A new, simple maxillary-sparing tongue depressor for external mandibular radiotherapy: a case report

Dosimetric benefits of customised mouth-bite for head neck cancer patients undergoing modern proton therapy - An audit

BACKGROUND AND AIMS

Proton therapy (PRT) for Head Neck Cancer (HNC), in view of the Bragg peak, spares critical structures like oral mucosa better than IMRT. In PRT, mouth-bites, besides immobilising and separating mucosal surfaces, may also negate the end-of-range effect. We retrospectively analysed the details and dosimetric impact of mouth-bites in PRT for HNC.

MATERIALS AND METHODS

The data of consecutive HNC patients treated with IMPT from May 2020 to August 2022 were studied retrospectively. Details of the mouth-bite used, compliance and resultant mucosal separation were noted. Further analysis, restricted to previously unirradiated patients, comprised volumetric dosimetric data pertaining to the mouth-bite and distal mucosal surfaces. High LET zones, corresponding to 6-12 keV/micron, for mouth-bite doses above 30 Gy, were recalculated from existing plans.

RESULTS

A mouth-bite was used in 69 of 80 consecutively treated patients, ranging from 8 to 42 mm in thickness, and 12 to 52 mm in the resultant mucosal sparing. In 42 patients in whom the mouth-bite V 32 Gy was > 0, median Dmean, absolute V32, V39, V50 and V60 GyE (Gray Equivalent) of the mouth bite was 35.65 GyE (Range: 2.65 - 60 GyE), 10 cc (Range: 0.1 - 32 cc), 7.6 cc (Range: 0.1 - 30.8 cc), 5.7 cc (Range: 0.2 - 29.2 cc) and 1.45 cc (Range: 0.2 - 18.1 cc) respectively, all significantly more than the spared adjacent mucosal surface. In absence of a mouth-bite, the spared mucosa would have at least partially received the high dose received by the mouth-bite. High LET zones were noted in 12 of 48 mouth-bites.

CONCLUSION

In PRT for HNC, mouth-bites play a vital role in improving the sparing of mucosa outside the target.

Assessment of mouth opening before and after head and neck radiotherapy in patients with intraoral stents

Background

We evaluated the evolution of mouth opening before and after radiotherapy of the head and neck in patients using intraoral stents.

Materials and methods

Twenty-one patients with head and neck cancer who were indicated for radiotherapy participated in this study. Maximum interincisal opening measurements were performed before and after radiotherapy. Paired analyses of the pre- and post-radiotherapy groups were performed using paired samples t-tests and correlation analyses using Spearman's correlation test, with p < 0.05 considered statistically significant.

Results

Paired analyses of the pre- and post-radiotherapy groups revealed a statistically significant reduction in post-radiotherapy maximum interincisal opening (p < 0.001). However, only four individuals were diagnosed with trismus after radiotherapy. Regarding the correlation tests, no statistically significant differences were observed between the differences in pre- and post-radiotherapy maximum interincisal opening values and the study variables.

Conclusion

The use of prosthetic devices during head and neck radiotherapy can reduce radiation doses in areas of no interest, thereby preventing the acute and late toxicities associated with cancer therapy.

Radiotherapy of tongue cancer using an intraoral stent: a pilot study

Aim:

The aim was to evaluate the feasibility of an intraoral stent (10 and 20 mm thickness) in radiotherapy of tongue cancer, and to measure the reduction in acute mucositis in the palate.

Materials and method:

There were six patients in the intervention group, and seven patients in the control group. Target coverage was measured by the minimum dose covering 98% of the clinical target volume (CTV). Data were collected from the planning CT and daily cone-beam computer tomography (CBCT).

Results:

The 10 and 20 mm stent yielded a mean distance of 26 and 36 mm, respectively, between the tongue and the hard palate. We found comparable dose coverage of the CTV in the treatment plan, and on the CBCT. The stent reduced mean dose to the hard palate by 61.0% (p = 0.002). Dose to the soft palate was not reduced (p = 0.18). Average Common Terminology Criteria for Adverse Events (CTCAE) mucositis scores of the hard palate were 0 and 0.8 in the intervention and control group, respectively. The mucositis scores of the soft palate were 1.2 and 1.8.

Findings:

Use of an intraoral stent substantially reduced the dose to the hard palate. CTV coverage was maintained. We did not find any significant reduction in visually scored radiation-induced mucositis.

Stopping-power ratio of mouthpiece materials for charged-particle therapy in head and neck cancer

In this study, the stopping-power ratios (SPRs) of mouthpiece materials were measured and the errors in the predicted SPRs based on conversion table values were further investigated. The SPRs of the five mouthpiece materials were predicted from their computed tomography (CT) numbers using a calibrated conversion table. Independently, the SPRs of the materials were measured from the Bragg peak shift of a carbon-ion beam passing through the materials. The errors in the SPRs of the materials were determined as the difference between the predicted and measured values. The measured SPRs (errors) of the Nipoflex 710™ and Bioplast™ ethylene–vinyl acetate copolymers (EVAs) were 0.997 (0.023) and 0.982 (0.007), respectively. The SPRs of the vinyl silicon impression material, light-curable resin, and bis-acrylic resin were 1.517 (0.134), 1.161 (0.068), and 1.26 (0.101), respectively. Among the five tested materials, the EVAs had the lowest SPR errors, indicating the highest human-tissue equivalency.

Are intraoral stents effective in reducing oral toxicities caused by radiotherapy? A systematic review and meta-analysis

STATEMENT OF PROBLEM

Intraoral stents have been provided to minimize acute and chronic toxicities induced by radiotherapy, including oral mucositis, salivary changes, trismus, radiation-related caries, and osteoradionecrosis. However, a systematic review and meta-analysis is necessary to determine their effectiveness.

PURPOSE

The purpose of this systematic review and meta-analysis was to determine the effectiveness of intraoral stent use and determine whether these prosthetic devices can reduce radiation dosage to nontargeted oral tissues and adverse effects related to head and neck radiation.

MATERIAL AND METHODS

Two independent reviewers made a systematic search for articles published from January 2010 to March 2020 in 3 databases, supplemented by a manual search. Studies were included if they were clinical trials (randomized controlled trials, both prospective and retrospective), published in English, and evaluated radiation dose and oral adverse side effects (acute or chronic) induced by radiotherapy of participants with and without intraoral stents.

RESULTS

The search strategy identified 201 studies; of which, 9 were included. A total of 251 participants were evaluated; of whom, 168 (77.3%) used intraoral stents and 57 (22.7%) were treated with radiotherapy without a prosthetic device. A statistically significant difference was found regarding the use of intraoral stents for preventing oral mucositis (P<.001), salivary changes (P=.003), and trismus (P<.02). A funnel plot showed asymmetry among the differences of means in all selected studies.

CONCLUSIONS

Intraoral stents have a positive effect on preventing oral mucositis. Further clinical trials are needed to address the flaws identified in the present systematic review.

3D-printed individualized tooth-borne tissue retraction devices compared to conventional dental splints for head and neck cancer radiotherapy: a randomized controlled trial

BACKGROUND

Despite modern treatment techniques, radiotherapy (RT) in patients with head and neck cancer (HNC) may be associated with high rates of acute and late treatment-related toxicity. The most effective approach to reduce sequelae after RT is to avoid as best as possible healthy tissues and organs at risk from the radiation target volume. Even small geometric changes can lead to a significant dose reduction in normal tissue and better treatment tolerability. The major objective of the current study is to investigate 3D printed, tooth-borne tissue retraction devices (TRDs) compared to conventional dental splints for head and neck RT.

METHODS

In the current two-arm randomized controlled phase II trial, a maximum of 34 patients with HNC will be enrolled. Patients will receive either TRDs or conventional dental splints (randomization ratio 1:1) for the RT. The definition of the target volume, modality, total dose, fractionation, and imaging guidance is not study-specific. The primary endpoint of the study is the rate of acute radiation-induced oral mucositis after RT. The quality of life, local control and overall survival 12 months after RT are the secondary endpoints. Also, patient-reported outcomes and dental status, as well as RT plan comparisons and robustness analyzes, will be assessed as exploratory endpoints. Finally, mesenchymal stem cells, derived from the patients' gingiva, will be tested in vitro for regenerative and radioprotective properties.

DISCUSSION

The preliminary clinical application of TRD showed a high potential for reducing acute and late toxicity of RT in patients with HNC. The current randomized study is the first to prospectively investigate the clinical tolerability and efficacy of TRDs for radiation treatment of head and neck tumors.

TRIAL REGISTRATION

ClinicalTrials.gov; NCT04454697; July 1st 2020; https://clinicaltrials.gov/ct2/show/record/NCT04454697 .

Benefits of intraoral stents in patients with head and neck cancer undergoing radiotherapy: Systematic review

Intraoral stents aim to reduce the oral complications associated with head and neck cancers radiotherapy. The aim of this study is to determine the benefits associated with these devices. A systematic review was conducted in PubMed, Web of Science, and Scopus databases selecting full articles published in English, Portuguese, or Spanish until June 6, 2020 (PROSPERO registration: CRD42020185065). The studies were evaluated by Hadorn and Somerfield criteria and guidelines were established. Nineteen studies were identified suggesting the use of intraoral stent for radiotherapy for patients with cancer on/near the mandible to reduce oral mucositis, trismus, xerostomia (LoE III), and dose in healthy structures (LoE IV) and for cancer on/near the maxilla to reduce oral mucositis and dose in healthy structures (LoE IV). Despite the limited scientific evidence, several benefits associated with the use of intraoral stent for radiotherapy of the head and neck neoplasia have been reported.

Development of a Tongue Immobilization Device Using a 3D Printer for Intensity Modulated Radiation Therapy of Nasopharyngeal Cancer Patients

Purpose

This study aimed to reduce radiation doses to the tongue, a patient-specific semi-customized tongue immobilization device (SCTID) was developed using a 3D printer for helical tomotherapy (HT) of nasopharyngeal cancer (NPCa). Dosimetric characteristics and setup stability of the SCTID were compared with those of a standard mouthpiece (SMP).

Materials and Methods

For displacement and robust immobilization of the tongue, the SCTID consists of four parts: upper and lower tooth stoppers, tongue guider, tongue-tip position guide bar, and connectors. With the SCTID and SMP, two sets of planning computed tomography and HT plans were obtained for 10 NPCa patients. Dosimetric and geometric characteristics were compared. Position reproducibility of the tongue with SCTID was evaluated by comparing with planned dose and adaptive accumulated dose of the tongue and base of the tongue based on daily setup mega-voltage computed tomography.

Results

Using the SCTID, the tongue was effectively displaced from the planning target volume compared to the SMP. The median mucosa of the tongue (M-tongue) dose was significantly reduced (20.7 Gy vs. 27.8 Gy). The volumes of the M-tongue receiving a dose of 15 Gy, 30 Gy, and 45 Gy and the volumes of the mucosa of oral cavity and oropharynx (M-OC/OP) receiving a dose of 45 Gy and 60 Gy were significantly lower than using the SMP. No significant differences was observed between the planned dose and the accumulated adaptive dose in any dosimetric characteristics of the tongue and base of tongue.

Conclusion

SCTID can not only reduce the dose to the M-tongue and M-OC/OP dramatically, when compared to SMP, but also provide excellent reproducibility and easy visual verification.

Are Intraoral Stents Effective for Reducing the Severity of Oral Mucositis During Radiotherapy for Maxillary and Nasal Cavity Cancer?

PURPOSE

The intraoral stent (IOS) is an individualized mouth opening device that can be used during radiotherapy (RT) for head and neck cancer to prevent unnecessary irradiation to normal tissues. The purpose of the present study was to compare the severity of oral mucositis (OM) between patients using and not using an IOS during RT for maxillary and nasal cavity cancer.

PATIENTS AND METHODS

We designed and implemented a retrospective cohort study. The study sample included patients with maxillary and nasal cavity cancer who had undergone RT. The primary predictor variable was IOS application, and the outcome variable was the grade of OM.

RESULTS

The IOS group included 18 patients with an IOS and the control group, 16 patients without an IOS. The parameters of the dose-volume histogram included the median dosage covering 1 mL (D1mL) for the tongue and the mean dosage. The D1mL (36.2 vs 65.4 Gy) and mean dosage (4.9 Gy vs 25.9 Gy) were both significantly lower in the IOS group than in the control group (P < .005). The incidence of OM using the National Cancer Institute Common Terminology Criteria for Adverse Events, version 4.0, were significantly different between the oral stomatitis grade and the use of an IOS (P = .028). A significant difference was found in opioid use between the IOS and control groups (P = .009).

CONCLUSIONS

The use of an IOS decreased the radiation dosage to the tongue, the grade of OM, and opioid usage during RT.

Are intraoral customized stents still necessary in the era of Highly Conformal Radiotherapy for Head & Neck cancer? Case series and literature review

Aim

To evaluate the dose sparing efficacy of intraoral customized stents in combination with IGRT/VMAT in Head & Neck cancer patients.

Background

Despite advances in high-dose conformal radiotherapy (RT) techniques, adverse effects (such as oral mucositis) during and after RT often require temporary suspension of treatment and affect the quality of life in survivors. Intraoral customized stents can decrease radiation doses in healthy tissues and minimize damage from radiations. At the best of our knowledge the clinical impact of such devices in combination with VMAT (volumetric modulated arc therapy) is not reported in the literature.

Cases description

Three Head & Neck cancer patients were submitted to image guided (IG) RT/VMAT in their treatment protocol. Dose distribution with and without the use of an intraoral stent was compared in each patient. Mean radiation doses proved to be lower in all patients, especially in the subsite: oral cavity.

Conclusions

There are several reports on the efficacy of IS during RT for Head & Neck cancer. Despite technological advances, the combination between high conformal RT and intraoral stents could still play a role in the management of this kind of patients. This strengthens the usefulness of the individualization of treatments and multidisciplinary approach.

Development of a semi-customized tongue displacement device using a 3D printer for head and neck IMRT

Purpose

To reduce radiation doses to the tongue, a patient-specific semi-customized tongue displacement device (SCTDD) was developed using a 3D printer (3DP) for head and neck (H&N) radiation therapy (RT). Dosimetric characteristics of the SCTDD were compared with those of a standard mouthpiece (SMP).

Materials and methods

The SCTDD consists of three parts: a mouthpiece, connector with an immobilization mask, and tongue displacer, which can displace the tongue to the contralateral side of the planning target volume. Semi-customization was enabled by changing the thickness and length of the SCTDD. The instrument was printed using a 3DP with a biocompatible material. With the SCTDD and SMP, two sets of planning computed tomography (CT) and tomotherapy plans were obtained for seven H&N cancer patients. Dosimetric and geometric characteristics were compared.

Results

Using the SCTDD, the tongue was effectively displaced from the planning target volume without significant tongue volume change compared to the SMP. The median tongue dose was significantly reduced (29.6 Gy vs. 34.3 Gy). The volumes of the tongue receiving a dose of 15 Gy, 30 Gy, 35 Gy, 45 Gy, and 60 Gy were significantly lower than using the SMP.

Conclusion

The SCTDD significantly decreased the radiation dose to the tongue compared to the SMP, which may potentially reduce RT-related tongue toxicity.

A custom-made mouthpiece incorporating tongue depressors and elevators to reduce radiation-induced tongue mucositis during carbon-ion radiation therapy for head and neck cancer

We introduce a custom-made mouthpiece for carbon-ion radiation therapy for head and neck malignancy. The mouthpiece incorporates either a tongue depressor or elevator depending on tumor location. The risk of tongue mucositis may be reduced without compromising therapeutic efficacy through mouthpiece shaping.