Evaluation of the effect of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc radiotherapy (VMAT) techniques on survival response in cell lines with a new radiobiological modeling.

BACKGROUND: The optimal radiobiological model, which assesses the biological effects of novel radiotherapy techniques that concurrently modify multiple physical factors, has not yet been defined. This study aimed to investigate the impact of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) on cellular response in head and neck cancer and melanoma models. METHODS: Clonogenic analysis, DNA double-strand break analysis, apoptosis, and cell cycle analysis were performed on cancer stem cell models, cancer models, and normal tissue cell models to assess radiation sensitivity. RESULTS: The segmented radiation approach used in IMRT applications enhanced radiosensitivity and cytotoxicity in the cancer models, while changes in dose rate had varying effects on cytotoxicity depending on the tumor cell type. VMAT increased cellular resistance, favoring treatment outcomes. CONCLUSIONS: The biological processes were influenced differently by dose rate, IMRT, and VMAT depending on the tumor cell type. The selection of the most appropriate technique is crucial in representing new radiotherapy approaches. The obtained data can serve as a model to address clinical questions in daily practice. The integration of non-standard outcomes with standard applications should be considered in clinical settings.

Profiling of circRNA expressions in radiation-treated head and neck cancer cells and the potential role of circPVT1.

OBJECTIVE: Radiotherapy is an indispensable treatment modality for head and neck cancers (HNCs). Due to their stable structure, circular RNAs (circRNA) have been implicated as potential biomarkers for clinical use in cancers. The purpose of this study was profiling the circRNA in radiation-treated head and neck cancer cells to identify potential differentially expressed circRNAs. DESIGN: The effects of radiation on the expression level of circRNAs were investigated in HNCs cells, compared to healthy cell lines. To predict the potential role of circRNAs in HNC patients, tissue expression levels, survival analyses of circRNAs, and circRNA-miRNA network were evaluated using TCGA/CPTAC datasets. Based on expression level in irradiated cells, circPVT1 (plasmacytoma variant translocation 1) was further investigated by sequence analysis. RESULTS: The study revealed the characterization of differentially expressed circRNAs in cancer cells and that irradiation made significant changes in the expression of circRNAs. These findings suggest that certain circRNAs, especially circPVT1, may be potential biomarkers to monitor radiotherapy effects in patients with HNCs. CONCLUSIONS: CircRNAs may be promising molecules for improving and understanding radiotherapy efficacy in HNCs.

Radiation-Induced Ocular Surface Disorders and Retinopathy: Ocular Structures and Radiation Dose-Volume Effect.

PURPOSE: This study aimed to evaluate the radiation-induced adverse effects on ocular structures in head and neck cancer patients and investigate the radiation dose-volume effects on the cornea, lacrimal gland, retina, optic nerve and chiasm. MATERIALS AND METHODS: A total of 38 eyes of 19 patients were included in this prospective, cohort study. All patients underwent complete ophthalmological examination in addition to contrast sensitivity, visual field and visual evoked potentials (VEP) tests. Ophthalmological examinations and psychophysical tests were performed in 6th, 12th, 18th, 24th months and in the last visit. The relationship between the ophthalmologic findings, and the radiation doses below and above the cut-off values was evaluated. RESULTS: Contrast sensitivity decrease and visual field deterioration were observed in 42% of the patients in the last visit (median 26 months) whereas a prolonged latency and decreased amplitude of P100 wave in VEP was observed in 58% and 33% of the eyes, respectively at 24th month. Totally 16 patients (84.2%) developed dry eye disease and eight of them received radiotherapy below tolerance doses and had mild to moderate dry eye findings. Radiation-induced retinopathy was observed in three of the eyes in eight patients who received radiation above tolerance dose. CONCLUSION: Head and neck cancers treated with radiotherapy, resulted in various ophthalmic complications. All patients who are treating with radiotherapy should be evaluated by an ophthalmologist in terms of anterior and posterior segment damage, even if the radiation dose is below the tolerance limit.

Radiation-Associated Chronic Dysphagia Assessment by Flexible Endoscopic Evaluation of Swallowing (FEES) in Head and Neck Cancer Patients: Swallowing-Related Structures and Radiation Dose-Volume Effect.

PURPOSE: We aimed to restore dose-volume parameters of swallowing-related structures (SRSs) by evaluating long-term swallowing dysfunctions after radiotherapy (RT) in head and neck cancer patients (HNCPs). MATERIALS AND METHODS: Head and neck cancer patients whose pharyngeal region was involved in RT portal and treated with definitive RT/chemoradiotherapy (CRT) were included in the analyses. Patients underwent objective swallowing assessment by flexible endoscopic evaluation of swallowing (FEES). Volumes of SRSs that received 55 Gy (V55) (mean dose [Dmean]) were evaluated according to the dose-volume histograms of each patient. For every SRS, optimal dose-volume cut-off values were determined by receiver operating characteristic curve analysis. RESULTS: Fifty-five patients at a median 20 months (range, 12-26 months) after their treatments were evaluated. There was a strong negative correlation between FEES scores and dose-volume parameters of SRS ( r ⩽ -0.5, P < .0001). According to our results, middle pharyngeal constrictor (MPC) and inferior pharyngeal constrictor (IPC) had a Dmean > 57 Gy, base of tongue (BOT) Dmean > 50 Gy, supraglottic larynx (SGL) and glottic larynx (GL) Dmean > 55 Gy, and cervical esophagus (CE) Dmean > 45 Gy. MPC V55 > 70%, IPC V55 > 50%, BOT V55 > 65%, CE V55 > 40%, and SGL and GL V55 > 50% were significant predictors for dysphagia. CONCLUSION: It was found that dysphagia correlates strongly with dose-volume parameters of SRSs. IPC, SGL, and CE were found to be structures significantly associated with dysphagia.