxia is an important characteristic of most solid malignancies, and is closely related to tumor prognosis and therapeutic resistance. Hypoxia is one of the most important factors associated with resistance to conventional radiotherapy and chemotherapy. Therapies targeting tumor hypoxia have attracted considerable attention. Hypoxia-activated prodrugs (HAPs) are bioreductive drugs that are selectively activated under hypoxic conditions and that can accurately target the hypoxic regions of solid tumors. Both single-agent and combined use with other drugs have shown promising antitumor effects. In this review, we discuss the mechanism of action and the current preclinical and clinical progress of several of the most widely used HAPs, summarize their existing problems and shortcomings, and discuss future research prospects.

Hypoxia-activated prodrug derivatives of anti-cancer drugs: a patent review 2006 - 2021

INTRODUCTION

The hypoxic tumor microenvironment represents a persistent obstacle in the treatment of most solid tumors. In the past years, significant efforts have been made to improve the efficacy of anti-cancer drugs. Therefore, hypoxia-activated prodrugs (HAPs) of chemotherapeutic compounds have attracted widespread interest as a therapeutic means to treat hypoxic tumors.

AREAS COVERED

This updated review paper covers key patents published between 2006 and 2021 on the developments of HAP derivatives of anti-cancer compounds.

EXPERT OPINION

Despite significant achievements in the development of HAP derivatives of anti-cancer compounds and although many clinical trials have been performed or are ongoing both as monotherapies and as part of combination therapies, there has currently no HAP anti-cancer agent been commercialized into the market. Unsuccessful clinical translation is partly due to the lack of patient stratification based on reliable biomarkers that are predictive of a positive response to hypoxia-targeted therapy.

Chitosan oligosaccharide decorated liposomes combined with TH302 for photodynamic therapy in triple negative breast cancer

BACKGROUND

Triple negative breast cancer (TNBC) is an aggressive tumor with extremely high mortality that results from its lack of effective therapeutic targets. As an adhesion molecule related to tumorigenesis and tumor metastasis, cluster of differentiation-44 (also known as CD44) is overexpressed in TNBC. Moreover, CD44 can be effectively targeted by a specific hyaluronic acid analog, namely, chitosan oligosaccharide (CO). In this study, a CO-coated liposome was designed, with Photochlor (HPPH) as the 660 nm light mediated photosensitizer and evofosfamide (also known as TH302) as the hypoxia-activated prodrug. The obtained liposomes can help diagnose TNBC by fluorescence imaging and produce antitumor therapy by synergetic photodynamic therapy (PDT) and chemotherapy.

RESULTS

Compared with the nontargeted liposomes, the targeted liposomes exhibited good biocompatibility and targeting capability in vitro; in vivo, the targeted liposomes exhibited much better fluorescence imaging capability. Additionally, liposomes loaded with HPPH and TH302 showed significantly better antitumor effects than the other monotherapy groups both in vitro and in vivo.

CONCLUSION

The impressive synergistic antitumor effects, together with the superior fluorescence imaging capability, good biocompatibility and minor side effects confers the liposomes with potential for future translational research in the diagnosis and CD44-overexpressing cancer therapy, especially TNBC.

Hypoxia and its impact on the tumour microenvironment of gastroesophageal cancers

The malfeasant role of the hypoxic tumour microenvironment (TME) in cancer progression was recognized decades ago but the exact mechanisms that augment the hallmarks of cancer and promote treatment resistance continue to be elucidated. Gastroesophageal cancers (GOCs) represent a major burden of worldwide disease, responsible for the deaths of over 1 million people annually. Disentangling the impact of hypoxia in GOCs enables a better overall understanding of the disease pathogenesis while shining a light on novel therapeutic strategies and facilitating precision treatment approaches with the ultimate goal of improving outcomes for patients with these diseases. This review discusses the underlying principles and processes of the hypoxic response and the effect of hypoxia in promoting the hallmarks of cancer in the context of GOCs. We focus on its bidirectional influence on inflammation and how it drives angiogenesis, innate and adaptive immune evasion, metastasis, and the reprogramming of cellular bioenergetics. The contribution of the hypoxic GOC TME to treatment resistance is examined and a brief overview of the pharmacodynamics of hypoxia-targeted therapeutics is given. The principal methods that are used in measuring hypoxia and how they may enhance prognostication or provide rationale for individually tailored management in the case of tumours with significant hypoxic regions are also discussed.

Development and pre-clinical testing of a novel hypoxia-activated KDAC inhibitor

Tumor hypoxia is associated with therapy resistance and poor patient prognosis. Hypoxia-activated prodrugs, designed to selectively target hypoxic cells while sparing normal tissue, represent a promising treatment strategy. We report the pre-clinical efficacy of 1-methyl-2-nitroimidazole panobinostat (NI-Pano, CH-03), a novel bioreductive version of the clinically used lysine deacetylase inhibitor, panobinostat. NI-Pano was stable in normoxic (21% O₂) conditions and underwent NADPH-CYP-mediated enzymatic bioreduction to release panobinostat in hypoxia (<0.1% O₂). Treatment of cells grown in both 2D and 3D with NI-Pano increased acetylation of histone H3 at lysine 9, induced apoptosis, and decreased clonogenic survival. Importantly, NI-Pano exhibited growth delay effects as a single agent in tumor xenografts. Pharmacokinetic analysis confirmed the presence of sub-micromolar concentrations of panobinostat in hypoxic mouse xenografts, but not in circulating plasma or kidneys. Together, our pre-clinical results provide a strong mechanistic rationale for the clinical development of NI-Pano for selective targeting of hypoxic tumors.

The Hypoxia-Activated Prodrug TH-302: Exploiting Hypoxia in Cancer Therapy

Hypoxia is an important feature of most solid tumors, conferring resistance to radiation and many forms of chemotherapy. However, it is possible to exploit the presence of tumor hypoxia with hypoxia-activated prodrugs (HAPs), agents that in low oxygen conditions undergo bioreduction to yield cytotoxic metabolites. Although many such agents have been developed, we will focus here on TH-302. TH-302 has been extensively studied, and we discuss its mechanism of action, as well as its efficacy in preclinical and clinical studies, with the aim of identifying future research directions.

Hypoxia and its therapeutic possibilities in paediatric cancers

In tumours, hypoxia-a condition in which the demand for oxygen is higher than its availability-is well known to be associated with reduced sensitivity to radiotherapy and chemotherapy, and with immunosuppression. The consequences of hypoxia on tumour biology and patient outcomes have therefore led to the investigation of strategies that can alleviate hypoxia in cancer cells, with the aim of sensitising cells to treatments. An alternative therapeutic approach involves the design of prodrugs that are activated by hypoxic cells. Increasing evidence indicates that hypoxia is not just clinically significant in adult cancers but also in paediatric cancers. We evaluate relevant methods to assess the levels and extent of hypoxia in childhood cancers, including novel imaging strategies such as oxygen-enhanced magnetic resonance imaging (MRI). Preclinical and clinical evidence largely supports the use of hypoxia-targeting drugs in children, and we describe the critical need to identify robust predictive biomarkers for the use of such drugs in future paediatric clinical trials. Ultimately, a more personalised approach to treatment that includes targeting hypoxic tumour cells might improve outcomes in subgroups of paediatric cancer patients.

Current and Future Perspectives of the Use of Organoids in Radiobiology

The majority of cancer patients will be treated with radiotherapy, either alone or together with chemotherapy and/or surgery. Optimising the balance between tumour control and the probability of normal tissue side effects is the primary goal of radiation treatment. Therefore, it is imperative to understand the effects that irradiation will have on both normal and cancer tissue. The more classical lab models of immortal cell lines and in vivo animal models have been fundamental to radiobiological studies to date. However, each of these comes with their own limitations and new complementary models are required to fill the gaps left by these traditional models. In this review, we discuss how organoids, three-dimensional tissue-resembling structures derived from tissue-resident, embryonic or induced pluripotent stem cells, overcome the limitations of these models and thus have a growing importance in the field of radiation biology research. The roles of organoids in understanding radiation-induced tissue responses and in moving towards precision medicine are examined. Finally, the limitations of organoids in radiobiology and the steps being made to overcome these limitations are considered.

Combining hypoxia-activated prodrugs and radiotherapy in silico: Impact of treatment scheduling and the intra-tumoural oxygen landscape

Hypoxia-activated prodrugs (HAPs) present a conceptually elegant approach to not only overcome, but better yet, exploit intra-tumoural hypoxia. Despite being successful in vitro and in vivo, HAPs are yet to achieve successful results in clinical settings. It has been hypothesised that this lack of clinical success can, in part, be explained by the insufficiently stringent clinical screening selection of determining which tumours are suitable for HAP treatments. Taking a mathematical modelling approach, we investigate how tumour properties and HAP-radiation scheduling influence treatment outcomes in simulated tumours. The following key results are demonstrated in silico: (i) HAP and ionising radiation (IR) monotherapies may attack tumours in dissimilar, and complementary, ways. (ii) HAP-IR scheduling may impact treatment efficacy. (iii) HAPs may function as IR treatment intensifiers. (iv) The spatio-temporal intra-tumoural oxygen landscape may impact HAP efficacy. Our in silico framework is based on an on-lattice, hybrid, multiscale cellular automaton spanning three spatial dimensions. The mathematical model for tumour spheroid growth is parameterised by multicellular tumour spheroid (MCTS) data.

Use of a Luciferase-Expressing Orthotopic Rat Brain Tumor Model to Optimize a Targeted Irradiation Strategy for Efficacy Testing with Temozolomide

Glioblastoma multiforme (GBM) is a common and aggressive malignant brain cancer with a mean survival time of approximately 15 months after initial diagnosis. Currently, the standard-of-care (SOC) treatment for this disease consists of radiotherapy (RT) with concomitant and adjuvant temozolomide (TMZ). We sought to develop an orthotopic preclinical model of GBM and to optimize a protocol for non-invasive monitoring of tumor growth, allowing for determination of the efficacy of SOC therapy using a targeted RT strategy combined with TMZ. A strong correlation (r = 0.80) was observed between contrast-enhanced (CE)-CT-based volume quantification and bioluminescent (BLI)-integrated image intensity when monitoring tumor growth, allowing for BLI imaging as a substitute for CE-CT. An optimized parallel-opposed single-angle RT beam plan delivered on average 96% of the expected RT dose (20, 30 or 60 Gy) to the tumor. Normal tissue on the ipsilateral and contralateral sides of the brain were spared 84% and 99% of the expected dose, respectively. An increase in median survival time was demonstrated for all SOC regimens compared to untreated controls (average 5.2 days, p < 0.05), but treatment was not curative, suggesting the need for novel treatment options to increase therapeutic efficacy.