Cluster-Based Toxicity Estimation of Osteoradionecrosis Via Unsupervised Machine Learning: Moving Beyond Single Dose-Parameter Normal Tissue Complication Probability by Using Whole Dose-Volume Histograms for Cohort Risk Stratification

PURPOSE

Given the limitations of extant models for normal tissue complication probability estimation for osteoradionecrosis (ORN) of the mandible, the purpose of this study was to enrich statistical inference by exploiting structural properties of data and provide a clinically reliable model for ORN risk evaluation through an unsupervised-learning analysis that incorporates the whole radiation dose distribution on the mandible.

METHODS AND MATERIALS

The analysis was conducted on retrospective data of 1259 patients with head and neck cancer treated at The University of Texas MD Anderson Cancer Center between 2005 and 2015. During a minimum 12-month posttherapy follow-up period, 173 patients in this cohort (13.7%) developed ORN (grades I to IV). The (structural) clusters of mandibular dose-volume histograms (DVHs) for these patients were identified using the K-means clustering method. A soft-margin support vector machine was used to determine the cluster borders and partition the dose-volume space. The risk of ORN for each dose-volume region was calculated based on incidence rates and other clinical risk factors.

RESULTS

The K-means clustering method identified 6 clusters among the DVHs. Based on the first 5 clusters, the dose-volume space was partitioned by the soft-margin support vector machine into distinct regions with different risk indices. The sixth cluster entirely overlapped with the others; the region of this cluster was determined by its envelopes. For each region, the ORN incidence rate per preradiation dental extraction status (a statistically significant, nondose related risk factor for ORN) was reported as the corresponding risk index.

CONCLUSIONS

This study presents an unsupervised-learning analysis of a large-scale data set to evaluate the risk of mandibular ORN among patients with head and neck cancer. The results provide a visual risk-assessment tool for ORN (based on the whole DVH and preradiation dental extraction status) as well as a range of constraints for dose optimization under different risk levels.

Prevalence of free flap failure in mandibular osteoradionecrosis reconstruction: a systematic review and meta-analysis

Our study aimed to estimate the prevalence of total free flap failure following free flap reconstruction for mandibular osteoradionecrosis (mORN) and assess the impact of potential moderators on this outcome. A comprehensive systematic literature search was independently conducted by two reviewers using the Medline, Scopus, Web of Science and Cochrane Library databases. Quality assessment of the selected studies was performed, and prevalence estimates with 95% confidence intervals (CI) were calculated. Outlier and influential analyses were conducted, and meta-regression analyses was employed to investigate the effects of continuous variables on the estimated prevalence. Ultimately, forty-six eligible studies (involving 1292 participants and 1344 free flaps) were included in our meta-analysis. The findings of our study revealed a prevalence of 3.1% (95% CI 1.3-5.4%) for total free flap failure after reconstruction for mORN. No study was identified as critically influential, and meta-regression analysis did not pinpoint any potential sources of heterogeneity. These findings provide valuable insights for researchers and serve as a foundation for future investigations into the management of mandibular osteoradionecrosis and the prevention of free flap failure in this context.

Irradiation Induced Biochemical Changes in Human Mandibular Bone: A Raman Spectroscopic Study

Understanding the biochemical changes in irradiated human mandible after radiotherapy of cancer patients is critical for oral rehabilitation. The underlying mechanism for radiation-associated changes in the bone at the molecular level could lead to implant failure and osteoradionecrosis. The study aimed to assess the chemical composition and bone quality in irradiated human mandibular bone using Raman spectroscopy. A total of 33 bone biopsies from 16 control and 17 irradiated patients were included to quantify different biochemical parameters from the Raman spectra. The differences in bone mineral and matrix band intensities between control and irradiated groups were analyzed using unpaired Student's t-test with statistical significance at p < 0.05. Findings suggest that the intensity of the phosphate band is significantly decreased and the carbonate band is significantly increased in the irradiated group. Further, the mineral crystallinity and carbonate to phosphate ratio are increased. The mineral to matrix ratio is decreased in the irradiated group. Principal component analysis (PCA) based on the local radiation dose and biopsy time interval of irradiated samples did not show any specific classification between irradiation sub-groups. Irradiation disrupted the interaction and bonding between the organic matrix and hydroxyapatite minerals affecting the bone biochemical properties. However, the normal clinical appearance of irradiated bone would have been accompanied by underlying biochemical and microscopical changes which might result in radiation-induced delayed complications.

[Impact of neck dissection in N2-3 oropharyngeal squamous cell carcinomas treated with definitive chemoradiotherapy: An observational real-life study]

PURPOSE

The purpose of this study was to assess the efficacy in terms of neck failure of an initial neck dissection before definitive chemoradiotherapy in N2-3 oropharyngeal squamous cell carcinomas, as well as the dosimetric impact and the acute and delayed morbidity of this approach.

MATERIALS AND METHODS

All patients consecutively treated between 2009 and 2018 with definitive chemoradiotherapy using intensity-modulated conformal radiotherapy (IMRT) for a histologically proven N2-3 oropharyngeal squamous cell carcinomas were retrospectively included. The therapeutic approach consisted of induction chemotherapy, followed by cisplatine-based chemoradiotherapy preceded or not by neck dissection. Neck dissection was discussed on a case-by-case basis in a dedicated multidisciplinary tumour board for patients with a dissociated response to induction chemotherapy, defined as a better response on the primary than on the node. Chemoradiotherapy without neck dissection was systematically performed in case of a major lymph node response to induction chemotherapy (decrease in size of 90% or more). Intensity-modulated radiotherapy using a simultaneous-integrated boost delivered 70Gy in 35 fractions on macroscopic tumour volumes, 63Gy on intermediate-risk levels or extra-nodal extension and 54Gy on prophylactic lymph node areas.

RESULTS

Two groups were constituted: 47 patients without an initial neck dissection (62.7%), and 28 patients with a neck dissection prior to definitive chemoradiotherapy (37.3%). Initial patient characteristics were not statistically different between the two groups. The median follow-up was 60.1months (range: 3.2-119months). Incidence of neck failure was higher in patients without neck dissection (P=0.015). The neck failure rate at 5years was 19.8% (95% confidence interval: 7.4-30.6%; P=0.015) without neck dissection versus 0% following neck dissection. All lymph node failures occurred in the planned target volume at 70Gy. Upfront neck dissection suggested a decrease in the mean dose received by the homolateral parotid gland (P=0.01), mandible (P=0.02), and thyroid gland (P=0.02). Acute toxicity of chemoradiotherapy after neck dissection suggested a reduction in grade≥3 adverse events (P=0.04), early discontinuation of concomitant chemotherapy (P=0.009) and feeding tube-dependence (P=0.008) in univariate analysis. During follow-up, there was no difference between the two groups in terms of xerostomia, dysgeusia, dysphagia or gastrostomy dependence in univariate analysis.

CONCLUSION

Neck dissection prior to definitive chemoradiotherapy in N2-3 oropharyngeal squamous cell carcinoma was associated with high neck control without additional mid and long-term morbidity.

Comparison of machine learning methods for prediction of osteoradionecrosis incidence in patients with head and neck cancer

OBJECTIVES

Mandible osteoradionecrosis (ORN) is one of the most severe toxicities in patients with head and neck cancer (HNC) undergoing radiotherapy (RT). The existing literature focuses on the correlation of mandible ORN and clinical and dosimetric factors. This study proposes the use of machine learning (ML) methods as prediction models for mandible ORN incidence.

METHODS

A total of 96 patients (ORN incidence ratio of 1:1) treated between 2011 and 2015 were selected from the local HNC toxicity database. Demographic, clinical and dosimetric data (based on the mandible dose-volume histogram) were considered as model variables. Prediction accuracy (measured using a stratified fivefold nested cross-validation), sensitivity, specificity, precision and negative predictive value were used to evaluate the prediction performance of a multivariate logistic regression (LR) model, a support vector machine (SVM) model, a random forest (RF) model, an adaptive boosting (AdaBoost) model and an artificial neural network (ANN) model. The different models were compared based on their prediction accuracy and using the McNemar's hypothesis test.

RESULTS

The ANN model (77% accuracy), closely followed by the SVM (76%), AdaBoost (75%) and LR (75%) models, showed the highest overall prediction accuracy. The RF model (71%) showed the lowest prediction accuracy. However, based on the McNemar's test applied to all model pair combinations, no statistically significant difference between the models was found.

CONCLUSION

Based on our results, we encourage the use of ML-based prediction models for ORN incidence as has already been done for other HNC toxicity end points.

ADVANCES IN KNOWLEDGE

This research opens a new path towards personalised RT for HNC using ML to predict mandible ORN incidence.

Challenges threaten, opportunity awaits hyperbaric medicine and the head and neck cancer patient

Over the past four decades, hyperbaric oxygen (HBO2) therapy has played a prominent role in both the prevention and treatment of mandibular osteoradionecrosis (ORN). It has done so on the strength of laboratory observations and clinical reports, yet only limited efficacy data. This dual role has come under increasing scrutiny in the modern radiotherapy (RT) and surgical eras. The ability to spare healthy "non-target" tissue has markedly improved since the two-dimensional planning and delivery techniques in use when HBO2's prophylactic value was first demonstrated. A recent study failed to identify this same benefit in patients who received high-precision imaging and conformal RT. HBO2 therapy is under challenge as preferred treatment for early stage ORN. A recently introduced "fibroatrophic" mechanism contrasts with the hypovascular-hypocellular-hypoxic injury pattern that formed the basis for HBO2's therapeutic use. This alternative pathophysiologic state appears to benefit from an oral antioxidant medication regimen. The continuing necessity of HBO2 in support of mandibular reconstruction for advanced ORN is in question. Microsurgery-based vascularized bone flaps increasingly represent standard care, invariably in the absence of perioperative HBO2. Renewed interest in hyperbaric oxygen as a radiation sensitizer offers some promise. Hypoxia remains a critical radio-resistant factor in many solid tumors. Malignant gliomas have been a primary focus of several small studies, with resulting improvements in local control and median survival. Hyperbaric radiation sensitization has recently addressed oropharyngeal cancer. Preliminary data indicates that addition of HBO2 to chemo-radiation standard of care is technically feasible, well tolerated and safe. A Phase II efficacy trial will investigate the potential for of HBO2 to improve progression-free and relapse-free survival in newly diagnosed locally advanced head and neck cancers. What follows is a review and summary of relevant peer-reviewed literature.

Comparison of the IPSA and HIPO algorithms for interstitial tongue high-dose-rate brachytherapy

Purpose

This study aimed to compare the inverse planning simulated annealing (IPSA) stochastic algorithm with the hybrid inverse planning and optimization (HIPO) algorithm for interstitial tongue high-dose-rate (HDR) brachytherapy.

Methods

Twenty patients who received radiotherapy for tongue cancer using interstitial HDR brachytherapy were retrospectively selected for this study. Oncentra Brachy v. 4.3 was used for IPSA and HIPO planning. Four to eight fixed catheter configurations were determined according to the target shape. During the optimization process, predetermined constrain values were used for each IPSA and HIPO plan. The dosimetric parameters and dwell time were analyzed to evaluate the performances of the plans.

Results

The total dwell time using IPSA was 4 seconds longer than that of HIPO. The number of active positions per catheter for the IPSA plans were approximately 2.5 fewer than those of the HIPO plans. The dose-volumetric parameters related to the clinical target volume with IPSA were lower than those with HIPO. In terms of the dose-volumetric parameters related to normal tissue, HIPO tended to associate with slightly higher values than IPSA, without statistical significance. After GrO, the target coverages were satisfied to clinical goal for all patients. The total dwell times was approximately increased by 10%.

Conclusions

The IPSA and HIPO dose optimization algorithms generate similar dosimetric results. In terms of the dwell time, HIPO appears to be more beneficial.

HOPON (Hyperbaric Oxygen for the Prevention of Osteoradionecrosis): a randomised controlled trial of hyperbaric oxygen to prevent osteoradionecrosis of the irradiated mandible: study protocol for a randomised controlled trial

BACKGROUND

Osteoradionecrosis of the mandible is the most common serious complication of radiotherapy for head and neck malignancy. For decades, hyperbaric oxygen has been employed in efforts to prevent those cases of osteoradionecrosis that are precipitated by dental extractions or implant placement. The evidence for using hyperbaric oxygen remains poor and current clinical practice varies greatly. We describe a protocol for a clinical trial to assess the benefit of hyperbaric oxygen in the prevention of osteoradionecrosis during surgery on the irradiated mandible.

METHODS/DESIGN

The HOPON trial is a phase III, randomised controlled, multi-centre trial. It employs an unblinded trial design, but the assessment of the primary endpoint, i.e. the diagnosis of osteoradionecrosis, is assessed on anonymised clinical photographs and radiographs by a blinded expert panel. Eligibility is through the need for a high-risk dental procedure in the mandible where at least 50-Gy radiotherapy has been received. Patients are randomised 1:1 to hyperbaric oxygen arm (Marx protocol) : control arm, but both groups receive antibiotics and chlorhexidine mouthwash. The primary endpoint is the presence of osteoradionecrosis at 6 months following surgery, but secondary endpoints include other time points, acute symptoms and pain, quality of life, and where implants are placed, their successful retention.

DISCUSSION

The protocol presented has evolved through feasibility stages and through analysis of interim data. The classification of osteoradionecrosis has undergone technical refinement to ensure that robust definitions are employed. The HOPON trial is the only multi-centre RCT conducted in this clinical setting despite decades of use of hyperbaric oxygen for the prevention of osteoradionecrosis.

TRIAL REGISTRATION

European Clinical Trials Database, ID: EudraCT200700622527 . First registered on 5 November 2007.

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.

Dose-volume correlates of mandibular osteoradionecrosis in Oropharynx cancer patients receiving intensity-modulated radiotherapy: Results from a case-matched comparison

PURPOSE

To determine dosimetric parameters associated with osteoradionecrosis (ORN) in oropharyngeal cancer (OPC) patients in the IMRT era.

MATERIAL AND METHODS

Subsequent to institutional review board approval, we identified ORN in OPC patients treated with IMRT from 2002 to 2013. 1:2 case-control matching was implemented. Mandibular dose-volume histograms (DVH) were extracted. Dosimetric parameters were compared using non-parametric stats. Recursive partitioning analysis (RPA) was done to identify DVH correlates of ORN.

RESULTS

68 ORN cases and 131 controls were matched. Median follow-up was 41months and median time to development of ORN was 16months. Mandibular mean dose was significantly higher in the ORN cohort (48.1 vs 43.6Gy, p<0.0001). However, the maximum dose was not statistically different. DVH bins from V35 to V73 were all significantly higher in the ORN cohort compared with controls (p<0.0006). Two DVH parameters were identified in RPA analysis, V43 and V58. The majority (81%) of ORN cases were observed with both V44≥42% and V58≥25%.

CONCLUSIONS

Our data demonstrate that a wide range of DVH parameters in the intermediate and high beam path were all significantly higher in ORN patients. Mandibular V44<42% and V58<25% represent reasonable DVH constraints for IMRT plan acceptability, when tumor coverage is not compromised.

Low-intensity pulsed ultrasound reduces periodontal atrophy in occlusal hypofunctional teeth

OBJECTIVE

To clarify whether low-intensity pulsed ultrasound (LIPUS) exposure has recovery effects on the hypofunctional periodontal ligament (PDL) and interradicular alveolar bone (IRAB).

MATERIALS AND METHODS

Twelve-week-old male Sprague-Dawley rats were divided into three groups (n = 5 each): a normal occlusion (C) group, an occlusal hypofunction (H) group, and an occlusal hypofunction group subjected to LIPUS (HL) treatment. Hypofunctional occlusion of the maxillary first molar (M1) of the H and HL groups was induced by the bite-raising technique. Only the HL group was irradiated with LIPUS for 5 days. The IRAB and PDL of M1 were examined by microcomputed tomography (micro-CT) analysis. To quantify mRNA expression of cytokines involved in PDL proliferation and development, real-time reverse transcription quantitative PCR (qRT-PCR) was performed for twist family bHLH transcription factor 1 (Twist1), periostin, and connective tissue growth factor (CTGF) in the PDL samples.

RESULTS

Micro-CT analysis showed that the PDL volume was decreased in the H group compared with that of the C and HL groups. Both bone volume per tissue volume (BV/TV) of IRAB was decreased in the H group compared with that in the C group. LIPUS exposure restored BV/TV in the IRAB of the HL group. qRT-PCR analysis showed that Twist1, periostin, and CTGF mRNA levels were decreased in the H group and increased in the HL group.

CONCLUSION

LIPUS exposure reduced the atrophic changes of alveolar bone by inducing the upregulation of periostin and CTGF expression to promote PDL healing after induction of occlusal hypofunction.

Refining the definition of mandibular osteoradionecrosis in clinical trials: The cancer research UK HOPON trial (Hyperbaric Oxygen for the Prevention of Osteoradionecrosis)

INTRODUCTION

Mandibular osteoradionecrosis (ORN) is a common and serious complication of head and neck radiotherapy for which there is little reliable evidence for prevention or treatment. The diagnosis and classification of ORN have been inconsistently and imprecisely defined, even in clinical trials.

METHODS

A systematic review of diagnosis and classifications of ORN with specific focus on clinical trials is presented. The most suitable classification was evaluated for consistency using blinded independent review of outcome data (clinical photographs and radiographs) in the HOPON trial.

RESULTS

Of 16 ORN classifications found, only one (Notani) appeared suitable as an endpoint in clinical trials. Clinical records of 217 timepoints were analysed amongst 94 randomised patients in the HOPON trial. The only inconsistency in classification arose where minor bone spicules (MBS) were apparent, which occurred in 19% of patients. Some trial investigators judged MBS as clinically unimportant and not reflecting ORN, others classified as ORN based on rigid definitions in common clinical use. When MBS was added as a distinct category to the Notani classification this ambiguity was resolved and agreement between observers was achieved.

DISCUSSION

Most definitions and clinical classifications are based on retrospective case series and may be unsuitable for prospective interventional trials of ORN prevention or treatment. When ORN is used as a primary or secondary outcome in prospective clinical trials, the use of Notani classification with the additional category of MBS is recommended as it avoids subjectivity and enhances reliability and consistency of reporting.

[Mandibular osteoradionecrosis (ORN) as a side effect of head and neck cancer treatment: Factors that induce it]

INTRODUCTION

Osteoradionecrosis of the mandible is a relatively common complication in patients with head and neck cancer undergoing radiotherapy or concomitant chemoradiotherapy, characterized by exposure of the mandibular bone either in the mouth or in the facial skin, with no improvement with conservative treatment for six months. The risk factors are radiotherapy in head and neck region, lack of dental prophylaxis before treatment and dental extraction.

MATERIAL AND METHODS

Retrospective observational study analyzing incidence and etiologic factors of osteoradionecrosis in 250 patients undergoing radiotherapy or combined treatment of cervicofacial area between 2002 and 2010.

RESULTS

25 patients were included; the horizontal branch was the most affected area, followed by the anterior arch. Associated factors were: stage (T4a and T4b), tumor location (oral cavity), dental extraction pre or post-radiotherapy, and radiotherapy time (pre-or postoperative); 72% had association with tooth extraction. Only five patients had control with conservative measures, and 20 required some type of mandibulectomy, only three of them were candidates for reconstruction with fibular free flap; none received treatment in a hyperbaric chamber.

CONCLUSIONS

The data suggest that osteoradionecrosis has a multifactorial origin, and prevention is the best alternative and includes pretreatment dental prophylaxis to avoid tooth extractions and close monitoring and surveillance in order to identify early osteoradionecrosis. Most patients require mandible resection as definitive treatment.

Role of parathyroid hormone in regeneration of irradiated bone in a murine model of mandibular distraction osteogenesis

BACKGROUND

The purpose of this study was to measure the histologic and histomorphometric effects of parathyroid hormone (PTH) treatment on irradiated bone undergoing distraction osteogenesis (DO).

METHODS

Thirty-four rats were divided into 3 groups. The control group underwent DO and the radiation control group underwent radiotherapy (RT) before DO. The PTH group underwent RT and received PTH during DO. Quantitative histology and histomorphometry were performed.

RESULTS

RT resulted in a depletion of osteocytes and increase in empty lacunae. Treatment with PTH resulted in an increase in osteocyte counts and decrease in empty lacunae (p < .05), restoring osteocytes to levels seen in nonradiated bone (p = .121). RT decreased bone volume to tissue volume (BV-TV) ratio and increased osteoid volume to tissue volume (OV-TV) ratio, signifying increased immature bone formation. PTH treatment restored OV-TV ratio to that observed in nonradiated bone.

CONCLUSION

PTH treatment of irradiated bone enhanced bone regeneration and restored osteocyte counts and OV-TV ratio to levels comparable to nonradiated bone. © 2016 Wiley Periodicals, Inc. Head Neck 39: 464-470, 2017.

The Effect of a Radiation Positioning Stent (RPS) in the Reduction of Radiation Dosage to the Opposing Jaw and Maintenance of Mouth opening after Radiation Therapy

The effect of a radiation positioning stent (RPS) in radiation dosage reduction to the opposing jaw and maintenance of mouth opening was audited. 55 Head and Neck cancer patients who received radiotherapy were reviewed. Radiation dosages at similar points in the primary/opposing jaws were measured along with the mouth opening. Results showed a significant reduction in the radiation dosage to the opposing jaw in patients given the RPS. Mouth opening was generally maintained in patients given the RPS (77.7% improvement in mouth opening) compared to patients without RPS. Patients undergoing radiotherapy who had an RPS showed a significant reduction in radiation dosage to the opposing jaw and maintained their mouth opening in the short-term.

Raman spectroscopy delineates radiation-induced injury and partial rescue by amifostine in bone: a murine mandibular model

Despite its therapeutic role in head and neck cancer, radiation administration degrades the biomechanical properties of bone and can lead to pathologic fracture and osteoradionecrosis. Our laboratories have previously demonstrated that prophylactic amifostine administration preserves the biomechanical properties of irradiated bone and that Raman spectroscopy accurately evaluates bone composition ex vivo. As such, we hypothesize that Raman spectroscopy can offer insight into the temporal and mechanical effects of both irradiation and amifostine administration on bone to potentially predict and even prevent radiation-induced injury. Male Sprague-Dawley rats (350-400 g) were randomized into control, radiation exposure (XRT), and amifostine pre-treatment/radiation exposure groups (AMF-XRT). Irradiated animals received fractionated 70 Gy radiation to the left hemi-mandible, while AMF-XRT animals received amifostine just prior to radiation. Hemi-mandibles were harvested at 18 weeks after radiation, analyzed via Raman spectroscopy, and compared with specimens previously harvested at 8 weeks after radiation. Mineral (ρ958) and collagen (ρ1665) depolarization ratios were significantly lower in XRT specimens than in AMF-XRT and control specimens at both 8 and 18 weeks. amifostine administration resulted in a full return of mineral and collagen depolarization ratios to normal levels at 18 weeks. Raman spectroscopy demonstrates radiation-induced damage to the chemical composition and ultrastructure of bone while amifostine prophylaxis results in a recovery towards normal, native mineral and collagen composition and orientation. These findings have the potential to impact on clinical evaluations and interventions by preventing or detecting radiation-induced injury in patients requiring radiotherapy as part of a treatment regimen.

Dose reduction in orthodontic lateral cephalography: dosimetric evaluation of a novel cephalographic thyroid protector (CTP) and anatomical cranial collimation (ACC)

OBJECTIVES

To test the dose-reducing capabilities of a novel thyroid protection device and a recently introduced cranial collimator to be used in orthodontic lateral cephalography.

METHODS

Cephalographic thyroid protector (CTP) was designed to shield the thyroid while leaving the cervical vertebrae depicted. Using a RANDO(®) head phantom (The Phantom Laboratory, Salem, NY) equipped with dosemeters and a Proline XC (Planmeca, Helsinki, Finland) cephalograph, lateral cephalograms were taken, and the effective dose (ED) was calculated for four protocols: (1) without shielding; (2) with CTP; (3) with CTP and anatomical cranial collimator (ACC); and (4) with a thyroid collar (TC).

RESULTS

The ED for the respective protocols was (1) 8.51; (2) 5.39; (3) 3.50; and (4) 4.97 µSv. The organ dose for the thyroid was reduced from 30.17 to 4.50 µSv in Protocols 2 and 3 and to 3.33 µSv in Protocol 4.

CONCLUSIONS

The use of just the CTP (Protocol 2) resulted in a 36.8% reduction of the ED of a lateral cephalogram. This was comparable to the classical TC (Protocol 4). A 58.8% reduction of the ED was obtained when combining CTP and ACC (Protocol 3). The dose to the radiosensitive thyroid gland was reduced by 85% in Protocols 2 and 3 and by 89% in Protocol 4.

Prophylactic administration of Amifostine protects vessel thickness in the setting of irradiated bone

Although often beneficial in the treatment of head and neck cancer (HNC), radiation therapy (XRT) leads to the depletion of vascular supply and eventually decreased perfusion of the tissue. Specifically, previous studies have demonstrated the depletion of vessel volume fraction (VVF) and vessel thickness (VT) associated with XRT. Amifostine (AMF) provides protection from the detrimental effects of radiation damage, allowing for reliable post-irradiation fracture healing in the murine mandible. The purpose of this study is to investigate the prophylactic ability of AMF to protect the vascular network in an irradiated field. Sprague-Dawley rats (n = 17) were divided into 3 groups: control (C, n = 5), radiated (XRT, n = 7), and radiated mandibles treated with Amifostine (AMF XRT, n = 5). Both groups receiving radiation underwent a previously established, human equivalent dose of XRT totaling 35 Gy, equally fractionated over 5 days. The AMF XRT group received a weight dependent (0.5 mg AMF/5 g body weight) subcutaneous injection of AMF 45 min prior to XRT. Following a 56-day recovery period, mandibles were perfused, dissected, and imaged with μCT. ANOVA was used for comparisons between groups and p < 0.05 was considered statistically significant. Stereologic analysis demonstrated a significant and quantifiable restoration of VT in AMF treated mandibles as compared to those treated with radiation alone (0.061 ± 0.011 mm versus 0.042 ± 0.004 mm, p = 0.027). Interestingly, further analysis demonstrated no significant difference in VT between control mandibles and those treated with AMF (0.067 ± 0.016 mm versus 0.061 ± 0.011 mm, p = 0.633). AMF treatment also showed an increase in VVF, however those results were not statistically significant from VVF values demonstrated by the XRT group. Our data support the contention that AMF therapy acts prophylactically to protect vessel thickness. Based on these findings, we support the continued investigation of this treatment paradigm in its potential translation for the prevention of vascular depletion after radiotherapy.

Laser acupuncture therapy in patients with treatment-resistant temporomandibular disorders

Objective

To investigate the clinical effects of laser acupuncture therapy for temporomandibular disorders (TMD) after ineffective previous treatments.

Methods

A retrospective observational study was conducted in 29 treatment-resistant TMD patients (25 women, 4 men; age range, 17–67 years). Subjects were treated 3 times per week for 4 weeks with the Handylaser Trion (GaAlAs laser diode, 810 nm, 150 mW, pulsed waves), which delivered 0.375 J of energy (5 s) to ST7, ST6, and LI4 and 3 J (40 s) to each Ashi point, 7.5–26.25 J/cm² in total. The visual analog scale (VAS) and maximal mouth opening (MMO) were evaluated before and after treatment.

Results

VAS analysis showed that the patients were free of pain at rest (endpoint) after 5.90±6.08 sessions of laser acupuncture for acute TMD and after 16.21±17.98 sessions for chronic TMD. The VAS score on palpation of the temporomandibular joint reduced to 0.30±0.67 for patients with acute TMD (p = 0.005) and to 0.47±0.84 for those with chronic TMD (p<0.001). The MMO significantly increased in patients with acute TMD (7.80±5.43 mm, p = 0.008) and in patients with chronic TMD (15.58±7.87 mm, p<0.001).

Conclusions

Our study shows that laser acupuncture therapy improves the symptoms of treatment-resistant TMD. Further studies with a more appropriate design, involving long-term follow-up examinations in a larger patient sample, are needed to evaluate its efficacy.

Impact of radiation history, gender and age on bone quality in sites for orthodontic skeletal anchorage device placement

AIMS

Stability of orthodontic miniscrew implants is prerequisite to their success and durability in orthodontic treatment. As investigations revealed a positive correlation of miniscrew stability to periimplant bone quality, it has been the aim of this study to analyze the bone structure of resection preparations of human mandibles histologically by investigating the samples according to age, gender and exposure to radiotherapy.

METHODS

Inflammation- and tumor-free alveolar bone sections from human mandibles (n = 31) with previously diagnosed carcinoma, chronic osteomyelitis or cysts were analyzed histomorphologically and histomorphometrically as to the dimension of trabeculae in cancellous areas. Group A investigated the impact of a history of radiation therapy, group B of gender and group C contrasted biopsies from individuals aging under 60 or over 60 years. Statistics were performed using the Kruskal-Wallis-test.

RESULTS

Radiation, gender and age did not significantly influence bone density. The mean bone density averaged 40.7 ± 15.0% of spongiosa for the total collective with a median age of 58.4 years ± 14.7 years.

CONCLUSIONS

Our findings provide new information on bone quality, thus contributing to a more precise evaluation of the parameters affecting and those not affecting miniscrew implant stability. On the basis of these results, the formulation of clinical guidelines for risk assessment of therapeutic approaches in patients prior to insertion of orthodontic skeletal anchorage devices seems to be conceivable.

Vascular analysis as a proxy for mechanostransduction response in an isogenic, irradiated murine model of mandibular distraction osteogenesis

INTRODUCTION

Head and neck cancer is a debilitating and disfiguring disease. Although numerous treatment options exist, an array of debilitating side effects accompany them, causing physiological and social problems. Distraction osteogenesis (DO) can avoid many of the pathologies of current reconstructive strategies; however, due to the deleterious effects of radiation on bone vascularity, DO is generally ineffective. This makes investigating the effects of radiation on neovasculature during DO and creating quantifiable metrics to gauge the success of future therapies vital. The purpose of this study was to develop a novel isogenic rat model of impaired vasculogenesis of the regenerate mandible in order to determine quantifiable metrics of vascular injury and associated damage.

METHODS

Male Lewis rats were divided into two groups: DO only (n=5) AND Radiation Therapy (XRT)+DO (n=7). Afterwards, a distraction device was surgically implanted into the mandible. Finally, they were distracted a total of 5.1mm. Animals were perfused with a radiopaque casting agent concomitant with euthanasia, and subsequently demineralization, microcomputed tomography, and vascular analysis were performed.

RESULTS

Vessel volume fraction, vessel thickness, vessel number, and degree of anisotropy were diminished by radiation. Vessel separation was increased by radiation.

CONCLUSION

The DO group experienced vigorous vessel formation during distraction and neovascularization with a clear, directional progression, while the XRT/DO group saw weak vessel formation during distraction and neovascularization. Further studies are warranted to more deeply examine the impairments in osteogenic mechanotransductive pathways following radiation in the murine mandible. This isogenic model provides quantifiable metrics for future studies requiring a controlled approach to immunogenicity.

Dental implant survival in irradiated oral cancer patients: a systematic review of the literature

PURPOSE

Oral cancer therapy with surgery and radiation is associated with comorbidities; this affects rehabilitation with osseointegrated dental implants. The aim of this systematic review was to evaluate the effect of radiation therapy on osseointegrated dental implant survival in oral cancer patients.

MATERIALS AND METHODS

A review of the literature published between 1990 and June 2012 was conducted. Pertinent studies evaluating the effect of radiation therapy on osseointegration of implants were identified through searches of PubMed, SCIRUS, and Google Scholar. Overall implant survival rates were compared with respect to timing of radiation (prior to or after implantation), site of implant placement (maxilla, mandible, vascularized free flaps, nonvascular bone grafts), radiation dose, time interval between radiation therapy and implant placement, and the effect of hyperbaric oxygen therapy.

RESULTS

Thirty-eight articles were eligible for inclusion in the review. Overall implant survival rates with radiation therapy done pre- and postimplantation were 88.9% and 92.2%, respectively. In preimplantation radiation therapy, the implant survival rate was significantly higher for the mandible (93.3%) than for the maxilla (78.9%) or for grafted bone (87.5%). Similarly, the implant survival rate was higher when implants were placed in free flaps (89.3%) than in nonvascularized bone grafts (81.7%). While a radiation dose above 55 Gy significantly decreased implant survival, no significant relationship between increased implant survival and the remaining variables were found.

CONCLUSION

There, was no significant difference in dental implant survival rates between preimplantation and postimplantation radiation therapy. The anatomical site of implant placement in preimplantation radiation therapy was the most pertinent variable affecting implant survival, with a better survival rate in the mandible compared to the maxilla and grafted bone.

The effect of Amifostine prophylaxis on bone densitometry, biomechanical strength and union in mandibular pathologic fracture repair

BACKGROUND

Pathologic fractures (Fx) of the mandibles are severely debilitating consequences of radiation (XRT) in the treatment of craniofacial malignancy. We have previously demonstrated Amifostine's effect (AMF) in the remediation of radiation-induced cellular damage. We posit that AMF prophylaxis will preserve bone strength and drastically reverse radiotherapy-induced non-union in a murine mandibular model of pathologic fracture repair.

MATERIALS AND METHODS

Twenty-nine rats were randomized into 3 groups: Fx, XRT/Fx, and AMF/XRT/Fx. A fractionated human equivalent dose of radiation was delivered to the left hemimandibles of XRT/Fx and AMF/XRT/Fx. AMF/XRT/Fx was pre-treated with AMF. All groups underwent left mandibular osteotomy with external fixation and setting of a 2.1mm fracture gap post-operatively. Utilizing micro-computed tomography and biomechanical testing, the healed fracture was evaluated for strength.

RESULTS

All radiomorphometrics and biomechanical properties were significantly diminished in XRT/Fx compared to both Fx and AMF/XRT/Fx. No difference was demonstrated between Fx and AMF/XRT/Fx in both outcomes.

CONCLUSION

Our investigation establishes the significant and substantial capability of AMF prophylaxis to preserve and enhance bone union, quality and strength in the setting of human equivalent radiotherapy. Such novel discoveries establish the true potential to utilize pharmacotherapy to prevent and improve the treatment outcomes of radiation-induced late pathologic fractures.