Epigenomic, genomic, and transcriptomic landscape of schwannomatosis.

Schwannomatosis (SWNTS) is a genetic cancer predisposition syndrome that manifests as multiple and often painful neuronal tumors called schwannomas (SWNs). While germline mutations in SMARCB1 or LZTR1, plus somatic mutations in NF2 and loss of heterozygosity in chromosome 22q have been identified in a subset of patients, little is known about the epigenomic and genomic alterations that drive SWNTS-related SWNs (SWNTS-SWNs) in a majority of the cases. We performed multiplatform genomic analysis and established the molecular signature of SWNTS-SWNs. We show that SWNTS-SWNs harbor distinct genomic features relative to the histologically identical non-syndromic sporadic SWNs (NS-SWNS). We demonstrate the existence of four distinct DNA methylation subgroups of SWNTS-SWNs that are associated with specific transcriptional programs and tumor location. We show several novel recurrent non-22q deletions and structural rearrangements. We detected the SH3PXD2A-HTRA1 gene fusion in SWNTS-SWNs, with predominance in LZTR1-mutant tumors. In addition, we identified specific genetic, epigenetic, and actionable transcriptional programs associated with painful SWNTS-SWNs including PIGF, VEGF, MEK, and MTOR pathways, which may be harnessed for management of this syndrome.

Prevalence of HPV Infection in Racial-Ethnic Subgroups of Head and Neck Cancer Patients.

The landscape of HPV infection in racial/ethnic subgroups of head and neck cancer (HNC) patients has not been evaluated carefully. In this study, a meta-analysis examined the prevalence of HPV in HNC patients of African ancestry. Additionally, a pooled analysis of subject-level data was also performed to investigate HPV prevalence and patterns of p16 (CDNK2A) expression amongst different racial groups. Eighteen publications (N = 798 Black HNC patients) were examined in the meta-analysis, and the pooled analysis included 29 datasets comprised of 3,129 HNC patients of diverse racial/ethnic background. The meta-analysis revealed that the prevalence of HPV16 was higher among Blacks with oropharyngeal cancer than Blacks with non-oropharyngeal cancer. However, there was great heterogeneity observed among studies (Q test P<0.0001). In the pooled analysis, after adjusting for each study, year of diagnosis, age, gender and smoking status, the prevalence of HPV16/18 in oropharyngeal cancer patients was highest in Whites (61.1%), followed by 58.0% in Blacks and 25.2% in Asians (P<0.0001). There was no statistically significant difference in HPV16/18 prevalence in non-oropharyngeal cancer by race (P=0.682). With regard to the pattern of HPV16/18 status and p16 expression, White patients had the highest proportion of HPV16/18+/p16+ oropharyngeal cancer (52.3%), while Asians and Blacks had significantly lower proportions (23.0% and 22.6%, respectively) [P <0.0001]. Our findings suggest that the pattern of HPV16/18 status and p16 expression in oropharyngeal cancer appears to differ by race and this may contribute to survival disparities.

Squamous Cell Carcinoma-related Oncogene (SCCRO) Family Members Regulate Cell Growth and Proliferation through Their Cooperative and Antagonistic Effects on Cullin Neddylation.

SCCRO (squamous cell carcinoma-related oncogene; also known as DCUN1D1) is a highly conserved gene that functions as an E3 in neddylation. Although inactivation of SCCRO in yeast results in lethality, SCCRO(-/-) mice are viable. The exclusive presence of highly conserved paralogues in higher organisms led us to assess whether compensation by SCCRO paralogues rescues lethality in SCCRO(-/-) mice. Using murine and Drosophila models, we assessed the in vivo activities of SCCRO and its paralogues in cullin neddylation. We found that SCCRO family members have overlapping and antagonistic activity that regulates neddylation and cell proliferation activities in vivo. In flies, both dSCCRO and dSCCRO3 promote neddylation and cell proliferation, whereas dSCCRO4 negatively regulates these processes. Analysis of somatic clones showed that the effects that these paralogues have on proliferation serve to promote cell competition, leading to apoptosis in clones with a net decrease in neddylation activity. We found that dSCCRO and, to a lesser extent, dSCCRO3 rescue the neddylation and proliferation defects promoted by expression of SCCRO4. dSCCRO and dSCCRO3 functioned cooperatively, with their coexpression resulting in an increase in both the neddylated cullin fraction and proliferation activity. In contrast, human SCCRO and SCCRO4 promote, and human SCCRO3 inhibits, neddylation and proliferation when expressed in flies. Our findings provide the first insights into the mechanisms through which SCCRO family members cooperatively regulate neddylation and cell proliferation.

The national landscape of human papillomavirus-associated oropharynx squamous cell carcinoma.

The head and neck squamous cell carcinoma (HNC) landscape is evolving with human papillomavirus (HPV) being a rising cause of oropharynx carcinoma (OPC). This study seeks to investigate a national database for HPV-associated oropharynx carcinoma (HPV-OPC). Using the National Cancer Data Base, we analyzed 22,693 patients with HPV-OPC and known HPV status. Chi-square tests and logistic regression models were utilized to examine differences between HPV positive and HPV negative OPC. 14,805 (65.2%) patients were HPV positive. Mean age at presentation was 58.4 years with HPV-HNC patients being 2.8 years younger compared to the HPV-negative cohort (58.4 vs. 61.2 years, p < 0.001). 67.6% of white patients were HPV-positive compared to 42.3% of African American patients and 57.1% of Hispanics (p < 0.001). When combining race and socioeconomic status (SES), we found African American patients in high SES groups had HPV-OPC prevalence that was significantly higher than African American patients in low SES groups (56.9% vs. 36.3%, p < 0.001). Geographic distribution of HPV-OPC was also analyzed and found to be most prevalent in Western states and least prevalent in the Southern states (p < 0.001). The distribution of HPV-OPC is variable across the country and among racial and socioeconomic groups. A broad understanding of these differences in HPV-OPC should drive educational programs and improve clinical trials that benefit both prevention and current treatments.

Integrative genomic analysis identifies ancestry-related expression quantitative trait loci on DNA polymerase ß and supports the association of genetic ancestry with survival disparities in head and neck squamous cell carcinoma.

BACKGROUND: African Americans with head and neck squamous cell carcinoma (HNSCC) have a lower survival rate than whites. This study investigated the functional importance of ancestry-informative single-nucleotide polymorphisms (SNPs) in HNSCC and also examined the effect of functionally important genetic elements on racial disparities in HNSCC survival. METHODS: Ancestry-informative SNPs, RNA sequencing, methylation, and copy number variation data for 316 oral cavity and laryngeal cancer patients were analyzed across 178 DNA repair genes. The results of expression quantitative trait locus (eQTL) analyses were also replicated with a Gene Expression Omnibus (GEO) data set. The effects of eQTLs on overall survival (OS) and disease-free survival (DFS) were evaluated. RESULTS: Five ancestry-related SNPs were identified as cis-eQTLs in the DNA polymerase ß (POLB) gene (false discovery rate [FDR] < 0.01). The homozygous/heterozygous genotypes containing the African allele showed higher POLB expression than the homozygous white allele genotype (P < .001). A replication study using a GEO data set validated all 5 eQTLs and also showed a statistically significant difference in POLB expression based on genetic ancestry (P = .002). An association was observed between these eQTLs and OS (P < .037; FDR < 0.0363) as well as DFS (P = .018 to .0629; FDR < 0.079) for oral cavity and laryngeal cancer patients treated with platinum-based chemotherapy and/or radiotherapy. Genotypes containing the African allele were associated with poor OS/DFS in comparison with homozygous genotypes harboring the white allele. CONCLUSIONS: Analyses show that ancestry-related alleles could act as eQTLs in HNSCC and support the association of ancestry-related genetic factors with survival disparities in patients diagnosed with oral cavity and laryngeal cancer. Cancer 2017;123:849-60. © 2016 American Cancer Society.

Robotic Ureteroplasty with Buccal Mucosa Graft for the Management of Complex Ureteral Strictures.

PURPOSE: Surgical management of proximal and mid ureteral strictures that are not amenable to primary excision and anastomosis is challenging. Although a buccal mucosa graft is commonly used during substitution urethroplasty, its use in substitution ureteroplasty is limited. We describe our technique of robotic ureteroplasty with a buccal mucosa graft to manage complex ureteral strictures and we report our outcomes. MATERIALS AND METHODS: We retrospectively reviewed the records of 12 patients who underwent robotic ureteroplasty with a buccal mucosa graft between September 2014 and June 2016. The indication for the procedure was a proximal or mid ureteral stricture not amenable to primary excision and anastomosis. The primary outcomes were clinical success, absent symptoms on ureteral pathology and radiological success, defined as absent ureteral obstruction on retrograde pyelography, renal scan and/or computerized tomography. RESULTS: Four of the 12 patients (33.3%) had a ureteropelvic junction stricture, 4 (33.3%) had a proximal stricture and 4 (33.3%) had a mid ureteral stricture. Eight of the 12 patients (66.7%) had previously undergone failed ureteral reconstruction. Median stricture length was 3 cm (range 2 to 5). Median operative time was 217 minutes (range 136 to 344) and mean estimated blood loss was 100 ml (range 50 to 200). Median length of stay was 1 day (range 1 to 6). At a median followup of 13 months (range 4 to 30) 10 of the 12 cases (83.3%) were clinically and radiologically successful. CONCLUSIONS: Robotic ureteroplasty with a buccal mucosa graft is associated with low inherent morbidity. It is an effective way to manage complex proximal and mid ureteral strictures.

Ancestral-derived effects on the mutational landscape of laryngeal cancer.

Laryngeal cancer disproportionately affects more African-Americans than European-Americans. Here, we analyze the genome-wide somatic point mutations from the tumors of 13 African-Americans and 57 European-Americans from TCGA to differentiate between environmental and ancestrally-inherited factors. The mean number of mutations was different between African-Americans (151.31) and European-Americans (277.63). Other differences in the overall mutational landscape between African-American and European-American were also found. The frequency of C>A, and C>G were significantly different between the two populations (p-value<0.05). Context nucleotide signatures for some mutation types significantly differ between these two populations. Thus, the context nucleotide signatures along with other factors could be related to the observed mutational landscape differences between two races. Finally, we show that mutated genes associated with these mutational differences differ between the two populations. Thus, at the molecular level, race appears to be a factor in the progression of laryngeal cancer with ancestral genomic signatures best explaining these differences.

Force maintenance and myosin filament assembly regulated by Rho-kinase in airway smooth muscle.

Smooth muscle contraction can be divided into two phases: the initial contraction determines the amount of developed force and the second phase determines how well the force is maintained. The initial phase is primarily due to activation of actomyosin interaction and is relatively well understood, whereas the second phase remains poorly understood. Force maintenance in the sustained phase can be disrupted by strains applied to the muscle; the strain causes actomyosin cross-bridges to detach and also the cytoskeletal structure to disassemble in a process known as fluidization, for which the underlying mechanism is largely unknown. In the present study we investigated the ability of airway smooth muscle to maintain force after the initial phase of contraction. Specifically, we examined the roles of Rho-kinase and protein kinase C (PKC) in force maintenance. We found that for the same degree of initial force inhibition, Rho-kinase substantially reduced the muscle's ability to sustain force under static conditions, whereas inhibition of PKC had a minimal effect on sustaining force. Under oscillatory strain, Rho-kinase inhibition caused further decline in force, but again, PKC inhibition had a minimal effect. We also found that Rho-kinase inhibition led to a decrease in the myosin filament mass in the muscle cells, suggesting that one of the functions of Rho-kinase is to stabilize myosin filaments. The results also suggest that dissolution of myosin filaments may be one of the mechanisms underlying the phenomenon of fluidization. These findings can shed light on the mechanism underlying deep inspiration induced bronchodilation.

Development and maintenance of force and stiffness in airway smooth muscle.

Airway smooth muscle (ASM) plays a central role in the excessive narrowing of the airway that characterizes the primary functional impairment in asthma. This phenomenon is known as airway hyper-responsiveness (AHR). Emerging evidence suggests that the development and maintenance of ASM force involves dynamic reorganization of the subcellular filament network in both the cytoskeleton and the contractile apparatus. In this review, evidence is presented to support the view that regulation of ASM contraction extends beyond the classical actomyosin interaction and involves processes within the cytoskeleton and at the interfaces between the cytoskeleton, the contractile apparatus, and the extracellular matrix. These processes are initiated when the muscle is activated, and collectively they cause the cytoskeleton and the contractile apparatus to undergo structural transformation, resulting in a more connected and solid state that allows force generated by the contractile apparatus to be transmitted to the extracellular domain. Solidification of the cytoskeleton also serves to stiffen the muscle and hence the airway. Oscillatory strain from tidal breathing and deep inspiration is believed to be the counter balance that prevents hypercontraction and stiffening of ASM in vivo. Dysregulation of this balance could lead to AHR seen in asthma.

Facial nerve function preservation with vacuum-assisted closure.

IMPORTANCE: Laboratory and clinical studies have shown that vacuum-assisted closure (VAC) therapy increases wound blood flow and granulation tissue formation and decreases accumulation of fluid and bacteria. Many publications outline the use of VAC dressings in the treatment of sternal, sacral, upper and lower extremity, perineal, and abdominal wounds, but few describe its use in the head and neck region. No report to date has addressed the use of VAC therapy in helping to preserve facial nerve integrity. OBSERVATIONS: We present a case of a 64-year-old woman who underwent tissue debridement for necrotizing fasciitis of the left face, neck, and upper chest. She subsequently had exposed facial nerve that was covered with a VAC dressing and demonstrated complete granulation by postoperative day 7 with preservation of function. CONCLUSIONS AND RELEVANCE: This case highlights the effectiveness of VAC in eliminating infectious material and promoting granulation tissue formation. This is the first time that VAC therapy has been shown to maintain neural function when placed directly on functioning cranial nerves.

Racial Disparities in Head and Neck Cancer: It's Not Just About Access.

OBJECTIVE: Medical literature identifies stark racial disparities in head and neck cancer (HNC) in the United States, primarily between non-Hispanic white (NHW) and non-Hispanic black (NHB) populations. The etiology of this disparity is often attributed to inequitable access to health care and socioeconomic status (SES). However, other contributors have been reported. We performed a systematic review to better understand the multifactorial landscape driving racial disparities in HNC. DATA SOURCES: A systematic review was conducted in Covidence following Preferred Reporting Items for Systematic Reviews and Meta-analyses Guidelines. A search of PubMed, SCOPUS, and CINAHL for literature published through November 2022 evaluating racial disparities in HNC identified 2309 publications. REVIEW METHODS: Full texts were screened by 2 authors independently, and inconsistencies were resolved by consensus. Three hundred forty publications were ultimately selected and categorized into themes including disparities in access/SES, treatment, lifestyle, and biology. Racial groups examined included NHB and NHW patients but also included Hispanic, Native American, and Asian/Pacific Islander patients to a lesser extent. RESULTS: Of the 340 articles, 192 focused on themes of access/SES, including access to high-quality hospitals, insurance coverage, and transportation contributing to disparate HNC outcomes. Additional themes discussed in 148 articles included incongruities in surgical recommendations, tobacco/alcohol use, human papillomavirus-associated malignancies, and race-informed silencing of tumor suppressor genes. CONCLUSION: Differential access to care plays a significant role in racial disparities in HNC, disproportionately affecting NHB populations. However, there are other significant themes driving racial disparities. Future studies should focus on providing equitable access to care while also addressing these additional sources of disparities in HNC.

Timing of postoperative radiation therapy for major salivary gland cancers.

BACKGROUND: The impact of timing of PORT initiation for major salivary gland cancers on survival is unknown. We aim to examine the impact of PORT timeliness on overall survival (OS) of patients with major salivary gland cancers. METHODS: This was a cross-sectional analysis using data from the National Cancer Database (2004-2017) and included patients with major salivary gland cancer treated with surgery and PORT. RESULTS: In total, 5701 patients were included (3133 [55%] male, 4644 [82%] white, mean age 59 ± 16 years). For the overall cohort, PORT >6 weeks was not associated with decreased OS (1.00 aHR, 95% CI 0.89-1.11). When specifically examining patients with mucoepidermoid carcinoma, PORT >6 weeks was associated with a decreased OS (1.27 aHR, 95% CI 1.01-1.58). CONCLUSIONS: Overall, this analysis did not demonstrate a survival benefit for initiating PORT within 6 weeks for patients with salivary gland malignancies. Subset analysis did support initiating PORT within 6 weeks after resection for patients with mucoepidermoid carcinomas. This was not demonstrated in other major salivary gland cancer histologies.

Myosin filaments in smooth muscle cells do not have a constant length.

Myosin molecules from smooth muscle and non-muscle cells are known to self-assemble into side-polar filaments in vitro. However, the in situ mechanism of filament assembly is not clear and the question of whether there is a unique length for myosin filaments in smooth muscle is still under debate. In this study we measured the lengths of 16,587 myosin filaments in three types of smooth muscle cells using serial electron microscopy (EM). Sheep airway and pulmonary arterial smooth muscle as well as rabbit carotid arterial smooth muscle were fixed for EM and serial ultra-thin (50-60 nm) sections were obtained. Myosin filaments were traced in consecutive sections to determine their lengths. The results indicate that there is not a single length for the myosin filaments; instead there is a wide variation in lengths. The plots of observation frequency versus myosin filament length follow an exponential decay pattern. Analysis suggests that in situ assembly of myosin filaments in smooth muscle is governed by random processes of linear polymerization and de-polymerization, and that the dynamic equilibrium of these processes determines the observed length distribution.

Racial survival disparities in head and neck cancer clinical trials.

BACKGROUND: Survival disparities between Black and White head and neck cancer patients are well documented, with access to care and socioeconomic status as major contributors. We set out to assess the role of self-reported race in head and neck cancer by evaluating treatment outcomes of patients enrolled in clinical trials, where access to care and socioeconomic status confounders are minimized. METHODS: Clinical trial data from the Radiation Therapy Oncology Group studies were obtained. Studies were included if they were therapeutic trials that employed survival as an endpoint. Studies that did not report survival as an endpoint were excluded; 7 Radiation Therapy Oncology Group Studies were included for study. For each Black patient enrolled in a clinical trial, a study arm-matched White patient was used as a control. RESULTS: A total of 468 Black participants were identified and matched with 468 White study arm-specific controls. White participants had better outcomes than Black participants in 60% of matched pairs (P < .001). Black participants were consistently more likely to have worse outcomes. When outcomes were measured by progression-free survival or disease-free survival, the failure rate was statistically significantly higher in Black participants (hazard ratio [HR] = 1.50, P < .001). Failure was largely due to locoregional failure, and Black participants were at higher risk (subdistribution HR =1.51, P = .002). The development of distant metastasis within the paired cohorts was not statistically significantly different. CONCLUSION: In this study of clinical trial participants using self-reported race, Black participants consistently had worse outcomes in comparison to study arm-specific White controls. Further study is needed to confirm these findings and to explore causes underlying this disparity.

Extensive set of African ancestry-informative markers (AIMs) to study ancestry and population health.

Introduction: Human populations are often highly structured due to differences in genetic ancestry among groups, posing difficulties in associating genes with diseases. Ancestry-informative markers (AIMs) aid in the detection of population stratification and provide an alternative approach to map population-specific alleles to disease. Here, we identify and characterize a novel set of African AIMs that separate populations of African ancestry from other global populations including those of European ancestry. Methods: Using data from the 1000 Genomes Project, highly informative SNP markers from five African subpopulations were selected based on estimates of informativeness (In) and compared against the European population to generate a final set of 46,737 African ancestry-informative markers (AIMs). The AIMs identified were validated using an independent set and functionally annotated using tools like SIFT, PolyPhen. They were also investigated for representation of commonly used SNP arrays. Results: This set of African AIMs effectively separates populations of African ancestry from other global populations and further identifies substructure between populations of African ancestry. When a subset of these AIMs was studied in an independent dataset, they differentiated people who self-identify as African American or Black from those who identify their ancestry as primarily European. Most of the AIMs were found to be in their intergenic and intronic regions with only 0.6% in the coding regions of the genome. Most of the commonly used SNP array investigated contained less than 10% of the AIMs. Discussion: While several functional annotations of both coding and non-coding African AIMs are supported by the literature and linked these high-frequency African alleles to diseases in African populations, more effort is needed to map genes to diseases in these genetically diverse subpopulations. The relative dearth of these African AIMs on current genotyping platforms (the array with the highest fraction, llumina's Omni 5, harbors less than a quarter of AIMs), further demonstrates a greater need to better represent historically understudied populations.

Quantitative Simulation of Enzymatic Breakdown of Alcohol in Human Metabolism.

The breakdown of ethanol, the active chemical in alcohol, is tightly regulated by the body, yet alcohol intoxication occurs in thousands of Americans annually. Many factors contribute to the concentration of ethanol in the bloodstream and the tolerance an individual has, including body size, previous drinking experience, and liver functionality. We propose a model that estimates both the blood alcohol concentration and the concentration of acetaldehyde (the toxic intermediate during catabolism) in the liver over time to quantify organ damage for an average person. From the current literature, we derived ordinary differential equations that govern the absorption of ethanol in the body and extended it with the metabolic enzyme mechanisms. We also altered the parameters of our system in order to show the effects of Asian flush, which impairs the body's processing of acetaldehyde. We demonstrated the accumulation of acetaldehyde in Asian flush patients was about 660 times higher compared to those without the disease.Clinical relevance-With further improvements and personalization, our model would be able to quantitatively describe the effects of alcohol consumption without having volunteers go through repetitive trials with extensive exposure to alcohol. Liver damage can also be estimated with the acetaldehyde buildup predicted by the model.

Virtual Tumor Boards for Remote Learning in Head and Neck Surgical Oncology.

Importance: In addition to their patient management value, multidisciplinary tumor boards have been recognized as effective learning tools. However, the value of using a virtual tumor board as a learning tool for head and neck surgical oncology fellows has not been studied. Objective: To describe the structure and content of the American Head and Neck Society (AHNS) Virtual Tumor Board and assess its educational value as perceived by attendees. Design, Setting, and Participants: All sessions of the AHNS Virtual Tumor Board from April 8, 2020, to June 1, 2022, were reviewed. Topics, presenters, participants, and viewership data were collected as of October 15, 2022, from session recordings posted to an online video sharing and social media platform. Additionally, an anonymous, 14-question online survey was designed to elicit feedback from head and neck surgery trainees on virtual tumor board engagement, strengths, and weaknesses. The survey was electronically distributed in June and July 2022 to the 101 fellows enrolled in AHNS-accredited programs between July 1, 2020, and June 30, 2022. Main Outcomes and Measures: The primary aim was to tabulate online viewership of the sessions. The secondary aim was to qualitatively assess the experience of head and neck trainees with the AHNS Virtual Tumor Board using a survey. Results: Forty-two sessions of the virtual tumor board were held between April 8, 2020, and June 1, 2022. Almost all sessions (41 [98%]) were case based. One hundred and sixteen cases were presented, representing 2 to 3 cases per session, by 75 unique faculty members. Each session was viewed a mean of 217 times (range, 64-2216 views). In the 2021 to 2022 academic year, a mean of 60 viewers (range, 30-92 viewers) attended each live session. In all, 29 survey responses were collected from 101 fellows in AHNS-accredited programs (29% response rate). Most respondents felt the format allowed for excellent teaching (18 of 26 respondents [69%]) and discussion (19 of 26 respondents [73%]). Most respondents (22 of 29 respondents [76%]) believed that practicing head and neck surgeons would benefit from the sessions. Conclusions and Relevance: This survey study found that the AHNS Virtual Tumor Board was well-attended and well-reviewed by head and neck surgical oncology trainees. The virtual tumor board format could be used as model of remote learning for other organizations.

Multiplatform molecular profiling uncovers two subgroups of malignant peripheral nerve sheath tumors with distinct therapeutic vulnerabilities.

Malignant peripheral nerve sheath tumor (MPNST) is a highly aggressive sarcoma, and a lethal neurofibromatosis type 1-related malignancy, with little progress made on treatment strategies. Here, we apply a multiplatform integrated molecular analysis on 108 tumors spanning the spectrum of peripheral nerve sheath tumors to identify candidate drivers of MPNST that can serve as therapeutic targets. Unsupervised analyses of methylome and transcriptome profiles identify two distinct subgroups of MPNSTs with unique targetable oncogenic programs. We establish two subgroups of MPNSTs: SHH pathway activation in MPNST-G1 and WNT/ß-catenin/CCND1 pathway activation in MPNST-G2. Single nuclei RNA sequencing characterizes the complex cellular architecture and demonstrate that malignant cells from MPNST-G1 and MPNST-G2 have neural crest-like and Schwann cell precursor-like cell characteristics, respectively. Further, in pre-clinical models of MPNST we confirm that inhibiting SHH pathway in MPNST-G1 prevent growth and malignant progression, providing the rational for investigating these treatments in clinical trials.

Osteoradionecrosis rate in oropharynx cancer treated with dose volume histogram based constraints.

OBJECTIVES: Mandibular dose constraints are designed to limit high dose to small volumes to avoid osteoradionecrosis (ORN). Based upon a published experience, intermediate-dose constraints were introduced but have not been independently validated. We hypothesize that these constraints lower ORN rate without compromising other organs at risk (OAR). METHODS: Oropharyngeal cancer patients treated with standard fractionation adjuvant/definitive VMAT from 01/2014-08/2020 were included. In 09/2017, mandibular dose constraint was changed from historical constraint (HC) of D 0.1 cc < 70 Gy to modified constraints (MC) of V 44 Gy < 42%, V 58 Gy < 25%, D 0.5 cc < 70 Gy. OAR dosimetric changes and ORN development were evaluated. Regression modelling predicted long-term ORN cases in MC group. RESULTS: There were 174 patients, 71 in MC group. Seven cases of ORN in HC group at a median follow up (FU) of 39 months and 1 case of ORN in MC group at a median FU of 11 months were observed. More patients in the MC group met V 44 Gy (87% vs 62%, p < 0.01) and V 58 Gy constraints (92% vs 73%, p < 0.01). Mean doses to OARs did not rise. Mandible V 44 Gy and V 58 Gy were significantly associated with ORN (p < 0.01 and p = 0.03, respectively) across all patients. In the HC group, V 44 Gy was independently associated with ORN (p = 0.01). To account for shorter FU in MC group, logistic regression of ORN based on V 44 Gy in HC patients was performed. This predicts 3.2 ORN cases in the MC group (95% CI: 0.00-6.4). CONCLUSION: Achieving V 44 Gy and V 58 Gy was successful in 87% of cases without sacrificing target coverage or OARs and resulted in non-significant ORN decrease.