The Path Toward PET-Guided Radiation Therapy for Glioblastoma in Laboratory Animals: A Mini Review

PET/SPECT/Spectral-CT/CBCT imaging in a small-animal radiation therapy platform: A Monte Carlo study-Part II: Biologically guided radiotherapy

BACKGROUND

This study addresses the technical gap between clinical radiation therapy (RT) and preclinical small-animal RT, hindering the comprehensive validation of innovative clinical RT approaches in small-animal models of cancer and the translation of preclinical RT studies into clinical practices.

PURPOSE

The main aim was to explore the feasibility of biologically guided RT implemented within a small-animal radiation therapy (SART) platform, with integrated quad-modal on-board positron emission tomography (PET), single-photon emission computed tomography, photon-counting spectral CT, and cone-beam CT (CBCT) imaging, in a Monte Carlo model as a proof-of-concept.

METHODS

We developed a SART workflow employing quad-modal imaging guidance, integrating multimodal image-guided RT and emission-guided RT (EGRT). The EGRT algorithm was outlined using positron signals from a PET radiotracer, enabling near real-time adjustments to radiation treatment beams for precise targeting in the presence of a 2-mm setup error. Molecular image-guided RT, incorporating a dose escalation/de-escalation scheme, was demonstrated using a simulated phantom with a dose painting plan. The plan involved delivering a low dose to the CBCT-delineated planning target volume (PTV) and a high dose boosted to the highly active biological target volume (hBTV) identified by the 18F-PET image. Additionally, the Bayesian eigentissue decomposition method illustrated the quantitative decomposition of radiotherapy-related parameters, specifically iodine uptake fraction and virtual noncontrast (VNC) electron density, using a simulated phantom with Kidney1 and Liver2 inserts mixed with an iodine contrast agent at electron fractions of 0.01-0.02.

RESULTS

EGRT simulations generated over 4,000 beamlet responses in dose slice deliveries and illustrated superior dose coverage and distribution with significantly lower doses delivered to normal tissues, even with a 2-mm setup error introduced, demonstrating the robustness of the novel EGRT scheme compared to conventional image-guided RT. In the dose-painting plan, doubling the dose to the hBTV while maintaining a low dose for the PTV resulted in an organ-at-risk (OAR) dose comparable to the low-dose treatment for the PTV alone. Furthermore, the decomposition of radiotherapy-related parameters in Kidney1 and Liver2 inserts, including iodine uptake fractions and VNC electron densities, exhibited average relative errors of less than 1.0% and 2.5%, respectively.

CONCLUSIONS

The results demonstrated the successful implementation of biologically guided RT within the proposed quad-model image-guided SART platform, with potential applications in preclinical RT and adaptive RT studies.

Biodistribution of andrographolide to assess the interior-exterior relationship between the lung and intestine using microPET

Background

One classic traditional Chinese medicine theory is that the “lung and intestine are exterior‐interiorly related”; however, this has not been confirmed experimentally. The aim of this study was to provide a biological basis for the theory by measuring the tissue distribution of andrographolide.

Methods

Acute pneumonia was induced in a mouse model by repeated stimulation with lipopolysaccharide. The distribution of andrographolide in mice was observed by positron emission tomography (PET) imaging with [¹⁸F]‐labeled andrographolide, and changes in the in vivo distribution before and after modeling were compared. Subsequently, the consistency of pathological changes in lung and intestine was confirmed by observation of pathological sections. Finally, the results were verified by cytokine detection.

Results

The value of organ uptake, pathological changes and inflammatory factor expression of the lung and intestine were consistent. The concentration of andrographolide in the lung and intestine increased significantly, and was confirmed by pathology and enzyme‐linked immunosorbent assays (ELISA).

Conclusions

Micro‐positron emission tomography (microPET) can be used to visually observe the distribution of medicinal ingredients in vivo, and [¹⁸F]‐andrographolide can be used as a tool to assess the interior‐exterior relationship between the lung and intestine.

Clinical Results of Fibroblast Activation Protein (FAP) Specific PET and Implications for Radiotherapy Planning: Systematic Review

Small molecules targeting fibroblast activation protein (FAP) have emerged as a new group of tracers for positron emission tomography (PET) in 2018. The purpose of this systematic review is therefore to summarize the evidence that has been gathered to date in patients and to discuss its possible implications for radiotherapy planning. The MEDLINE database was searched for the use of FAP-specific PET in cancer patients and the records were screened according to PRISMA guidelines. Nineteen studies were included. While dedicated analyses of FAP-specific PET for radiotherapy planning were available for glioblastoma, head and neck cancers, lung cancer, and tumors of the lower gastrointestinal tract, there is still very limited data for several epidemiologically significant cancers. In conclusion, FAP-specific PET represents a promising imaging modality for radiotherapy planning that warrants further research.

FGD5-AS1 facilitates glioblastoma progression by activation of Wnt/β-catenin signaling via regulating miR-129-5p/HNRNPK axis

AIMS

Accumulating evidence elucidates the biological significance of long non-coding RNA (lncRNAs) in tumorigenesis and development. FGD5 antisense RNA 1 (FGD5-AS1) was previously revealed as an oncogene in several types of malignancies. However, the roles of FGD5-AS1 in glioblastoma (GBM) and its potential molecular mechanisms remain unclear.

MATERIALS AND METHODS

The expression of FGD5-AS1, miR-129-5p, and heterogeneous nuclear ribonucleoprotein K (HNRNPK) mRNA were measured by qRT-PCR. Cell proliferation, invasion and apoptosis were determined by MTT, colony formation, transwell and flow cytometry assays. The protein levels of Ki-67, HNRNPK and Wnt signaling-associated genes were examined by western blot assay. The possible action mechanism of FGD5-AS1 was detected by bioinformatic tools, luciferase reporter, RIP and TOP/FOP Flash reporter assays. A nude mouse xenograft model was built to analyze the function of FGD5-AS1 in vivo.

KEY FINDINGS

FGD5-AS1 expression was increased in GBM tumor tissues and cells. Knockdown of FGD5-AS1 inhibited cell proliferation and invasion in vitro, and slowed tumor growth in vivo. Mechanistically, FGD5-AS1 served as a sponge of miR-129-5p to relieve its suppression on HNRNPK. Moreover, down-regulation of HNRNPK repressed cell proliferation and invasion, while enhanced apoptosis. Additionally, si-FGD5-AS1-mediated suppression of cell proliferation and invasion was obviously reversed by the decrease of miR-129-5p or restoration of HNRNPK. Furthermore, FGD5-AS1 promoted cell growth and invasion by stimulating Wnt/β-catenin signaling via regulation of miR-129-5p/HNRNPK.

SIGNIFICANCE

FGD5-AS1 promoted GBM progression at least partly by regulating miR-129-5p/HNRNPK to activate Wnt/β-catenin signaling, suggesting the potential of FGD5-AS1 as a candidate target to improve GBM therapy.

Therapeutic Efficiency of Multiple Applications of Magnetic Hyperthermia Technique in Glioblastoma Using Aminosilane Coated Iron Oxide Nanoparticles: In Vitro and In Vivo Study

Magnetic hyperthermia (MHT) has been shown as a promising alternative therapy for glioblastoma (GBM) treatment. This study consists of three parts: The first part evaluates the heating potential of aminosilane-coated superparamagnetic iron oxide nanoparticles (SPIONa). The second and third parts comprise the evaluation of MHT multiple applications in GBM model, either in vitro or in vivo. The obtained heating curves of SPIONa (100 nm, +20 mV) and their specific absorption rates (SAR) stablished the best therapeutic conditions for frequencies (309 kHz and 557 kHz) and magnetic field (300 Gauss), which were stablished based on three in vitro MHT application in C6 GBM cell line. The bioluminescence (BLI) signal decayed in all applications and parameters tested and 309 kHz with 300 Gauss have shown to provide the best therapeutic effect. These parameters were also established for three MHT applications in vivo, in which the decay of BLI signal correlates with reduced tumor and also with decreased tumor glucose uptake assessed by positron emission tomography (PET) images. The behavior assessment showed a slight improvement after each MHT therapy, but after three applications the motor function displayed a relevant and progressive improvement until the latest evaluation. Thus, MHT multiple applications allowed an almost total regression of the GBM tumor in vivo. However, futher evaluations after the therapy acute phase are necessary to follow the evolution or tumor total regression. BLI, positron emission tomography (PET), and spontaneous locomotion evaluation techniques were effective in longitudinally monitoring the therapeutic effects of the MHT technique.

Technical feasibility of [18F]FET and [18F]FAZA PET guided radiotherapy in a F98 glioblastoma rat model

Background

Glioblastoma (GB) is the most common primary malignant brain tumor. Standard medical treatment consists of a maximal safe surgical resection, subsequently radiation therapy (RT) and chemotherapy with temozolomide (TMZ). An accurate definition of the tumor volume is of utmost importance for guiding RT. In this project we investigated the feasibility and treatment response of subvolume boosting to a PET-defined tumor part.

Method

F98 GB cells inoculated in the rat brain were imaged using T2- and contrast-enhanced T1-weighted (T1w) MRI. A dose of 20 Gy (5 × 5 mm²) was delivered to the target volume delineated based on T1w MRI for three treatment groups. Two of those treatment groups received an additional radiation boost of 5 Gy (1 × 1 mm²) delivered to the region either with maximum [¹⁸F]FET or [¹⁸F]FAZA PET tracer uptake, respectively. All therapy groups received intraperitoneal (IP) injections of TMZ. Finally, a control group received no RT and only control IP injections. The average, minimum and maximum dose, as well as the D₉₀-, D₅₀- and D₂- values were calculated for nine rats using both RT plans. To evaluate response to therapy, follow-up tumor volumes were delineated based on T1w MRI.

Results

When comparing the dose volume histograms, a significant difference was found exclusively between the D₂-values. A significant difference in tumor growth was only found between active therapy and sham therapy respectively, while no significant differences were found when comparing the three treatment groups.

Conclusion

In this study we showed the feasibility of PET guided subvolume boosting of F98 glioblastoma in rats. No evidence was found for a beneficial effect regarding tumor response. However, improvements for dose targeting in rodents and studies investigating new targeted drugs for GB treatment are mandatory.

Electronic supplementary material

The online version of this article (10.1186/s13014-019-1290-4) contains supplementary material, which is available to authorized users.