nTMS-derived DTI-based motor fiber tracking in radiotherapy treatment planning of high-grade gliomas for avoidance of motor structures.

BACKGROUND: Management of high-grade gliomas (HGGs) close to motor areas is challenging due to the risk of treatment-related morbidity. Thus, for resection, functional mapping of the corticospinal tract (CST) with navigated transcranial magnetic stimulation (nTMS) combined with diffusion tensor imaging (DTI)-based fiber tracking (DTI-FTTMS) is increasingly used. This study investigated the application of DTI-FTTMS in adjuvant radiation therapy (RT) planning of HGGs for CST avoidance. METHODS: The preoperative DTI-FTTMS-based CST reconstructions of 35 patients harboring HGGs were incorporated into the RT planning system and merged with planning imaging. The CST was delineated as the planning risk volume (PRV-FTTMS). Intensity-modulated RT (IMRT) plans were optimized to preserve PRV-FTTMS. Segments within the planning target volume (PTV) were not spared (overlap). RESULTS: With plan optimization, mean dose (Dmean) of PRV-FTTMS can be reduced by 17.1% on average (range 0.1-37.9%), thus from 25.5 Gy to 21.2 Gy (p < 0.001). For PRV-FTTMS segments beyond the PTV dose, reduction is possible by 26.8% (range 0.1-43.9%, Dmean 17.4 Gy vs. 12.5 Gy, p < 0.001). Considering only portions within the 50% isodose level, Dmean is decreased by 46.7% from 38.6 Gy to 20.5 Gy (range 19.1-62.8%, p < 0.001). PTV coverage was not affected: V95% and V90% were 96.4 ± 3.1% and 98.0 ± 3.9% vs. 96.1 ± 3.5% (p = 0.34) and 98.3 ± 2.9% (p = 0.58). Dose constraints for organs at risk (OARs) were all met. CONCLUSION: This study demonstrates that DTI-FTTMS can be utilized in the RT planning of HGGs for CST sparing. However, the degree of dose reduction depends on the overlap with the PTV. The functional benefit needs to be investigated in future prospective clinical trials.

Dose Reduction to Motor Structures in Adjuvant Fractionated Stereotactic Radiotherapy of Brain Metastases: nTMS-Derived DTI-Based Motor Fiber Tracking in Treatment Planning.

Background: Resection of brain metastases (BM) close to motor structures is challenging for treatment. Navigated transcranial magnetic stimulation (nTMS) motor mapping, combined with diffusion tensor imaging (DTI)-based fiber tracking (DTI-FTmot.TMS), is a valuable tool in neurosurgery to preserve motor function. This study aimed to assess the practicability of DTI-FTmot.TMS for local adjuvant radiotherapy (RT) planning of BM. Methods: Presurgically generated DTI-FTmot.TMS-based corticospinal tract (CST) reconstructions (FTmot.TMS) of 24 patients with 25 BM resected during later surgery were incorporated into the RT planning system. Completed fractionated stereotactic intensity-modulated RT (IMRT) plans were retrospectively analyzed and adapted to preserve FTmot.TMS. Results: In regular plans, mean dose (Dmean) of complete FTmot.TMS was 5.2 ± 2.4 Gy. Regarding planning risk volume (PRV-FTTMS) portions outside of the planning target volume (PTV) within the 17.5 Gy (50%) isodose line, the DTI-FTmot.TMS Dmean was significantly reduced by 33.0% (range, 5.9−57.6%) from 23.4 ± 3.3 Gy to 15.9 ± 4.7 Gy (p < 0.001). There was no significant decline in the effective treatment dose, with PTV Dmean 35.6 ± 0.9 Gy vs. 36.0 ± 1.2 Gy (p = 0.063) after adaption. Conclusions: The DTI-FTmot.TMS-based CST reconstructions could be implemented in adjuvant IMRT planning of BM. A significant dose reduction regarding motor structures within critical dose levels seems possible.

Inhibition of SphK1 reduces radiation-induced migration and enhances sensitivity to cetuximab treatment by affecting the EGFR / SphK1 crosstalk.

SphK1 is known to play a role in tumor progression, resistance to radiochemotherapy, and migration patterns. As the overall survival rates of squamous cell carcinoma of the head and neck (HNSCC) remain poor due to limitations in surgery and irradiation and chemotherapy resistance, SphK1 is an important enzyme to investigate. The purpose of this study was to elucidate the impact of SphK1 on irradiation efficacy of HNSCC in-vitro with emphasis on EGFR signaling. By immunhistochemical staining we found a positive correlation between EGFR and SphK1 expression in patient specimens. In colony formation assays irradiation sensitive cell lines showed a poor response to cetuximab, an EGFR inhibitor, and SKI-II, a SphK1 inhibitor, and vice versa. In irradiation sensitive cells an enhanced reduction of cell migration and survival was found upon simultaneous targeting of EGFR and SphK1. In the present study, we elucidated a linkage between the two signaling pathways with regard to the efficacy of cetuximab treatment and the impact on the migration behavior of tumor cells. We investigated the biological impact of inhibiting these pathways and examined the biochemical implications after different treatments. An understanding of the processes involved could help to improve the treatment of patients with HNSCC.

²¹³Bi-anti-EGFR radioimmunoconjugates and X-ray irradiation trigger different cell death pathways in squamous cell carcinoma cells.

INTRODUCTION: Treatment of patients with squamous cell carcinoma of head and neck is hampered by resistance of tumor cells to irradiation. Additional therapies enhancing the effect of X-ray irradiation may be beneficial. Antibodies targeting EGFR have been shown to improve the efficacy of radiation therapy. Therefore, we analyzed cytotoxicity of (213)Bi-anti-EGFR immunoconjugates in combination with X-ray irradiation. METHODS: The monoclonal anti-EGFR antibody matuzumab was coupled to CHX-A"-DTPA forming stable complexes with (213)Bi. Cytotoxicity of X-ray radiation, of treatment with (213)Bi-anti-EGFR monoclonal antibodies (MAb) or of a combined treatment regimen was assayed using cell proliferation and colony formation assays in UD-SCC5 cells. Key proteins of cell-cycle arrest and cell death were examined by Western blot analysis. Cell cycle analysis was performed by flow cytometry. DNA double-strand breaks were detected via γH2AX and quantified using Definiens™ software. RESULTS: Irradiation with X-rays or treatment with (213)Bi-anti-EGFR-MAb resulted in median lethal dose (LD50) values of 12 Gy or 130 kBq/mL, respectively. Treatment with 37 kBq/mL of (213)Bi-anti-EGFR-MAb or 2 Gy of X-rays had only little effect on colony formation of UD-SCC5 cells. In contrast, a combined treatment regimen (37 kBq/mL plus 2 Gy) significantly decreased colony formation and enhanced the formation of DNA double-strand breaks. As revealed by flow cytometry, radiation treatments caused accumulation of cells in the G0/G1 phase. Both treatment with (213)Bi-anti-EGFR immunoconjugates and application of the combined treatment regimen triggered activation of genes of signaling pathways involved in cell-cycle arrest and induction of apoptosis like p21/Waf, GADD45, Puma and Bax, which were only marginally modulated by X-ray irradiation of cells. CONCLUSIONS: (213)Bi-anti-EGFR-MAb enhances cytotoxicity of X-ray irradiation in UD-SCC5 cells most probably due to effective induction of DNA double-strand breaks. Induction of genes involved in cell-cycle arrest and cell death is almost exclusively due to (213)Bi-anti-EGFR-MAb and seems to be independent of p53 function.

The kallikrein-kinin-system in head and neck squamous cell carcinoma (HNSCC) and its role in tumour survival, invasion, migration and response to radiotherapy.

BACKGROUND: In this study, we investigated the role of the kallikrein-kinin-system in head and neck squamous cell carcinoma (HNSCC) and its implication on tumour survival, invasion, migration and response to radiotherapy. METHODS: The expression of BKB2R was studied in a series of 180 tumour samples to determine the functional significance of BKB2R in HNSCC. Additionally, four different HNSCC cell lines were treated with an irradiation dose of 8Gy following bradykinin receptor stimulation or blockage. Tumour cell survival was tested using a colony formation assay. The invasive potential of tumour cells was assessed using Matrigel invasion chambers, the cells' ability to migrate was determined with a wound-healing assay. To examine the biochemical activation of BKB2R, the epidermal growth factor receptor (EGFR) and its downstream pathways, western blot analyses were conducted. RESULTS: Immunohistochemistry revealed an over-expression of BKB2R in HNSCC tumour cells in comparison to normal peritumoural tissue. Blocking the BKB2R at irradiated tumour cells led to a reduced response to radiotherapy of tumour cells and led to an activation of the EGFR and its downstream pathways, known mediators of tumour cell survival, migration and invasion. Bradykinin stimulation also resulted in a better tumour cell survival, but these effects were achieved via an EGFR-independent signalling. CONCLUSIONS: Our results demonstrate that the kallikrein-kinin-system is involved in survival, invasion and migration of HNSCC cells.