Predictive modelling for swallowing dysfunction after primary (chemo)radiation: results of a prospective observational study

Clinical Trial Strategies to Compare Protons With Photons

The favorable beam properties of protons can be translated into clinical benefits by target dose escalation to improve local control without enhancing unacceptable radiation toxicity or to spare normal tissues to prevent radiation-induced side effects without jeopardizing local tumor control. For the clinical validation of the added value of protons to improve local control, randomized controlled trials are required. For the clinical validation of the added value of protons to prevent side effects, both model-based validation or randomized controlled trials can be used. Model-based patient selection for proton therapy is crucial, independent of the validation approach. Combining these approaches in rapid learning health care systems is expected to yield the most efficient and scientifically sound way to continuously improve patient selection and the therapeutic window, eventually leading to more cancer survivors with better quality of life.

Radiation-induced late dysphagia after intensity-modulated radiotherapy in nasopharyngeal carcinoma patients: a dose-volume effect analysis

Dysphagia is a side effect of nasopharyngeal carcinoma chemo-radiotherapy (CRT) which greatly influences the quality of life of the patients. We analyzed late dysphagia in 134 patients with nasopharyngeal cancer undergoing radical radiotherapy (RT), and correlated these findings with dose–volume histogram (DVH) parameters of the swallowing organs at risk (SWOARs). DVH parameters of SWOARs were correlated with late dysphagia, and with RTOG/EORTC scale score and the M. D. Anderson dysphagia inventory (MDADI) score. The mean dose (D_mean) to the superior and inferior constrictor muscles (SCM and ICM) and age were associated with grade 2 late dysphagia. Receiver operating characteristic (ROC) curves showed that the threshold values for grade 2 late dysphagia were: D_mean to SCM ≥ 67 Gy, partial volume receiving specified dose of 60 Gy (V₆₀) of SCM ≥ 95%, D_mean to ICM ≥ 47 Gy, and V₅₀ of ICM ≥ 23%. The areas under the ROC curve were 0.681 (p = 0.02), 0.677 (p = 0.002), 0.71 (p < 0.001) and 0.726 (p < 0.001) respectively. Our study demonstrates a significant relationship between late dysphagia and the radiation doses delivered to the SCM and ICM. Our findings suggest that physicians should be cautious in reducing the RT dose to SWOARs in order to avoid severe dysphagia. Further prospective trials are necessary to recommend this as part of routine clinical practice.

Accelerated Hypofractionated Active Raster-Scanned Carbon Ion Radiotherapy (CIRT) for Laryngeal Malignancies: Feasibility and Safety

(1) Background: The authors present the first results of active raster-scanned carbon ion radiotherapy (CIRT) for radioresistant laryngeal malignancies regarding efficacy and toxicity. (2) Methods: 15 patients with laryngeal adenoid cystic carcinoma (ACC; n = 8; 53.3%) or chondrosarcoma (CS; n = 7; 46.7%) who underwent radiotherapy with carbon ions (C12) at the Heidelberg Ion Beam Therapy Center (HIT) between 2013 and 2018 were identified retrospectively and analyzed for local control (LC), overall survival (OS), and distant progression-free survival using the Kaplan–Meier method. CIRT was applied either alone (n = 7, 46.7%) or in combination with intensity modulated radiotherapy (IMRT) (n = 8, 53.3%). The toxicity was assessed according to the Common Toxicity Terminology Criteria for Adverse Events (CTCAE) v4.03. (3). Results: the median follow-up was 24 months (range 5–61 months). Overall, the therapy was tolerated very well. No grade >3 acute and chronic toxicity could be identified. The most reported acute grade 3 side effects were acute dysphagia (n = 2; 13%) and acute odynophagia (n = 3; 20%), making supportive nutrition via gastric tube (n = 2; 13.3%) and via high caloric drinks (n = 1; 6.7%) necessary due to swallowing problems (n = 4; 27%). Overall, chronic grade 3 toxicity in the form of chronic hoarseness occurred in 7% of the patients (n = 1; 7%). At the last follow-up, all the patients were alive. No local or locoregional recurrence could be identified. Only one patient with laryngeal ACC developed lung metastases three years after the first diagnosis. (4) Conclusions: the accelerated hypofractionated active raster-scanned carbon ion radiotherapy for radioresistant laryngeal malignancies is feasible in practice with excellent local control rates and moderate acute and late toxicity. Further follow-ups are necessary to evaluate the long-term clinical outcome.

18F-FDG Metabolic Tumor Volume: Association with Short- and Long-Term Feeding Tube Use in Head and Neck IMRT

The purpose of this study was to investigate whether the metabolic tumor volume (MTV) of head and neck primary tumors may be a significant prognostic factor for feeding tube (FT) use and FT dependence. Seventy-nine patients with evaluable primary tumors, pre-therapy FDG-PET scans, treated with definitive intensity-modulated radiotherapy (IMRT) (± concurrent chemotherapy) for head and neck mucosal cancers were included. MTV was quantified and recorded for the primary lesion using a minimum standardized uptake value (SUV) threshold of 2.0. Patients were recommended prophylactic FT and followed up by a dietician for at least eight weeks of post-radiotherapy. Associations between MTV, dose to swallowing organs at risk, FT use, and FT dependence were analyzed. MTV was positively correlated with gross tumor volume (GTV) (r = 0.7357; p < 0.0001). MTVs larger than 17 cc were associated with higher rates of FT use (87.8% vs. 69.5%, p = 0.0067) and FT dependence at six weeks (76.7% vs. 41.7%, p = 0.0024) and six months (25.0% vs. 8.7%, p = 0.0088). Increasing MTV was associated with increasing mean dose to the oral cavity (p = < 0.0001), tongue base (p = 0.0009), and superior (SPCM) (p = 0.0001) and middle pharyngeal constrictor muscles (MPCM) (p = 0.0005). Increasing MTV was associated with increasing maximum dose to oral cavity (p = 0.0028), tongue base (p = 0.0056), SPCM (p = 0.0037), and MPCM (p = 0.0085). Pre-treatment MTV is a reproducible parameter that can be generated at or prior to a pre-treatment Multidisciplinary Tumor Board and may expedite decisions regarding placement of prophylactic FTs. Prospective evaluation in larger series is required to determine whether MTV is a more useful prognostic variable for FT use than clinical T-classification.

Revisiting the dose constraints for head and neck OARs in the current era of IMRT

Head and neck cancer poses a particular challenge in radiation therapy, whilst being an effective treatment modality it requires very high doses of radiation to provide effective therapy. This is further complicated by the fact that the head and neck region contains a large number of radiosensitive tissues, often resulting in patients experiencing debilitating normal tissue complications. In the era of intensity-modulated radiation therapy (IMRT) treatments can be delivered using non-uniform dose distributions selectively aimed at reducing the dose to critical organs-at-risk while still adequately covering the tumor target. Dose-volume constraints for the different risk organs play a vital role in one's ability to devise the best IMRT treatment plan for a head and neck cancer patient. To this end, it is pivotal to have access to the latest and most relevant dose constraints available and as such the goal of this review is to provide a summary of suggested dose-volume constraints for head and neck cancer RT that have been published after the QUANTEC reports were made available in early 2010.

The impact of margin reduction on outcome and toxicity in head and neck cancer patients treated with image-guided volumetric modulated arc therapy (VMAT)

BACKGROUND AND PURPOSE

In recent decades, outcomes of patients with head and neck cancer (HNC) have improved as a result of implementing several strategies, such as chemoradiation. However, these improvements were achieved at the cost of increased toxicity. One way to reduce radiation-related toxicity is by reducing the margins.

MATERIALS AND METHODS

Between 2013 and 2016, 206 consecutive patients were treated with CTV-PTV margin of 5 mm and subsequently 208 patients with 3 mm margin. This study evaluates the impact of reducing clinical target volume (CTV) to planning target volume (PTV) margin on outcome and toxicity.

RESULTS

All patients were treated with volumetric modulated arc therapy (VMAT) with daily-image guidance using cone-beam CT (CBCT). Overall acute grade 3 toxicity was significantly lower in 3 mm-group, compared to 5 mm-group (53.8% vs. 65%, respectively, p = 0.032). The same was true for acute grade 3 mucositis (30.8% vs. 42.2%, p = 0.008) and for acute grade 3 dysphagia (feeding tube-dependence) (22.1% vs. 33.5%, p = 0.026). The incidence of ongoing feeding tube-dependence after 3 months of radiotherapy was 11.1% and 20.4%, respectively (p = 0.012). The 2-year incidence of late grade ≥2 xerostomia was 15.8% and 19.4% (p = 0.8). The 2-year loco-regional control rates of patients treated in 3 mm and 5 mm-groups were 79.9% and 79.2% (p = 1.0). The figures for disease-free survival were 71.5% and 72.7 (p = 0.6) and for overall survival were 75.2% and 75.1% (p = 0.9).

CONCLUSION

Reducing the CTV-PTV margin from 5 to 3 mm combined with daily CBCT-guided VMAT reduced the severity, frequency, and duration of radiation-related toxicity without jeopardizing outcome.

Data Analysis in Radiotherapy Treatments

Radiotherapy is one of the main cancer treatments available today, together with chemotherapy and surgery. Radiotherapy treatments have to be planned for each patient in an individualized manner. The knowledge acquired from one single treatment can be used to improve the treatment planning and outcome of several other patients. In the last years, attention has been drawn to the added value of using data analysis for radiotherapy treatment planning, prediction of treatment outcomes, survival analysis and quality assurance. In this article, existing literature is reviewed.

Radiotherapy dose-volume parameters predict videofluoroscopy-detected dysphagia per DIGEST after IMRT for oropharyngeal cancer: Results of a prospective registry

PURPOSE

Our primary aim was to prospectively validate retrospective dose-response models of chronic radiation-associated dysphagia (RAD) after intensity modulated radiotherapy (IMRT) for oropharyngeal cancer (OPC). The secondary aim was to validate a grade ≥2 cut-point of the published videofluoroscopic dysphagia severity (Dynamic Imaging Grade for Swallowing Toxicity, DIGEST) as radiation dose-dependent.

MATERIAL AND METHODS

Ninety-seven patients enrolled on an IRB-approved prospective registry protocol with stage I-IV OPC underwent pre- and 3-6 month post-RT videofluoroscopy. Dose-volume histograms (DVH) for swallowing regions of interest (ROI) were calculated. Dysphagia severity was graded per DIGEST criteria (dichotomized with grade ≥2 as moderate/severe RAD). Recursive partitioning analysis (RPA) and Bayesian Information Criteria (BIC) were used to identify dose-volume effects associated with moderate/severe RAD.

RESULTS

31% developed moderate/severe RAD (i.e. DIGEST grade ≥2) at 3-6 months after RT. RPA found DVH-derived dosimetric parameters of geniohyoid/mylohyoid (GHM), superior pharyngeal constrictor (SPC), and supraglottic region were associated with DIGEST grade ≥2 RAD. V61 ≥ 18.57% of GHM demonstrated optimal model performance for prediction of DIGEST grade ≥2.

CONCLUSION

The findings from this prospective longitudinal registry validate prior observations that dose to submental musculature predicts for increased burden of dysphagia after oropharyngeal IMRT. Findings also support dichotomization of DIGEST grade ≥2 as a dose-dependent split for use as an endpoint in trials or predictive dose-response analysis of videofluoroscopy results.

Prospective in silico study of the feasibility and dosimetric advantages of MRI-guided dose adaptation for human papillomavirus positive oropharyngeal cancer patients compared with standard IMRT

PURPOSE

We aim to determine the feasibility and dosimetric benefits of a novel MRI-guided IMRT dose-adaption strategy for human papillomavirus positive (HPV+) oropharyngeal squamous cell carcinoma (OPC).

MATERIALS/METHODS

Patients with locally advanced HPV+ OPC underwent pre-treatment and in-treatment MRIs every two weeks using RT immobilization setup. For each patient, two IMRT plans were created (i.e. standard and adaptive). The prescription dose for the standard plans was 2.12 Gy/fx for 33 fractions to the initial PTV. For adaptive plans, a new PTVadaptive was generated based on serial MRIs in case of detectable tumor shrinkage. Prescription dose to PTVadaptive was 2.12 Gy/fx to allow for maximum dose to the residual disease. Any previously involved volumes received minimally a floor dose of 50.16 Gy. Uninvolved elective nodal volumes were prescribed 50.16 Gy in 1.52 Gy/fx. Dosimetric parameters of organs at risk (OARs) were recorded for standard vs. adaptive plans. Normal tissue complication probability (NTCP) for toxicity endpoints was calculated using literature-derived multivariate logistic regression models.

RESULTS

Five patients were included in this pilot study, 3 men and 2 women. Median age was 58 years (range 45-69). Three tumors originated at the tonsillar fossa and two at the base of tongue. The average dose to 95% of initial PTV volume was 70.7 Gy (SD,0.3) for standard plans vs. 58.5 Gy (SD,2.0) for adaptive plans. The majority of OARs showed decrease in dosimetric parameters using adaptive plans vs. standard plans, particularly swallowing related structures. The average reduction in the probability of developing dysphagia ≥ grade2, feeding tube persistence at 6-month post-treatment and hypothyroidism at 1-year post-treatment was 11%, 4%, and 5%, respectively. The probability of xerostomia at 6-month was only reduced by 1% for adaptive plans vs. standard IMRT.

CONCLUSION

These in silico results showed that the proposed MRI-guided adaptive approach is technically feasible and advantageous in reducing dose to OARs, especially swallowing musculature.

Proton Therapy for Head and Neck Cancers

Because of its sharp lateral penumbra and steep distal fall-off, proton therapy offers dosimetric advantages over photon therapy. In head and neck cancer, proton therapy has been used for decades in the treatment of skull-base tumors. In recent years the use of proton therapy has been extended to numerous other disease sites, including nasopharynx, oropharynx, nasal cavity and paranasal sinuses, periorbital tumors, skin, and salivary gland, or to reirradiation. The aim of this review is to present the physical properties and dosimetric benefit of proton therapy over advanced photon therapy; to summarize the clinical benefit described for each disease site; and to discuss issues of patient selection and cost-effectiveness.

Pretreatment risk stratification of feeding tube use in patients treated with intensity-modulated radiotherapy for head and neck cancer

BACKGROUND

The purpose of this study was to establish a risk stratification model for feeding tube use in patients who undergo intensity-modulated radiotherapy (IMRT) for head and neck cancers.

METHODS

One hundred thirty-nine patients treated with definitive IMRT (+/- concurrent chemotherapy) for head and neck mucosal cancers were included in this study. Patients were recommended a prophylactic feeding tube and followed up by a dietician for at least 8 weeks postradiotherapy (post-RT). Potential prognostic factors were analyzed for risk and duration of feeding tube use for at least 25% of dietary requirements.

RESULTS

Many variables had significant effects on risk and/or duration of feeding tube use in univariate analyses. Subsequent multivariable analysis showed that T classification ≥3 and level 2 lymphadenopathy were the best independent significant predictors of higher risk and duration of feeding tube use, respectively, in oral cavity, pharyngeal, and supraglottic primaries.

CONCLUSION

In patients treated with definitive IMRT, T classification ≥3 and level 2 lymphadenopathy can potentially stratify patients into 4 risk groups for developing severe dysphagia requiring feeding tube use.

Volumetric modulated arc therapy of head-and-neck cancer on a fast-rotating O-ring linac: Plan quality and delivery time comparison with a C-arm linac

BACKGROUND AND PURPOSE

Linac improvements in gantry speed, leaf speed and dose rate may increase the time-efficiency of volumetric modulated arc therapy (VMAT) delivery. The plan quality achievable with faster VMAT however remains to be investigated. In this study, a fast-rotating O-ring linac with fast-moving leaves is compared with a C-arm linac in terms of plan quality and delivery time for VMAT of head-and-neck cancer (HNC).

MATERIAL AND METHODS

For 30 patients with HNC, treatment planning was performed using dual-arc (HA2) and triple-arc (HA3) VMAT on a Halcyon fast-rotating O-ring linac and using dual-arc VMAT on a TrueBeam C-arm linac (TB2). Target coverage metrics and complication probabilities were compared. Plan delivery was verified using 3%/3 mm gamma-index analysis of helical diode array measurements. Volumetric image acquisition and plan delivery times were compared.

RESULTS

All studied VMAT-techniques fulfilled the target coverage objectives. D_2% to the boost volume was higher for HA2 (median 103.7%, 1st-3rd quartile [103.5%;104.0%]) and HA3 (103.2% [103.0%;103.7%)] than for TB2 (102.6% [102.3%;103.0%)], resulting in an increased boost target dose heterogeneity for HA2 and HA3. Complication probabilities were comparable between HA2 and TB2, while HA3 showed a xerostomia probability reduction (0.8% [0.2%;1.8%]) and dysphagia probability reduction (1.0% [0.2%;1.8%]) compared with TB2. Gamma-index agreement scores were never below 93.0% for HA2, HA3 and TB2. Volumetric imaging and plan delivery time was shorter for HA2 (1 m 24 s ± 1 s) and HA3 (1 m 54 s ± 1 s) than for TB2 (2 m 47 s ± 1 s).

CONCLUSION

For VMAT of HNC, the fast-rotating O-ring linac at least maintains the plan quality of two arcs on a C-arm linac while reducing the image acquisition and plan delivery time.

Clinical factors impacting on late dysphagia following radiotherapy in patients with head and neck cancer

OBJECTIVE

Patient and treatment characteristics of patients with head and neck cancer (HNSCC) were correlated with dysphagia scored on swallowing-videofluoroscopy (VFS) and with patient- and physician-scored dysphagia.

METHODS

63 HNSCC patients treated with radiotherapy (RT) were evaluated at baseline, and 6 and 12 months post-RT. VFS was scored with Penetration Aspiration Scale (PAS) and Swallowing Performance Scale (SPS). Physician- and patient-scored dysphagia were prospectively recorded according to Common Terminology Criteria for Adverse Events scoring system, Radiation Therapy Oncology Group/EORTC scoring system and European Organization for Research and Treatment of Cancer Quality of Life questionnaire (EORTC-QLQ H&N35).

RESULTS

Univariable analysis revealed a significant association between tumour-subsite and higher SPS (p = 0.02) and patient-scored dysphagia (p = 0.02) at baseline. At 12 months, tumour-subsite was significantly associated with higher PAS and SPS. Multivariable analysis and pairwise comparison showed that hypopharyngeal cancer and carcinoma of unknown primary  were associated with higher SPS at baseline and at 12 months, respectively (p = 0.03 and p = 0.01). Upfront neck dissection (UFND) was significantly associated with higher SPS and physician-scored dysphagia in univariable analysis at all timepoints. At 12 months, there was also a significant association with higher PAS (p < 0.01) and patient-scored dysphagia (p < 0.01). After multivariable analysis, the association between UFND and higher PAS (p < 0.01) and SPS (p < 0.01) remained significant at 12 months.

CONCLUSION

Hypopharyngeal tumours and carcinoma of unknown primary were related to more dysphagia at baseline and at 12 months, respectively. Furthermore, UFND was associated with more severe dysphagia scored by physicians and patients and on VFS at 12 months. Advances in knowledge: This is the first paper reporting a significant link between UFND and late dysphagia scored with VFS. We advocate abandoning UFND and preserving neck dissection as a salvage option post-RT.

Dosimetric Evaluation of Incorporating Patient Geometric Variations Into Adaptive Plan Optimization Through Probabilistic Treatment Planning in Head and Neck Cancers

PURPOSE

Four-dimensional (4D) adaptive radiation therapy (ART) treatment planning is an alternative to the conventional margin-based treatment planning approach. In 4D ART, interfraction patient geometric variations, gathered from computed tomography (CT) or cone beam CT (CBCT) images acquired during the patient treatment course, are directly incorporated into the adaptive plan optimization using a probabilistic treatment planning method. The goal of the present planning study was to evaluate the dosimetric differences between 4D ART and conventional margin-based adaptive planning strategies for head and neck cancers. In addition, we examined whether the dose differences achieved with 4D ART would translate into clinically relevant toxicity reductions using the existing normal tissue complication probability (NTCP) models.

METHODS AND MATERIALS

For 18 head and neck cancer patients, the treatment plans were retrospectively generated for 4 different treatment strategies, including a solely image guided radiation therapy (IGRT) strategy (IGRT-only), 2 conventional adaptive treatment planning strategies using 3- and 0-mm planning target volume (PTV) margins, and the 4D ART strategy. In the IGRT-only strategy, a conventional 3-mm PTV margin treatment plan was applied for the entire treatment course. In the 2 conventional adaptive strategies, 2 new treatment plans were generated during the treatment course using diagnostic planning CT scans acquired after the 10th and 22nd fractions. The 4D ART followed the same adaptive schedule, except that the 4D adaptive plan was generated using 5 CBCT images acquired during the 5 most recent treatment fractions. For each strategy, the actual delivered dose for the entire treatment course was constructed by calculating the daily doses on 35 CBCT scans, deforming back to the pretreatment planning CT scan, and accumulating over all 35 fractions. The target coverage was evaluated using the percentage of target volume receiving ≥100% of the prescription dose (V_100%) and the minimum dose to 99% of the target volume (D₉₉). It was considered adequate if the V_100% was ≥95% and the dose deficit in D₉₉ was ≤2 Gy (with respect to the prescription dose). For each strategy, the dose received by the organs at risk (OARs) was also evaluated, and the corresponding NTCP values were subsequently calculated using 3 NTCP models.

RESULTS

Adequate target coverage was achieved for the primary clinical target volume (CTV1) and elective nodal CTV (CTV2) with a 3-mm PTV margin, regardless of adaptation. The 3-mm ART plan reduced the OAR mean dose by 1 to 2 Gy compared with the IGRT-only plan. The 0-mm ART plan further reduced the OAR dose by another 2 to 3 Gy at the expense of target coverage: 3 and 1 patient had V_100% <95%, and 6 and 5 patients had a >2 Gy dose deficit in D₉₉ for the CTV1 and CTV2, respectively. Use of 4D ART improved target coverage and attained OAR sparing similar to that with 0-mm ART. The number of patients with V_100% <95% and >2 Gy D₉₉ deficit decreased to 0 and 0 for CTV1 and 0 and 2 for CTV2, respectively. The NTCP calculations suggested that 4D ART could benefit a substantial portion of patients compared with IGRT-only because 17 and 12 patients had ≥5% and ≥10% NTCP reductions for parotid toxicity and 18 and 3 patients had ≥5% and ≥10% NTCP reductions for swallowing toxicity, respectively.

CONCLUSIONS

Compared with margin-based adaptive planning strategies, 4D ART provides a better balance between target coverage and OAR sparing. NTCP estimation predicted for theoretical clinical benefits that warrant further clinical validation.

Incorporating spatial dose metrics in machine learning-based normal tissue complication probability (NTCP) models of severe acute dysphagia resulting from head and neck radiotherapy

Severe acute dysphagia commonly results from head and neck radiotherapy (RT). A model enabling prediction of severity of acute dysphagia for individual patients could guide clinical decision-making. Statistical associations between RT dose distributions and dysphagia could inform RT planning protocols aiming to reduce the incidence of severe dysphagia. We aimed to establish such a model and associations incorporating spatial dose metrics. Models of severe acute dysphagia were developed using pharyngeal mucosa (PM) RT dose (dose-volume and spatial dose metrics) and clinical data. Penalized logistic regression (PLR), support vector classification and random forest classification (RFC) models were generated and internally (173 patients) and externally (90 patients) validated. These were compared using area under the receiver operating characteristic curve (AUC) to assess performance. Associations between treatment features and dysphagia were explored using RFC models. The PLR model using dose-volume metrics (PLRstandard) performed as well as the more complex models and had very good discrimination (AUC = 0.82) on external validation. The features with the highest RFC importance values were the volume, length and circumference of PM receiving 1 Gy/fraction and higher. The volumes of PM receiving 1 Gy/fraction or higher should be minimized to reduce the incidence of severe acute dysphagia.

Impact of model and dose uncertainty on model-based selection of oropharyngeal cancer patients for proton therapy

BACKGROUND

Proton therapy is becoming increasingly available, so it is important to apply objective and individualized patient selection to identify those who are expected to benefit most from proton therapy compared to conventional intensity modulated radiation therapy (IMRT). Comparative treatment planning using normal tissue complication probability (NTCP) evaluation has recently been proposed. This work investigates the impact of NTCP model and dose uncertainties on model-based patient selection.

MATERIAL AND METHODS

We used IMRT and intensity modulated proton therapy (IMPT) treatment plans of 78 oropharyngeal cancer patients, which were generated based on automated treatment planning and evaluated based on three published NTCP models. A reduction in NTCP of more than a certain threshold (e.g. 10% lower NTCP) leads to patient selection for IMPT, referred to as 'nominal' selection. To simulate the effect of uncertainties in NTCP-model coefficients (based on reported confidence intervals) and planned doses on the accuracy of model-based patient selection, the Monte Carlo method was used to sample NTCP-model coefficients and doses from a probability distribution centered at their nominal values. Patient selection accuracy within a certain sample was defined as the fraction of patients which had similar selection in both the 'nominal' and 'sampled' scenario.

RESULTS

For all three NTCP models, the median patient selection accuracy was found to be above 70% when only NTCP-model uncertainty was considered. Selection accuracy decreased with increasing uncertainty resulting from differences between planned and delivered dose. In case of excessive dose uncertainty, selection accuracy decreased to 60%.

CONCLUSION

Model and dose uncertainty highly influence the accuracy of model-based patient selection for proton therapy. A reduction of NTCP-model uncertainty is necessary to reach more accurate model-based patient selection.

The impact of treatment accuracy on proton therapy patient selection for oropharyngeal cancer patients

BACKGROUND AND PURPOSE

The impact of treatment accuracy on NTCP-based patient selection for proton therapy is currently unknown. This study investigates this impact for oropharyngeal cancer patients.

MATERIALS AND METHODS

Data of 78 patients was used to automatically generate treatment plans for a simultaneously integrated boost prescribing 70 Gy_RBE/54.25 Gy_RBE in 35 fractions. IMRT treatment plans were generated with three different margins; intensity modulated proton therapy (IMPT) plans for five different setup and range robustness settings. Four NTCP models were evaluated. Patients were selected for proton therapy if NTCP reduction was ≥10% or ≥5% for grade II or III complications, respectively.

RESULTS

The degree of robustness had little impact on patient selection for tube feeding dependence, while the margin had. For other complications the impact of the robustness setting was noticeably higher. For high-precision IMRT (3 mm margin) and high-precision IMPT (3 mm setup/3% range error), most patients were selected for proton therapy based on problems swallowing solid food (51.3%) followed by tube feeding dependence (37.2%), decreased parotid flow (29.5%), and patient-rated xerostomia (7.7%).

CONCLUSIONS

Treatment accuracy has a significant impact on the number of patients selected for proton therapy. Therefore, it cannot be ignored in estimating the number of patients for proton therapy.

Systematic Review of Normal Tissue Complication Models Relevant to Standard Fractionation Radiation Therapy of the Head and Neck Region Published After the QUANTEC Reports

There has recently been an increasing interest in model-based evaluation and comparison of different treatment options in radiation oncology studies. This is partly driven by the considerable technical advancements in radiation therapy of the last decade, leaving radiation oncologists with a multitude of options to consider. In lieu of randomized trials comparing all of these different treatment options for varying indications, which is unfeasible, treatment evaluations based on normal tissue complication probability (NTCP) models offer a practical alternative. The Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC) effort, culminating in a number of reports published in 2010, provided a basis for many of the since-implemented dose-response models and dose-volume constraints and was a key component for model-based treatment evaluations. Given that 7 years have passed since the QUANTEC publications and that patient-reported outcomes have emerged as an important consideration in recent years, an updated summary of the published radiation dose-response literature, which includes a focus on patient-reported quality of life outcomes, is warranted. Here we provide a systematic review of quantitative dose-response models published after January 1, 2010 for endpoints relevant to radiation therapy for head and neck cancer, because these patients are typically at risk for a variety of treatment-induced normal tissue complications.

Treatment of late sequelae after radiotherapy for head and neck cancer

Radiotherapy (RT) is used to treat approximately 80% of patients with cancer of the head and neck. Despite enormous advances in RT planning and delivery, a significant number of patients will experience radiation-associated toxicities, especially those treated with concurrent systemic agents. Many effective management options are available for acute RT-associated toxicities, but treatment options are much more limited and of variable benefit among patients who develop late sequelae after RT. The adverse impact of developing late tissue damage in irradiated patients may range from bothersome symptoms that negatively affect their quality of life to severe life-threatening complications. In the region of the head and neck, among the most problematic late effects are impaired function of the salivary glands and swallowing apparatus. Other tissues and structures in the region may be at risk, depending mainly on the location of the irradiated tumor relative to the mandible and hearing apparatus. Here, we review the available evidence on the use of different therapeutic strategies to alleviate common late sequelae of RT in head and neck cancer patients, with a focus on the critical assessment of the treatment options for xerostomia, dysphagia, mandibular osteoradionecrosis, trismus, and hearing loss.

[Proton therapy for head and neck cancers]

The absence of exit dose and the sharp lateral penumbra are key assets for proton therapy, which are responsible for its dosimetric superiority over advanced photon radiotherapy. Dosimetric comparisons have consistently shown a reduction of the integral dose and the dose to organs at risk favouring intensity-modulated proton therapy (IMPT) over intensity-modulated radiotherapy (IMRT). The structures that benefit the most of these dosimetric improvements in head and neck cancers are the anterior oral cavity, the posterior fossa, the visual apparatus and swallowing structures. A number of publications have concluded that these dosimetric differences actually translate into reduced toxicities with IMPT, for example with regards to reduced weight loss or need for feeding tube. Patient survival is usually similar to IMRT series, except in base of skull or sinonasal malignancies, where a survival advantage of IMPT could exist. The goals of the present review is to describe the major characteristics of proton therapy, to analyse the clinical data with regards to head and neck cancer patients, and to highlight the issue of patient selection and physical and biological uncertainties.

Geometric Image Biomarker Changes of the Parotid Gland Are Associated With Late Xerostomia

PURPOSE

To identify a surrogate marker for late xerostomia 12 months after radiation therapy (Xer_12m), according to information obtained shortly after treatment.

METHODS AND MATERIALS

Differences in parotid gland (PG) were quantified in image biomarkers (ΔIBMs) before and 6 weeks after radiation therapy in 107 patients. By performing stepwise forward selection, ΔIBMs that were associated with Xer_12m were selected. Subsequently other variables, such as PG dose and acute xerostomia scores, were added to improve the prediction performance. All models were internally validated.

RESULTS

Prediction of Xer_12m based on PG surface reduction (ΔPG-surface) was good (area under the receiver operating characteristic curve, 0.82). Parotid gland dose was related to ΔPG-surface (P<.001, R² = 0.27). The addition of acute xerostomia scores to the ΔPG-surface improved the prediction of Xer_12m significantly, and vice versa. The final model including ΔPG-surface and acute xerostomia had outstanding performance in predicting Xer_12m early after radiation therapy (area under the receiver operating characteristic curve, 0.90).

CONCLUSIONS

Parotid gland surface reduction was associated with late xerostomia. The early posttreatment model with ΔPG-surface and acute xerostomia scores can be considered as a surrogate marker for late xerostomia.

Voxel-based analysis unveils regional dose differences associated with radiation-induced morbidity in head and neck cancer patients

The risk of radiation-induced toxicity in patients treated for head and neck (HN) cancer with radiation therapy (RT) is traditionally estimated by condensing the 3D dose distribution into a monodimensional cumulative dose-volume histogram which disregards information on dose localization. We hypothesized that a voxel-based approach would identify correlations between radiation-induced morbidity and local dose release, thus providing a new insight into spatial signature of radiation sensitivity in composite regions like the HN district. This methodology was applied to a cohort of HN cancer patients treated with RT at risk of radiation-induced acute dysphagia (RIAD). We implemented an inter-patient elastic image registration framework that proved robust enough to match even the most elusive HN structures and to provide accurate dose warping. A voxel-based statistical analysis was then performed to test regional dosimetric differences between patients with and without RIAD. We identified a significantly higher dose delivered to RIAD patients in two voxel clusters in correspondence of the cricopharyngeus muscle and cervical esophagus. Our study goes beyond the well-established organ-based philosophy exploring the relationship between radiation-induced morbidity and local dose differences in the HN region. This approach is generally applicable to different HN toxicity endpoints and is not specific to RIAD.

Dose-volume toxicity modeling for de-intensified chemo-radiation therapy for HPV-positive oropharynx cancer

BACKGROUND AND PURPOSE

The aim is to determine the radiobiological parameters of four popular normal tissue complication probability (NTCP) models that describe the dose-response relations of salivary glands and pharyngeal constrictors to the severity of patient reported xerostomia and dysphagia, respectively 6 and 12months post chemo-radiotherapy, furthermore, to evaluate the goodness-of-fit of the NTCP models for different combinations of glands and constrictors.

MATERIAL AND METHODS

Forty-three patients were treated on a prospective multi-institutional phase II study (ClinicalTrials.gov, NCT01530997) assessing the efficacy of de-intensified chemoradiotherapy in patients with favorable risk, HPV-associated oropharyngeal squamous cell carcinoma. All patients received 60Gy intensity modulated radiotherapy with concurrent weekly intravenous cisplatinum. All patients reported severity of their xerostomia and dysphagia (pre- and post-treatment) using the patient reported outcome version of the CTCAE (PRO-CTCAE). A change in severity (from baseline) of ≥2 was considered clinically meaningful. The Lyman-Kutcher-Burman (LKB), Relative Seriality (RS), Logit, and Relative Seriality Logit (RSL) NTCP models were used to fit the patients' dose/volume data to changes in PRO-CTCAE severity of xerostomia and dysphagia (from baseline to 6 and 12months post-treatment). The correlation of the models with the patient outcomes was performed for different combinations of salivary glands and different sections of pharyngeal constrictors. The goodness-of-fit of the different models was assessed through the area under the receiver operating characteristic curve (AUC), maximum of the log-likelihood function, normal error distribution and Akaike information criterion (AIC).

RESULTS

The dose/volume metrics of the combined contralateral (parotid+submandibular) glands appear to correlate best with xerostomia, at both 6- and 12-months. Among the different sections of pharyngeal constrictors, the dose/volume metrics of the superior pharyngeal constrictors appear to correlate best with dysphagia at 6months. The AUC values ranged from 0.72 to 0.85 in the case of xerostomia and 0.73 to 0.74 in the case of dysphagia over the different models. The four NTCP models showed similar goodness-of-fit. The differences in AIC between the different models were less than 2 and ranged within 0.7 and 0.8 in the cases of xerostomia and dysphagia, respectively. The calculated parameters of the LKB model were D₅₀=26.9Gy, m=0.63, n=1.0 for the combined contralateral glands at 12months and D₅₀=62.0Gy, m=0.10, n=0.49 for the superior pharyngeal constrictors at 6months.

CONCLUSIONS

The values of the parameters of four NTCP models were determined for salivary glands and pharyngeal constrictors. All four models could fit the clinical data equally well. The NTCP predictions of the combined contralateral glands and superior pharyngeal constrictors showed the best correlation with the patient reported outcomes of xerostomia and dysphagia, respectively.

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.

Tongue-out versus tongue-in position during intensity-modulated radiotherapy for base of tongue cancer: Clinical implications for minimizing post-radiotherapy swallowing dysfunction

BACKGROUND

The purpose of this study was to assess whether different tongue positions change the radiation doses to swallowing organs at risks: the pharyngeal constrictor, oral cavity, and larynx during intensity-modulated radiotherapy (IMRT) for base of tongue (BOT) cancer.

METHODS

IMRT plans with Tongue-out (IMRT-TO) and tongue-in position (IMRT-TI) was compared in 3 cases.

RESULTS

Distance from BOT to pharyngeal constrictor was increased to 1.8 ± 0.8 cm with IMRT-TO from 0.9 ± 0.6 cm with IMRT-TI (P < .01). Compared to IMRT-TI, IMRT-TO significantly decreased the radiation dose to the anterior oral cavity, oral tongue, superior pharyngeal constrictor, middle pharyngeal constrictor, and supraglottic larynx (all P ≤ .04). IMRT-TO also had a smaller volume irradiated than IMRT-TI to the anterior oral cavity and the oral tongue receiving ≥30 Gy (V30) and V35, and superior pharyngeal constrictor and middle pharyngeal constrictor for V55 and V65 (all P ≤ .04).

CONCLUSION

Dosimetric advantage with IMRT-TO over IMRT-TI may potentially reduce post-IMRT swallowing dysfunction in selected patients with BOT cancer.

Optimizing Radiotherapy in HPV-Associated Oropharyngeal Cancer Patients

Concurrent chemoradiation is considered the golden standard in the treatment of locally advanced OPC. However, given the very high survival rates in favorable HPV-positive OPC and the high rates of acute and late treatment-related side effects, de-escalation strategies have to be considered. In this chapter, the potential benefit of a number of de-escalation strategies is described, including of replacement of concurrent chemotherapy by cetuximab, radiation dose de-escalation based on response to induction chemotherapy, radiotherapy alone without systemic treatment, and limiting elective nodal target volumes for radiation. In addition to de-escalation, modern radiation technologies like protons will offer increasing opportunities to decrease the dose to normal tissues in order to prevent radiation-induced toxicities. Initial analysis showed that radiation dose de-escalation based on response to induction chemotherapy in combination with intensity-modulated proton therapy (IMPT) has the highest potential to decrease acute and late toxicities.

How to minimize morbidity in radiotherapy of pharyngolaryngeal tumors?

PURPOSE OF REVIEW

Radiotherapy is one of the most effective treatment modalities for head and neck cancer. However, because of the intricacy between tumors and normal tissues, it can induce morbidity, such as mucositis, dermatitis, xerostomia, dysphagia, hearing loss, vision impairment, skin fibrosis, and osteoradionecrosis of the jaw, and it can dramatically impact on patient quality of life.

RECENT FINDINGS

Throughout the last decade, significant improvements have been made in head and neck cancer radiotherapy, especially with the introduction on a routine basis of intensity-modulated radiotherapy.

SUMMARY

In this context, this review manuscript will focus on how the implementation of intensity-modulated radiotherapy influences treatment morbidity. Specifically, the issues of target volume and organ-at-risk delineation, sparing of organs at risk, tailored treatment intensity, adaptive treatment, and the use of proton therapy will be discussed.

Recurrent oropharyngeal cancer after organ preserving treatment: pattern of failure and survival

The objectives is to thoroughly analyze the pattern of failure and oncologic outcome in recurrent oropharyngeal cancer (OPC) after (chemo)radiotherapy and correlate the site of failure to the planned radiation dose. Between January 2010 and April 2014, 57 patients with recurrent OPC after (chemo)radiotherapy were analyzed. Endpoints were pattern of failure and overall survival (OS). Local (LF) and regional failure (RF) were classified as in-field [>50% within gross tumor volume (GTV)], marginal [<50% within GTV but >50% within clinical target volume (CTV)], or out-of-field (>50% outside CTV) recurrences. In the whole group, 70 recurrences were reported. Of the 31 LF, 29 (93.5%) were in-field and 2 (6.5%) were marginal. No out-field LF was reported. Of the 21 RF, 13 RF (62%) were in-field, 6 (28.5%) marginal, and 2 (9.5%) out-of-field recurrences. Forty-three percent of RF was developed in an electively treated neck level, and 2 of them were contralateral. OS at 2 years in recurrent HPV positive, compared to HPV-negative OPC, were 66 and 18%, respectively (p = 0.011). OS was also significantly better in patients that were salvage treatment which was possible (70 vs. 6%, p < 0.001). Median survival after distant failure was 3.6 months. The great majority of LFs were located within the GTV and 43% of RFs developed in an electively treated neck level. The currently used margins and dose recipe and the indication for bilateral nodal irradiation need to be reevaluated. OS was significantly better in recurrent HPV-positive OPC and in patients, where salvage treatment was possible.

Toward a model-based patient selection strategy for proton therapy: External validation of photon-derived normal tissue complication probability models in a head and neck proton therapy cohort

OBJECTIVE

To externally validate head and neck cancer (HNC) photon-derived normal tissue complication probability (NTCP) models in patients treated with proton beam therapy (PBT).

METHODS

This prospective cohort consisted of HNC patients treated with PBT at a single institution. NTCP models were selected based on the availability of data for validation and evaluated by using the leave-one-out cross-validated area under the curve (AUC) for the receiver operating characteristics curve.

RESULTS

192 patients were included. The most prevalent tumor site was oropharynx (n=86, 45%), followed by sinonasal (n=28), nasopharyngeal (n=27) or parotid (n=27) tumors. Apart from the prediction of acute mucositis (reduction of AUC of 0.17), the models overall performed well. The validation (PBT) AUC and the published AUC were respectively 0.90 versus 0.88 for feeding tube 6months PBT; 0.70 versus 0.80 for physician-rated dysphagia 6months after PBT; 0.70 versus 0.68 for dry mouth 6months after PBT; and 0.73 versus 0.85 for hypothyroidism 12months after PBT.

CONCLUSION

Although a drop in NTCP model performance was expected for PBT patients, the models showed robustness and remained valid. Further work is warranted, but these results support the validity of the model-based approach for selecting treatment for patients with HNC.

Contribution of submandibular gland and swallowing structure sparing to post-radiation therapy PEG dependence in oropharynx cancer patients treated with split-neck IMRT technique

Background

Radiation therapy-related dysphagia is worsened by xerostomia. The submandibular glands (SMG) produce saliva rich in lubricating mucins, and sparing the SMG has been shown to reduce xerostomia. The goal of this study was to determine whether SMG sparing IMRT is associated with reduced post-treatment PEG dependence in locally advanced oropharynx cancer patients.

Methods

Patients treated with definitive radiation therapy for oropharynx cancer were included in this retrospective study. Those with disease recurrence were excluded. Salivary glands and swallowing-related organs at risk, including pharyngeal constrictors, were contoured. Primary endpoint was time from end of radiation treatment to freedom from gastrostomy (PEG) tube dependence. Cox proportional hazards regression and logistic regression were used to assess influence of normal tissue doses on swallowing related endpoints.

Results

Sixty-nine patients were included. All had stage III/IV disease and 97% received concurrent systemic therapy. Fifty-seven percent had contralateral SMG (cSMG) mean dose <50 Gy, a level shown to predict for xerostomia. Eighty four percent of patients had a PEG tube placed electively. On univariate analysis, the strongest predictor of time to freedom from PEG tube dependence was cSMG dose (HR 0.97 per Gy (95% CI 0.95–0.98), p < 0.0001). This relationship persisted on multivariate analysis (p = 0.052). The dose to superior and middle pharyngeal constrictor muscles, and larynx were also significant on univariate analysis. Patients with cSMG dose less than median (42 Gy, n = 34) had a significantly shorter time to freedom from PEG dependence: median 1.9 vs. 3.5 months, p < 0.0001. At 6 months, 3% of patients with cSMG dose < 42 Gy were PEG dependent compared to 31% with cSMG dose > 42 Gy (p = 0.002).

Conclusions

Patients treated with cSMG sparing radiotherapy had significantly shorter time to PEG tube removal after treatment, suggesting a clinically meaningful reduction in subacute dysphagia compared to non-cSMG sparing treatment.

Treatment de-intensification strategies for head and neck cancer

Increasingly, squamous cell carcinoma of the oropharynx (OPSCC) is attributable to transformation resulting from high-risk human papillomavirus (HPV) infection. Such cancers are significantly more responsive to treatment than traditional tobacco- and alcohol-associated squamous cell cancers of the head and neck. Conventional management with definitive chemoradiation, surgery and adjuvant radiation, or radiation given with altered fractionation schemes, while effective, incurs long-term morbidity that escalates with treatment intensity and significantly impairs quality of life. Recent trials have suggested that less intensive treatment regimens may achieve similar efficacy with decreased toxicity. In this article, we review the primary strategies used for de-escalation of treatment, which include the reduction of radiation dose, substitution and/or elimination of concurrent radiosensitising chemotherapy, and the use of minimally invasive surgery. We discuss the rationale behind these approaches and the preliminary data demonstrating the success of de-escalation, as well as potential considerations raised by treatment de-intensification in HPV-associated OPSCC.

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

BACKGROUND

Persistent 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/DESIGN

The 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.

DISCUSSION

DARS 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 REGISTRATION

This study is registered with the International Standard Randomised Controlled Trial register, ISRCTN25458988 (04/01/2016).

Dysphagia - Results from multivariable predictive modelling on aspiration from a subset of the ARTSCAN trial

PURPOSE

To establish predictive models for late objective aspiration and late patient-reported choking based on dose-volume parameters and baseline patient and treatment characteristics, for patients with head and neck cancer undergoing definitive radiotherapy (RT). The impact of electively treated volume on late aspiration was also investigated.

METHODS AND MATERIAL

This prospective cohort is a subsample of 124 survivors from the ARTSCAN study. Late aspiration was identified with videofluoroscopy, at a minimum of 25months after the start of RT. Patient-reported choking was analysed at 12 and 60months post RT using the EORTC Quality of Life Module for Head and Neck Cancer 35. Univariable and multivariable analyses were performed to describe the association between clinical factors and dose-volume descriptors for organs at risk (OARs) and late dysphagia.

RESULTS

Aspiration was found in 47% of the eligible patients. Mean dose to the middle pharyngeal constrictor (MPC), neck dissection post RT and age at randomisation in ARTSCAN were associated to late aspiration. Mean dose to the superior pharyngeal constrictor (SPC) and swallowing complaints at baseline were associated to patient reported choking at both time-points.

CONCLUSIONS

Three separate risk groups for late aspiration, and two risk groups for late patient-reported choking were identified based on number of risk factors. The size of the electively treated volume could be used as a surrogate for individual OARs predicting late aspiration.

Automatic treatment planning improves the clinical quality of head and neck cancer treatment plans

Background

Treatment plans for head and neck (H&N) cancer are highly complex due to multiple dose prescription levels and numerous organs at risk (OARs) close to the target. The plan quality is inter-planner dependent since it is dependent on the skills and experience of the dosimetrist. This study presents a blinded prospective clinical comparison of automatic (AU) and manually (MA) generated H&N VMAT plans made for clinical use.

Methods

MA and AU plans were generated for 30 consecutive patients in Pinnacle³ using the IMRT optimisation module and the new Autoplan module, respectively. The plan quality was blindedly compared by three senior oncologists and the best plan was selected for treatment of the patient. Planning time was measured as the active operator time used. The plan quality was analysed with DVH metrics and the dose delivery accuracy validated on the ArcCheck phantom.

Results

For twenty-nine out of the thirty patients the AU plan was chosen for treatment. Target doses were more homogenous with the AU plans and the OAR doses were significantly reduced, between 0.5 and 6.5 Gy. The average operator time spent on creating a manual plan was 64 min which was halved by Autoplan. The AU plans were more modulated as illustrated by an increase in MUs, which might cause the slightly lower pass rate of 97.7% in the ArcCheck measurements.

Conclusions

Target doses were similar between MA and AU plan, while AU plans spared all OAR considerably better than the MA plans.

Multivariable normal tissue complication probability model-based treatment plan optimization for grade 2-4 dysphagia and tube feeding dependence in head and neck radiotherapy

BACKGROUND AND PURPOSE

Radiotherapy of the head and neck is challenged by the relatively large number of organs-at-risk close to the tumor. Biologically-oriented objective functions (OF) could optimally distribute the dose among the organs-at-risk. We aimed to explore OFs based on multivariable normal tissue complication probability (NTCP) models for grade 2-4 dysphagia (DYS) and tube feeding dependence (TFD).

MATERIALS AND METHODS

One hundred head and neck cancer patients were studied. Additional to the clinical plan, two more plans (an OF_DYS and OF_TFD-plan) were optimized per patient. The NTCP models included up to four dose-volume parameters and other non-dosimetric factors. A fully automatic plan optimization framework was used to optimize the OF_NTCP-based plans.

RESULTS

All OF_NTCP-based plans were reviewed and classified as clinically acceptable. On average, the Δdose and ΔNTCP were small comparing the OF_DYS-plan, OF_TFD-plan, and clinical plan. For 5% of patients NTCP_TFD reduced >5% using OF_TFD-based planning compared to the OF_DYS-plans.

CONCLUSIONS

Plan optimization using NTCP_DYS- and NTCP_TFD-based objective functions resulted in clinically acceptable plans. For patients with considerable risk factors of TFD, the OF_TFD steered the optimizer to dose distributions which directly led to slightly lower predicted NTCP_TFD values as compared to the other studied plans.

[Head and neck intensity-modulated radiation therapy: Normal tissues dose constraints. Pharyngeal constrictor muscles and larynx]

Radio-induced pharyngolaryngeal chronic disorders may challenge the quality of life of head and neck cancer long survivors. Many anatomic structures have been identified as potentially impaired by irradiation and responsible for laryngeal edema, dysphonia and dysphagia. Some dose constraints might be plausible such as keeping the mean dose to the pharyngeal constrictor muscles under 50 to 55Gy, the mean dose to the supra-glottic larynx under 40 to 45Gy and, if feasible, the mean dose to the glottic larynx under 20Gy. A reduction of the dose delivered to the muscles of the floor of the mouth and the cervical esophagus would be beneficial as well. Nevertheless, the publications available do not provide an extensive enough level of proof. One should consider limiting as low as possible the dose delivered to these structures without compromising the quality of irradiation of the target tumor volumes.

Feeding Tube Utilization in Patients with Salivary Gland Malignancies

Objectives To evaluate feeding tube utilization in patients with salivary gland malignancies (SGMs). Study Design Case series with planned data collection. Setting The University of Texas MD Anderson Cancer Center, Houston, Texas, USA. Subjects and Methods Patients (N = 287) were sampled from an epidemiologic SGM registry during a 12-year period. Feeding tube history was retrospectively reviewed. Patients with outside locoregional therapy or palliative treatment were excluded. Enteral feeding and length of dependence were analyzed as a function treatment modality and site of SGM. Results Of 287 patients, 79 (28%) required temporary nasogastric tube feeding (median duration: 13 days, interquartile range: 6-21). Among those 79, 30 (10% of total cohort) required conversion to percutaneous gastrostomy tube (G-tube). Median G-tube duration was 4.8 months (interquartile range: 3.7-13.1). G-tube placement was necessary only in patients receiving multimodality therapy ( P < .001), and among those, 50% with SGMs arising from pharyngeal/laryngeal sites required G-tube, as compared with 8% to 19% of SGMs arising from all other sites ( P < .01). At a median follow-up of 2.4 years, 9 (3%) of all SGM patients were G-tube dependent, but 14% (3 of 22) with laryngeal/pharyngeal sites treated with multimodality therapy remained chronically G-tube dependent. Conclusion While almost 30% of SGM survivors require a temporary nasogastric tube, G-tube utilization is uncommon, in roughly 10% of SGM overall. G-tube utilization appears exclusive to patients treated with multimodality therapy, and chronic gastrostomy remains high (14%) in patients with minor gland cancers arising in the pharynx/larynx, suggesting impetus for dysphagia prophylaxis in these higher-risk subsets, similar to patients treated for squamous cancers.

Reduction of the dose of radiotherapy to the elective neck in head and neck squamous cell carcinoma; a randomized clinical trial. Effect on late toxicity and tumor control

BACKGROUND AND PURPOSE

A multi-center prospective randomized clinical trial has been performed investigating whether a reduction of the dose to the elective nodal sites in head and neck cancer delivered by intensity modulated radiotherapy (IMRT) would result in a reduction of late side effects without compromising tumor control.

MATERIALS AND METHODS

Two hundred patients were included. The prescription dose to the elective nodal volumes was a normalized iso-effective dose in 2Gy fractions (NID_2Gy) of 50Gy in the standard arm and of 40Gy in the experimental arm. Late toxicity was scored at 6, 12, 18 and 24months using the RTOG scoring system.

RESULTS

We observed a trend toward less dysphagia at 6months in the experimental arm, however this was not confirmed after longitudinal analysis. Regarding moderate salivary gland toxicity we observed lower incidence of salivary gland toxicity ⩾grade 1, at 6 (p=0.01) and 18months (p=0.03). After two years of follow up, we did not observe significant differences in estimated local failure rate (14.1% in the 40Gy arm vs 14.4% in the 50Gy arm), estimated regional failure rate (13.0% vs 5.5% in the 40 and the 50Gy arm respectively), estimated metastatic recurrence (13.4% vs 18.5% in the 40 and the 50Gy arm respectively), estimated disease-free survival (57.9% vs 65.3% in the 40 and the 50Gy arm respectively) nor estimated overall survival (72.0% vs 73.2% in the 40 and the 50Gy arm respectively).

CONCLUSIONS

In our study population there was no statistically significant difference regarding survival and estimated recurrence rates between both arms of this study. We found a trend toward less dysphagia at 6months (however not significant after longitudinal analysis) and found a significant reduction of any salivary gland toxicity at 6 and 18months in the 40Gy arm.

Comparison of organ-at-risk sparing and plan robustness for spot-scanning proton therapy and volumetric modulated arc photon therapy in head-and-neck cancer

PURPOSE

Proton radiotherapy for head-and-neck cancer (HNC) aims to improve organ-at-risk (OAR) sparing over photon radiotherapy. However, it may be less robust for setup and range uncertainties. The authors investigated OAR sparing and plan robustness for spot-scanning proton planning techniques and compared these with volumetric modulated arc therapy (VMAT) photon plans.

METHODS

Ten HNC patients were replanned using two arc VMAT (RapidArc) and spot-scanning proton techniques. OARs to be spared included the contra- and ipsilateral parotid and submandibular glands and individual swallowing muscles. Proton plans were made using Multifield Optimization (MFO, using three, five, and seven fields) and Single-field Optimization (SFO, using three fields). OAR sparing was evaluated using mean dose to composite salivary glands (CompSal) and composite swallowing muscles (CompSwal). Plan robustness was determined for setup and range uncertainties (±3 mm for setup, ±3% HU) evaluating V95% and V107% for clinical target volumes.

RESULTS

Averaged over all patients CompSal/CompSwal mean doses were lower for the three-field MFO plans (14.6/16.4 Gy) compared to the three-field SFO plans (20.0/23.7 Gy) and VMAT plans (23.0/25.3 Gy). Using more than three fields resulted in differences in OAR sparing of less than 1.5 Gy between plans. SFO plans were significantly more robust than MFO plans. VMAT plans were the most robust.

CONCLUSIONS

MFO plans had improved OAR sparing but were less robust than SFO and VMAT plans, while SFO plans were more robust than MFO plans but resulted in less OAR sparing. Robustness of the MFO plans did not increase with more fields.

CT image biomarkers to improve patient-specific prediction of radiation-induced xerostomia and sticky saliva

BACKGROUND AND PURPOSE

Current models for the prediction of late patient-rated moderate-to-severe xerostomia (XER_12m) and sticky saliva (STIC_12m) after radiotherapy are based on dose-volume parameters and baseline xerostomia (XER_base) or sticky saliva (STIC_base) scores. The purpose is to improve prediction of XER_12m and STIC_12m with patient-specific characteristics, based on CT image biomarkers (IBMs).

METHODS

Planning CT-scans and patient-rated outcome measures were prospectively collected for 249 head and neck cancer patients treated with definitive radiotherapy with or without systemic treatment. The potential IBMs represent geometric, CT intensity and textural characteristics of the parotid and submandibular glands. Lasso regularisation was used to create multivariable logistic regression models, which were internally validated by bootstrapping.

RESULTS

The prediction of XER_12m could be improved significantly by adding the IBM "Short Run Emphasis" (SRE), which quantifies heterogeneity of parotid tissue, to a model with mean contra-lateral parotid gland dose and XER_base. For STIC_12m, the IBM maximum CT intensity of the submandibular gland was selected in addition to STIC_base and mean dose to submandibular glands.

CONCLUSION

Prediction of XER_12m and STIC_12m was improved by including IBMs representing heterogeneity and density of the salivary glands, respectively. These IBMs could guide additional research to the patient-specific response of healthy tissue to radiation dose.

Treatment failure prediction for head-and-neck cancer radiation therapy

PURPOSE

Treatment outcome prediction is an important emerging topic in oncologic care. To support radiation oncologists on their decisions, with individualized, tailored treatment regimens increasingly becoming the standard of care, accurate tools to predict tumour response to treatment are needed. The goal of this work is to identify the most determinant factor(s) for treatment response aiming to develop prediction models that robustly estimate tumour response to radiation therapy in patients with head-and-neck cancer.

PATIENTS AND METHODS

A population-based cohort study was performed on 92 patients with head-and-neck cancer treated with radiation from 2007 until 2014 at the Portuguese Institute of Oncology of Coimbra (IPOCFG). Correlation analysis and multivariate binary logistic regression analysis were conducted in order to explore the predictive power of the considered predictors. Performance of the models is expressed as the area under the curve (AUC) of the receiver operating characteristics (ROC) curve. A nomogram to predict treatment failure was developed.

RESULTS

Significant prognostic factors for treatment failure, after multivariate regression, were older age, non-concomitant radiation therapy and larger primary tumour volume. A regression model with these predictors revealed an AUC of .78 for an independent data set.

CONCLUSION

For patients with head-and-neck cancer treated with definitive radiation, we have developed a prediction nomogram based on models that presented good discriminative ability in making predictions of tumour response to treatment. The probability of treatment failure is higher for older patients with larger tumours treated with non-concomitant radiation.

The price of robustness; impact of worst-case optimization on organ-at-risk dose and complication probability in intensity-modulated proton therapy for oropharyngeal cancer patients

PURPOSE

To quantify the impact of the degree of robustness against setup errors and range errors on organ-at-risk (OAR) dose and normal tissue complication probabilities (NTCPs) in intensity-modulated proton therapy for oropharyngeal cancer patients.

MATERIAL AND METHODS

For 20 oropharyngeal cases (10 unilateral and 10 bilateral), robust treatment plans were generated using 'minimax' worst-case optimization. We varied the robustness against setup errors ('setup robustness') from 1 to 7mm and the robustness against range errors ('range robustness') from 1% to 7% (+1mm). We evaluated OAR doses and NTCP-values for xerostomia, dysphagia and larynx edema.

RESULTS

Varying the degree of setup robustness was found to have a considerably larger impact than varying the range robustness. Increasing setup robustness from 1mm to 3, 5, and 7mm resulted in average NTCP-values to increase by 1.9, 4.4 and 7.5 percentage point, whereas they increased by only 0.4, 0.8 and 1.2 percentage point when increasing range robustness from 1% to 3%, 5% and 7%. The degree of setup robustness was observed to have a clinically significant impact in bilateral cases in particular.

CONCLUSIONS

For oropharyngeal cancer patients, minimizing setup errors should be given a higher priority than minimizing range errors.

A longitudinal evaluation of improvements in radiotherapy treatment plan quality for head and neck cancer patients

PURPOSE

To investigate changes in head-and-neck cancer (HNC) plan quality following the introduction of new technologies and planning techniques in the last decade.

METHODS AND MATERIALS

Thirty plans were selected from each of four successive periods (P). P1: 7-field static intensity-modulated radiotherapy (IMRT) with parotid gland sparing; P2: dual-arc volumetric-modulated arc therapy (VMAT, similar to P3-P4), including submandibular gland sparing; P3: inclusion of individual swallowing muscles and attempts to further reduce parotid and oral cavity doses through manual interactive optimization; P4: containing the same organs-at-risk (OARs) as P3, but automatically interactively optimized. Plan benchmarking included mean salivary gland/swallowing muscle/oral cavity (Dsal/Dswal/Doc) doses. Differences in mean doses between the periods were analyzed by an ANCOVA, taking geometric differences across periods into account.

RESULTS

Compared to P1, P2 plans improved Dsal by 3.4Gy on average. P3 improved Dsal/Dswal/Doc by 6.9/11.5/7.2Gy over P2, showing that Dswal and Dsal could be improved simultaneously. In P4, Doc/Dswal slightly improved over P3 by 1.7/3.8Gy. Improved OAR sparing in P3/P4 did not come at the cost of increased dose deposition elsewhere and planning target volume (PTV) dose homogeneity was similar.

CONCLUSIONS

New technologies and planning techniques were successfully implemented into routine clinical care and resulting in improved HNC plan quality.