Post-Irradiation Sinus Mucosa Disease in Nasopharyngeal Carcinoma Patients Treated with Intensity-Modulated Proton Therapy

In the past decade, patients with nasopharyngeal cancer (NPC) have been deemed candidates for proton radiotherapy, due to the large and comprehensive target volumes and the necessity for the retention of the surrounding healthy tissues. In this study, we aimed to compare the incidence and severity of post-irradiation sinusitis by detecting sinus mucosa diseases (SMDs) via the magnetic resonance imaging (MRI) of patients with NPC after intensity-modulated proton therapy (IMPT) and volume-modulated arc therapy (VMAT). A total of 53 patients in the IMPT group and 54 patients in the VMAT group were enrolled in this study. There were significantly lower endoscopic scores and Lund–Mackay staging scores determined from MRI scans in the IMPT group during different follow-up periods. For the most vulnerable sinuses, the incidence and severity of SMD were the highest during the third post-radiotherapy month in both groups. These decreased steadily, and there was no significant increase in the incidence and severity of SMD during the second post-radiotherapy year in the IMPT group. Our data show that NPC patients with IMPT have a significantly lower incidence and decreased severity of SMD than those with VMAT. A better and faster recovery of sinonasal function after radiotherapy in the IMPT group was also observed.

Estimation of Clinical Size of Breast Tumour Lesions Using Contrast Enhanced Magnetic Resonance Imaging: Delineation of Tumour Boundaries

This study covers an extended spectrum of clinical cases (1) to analyze the accurate tumour size, (2) to demarcate accurate tumour boundaries in order to plan an effective target volumes for radiotherapy, thermal ablation including radiofrequency ablation and nanoparticles induced thermal ablation. Once the clinical size of the tumour is established, realistic three-dimensional volume of the tumour can be calculated. Accurate margins (0.5 cm -1 cm) can only be sacrificed if true tumour boundaries with irregular nodal spread can be retrieved.

DOSIMETRIC ANALYSIS OF ADAPTIVE RADIOTHERAPY(ART) IN LOCALLY ADVANCED HEAD AND NECK CANCER

PURPOSE/OBJECTIVE: The objective of this study is to evaluate the dosimetric parameters in adaptive radiotherapy for locally advanced head and neck cancers METHODS AND MATERIALS: This is a Hospital-based Prospective study conducted in the period from Dec 2020 to March 2021. Histologically proven Head and Neck Carcinoma patients with Stage III to IV (locally advanced) were selected for the study. A total of 10 patients receiving denitive, conformal radiation therapy to the head and neck region were evaluated for the study. After the acquisition of CT images, target volumes, OARs were contoured in the planning CT. Images were again acquired midway during the planned course of radiation therapy. Body contours, target volumes, and organs at risk were redrawn on the new set of images. Two sets of additional treatment plans were generated: 1) a non-optimized plan (plan 2), which is an overlay of the original plan (plan 1) on the new set of contours, and 2) an optimized plan(plan 3) with the new set of contours. These 3 sets of plans were then compared for dosimetric differences. RESULTS: Four patients had locally advanced nasopharyngeal cancers, 4 patients had locally advanced oropharyngeal cancers, 2 patients had locally advanced hypopharyngeal cancer. The average reduction in gross tumour volume was 37.1 ml. The average changes in right and left parotid volume were 5.94 and 5.49 ml, respectively. With the non-optimized plan, the average increase in the maximum dose to the spinal cord was 9.8% (58.96-68.76; p= 0.156). With reoptimization, the maximum dose to the spinal cord decreased from 68.76% to 54.97% (mean difference, -13.79%, p=0.03). The average D99 for the planning target volume( dose received by 99% of the target volume) was 98.68% and 98.65% with the original and reoptimized plans, respectively. Most of the patients during radiation had Grade 2 skin toxicity and Grade 2 mucositis which was managed conservatively. CONCLUSIONS: This study demonstrates that during radiation there is gross changes of volumes in locally advanced head and neck cancers and thus adaptive radiation therapy plays a pivotal role in locally advanced head and neck cancer

Accelerated hypofractionated radiotherapy for chest wall and nodal irradiation using hybrid techniques

Aim: This study compares three different hybrid plans, for left-sided chest wall (CW) and nodal stations irradiation using a hypofractionated dose regimen. Materials and methods: Planning target volumes (PTVs) of 25 breast cancer patients that included CW, supraclavicular (SCL) and internal mammary node (IMN) were planned with 3 different hybrid techniques: 3DCRT+IMRT, 3DCRT+VMAT and IMRT+VMAT. All hybrid plans were generated with a hypofractionated dose prescription of 40·5 Gy in 15 fractions. Seventy per cent of the dose was planned with the base-dose component and remaining 30% of the dose was planned with the hybrid component. All plans were evaluated based on the PTVs and organs at risk (OARs) dosimetric parameters. Results: The results for PTVs parameters have shown that the 3DCRT+IMRT and 3DCRT+VMAT plans were superior in uniformity index to the IMRT+VMAT plan. The OARs dose parameters were comparable between hybrid plans. The IMRT+VMAT plan provided a larger low dose volume spread to the heart and ipsilateral lung (p < 0·001). The 3DCRT+VMAT plan required less monitor units and treatment time (p = 0·005) than other plans. Conclusion: The 3DCRT+VMAT hybrid plan showed superior results with efficient treatment delivery and provide clinical benefit by reducing both low and high dose levels.

Evaluation of the impact of teaching on delineation variation during a virtual stereotactic ablative radiotherapy contouring workshop

Introduction: Variation in delineation of target volumes/organs at risk (OARs) is well recognised in radiotherapy and may be reduced by several methods including teaching. We evaluated the impact of teaching on contouring variation for thoracic/pelvic stereotactic ablative radiotherapy (SABR) during a virtual contouring workshop. Materials and methods: Target volume/OAR contours produced by workshop participants for three cases were evaluated against reference contours using DICE similarity coefficient (DSC) and line domain error (LDE) metrics. Pre- and post-workshop DSC results were compared using Wilcoxon signed ranks test to determine the impact of teaching during the workshop. Results: Of 50 workshop participants, paired pre- and post-workshop contours were available for 21 (42%), 20 (40%) and 22 (44%) participants for primary lung cancer, pelvic bone metastasis and pelvic node metastasis cases, respectively. Statistically significant improvements post-workshop in median DSC and LDE results were observed for 6 (50%) and 7 (58%) of 12 structures, respectively, although the magnitude of DSC/LDE improvement was modest in most cases. An increase in median DSC post-workshop ≥0·05 was only observed for GTVbone, IGTVlung and SacralPlex, and reduction in median LDE > 1 mm was only observed for GTVbone, CTVbone and SacralPlex. Post-workshop, median DSC values were >0·7 for 75% of structures. For 92% of the structures, post-workshop contours were considered to be acceptable or within acceptable variation following review by the workshop faculty. Conclusions: This study has demonstrated that virtual SABR contouring training is feasible and was associated with some improvements in contouring variation for multiple target volumes/OARs.

Delineation guidelines for the lymphatic target volumes in ‘prone crawl’ radiotherapy treatment position for breast cancer patients

Our recently developed prone crawl position (PCP) for radiotherapy of breast cancer patients with lymphatic involvement showed promising preliminary data and it is being optimized for clinical use. An important aspect in this process is making new, position specific delineation guidelines to ensure delineation (for treatment planning) is uniform across different centers. The existing ESTRO and PROCAB guidelines for supine position (SP) were adapted for PCP. Nine volunteers were MRI scanned in both SP and PCP. Lymph node regions were delineated in SP using the existing ESTRO and PROCAB guidelines and were then translated to PCP, based on the observed changes in reference structure position. Nine PCP patient CT scans were used to verify if the new reference structures were consistently identified and easily applicable on different patient CT scans. Based on these data, a team of specialists in anatomy, CT- and MRI radiology and radiation oncology postulated the final guidelines. By taking the ESTRO and PROCAB guidelines for SP into account and by using a relatively big number of datasets, these new PCP specific guidelines incorporate anatomical variability between patients. The guidelines are easily and consistently applicable, even for people with limited previous experience with delineations in PCP.

Volumetric and dosimetric impact of Post-Surgical MRI guided radiotherapy for Glioblastoma: A pilot study

Objectives: Glioblastoma (GBM) radiotherapy (RT) target delineation requires MRI, ideally concurrent with CT simulation (pre-RT MRI). Due to limited MRI availability, <72 h post-surgery MRI is commonly used instead. Whilst previous investigations assessed volumetric differences between post-surgical and pre-RT delineations, dosimetric impact remains unknown. We quantify volumetric and dosimetric impact of using post-surgical MRI for GBM target delineation. Methods: Gross tumour volumes (GTVs) for five GBM patients receiving chemo-RT with post-surgical and pre-RT MRIs were delineated by three independent observers. Planning target volumes (PTVs) and RT plans were generated for each GTV. Volumetric and dosimetric differences were assessed through: absolute volumes, volume-distance histograms, and dose-volume histogram statistics. Results: Post-surgical MRI delineations had significantly (p < 0.05) larger GTV and PTV volumes (median 16.7 and 64.4 cm3 respectively). Post-surgical RT plans, applied to pre-RT delineations, had significantly decreased (p < 0.01) median PTV doses (ΔD99% = −8.1 Gy and ΔD95% = −2.0 Gy). Median organ at risk (OAR) dose increases (brainstem ΔD5% =+0.8, normal brain mean dose =+2.9 and normal brain ΔD10% = 5.3 Gy) were observed. Conclusion: Post-surgical MRI delineation significantly impacted RT planning, with larger normal-appearing tissue volumes irradiated and increased OAR doses, despite a reduced coverage of the pre-RT defined target. Advances in knowledge: We believe this is the first investigation assessing the dosimetric impact of using post-surgical MRI for GBM target delineation. It highlights the potential of significantly degraded RT plans, showing the clinical-need for dedicated MRI for GBM RT.

Assessing the dose rate delivery of helical TomoTherapy prostate and head & neck treatments

The dose rate distributions delivered to 55 prostate and head & neck (H&N) cancer patients treated with a helical TomoTherapy (HT) system were resolved and assessed with regard to pitch and field width defined during treatment planning. Statistical analysis of the studied cases showed that the median treatment delivery time was 4.4 min and 6.3 min for the prostate and H&N cases, respectively. Dose rate volume histogram data for the studied cases showed that the 25% and 12% of the volume of the planning target volumes of the prostate and H&N cases are irradiated with a dose rate of greater or equal to 1 Gy/min. Quartile dose rate (QDR) data confirmed that in HT, where the target is irradiated in slices, most of the dose is delivered to each voxel of the target when it travels within the beam. Analysis of the planning data from all cases showed that this lasts for 68 s (median value). QDRs results showed that using the 2.5 cm field width, 75% of the prescribed dose is delivered to target voxels with a median dose rate of at least 3.2 Gy/min and 4.5 Gy/min, for the prostate and H&N cases, respectively. Systematically higher dose rates were observed for the H&N cases due to the shallower depths of the lesions in this anatomical site. Delivered dose rates were also found to increase with field width and pitch setting, due to the higher output of the system which, in general, results in accordingly decreased total treatment time. The biological effect of the dose rate findings of this work needs to be further investigated using in-vitro studies and clinical treatment data.