Swallowing Structures Research Articles

Impact of Radiation on Dysphagia-Related Structures: A Dosimetric and Clinical Comparative Analysis of Three-Dimensional Conformal Radiotherapy (3D-CRT) and Intensity-Modulated Radiation Therapy (IMRT) Techniques in Patients With Head and Neck Cancer.

Introduction Head and neck squamous cell carcinoma (HNSCC)is a significant health concern in India, with around one million new cases annually. The prevalence of HNSCC is notably high in Asia, especially in India, due to habitslike tobacco chewing, betel nut usage, and alcohol consumption. Treatment typically involves a combination of surgery, radiation, chemotherapy, and biological therapy, aiming for tumor control while preserving function and quality of life. However, survivors often face long-term side effectslike difficulty swallowing, leading to complicationssuch as aspiration pneumonia. Intensity-modulated radiotherapy (IMRT) has shown promise in improving outcomes by sparing critical swallowing structures. Efforts to minimize radiation-related dysphagia are crucial for enhancing patients' quality of life post-treatment. Our study focuses on examining dosimetric parameters associated with dysphagia aspiration, alongside evaluating dysphagia grades in both treatment groups using the RTOGscale. Material and methods Patients with histologically confirmed non-metastatic head and neck carcinomas were included in our study in November 2018-April 2020. A total of 56 patients were taken into our study with 28 in each arm. They underwent radical radiotherapy (RT) with a total dose of 66-70 Gy, with or without concurrent chemotherapy, meeting specific inclusion criteria and excluding those receiving reirradiation or with distant metastasis. Patients were divided into two groups: Group I received three-dimensional conformal radiotherapy (3D-CRT), and Group II received IMRT. Treatment planning involved immobilization, CT imaging, delineation of target volumes and organs at risk, and contouring of swallowing structures. Dose-volume histogram parameters (mean dose, maximum dose, V30, V70, V80, D50, and D80) were used to assess mean dose to swallowing structures outside the planning target volume (PTV), with a mean dose constraint of 50 Gy. Dysphagia was evaluated using the RTOGcriteria at baseline, during treatment, and six months post-treatment. Statistical analysis was performed using SPSS, with significance set at p < 0.05. Results In our study, the mean age at presentation differed slightly between the IMRT and 3D-CRT arms: 58 years versus 55 years, respectively. A higher proportion of patients in both arms experienced symptoms for three to six months, with 53.6% in 3D-CRT and 42.9% in IMRT. Stage distribution varied, with IV being most common in 3D-CRT and stage II in IMRT. Approximately 56% of patients in both groups had a history of smoking. Significant differences were observed in spinal cord dose between 3DCRT and IMRT techniques (p < 0.001). Similarly, a significant difference was found in the mean dose received by dysphagia aspiration-related structures (DARSs) between the 3D-CRT and IMRT arms (p = 0.04). Patients in the IMRT arm exhibited superior dysphagia grades compared to those in the 3D-CRT arm, with statistical significance observed in the third month (p = 0.008) and sixth month (p = 0.048). Conclusion Our study found a notable decrease in the mean DARS dose and reduced dysphagia severity at three and six months in the IMRT group compared to the 3D-CRT group. However, due to the diverse study population, establishing a definitive correlation between the DARS dose and dysphagia severity was challenging. Future large-scale studies are needed to validate these findings for improved preservation of DARS structures.

Dose distribution prediction for head-and-neck cancer radiotherapy using a generative adversarial network: influence of input data.

A three-dimensional deep generative adversarial network (GAN) was used to predict dose distributions for locally advanced head and neck cancer radiotherapy. Given the labor- and time-intensive nature of manual planning target volume (PTV) and organ-at-risk (OAR) segmentation, we investigated whether dose distributions could be predicted without the need for fully segmented datasets. GANs were trained/validated/tested using 320/30/35 previously segmented CT datasets and treatment plans. The following input combinations were used to train and test the models: CT-scan only (C); CT+PTVboost/elective (CP); CT+PTVs+OARs+body structure (CPOB); PTVs+OARs+body structure (POB); PTVs+body structure (PB). Mean absolute errors (MAEs) for the predicted dose distribution and mean doses to individual OARs (individual salivary glands, individual swallowing structures) were analyzed. For the five models listed, MAEs were 7.3 Gy, 3.5 Gy, 3.4 Gy, 3.4 Gy, and 3.5 Gy, respectively, without significant differences among CP-CPOB, CP-POB, CP-PB, among CPOB-POB. Dose volume histograms showed that all four models that included PTV contours predicted dose distributions that had a high level of agreement with clinical treatment plans. The best model CPOB and the worst model PB (except model C) predicted mean dose to within ±3 Gy of the clinical dose, for 82.6%/88.6%/82.9% and 71.4%/67.1%/72.2% of all OARs, parotid glands (PG), and submandibular glands (SMG), respectively. The R2 values (0.17/0.96/0.97/0.95/0.95) of OAR mean doses for each model also indicated that except for model C, the predictions correlated highly with the clinical dose distributions. Interestingly model C could reasonably predict the dose in eight patients, but on average, it performed inadequately. We demonstrated the influence of the CT scan, and PTV and OAR contours on dose prediction. Model CP was not statistically different from model CPOB and represents the minimum data statistically required to adequately predict the clinical dose distribution in a group of patients.

Distribution pattern of medial group retropharyngeal lymph nodes and its implication in optimizing clinical target volume in nasopharyngeal carcinoma.

This study aimed to determine the diagnostic value of diffusion-weighted imaging (DWI) and to elucidate the clinical characteristics of medial group retropharyngeal lymph nodes (RLNs) based on multi-modal imaging. Also, we intended to explore the feasibility of optimizing the CTV60 boundary based on the characteristics of medial group RLNs. A total of 549 patients with nasopharyngeal carcinoma received magnetic resonance imaging (MRI), DWI, and contrast-enhanced computed tomography (CT) to detect and evaluate clinical characteristics of medial group RLNs. [18F]Fluorodeoxyglucose positron emission tomography/computed tomography was utilized to identify fluorodeoxyglucose uptaking and contrast-enhanced CT to ensure the reliability of CTV optimization during radiotherapy. The DESdC (Drinking, Eating, Swallowing Difficulties, and Coughing while Eating or Drinking) score was utilized to evaluate swallowing disability. Fourteen of 549 patients had medial group RLNs with a transverse diameter of 2.0-19.0 mm, which distributed between the upper margin of 1st cervical vertebra (C1) and the upper one-third of C3. Lasso regression and Pearson chi-square test suggested that its occurrence was associated with stage N, bilateral cervical lymph node metastases, especially when the transverse diameter of cervical lymph nodes was > 3cm. The sensitivity of DWI, T2 STIR, and contrast-enhanced CT was 100%, 57.1%, and 21.4%, respectively. We optimized CTV60 of medial group RLNs from the base of skull to the upper edge of C2 excluding specific cases. For patients with CTV60 optimization, radiation dose and volume of swallowing structures decreased obviously. Based on our radiotherapy strategy on CTV60, acute toxicities of enrolled patients were well tolerated. Ninety-six of 549 patients had scores with DESdC score. Eighty-three patients scored 1, seven patients scored 2, one patient scored 3, and three patients scored 4. The median interval from the onset of symptoms was 72 (4-114) months. The 5-year overall survival, progression-free survival, local recurrence-free survival, and distant metastasis-free survival were 87%, 80%, 93%, and 85%, respectively. None of the patients with regional recurrence happened in the optimized region. DWI possesses superiorities in displaying lymph nodes. Based on the low incidence of the medial RLNs, CTV60 of medial group RLNs from the base of skull to the upper edge of C2 is feasible and has dosimetric advantages for protecting swallowing structures.

Dose to swallowing structures and dysphagia in head and neck Intensity Modulated Radiation Therapy - A long term prospective analysis.

To analyse the long term swallowing function in head and neck cancer patients and correlate with the dose to midline swallowing structures. The use of concurrent chemo radiation (CRT) as the present standard of care resulted in high rates of early and late toxicities. Dysphagia, aspiration, and xerostomia are early as well as late effects of radiation. Not many studies on the dysphagia scores during radiation and follow-up period have correlated dose to the swallowing structures, hence this study. Histologically proven head and neck cancer patients treated with intensity modulated radiation therapy were accrued in this study. The pharyngeal constrictors, larynx and cervical oesophagus were contoured and labelled as midline swallowing structures. The volume of the midline swallowing structures which were outside the PTV was delineated separately and was given a mean dose constraint of 45Gy. Dysphagia was assessed at baseline, weekly intervals during irradiation and follow-up at six years. The dose to the structures for swallowing was correlated with degree of dysphagia. There was a gradual increase in the dysphagia grade during the course of radiation. There was a significant recovery of late dysphagia compared to dysphagia during the completion of radiation therapy in patients who received <45Gy to the swallowing structures (p<0.0001). Giving a constraint to the swallowing structure and limiting it to <45Gy resulted in earlier recovery of swallowing function resulted in good physical, mental and social well being of the patients when compared to those who received >45Gy.

Mid-treatment MRI Perfusion Changes in Constrictor Muscles Correlate with Dysphagia

Individualized radiation therapy requires assessment of an individual patient’s susceptibility to dysphagia beyond population-based clinical and dosimetric factors. We have previously shown that radiation effects on the pharyngeal constrictors are dose-dependent and that mid-treatment DCE-MRI blood volume (BV) in the constrictors correlate with RT dose. In this study, we aim to evaluate pre- and mid-treatment DCE-MRI imaging parameters in the pharyngeal constrictor muscles and their correlation with dysphagia. Patients with “poor prognosis” head and neck (HN) cancer including human papilloma virus negative (HPV-) loco-regionally advanced HN cancer or stage III AJCC 8 p16+ OPSCC (oropharyngeal squamous cell carcinoma) were enrolled in a randomized phase II trial where high risk tumor subvolumes received 70 vs 86Gy EQD2 with concurrent cisplatin or carboplatin. Multiparametric MRI were acquired at baseline and between fraction (fx) 8-12 of radiation. Analysis were performed on the first 23 patients free of loco-regional recurrence with minimum 12 months of follow-up. Superior, middle and inferior pharyngeal constrictor muscles (SPCM, MPCM and IPCM) were contoured on post contrast T1 MR images and transferred onto BV maps derived from DCE-MRI. Sternocleidomastoid muscle (SCM) was contoured as control. BV changes in the swallowing structures were correlated with RT dose and the following parameters at 3 and 12 months post-RT: IMRT swallow score of videofluoroscopy, EORTC HN35 PRO and any feeding tube use using Spearman rank coefficient. Mean doses to the SPCM, MPCM and IPCM were 59Gy (+/- 6), 56Gy (+/- 9), 33Gy (+/- 17) and respectively. Average BV values were 6.8 (SPCM), 5.8 (MPCM), 5.7 (IPCM) and 2.9 ml/100g (SCM) pretreatment, and changed to 10.4 (SPCM), 9.5 (MPCM), 7.4 (IPCM) and 2.6 (SCM) at 2wk. The increases in BV between pre-treatment and 2wk were significant in SPCM (p=0.01), MPCM (p<0.01), and IPCM (p=0.03), but not in SCM control (p=0.4). There was a significant correlation between the increased BV value at 2wk vs pretreatment and the mean dose in the total constrictor musculature (TPCM) (p=0.03, Spearmen rank correlation). Any feeding tube use was present in 16% of patients at 3 months and 0% at 12 months post-RT. The increased mid-treatment BV values in SPCM and MPCM were significantly correlated with the use of feeding tube at 3 months post-RT (p=0.02 and 0.05, respectively). These findings suggest that MRI BV is a sensitive early indicator of pharyngeal constrictor inflammation and edema. We have also seen significant dispersion of BV estimates between patients, suggesting substantial individual differences in dose-effect relationships. These findings provide a rationale for individualizing swallowing structures doses based on early toxicity prediction. The lack of any feeding tube use at 12mo in this population receiving 70-86Gy to PTVhigh is encouraging.

Optimising Radiation Therapy Dose to the Swallowing Organs at Risk: An In Silico Study of feasibility for Patients with Oropharyngeal Tumours.

Recent evidence suggests that reducing radiotherapy dose delivered to specific anatomical swallowing structures [Swallowing Organs at Risk (SWOARs)] may improve swallowing outcomes post-treatment for patients with head and neck cancer. However, for those patients with tumours of the oropharynx, which typically directly overlap the SWOARs, reducing dose to these structures may be unachievable without compromising on the treatment of the disease. To assess the feasibility of dose reduction in this cohort, standard IMRT plans (ST-IMRT) and plans with reduced dose to the SWOARs (SW-IMRT) were generated for 25 oropharyngeal cancer patients (Brouwer et al. in Radiother Oncol 117(1):83-90, https://doi.org/10.1016/j.radonc.2015.07.041 , 2015; Christianen et al. in Radiother Oncol 101(3):394-402, https://doi.org/10.1016/j.radonc.2011.05.015 , 2011). ST-IMRT and SW-IMRT plans were compared for: mean dose to the SWOARs, volume of pharynx and larynx receiving 50Gy and 60Gy (V50 and V60 respectively) and overlap between the tumour volume and the SWOARs. Additionally, two different SWOARs delineation guidelines (Brouwer et al. in Radiother Oncol 117(1):83-90, https://doi.org/10.1016/j.radonc.2015.07.041 , 2015; Christianen et al. in Radiother Oncol 101(3):394-402, https://doi.org/10.1016/j.radonc.2011.05.015 , 2011) were used to highlight differences in calculated volumes between existing contouring guidelines. Agreement in SWOARs volumes between the two guidelines was calculated using a concordance index (CI). Despite a large overlap between the tumour and SWOARs, significant (p < 0.05) reductions in mean dose to 4 of the 5 SWOARs, and V50/V60 for the pharynx and larynx were achieved with SW-IMRT plans. Low CIs per structure (0.15-0.45) were found between the two guidelines highlighting issues comparing data between studies when different guidelines have been used (Hawkins et al. in Semin Radiat Oncol 28(1):46-52, https://doi.org/10.1016/j.semradonc.2017.08.002 , 2018; Brodin et al. in Int J Radiat Oncol Biol Phys 100(2):391-407, https://doi.org/10.1016/j.ijrobp.2017.09.041 , 2018). This study found reducing dose to the SWOARs is a feasible practice for patients with oropharyngeal cancer. However, future prospective research is needed to determine if the extent of dose reduction achieved equates to clinical benefits.

Systematic review and meta-analysis of the impact of dosimetry to dysphagia and aspiration related structures.

Technological advances in radiotherapy have allowed investigations into new methods to spare healthy tissue in those treated for head and neck cancer. This systematic review with meta-analysis demonstrates the effect that radiation has on swallowing. Selection and analysis of studies examining the effect of radiation to swallowing structures. A fixed effects meta-analysis calculated the pooled proportions for select outcomes of dysphagia, common across many studies. The majority of the papers found a correlation between radiation dose to the swallowing structures and dysphagia, however a meta-analysis found the studies carried a significant degree of heterogeneity. The appraisal demonstrates the need for large-scale studies using a randomized design and instrumental dysphagia assessments. Radiation dose to dysphagia and aspiration structures is correlated with incidence of dysphagia and aspiration. The variables in this population contribute to the heterogeneity within and cross studies and future studies should consider controlling for this.

Imaging diagnosis of the medial group of retropharyngeal lymph nodes and the exploration of the optimization of target volume for protecting the swallowing structure in nasopharyngeal carcinoma

Objective To clarify the diagnostic value of diffusion-weighed imaging (DWI) in the medial group of retropharyngeal lymph nodes in nasopharyngeal carcinoma, understand the clinical characteristics of retropharyngeal lymph nodes and explore the feasibility of optimizing the target volume of CTV60. Methods Clinical data of 437 patients with clinical stage Ⅰ-IVa nasopharyngeal carcinoma admitted to Jiangsu Cancer Hospital from 2011 to 2017 were retrospectively analyzed. All patients underwent magnetic resonance imaging (MRI), DWI (1 000 s/mm2) and enhanced CT scans to analyze the clinical characteristics of retropharyngeal lymph nodes and investigate the dosimetric advantage and safety of CTV60 lower margin on the upper margin of C2. Results The medial lymph nodes with a transverse diameter of 2.0-19.0 mm were detected 13 of 437 patients, and 53.8% of the lymph nodes were measured 2-5 mm in transverse diameter. The medial lymph nodes were distributed between the superior margin of C1 and 1/3 of C3.Its occurrence was related to N stage, double cervical lymph node metastases, especially the transverse diameter of cervical lymph node> 3 cm. The sensitivity of DWI, T2 and enhanced CT were 100%, 61.5% and 23.1%.After the special cases were excluded, the lower margin of CTV60 on the superior margin of C2 was separated. The radiation dose and volume of the swallowing structures were significantly decreased. The 5-year survival rate was 80% without recurrence in the optimized region. Conclusions The incidence of the medial group of retropharyngeal lymph nodes is low with a diameter of less than 5 mm. DWI possesses advantages in displaying the medial group of retropharyngeal lymph nodes. Isolating the lower margin of CTV60 from the superior margin of C2 is safe and feasible and has dosimetric advantages for protecting swallowing structure. Key words: Nasopharyngeal neoplasm; Lymph node; Diffusion-weighed imaging; Swallowing structure

Dysphagia-optimised Intensity-modulated Radiotherapy Techniques in Pharyngeal Cancers: Is Anyone Going to Swallow it?

Dysphagia after primary chemoradiotherapy or radiation alone in pharyngeal cancers can have a devastating impact on a patient’s physical, social and emotional state. Establishing and validating efficient dysphagia-optimised radiotherapy techniques is, therefore, of paramount importance in an era where health-related quality of life measures are increasingly influential determinants of curative management strategies, particularly as the incidence of good prognosis, human papillomavirus-driven pharyngeal cancer in younger patients continues to rise. The preferential sparing achievable with intensity-modulated radiotherapy (IMRT) of key swallowing structures implicated in post-radiation dysfunction, such as the pharyngeal constrictor muscles (PCM), has generated significant research into toxicity-mitigating strategies. The lack of randomised evidence, however, means that there remains uncertainty about the true clinical benefits of the dosimetric gains offered by technological advances in radiotherapy. As a result, we feel that IMRT techniques that spare PCM cannot be incorporated into routine practice. In this review, we discuss the swallowing structures responsible for functional impairment, analyse the studies that have explored the dose–response relationship between these critical structures and late dysphagia, and consider the merits of reported dysphagia-optimised IMRT (Do-IMRT) approaches, thus far. Finally, we discuss the dysphagia/aspiration-related structures (DARS) study (ISRCTN 25458988), which is the first phase III randomised controlled trial designed to investigate the impact of swallow-sparing strategies on improving long-term function. To maximise patient benefits, improvements in radiation delivery will need to integrate with novel treatment paradigms and comprehensive rehabilitation strategies to eventually provide a patient-centric, personalised treatment plan.

The Challenges of Dysphagia Management and Rehabilitation in Two Complex Cases Post Chemical Ingestion Injury.

Dysphagia is common sequelae of chemical ingestion injury, resulting from damage to critical swallowing structures. From a speech-language pathology perspective, this study outlines the physiological deficits in 2 individuals with severe injury (1 woman, acid; 1 man, alkali) and the pattern of dysphagia rehabilitation and recovery. A retrospective chart review of clinical and instrumental assessments was conducted to examine swallow characteristics and speech-language pathology management (compensatory and rehabilitation strategies) at multiple time points. Chemical ingestion injury resulted in severe pharyngeal dysphagia for both participants, warranting speech-language pathology management. Dysphagia was characterized by poor base of tongue mobility and reduced laryngeal excursion. Decreased airway patency and protection, secondary to mucosal sloughing, widespread edema, and structural deficits necessitated tracheostomy. Recovery was complicated by physical alterations of pharyngeal and laryngeal structures (e.g., interarytenoid adhesions) and esophageal strictures. Participant 1 was discharged (Day 135) consuming a texture-modified diet; Participant 2 remained nil by mouth (Day 329). Dysphagia recovery subsequent to chemical ingestion is protracted and complex. Clinical outcomes may be improved through individualized and intensive rehabilitation by speech-language pathologists.

DARS: a phase III randomised multicentre study of dysphagia- optimised intensity- modulated radiotherapy (Do-IMRT) versus standard intensity- modulated radiotherapy (S-IMRT) in head and neck cancer.

BackgroundPersistent dysphagia following primary chemoradiation (CRT) for head and neck cancers can have a devastating impact on patients’ quality of life. Single arm studies have shown that the dosimetric sparing of critical swallowing structures such as the pharyngeal constrictor muscle and supraglottic larynx can translate to better functional outcomes. However, there are no current randomised studies to confirm the benefits of such swallow sparing strategies. The aim of Dysphagia/Aspiration at risk structures (DARS) trial is to determine whether reducing the dose to the pharyngeal constrictors with dysphagia-optimised intensity- modulated radiotherapy (Do-IMRT) will lead to an improvement in long- term swallowing function without having any detrimental impact on disease-specific survival outcomes.Methods/designThe DARS trial (CRUK/14/014) is a phase III multicentre randomised controlled trial (RCT) for patients undergoing primary (chemo) radiotherapy for T1-4, N0-3, M0 pharyngeal cancers. Patients will be randomised (1:1 ratio) to either standard IMRT (S-IMRT) or Do-IMRT. Radiotherapy doses will be the same in both groups; however in patients allocated to Do-IMRT, irradiation of the pharyngeal musculature will be reduced by delivering IMRT identifying the pharyngeal muscles as organs at risk. The primary endpoint of the trial is the difference in the mean MD Anderson Dysphagia Inventory (MDADI) composite score, a patient-reported outcome, measured at 12 months post radiotherapy. Secondary endpoints include prospective and longitudinal evaluation of swallow outcomes incorporating a range of subjective and objective assessments, quality of life measures, loco-regional control and overall survival. Patients and speech and language therapists (SLTs) will both be blinded to treatment allocation arm to minimise outcome-reporting bias.DiscussionDARS is the first RCT investigating the effect of swallow sparing strategies on improving long-term swallowing outcomes in pharyngeal cancers. An integral part of the study is the multidimensional approach to swallowing assessment, providing robust data for the standardisation of future swallow outcome measures. A translational sub- study, which may lead to the development of future predictive and prognostic biomarkers, is also planned.Trial registrationThis study is registered with the International Standard Randomised Controlled Trial register, ISRCTN25458988 (04/01/2016)

IMRT for head and neck cancer: reducing xerostomia and dysphagia.

Dysphagia and xerostomia are the main sequellae of chemoradiotherapy for head and neck cancer, and the main factors in reducing long-term patient quality of life. IMRT uses advanced technology to focus the high radiation doses on the targets and avoid irradiation of non-involved tissues. The decisions about sparing organs and tissues whose damage causes xerostomia and dysphagia depends on the evidence for dose–response relationships for the organs causing these sequellae. This paper discusses the evidence for the contribution of radiotherapy to xerostomia via damage of the major salivary glands (parotid and submandibular) and minor salivary glands within the oral cavity, and the contribution of radiotherapy-related effect on important swallowing structures causing dysphagia. Recommendations for dose limits to these organs, based on measurements of xerostomia and dysphagia following radiotherapy, are provided here.

Volumetric modulated arc therapy (VMAT) and simultaneous integrated boost in head-and-neck cancer: is there a place for critical swallowing structures dose sparing?

To explore the potential of volumetric-modulated arc therapy (VMAT) to reduce the risk of swallowing problems after curative chemoradiotherapy. 20 patients with head and neck cancer who previously underwent radiotherapy were selected. Radiotherapy was prescribed according to simultaneous integrated boost technique with all targets irradiated simultaneously over 30 daily fractions. Doses of 70.5 (67.5), 60.0 and 55.5 Gy were prescribed to primary tumour, high-risk nodal regions and low-risk nodal regions, respectively. Pharyngeal constrictor muscles (PCM) and glottic and supraglottic larynx (SGL) were considered organs at risk related to swallowing dysfunction (SW-OARs). Upper pharyngeal constrictor muscles (uPCM), middle pharyngeal constrictor muscles (mPCM) and lower pharyngeal constrictor muscles (lPCM) part of PCM were also outlined separately. Clinical standard plans (standard-VMAT) and plans aiming to spare SW-OARs (swallowing dysfunction-VMAT) were also created. Normal tissue complication probabilities (NTCP) for physician-rated swallowing dysfunction were calculated using a recently predictive model developed by Christianen et al. Planning with two strategies demonstrated comparable planning target volume coverage and no differences in sparing of parotid glands and other non-swallowing organs at risk. SW-VMAT plans provided mean dose reduction for uPCM and SGL by 3.9 and 4.5 Gy, respectively. NTCP values for Radiation Therapy Oncology Group grade 2-4 swallowing dysfunction was decreased by 9.2%. Dose reductions with SW-VMAT depended on tumour location and overlap with SW-OARs. VMAT plans aiming at sparing swallowing structures are feasible, providing a significant reduction in NTCP swallowing dysfunction with respect to conventional VMAT. Dysphagia is today considered one of the dose-limiting toxicities of chemoradiotherapy. The dose sparing of swallowing structures represents a major challenge in radiotherapy. VMAT is a complex new technology having the potential to significantly reduce the risk of dysphagia after curative chemoradiotherapy.

Effect of Dosimetric Outliers on the Performance of a Commercial Knowledge-Based Planning Solution

RapidPlan, a commercial knowledge-based planning solution, uses a model library containing the geometry and associated dosimetry of existing plans. This model predicts achievable dosimetry for prospective patients that can be used to guide plan optimization. However, it is unknown how suboptimal model plans (outliers) influence the predictions or resulting plans. We investigated the effect of, first, removing outliers from the model (cleaning it) and subsequently adding deliberate dosimetric outliers. Clinical plans from 70 head and neck cancer patients comprised the uncleaned (UC) ModelUC, from which outliers were cleaned (C) to create ModelC. The last 5 to 40 patients of ModelC were replanned with no attempt to spare the salivary glands. These substantial dosimetric outliers were reintroduced to the model in increments of 5, creating Model5 to Model40 (Model5-40). These models were used to create plans for a 10-patient evaluation group. Plans from ModelUC and ModelC, and ModelC and Model5-40 were compared on the basis of boost (B) and elective (E) target volume homogeneity indexes (HIB/HIE) and mean doses to oral cavity, composite salivary glands (compsal) and swallowing (compswal) structures. On average, outlier removal (ModelC vs ModelUC) had minimal effects on HIB/HIE (0%-0.4%) and sparing of organs at risk (mean dose difference to oral cavity and compsal/compswal were ≤0.4 Gy). Model5-10 marginally improved compsal sparing, whereas adding a larger number of outliers (Model20-40) led to deteriorations in compsal up to 3.9 Gy, on average. These increases are modest compared to the 14.9 Gy dose increases in the added outlier plans, due to the placement of optimization objectives below the inferior boundary of the dose-volume histogram-predicted range. Overall, dosimetric outlier removal from or addition of 5 to 10 outliers to a 70-patient model had marginal effects on resulting plan quality. Although the addition of >20 outliers deteriorated plan quality, the effect was modest. In this study, RapidPlan demonstrated robustness for moderate proportions of salivary gland dosimetric outliers.

SU‐E‐J‐193: Application of Surface Mapping in Detecting Swallowing for Head‐&amp;‐Neck Cancer

Purpose:Recent evidence is emerging that long term swallowing function may be improved after radiotherapy for head‐&amp;‐neck cancer if doses are limited to certain swallowing structures. Immobilization of patients with head‐&amp;‐neck cancer is typically done with a mask. This mask, however, doesn't limit patient swallowing. Patient voluntary or involuntary swallowing may introduce significant tumor motion, which can lead to suboptimal delivery. In this study, we have examined the feasibility of using surface mapping technology to detect patient swallowing during treatment and evaluated its magnitude.Methods:The C‐RAD Catalyst system was used to detect the patient surface map. A volunteer lying on the couch was used to simulate the patient under treatment. A virtual marker was placed near the throat and was used to monitor the swallowing action. The target motion calculated by the Catalyst system through deformable registration was also collected. Two treatment isocenters, one placed close to the throat and the other placed posterior to the base‐of‐tongue, were used to check the sensitivity of surface mapping technique.Results:When the patient's throat is not in the shadow of the patient's chest, the Catalyst system can clearly identify the swallowing motion. In our tests, the vertical motion of the skin can reach to about 5mm. The calculated target motion can reach up to 1 cm. The magnitude of this calculated target motion is more dramatic when the plan isocenter is closer to the skin surface, which suggests that the Catalyst motion tracking technique is more sensitive to the swallowing motion with a shallower isocenter.Conclusion:Surface mapping can clearly identify patient swallowing during radiation treatment. This information can be used to evaluate the dosimetric impact of the involuntary swallowing. It may also be used to potentially gate head‐&amp;‐neck radiation treatments. A prospective IRB approved study is currently enrolling patients in our institution.Research was funded through an Elekta grant

Automatic interactive optimization for volumetric modulated arc therapy planning

BackgroundIntensity modulated radiotherapy treatment planning for sites with many different organs-at-risk (OAR) is complex and labor-intensive, making it hard to obtain consistent plan quality. With the aim of addressing this, we developed a program (automatic interactive optimizer, AIO) designed to automate the manual interactive process for the Eclipse treatment planning system. We describe AIO and present initial evaluation data.MethodsOur current institutional volumetric modulated arc therapy (RapidArc) planning approach for head and neck tumors places 3-4 adjustable OAR optimization objectives along the dose-volume histogram (DVH) curve that is displayed in the optimization window. AIO scans this window and uses color-coding to differentiate between the DVH-lines, allowing it to automatically adjust the location of the optimization objectives frequently and in a more consistent fashion. We compared RapidArc AIO plans (using 9 optimization objectives per OAR) with the clinical plans of 10 patients, and evaluated optimal AIO settings. AIO consistency was tested by replanning a single patient 5 times.ResultsAverage V95&V107 of the boost planning target volume (PTV) and V95 of the elective PTV differed by ≤0.5%, while average elective PTV V107 improved by 1.5%. Averaged over all patients, AIO reduced mean doses to individual salivary structures by 0.9-1.6Gy and provided mean dose reductions of 5.6Gy and 3.9Gy to the composite swallowing structures and oral cavity, respectively. Re-running AIO five times, resulted in the aforementioned parameters differing by less than 3%.ConclusionsUsing the same planning strategy as manually optimized head and neck plans, AIO can automate the interactive Eclipse treatment planning process and deliver dosimetric improvements over existing clinical plans.

Toward optimal organ at risk sparing in complex volumetric modulated arc therapy: An exponential trade‐off with target volume dose homogeneity

Conventional radiotherapy typically aims for homogenous dose in the planning target volume (PTV) while sparing organs at risk (OAR). The authors quantified and characterized the trade-off between PTV dose inhomogeneity (IH) and OAR sparing in complex head and neck volumetric modulated arc therapy plans. Thirteen simultaneous integrated boost plans were created per patient, for ten patients. PTV boost(B)/elective(E) optimization priorities were systematically increased. IHB and IHE, defined as (100% - V95%) + V107%, were evaluated against the average of the mean dose to the combined composite swallowing and combined salivary organs (D-OAR(comp)). To investigate the influence of OAR size and position with respect to PTVB/E, OAR dose was evaluated against a modified Euclidean distance (DMB/DME) between OAR and PTV. Although the achievable D-OAR(comp) for a given level of PTV IH differed between patients, excellent logarithmic fits described the D-OAR(comp)/IHB and IHE relationship in all patients (mean R(2) of 0.98 and 0.97, respectively). Allowing an increase in average IHB and IHE over a clinically acceptable range, e.g., from 0.4% ± 0.5% to 2.0% ± 2.0% and 6.9% ± 2.8% to 14.8% ± 2.7%, respectively, corresponded to a decrease in average dose to the composite salivary and swallowing structures from 30.3 ± 6.5 to 23.6 ± 4.7 Gy and 32.5 ± 8.3 to 26.8 ± 9.3 Gy. The increase in PTVE IH was mainly accounted for by an increase in V107, by on average 5.9%, rather than a reduction in V95, which was on average only 2%. A linear correlation was found between the OAR dose to composite swallowing structures and contralateral parotid and submandibular gland, with DME (R(2) = 0.83, 0.88, 0.95). Only mean ipsilateral parotid dose correlated with DMB (R(2) = 0.87). OAR sparing is highly dependent on the permitted PTVB/E IH. PTVE IH substantially influences OAR doses. These results are relevant for clinical practice and for future automated treatment-planning strategies.

Dose to the inferior pharyngeal constrictor predicts prolonged gastrostomy tube dependence with concurrent intensity-modulated radiation therapy and chemotherapy for locally-advanced head and neck cancer

Background and purposeTo determine if dose and/or dose-volume parameters to anatomic swallowing structures are predictive of gastrostomy tube (PEG) dependence from chemotherapy-intensity modulated radiotherapy (IMRT) in locally advanced head and neck cancer (LAHNC). Methods and materialsA retrospective study was performed on 141 consecutive patients with LAHNC (squamous cell) treated with definitive chemoIMRT with weekly concurrent carboplatin and paclitaxel. Late dysphagia was assessed by length of PEG requirement. Analysis of IMRT dose was retrospectively performed for critical swallowing structures. ResultsApproximately 62% of patients required PEG, the majority placed during treatment. Mean and median time for PEG was 7.7 and 4.4months respectively (range 1.4–43.8). Only IMRT dose to the inferior constrictor was significantly associated with length of PEG. Mean dose (of individual mean doses) was 47Gy for prolonged PEG use versus 41Gy for PEG ⩽12months. V40 to the inferior constrictor also correlated with PEG >12months (p=0.02) with a mean V40 of 48% versus 41% for PEG ⩽12months. ConclusionsIMRT dose to the inferior constrictor correlated with persistent dysphagia requiring prolonged PEG use. Maintaining mean inferior constrictor dose to ⩽41Gy and V40 to ⩽41% may help minimize gastrostomy tube dependence.

Selective Nodal Irradiation by Intensity Modulated Radiation Therapy for Nasopharyngeal Carcinoma Aiming to Reduce Dysphagia and Xerostomia

To prospectively explore the clinical and functional outcomes of chemoradiation therapy for locally advanced nasopharyngeal carcinoma (NPC), using intensity-modulated radiation therapy (IMRT) to spare the salivary glands and related swallowing structures to reduce xerostomia and dysphagia.

Aspiration pneumonia after chemo–intensity‐modulated radiation therapy of oropharyngeal carcinoma and its clinical and dysphagia‐related predictors

The purpose of this study was to assess aspiration pneumonia (AsPn) rates and predictors after chemo-irradiation for head and neck cancer. The was a prospective study of 72 patients with stage III to IV oropharyngeal cancer treated definitively with intensity-modulated radiotherapy (IMRT) concurrent with weekly carboplatin and paclitaxel. AsPn was recorded prospectively and dysphagia was evaluated longitudinally through 2 years posttherapy by observer-rated (Common Toxicity Criteria version [CTCAE]) scores, patient-reported scores, and videofluoroscopy. Sixteen patients (20%) developed AsPn. Predictive factors included T classification (p = .01), aspiration detected on videofluoroscopy (videofluoroscopy-asp; p = .0007), and patient-reported dysphagia (p = .02-.0003), but not observer-rated dysphagia (p = .4). Combining T classification, patient reported dysphagia, and videofluoroscopy-asp, provided the best predictive model. AsPn continues to be an under-reported consequence of chemo-irradiation for head and neck cancer. These data support using patient-reported dysphagia to identify high-risk patients requiring videofluoroscopy evaluation for preventive measures. Reducing videofluoroscopy-asp rates, by reducing swallowing structures radiation doses and by trials reducing treatment intensity in patients predicted to do well, are likely to reduce AsPn rates.