Antiresorptive agents enhance ossification of free flap reconstructions of the mandible: a radiological retrospective cohort study.

Background: The aim of this study was to investigate the effect of antiresorptive agents on the ossification of reconstructed mandibles by free bone grafts for the first time. Methods: A total of 38 reconstructions of the jaw were retrospectively evaluated for ossification between bone segments by two raters based on postoperative panoramic radiographs. The study group (n = 13) had segmental resection of the mandible and free bone flap reconstruction due to medication-related osteonecrosis of the jaw (MRONJ). The control group (noMRONJ, n = 25) comprised segmental mandibular resections and free bone flap reconstructions due to tumors, chronic osteomyelitis, or trauma without any radiation. Ossification time and influencing factors were evaluated. Results: Both duration of surgery (346 ± 90 min. vs. 498 ± 124 min.; p < 0.001) and hospitalization (8.7 ± 2.8 days vs. 13.4 ± 5.3 days, p = 0.006) were shorter in the MRONJ group compared to the noMRONJ group. Ossification after mandibular reconstruction was significantly faster in the MRONJ study group [224 days, interquartile range (IQR) 175-287] compared to the control group (288 days, IQR 194-445; p < 0.001). Moreover, good initial contact between the segments resulted in faster ossification (p < 0.001) in the MRONJ group. Ossification rate between original and grafted bone or between grafted bone segments only did not differ in both the study and control groups (MRONJ, p = 0.705 vs. control, p = 0.292). The type of antiresorptive agent did not show any significance for ossification. The rate of wound healing disturbances did also not differ between the study and control groups (p = 0.69). Conclusion: Advanced MRONJ (stage 3) can be resected and reconstructed safely with free microvascular bone flaps. Antiresorptive agents enhance the ossification of the bone segments. Optimal initial contact of the bone segments accelerates bone healing. Surgery and hospitalization are markedly shortened in this vulnerable group of MRONJ patients compared to oncologic patients.

Patient's Perception of Outcome after Extracapsular Fractures of the Mandibular Condyle Differs from Objective Evaluation-Experience of a Third-Level Hospital.

Background: The aim of this study is to assess patients' subjective perception of treatment outcome after extracapsular fractures of the mandibular condyle. Methods: A questionnaire survey regarding facial nerve palsy (FNP), malocclusion, pain, reduction in maximum mouth opening (MMO) and further discomfort after 3, 6, and 12 months was carried out. Patients aged 18 or more presenting with an extracapsular condylar fracture between 2006 and 2020 were identified by purposive sampling Questionnaires were received from 115 patients. Fractures were classified on the basis of the pre-treatment imaging, the way of treatment was obtained from patients' medical records. Data were analyzed using Pearsons' chi-square-test, descriptive statistics and Student's t-test. Results: 93.0% of the fractures were treated by open reduction and internal fixation (ORIF). MMO reduction was the most common post-treatment complication (55.6%). ORIF was associated with less pain after 3 months (p = 0.048) and lower VAS scores compared to conservative treatment (p = 0.039). Comminuted fractures were more frequently associated with post-treatment malocclusion (p = 0.048), FNP (p = 0.016) and MMO reduction (p = 0.001). Bilateral fractures were significantly accompanied by malocclusion (p = 0.029), MMO reduction (p = 0.038) and pain occurrence (p < 0.001). Conclusions: Patients report less pain after ORIF. Comminuted and bilateral fractures seem to be major risk factors for complications. Subjective perception of complications after extracapsular condylar fractures differs from objectively assessed data.

Correction: Schuderer et al. Risk Factors for Flap Loss: Analysis of Donor and Recipient Vessel Morphology in Patients Undergoing Microvascular Head and Neck Reconstructions. J. Clin. Med. 2023, 12, 5206.

In the original publication by Schuderer et al., there was a mistake in Table 1 as published [...].

Treatment of late-onset temporomandibular joint prosthesis infection by prosthesis revision: a case report.

Late-onset infection of an inserted temporomandibular joint prosthesis is a difficult complication to treat. Most treatment protocols for late prosthetic infections include device replacement. A 40-year-old female patient with an infected and exposed temporomandibular joint prosthesis presented 3 years after implant placement. The patient was treated with prosthesis revision including fistula coverage with a temporalis muscle flap and prolonged antibiotic therapy for 10 weeks. Since completion of treatment, the patient has been infection-free.

Animal Bite Injuries to the Face: A Retrospective Evaluation of 111 Cases.

The treatment of bite wounds to the face is discussed controversially in relation to surgery and antibiotics. The aim of this study is a retrospective evaluation of 111 cases of animal bite injuries to the face that presented to our unit of oral and maxillofacial surgery over a 13-year period. Children under 10 years of age were predominantly involved. A total of 94.5% of the assessed injuries were caused by dogs. Wound infections occurred in 8.1%. Lackmann type II was the most common type of injury (36.9%). The perioral area was affected most frequently (40.5%). Primary wound closure was carried out in 74.8% of the cases. In 91.9% of the cases, antibiotic prophylaxis was prescribed. The most often administered type of antibiotic was amoxicillin with clavulanic acid (62.1%). Patients without antibiotics showed an increased infection rate without significance. Wound infections occurred significantly more frequently in wounds to the cheeks (p = 0.003) and when local flap reconstruction was necessary (p = 0.048). Compared to the other surgical treatment options, primary closure showed the lowest infection rates (4.8%, p = 0.029). We recommend antibiotic prophylaxis using amoxicillin with clavulanic acid and wound drains for wounds of Lackmann class II or higher. Primary closure seems to be the treatment of choice whenever possible.

Risk Factors for Flap Loss: Analysis of Donor and Recipient Vessel Morphology in Patients Undergoing Microvascular Head and Neck Reconstructions.

In microvascular head and neck reconstruction, various factors such as diabetes, alcohol consumption, and preoperative radiation hold a risk for flap loss. The primary objective of this study was to examine the vessel morphology of both recipient and donor vessels and to identify predictors for changes in the diameters of H.E.-stained specimens associated with flap loss in a prospective setting. Artery and vein samples (N = 191) were collected from patients (N = 100), with sampling from the recipient vessels in the neck area and the donor vessels prior to anastomosis. External vessel diameter transverse (ED), inner vessel diameter transverse (ID), thickness vessel intima (TI), thickness vessel media (TM), thickness vessel wall (TVW), and intima-media ratio (IMR) for the recipient (R) and transplant site (T) in arteries (A) and veins (V) were evaluated using H.E. staining. Flap loss (3%) was associated with increased ARED (p = 0.004) and ARID (p = 0.004). Preoperative radiotherapy led to a significant reduction in the outer diameter of the recipient vein in the neck (p = 0.018). Alcohol consumption (p = 0.05), previous thrombosis (p = 0.007), and diabetes (p = 0.002) were associated with an increase in the total thickness of venous recipient veins in the neck. Diabetes was also found to be associated with dilation of the venous media in the neck vessels (p = 0.007). The presence of cardiovascular disease (CVD) was associated with reduced intimal thickness (p = 0.016) and increased total venous vessel wall thickness (p = 0.017) at the transplant site. Revision surgeries were linked to increased internal and external diameters of the graft artery (p = 0.04 and p = 0.003, respectively), while patients with flap loss showed significantly increased artery diameters (p = 0.004). At the transplant site, alcohol influenced the enlargement of arm artery diameters (p = 0.03) and the intima-media ratio in the radial forearm flap (p = 0.013). In the anterolateral thigh, CVD significantly increased the intimal thickness and the intima-media ratio of the graft artery (p = 0.01 and p = 0.02, respectively). Patients with myocardial infarction displayed increased thickness in the A. thyroidea and artery media (p = 0.003). Facial arteries exhibited larger total vessel diameters in patients with CVD (p = 0.03), while facial arteries in patients with previous thrombosis had larger diameters and thicker media (p = 0.01). The presence of diabetes was associated with a reduced intima-media ratio (p < 0.001). Although the presence of diabetes, irradiation, and cardiovascular disease causes changes in vessel thickness in connecting vessels, these alterations did not adversely affect the overall success of the flap.

OSCC in Never-Smokers and Never-Drinkers Is Associated with Increased Expression of Tumor-Infiltrating Lymphocytes and Better Survival.

The aim of this study was to investigate the clinical, histopathologic, and immunologic differences of oral squamous cell carcinoma of never-smokers/never-drinkers and smokers/drinkers. Immunohistochemical staining for CD4, CD8, FoxP3, CD1a, and p16 was performed in 131 oral squamous cell carcinomas from smokers/drinkers and never-smokers/never-drinkers. Associations of smoking/drinking status with clinicopathologic data, immunohistochemical antibody expression, and survival were examined. Oral squamous cell carcinoma in never-smokers/never-drinkers was associated with the female gender (p < 0.001). Never-smokers/never-drinkers were older at diagnosis than smokers/drinkers (p < 0.001). Never-smokers/never-drinkers had more tumors in the maxilla, mandible, and tongue (p < 0.001). Pre-existing oral potentially malignant disorders appeared to be more common in never-smokers/never-drinkers (p < 0.001). Perineural invasion was more common in smokers/drinkers (p = 0.039). Never-smoking/never-drinking was associated with better overall survival (p = 0.004) and disease-specific survival (p = 0.029). High CD4+ T cell infiltration was associated with never-smoking/never-drinking (p = 0.008). Never-smokers/never-drinkers also showed increased CD8+ T cell infiltration (p = 0.001) and increased FoxP3+ Treg infiltration (p = 0.023). Furthermore, the total group of tumor-infiltrating lymphocytes was associated with never smoking/never drinking (p = 0.005). To conclude oral squamous cell carcinoma of the never-smokers/never-drinkers appears to be a distinct type of tumor, as it appears to have unique clinical and pathologic features and a more immunogenic microenvironment.

The Folded Radial Forearm Flap in Lip and Nose Reconstruction-Still a Unique Choice.

(1) Background: The radial forearm flap (RFF) has evolved as the flap of choice for intraoral mucosal reconstructions, providing thin and pliable skin with a safe blood supply. Perforator flaps such as the anterolateral thigh (ALT) flap are increasingly being discussed for the same applications. (2) Methods: Patient history, treatment details, and outcome of 12 patents with moderate to extended defects of the lip and/or nose area that were reconstructed by a folded radial forearm flap were retrospectively evaluated for oncologic and functional outcomes. (3) Results: The mean oncologic and functional follow-up were 21.1 (min. 3.8; max. 83.3) and 31.2 (min. 6; max. 96) months, respectively. All flaps survived without revision. In eight cases, major lip defects were reconstructed by an RFF; in six patients, the palmaris longus tendon was included for lip suspension. The functional results in terms of eating, drinking, and mouth opening were good in five cases, while three patients were graded as fair due to moderate drooling. In seven cases, the major parts of the nose were reconstructed with two good and five fair (nostril constriction in three cases) functional results. (4) Conclusions: The folded RFF remains a unique free flap option for complex three-dimensional lip and nose reconstructions in terms of flexibility, versatility, and robustness.

Direct Anthropometry Overestimates Cranial Asymmetry-3D Digital Photography Proves to Be a Reliable Alternative.

This study compared manual and digital measurements of plagiocephaly and brachycephaly in infants and evaluated whether three-dimensional (3D) digital photography measurements can be used as a superior alternative in everyday clinical practice. A total of 111 infants (103 with plagiocephalus and 8 with brachycephalus) were included in this study. Head circumference, length and width, bilateral diagonal head length, and bilateral distance from the glabella to the tragus were assessed by manual assessment (tape measure and anthropometric head calipers) and 3D photographs. Subsequently, the cranial index (CI) and cranial vault asymmetry index (CVAI) were calculated. Measured cranial parameters and CVAI were significantly more precise using 3D digital photography. Manually acquired cranial vault symmetry parameters were at least 5 mm lower than digital measurements. Differences in CI between the two measuring methods did not reach significance, whereas the calculated CVAI showed a 0.74-fold decrease using 3D digital photography and was highly significant (p < 0.001). Using the manual method, CVAI calculations overestimated asymmetry, and cranial vault symmetry parameters were measured too low, contributing to a misrepresentation of the actual anatomical situation. Considering consequential errors in therapy choices, we suggest implementing 3D photography as the primary tool for diagnosing deformational plagiocephaly and positional head deformations.

TIGIT Expression on Intratumoral Lymphocytes Correlates with Improved Prognosis in Oral Squamous Cell Carcinoma.

(1) Background: T-cell immunoglobulin and ITIM domain (TIGIT) is a potential immunotherapeutic target in a variety of malignant entities, and antibody-based treatments are currently under investigation in clinical trials. While promising results were observed in patients with lung cancer, the role of TIGIT in oral squamous cell carcinoma (OSCC) as a biomarker as well as a therapeutic target remains elusive. Therefore, we evaluated the role of TIGIT as a prognostic factor in OSCC. (2) Methods: Here, we describe the results of a retrospective tissue microarray (TMA) OSCC cohort. Using immunohistochemistry, TIGIT expression was correlated with overall and recurrence-free survival (OAS and RFS, respectively). Additionally, in silico analysis was performed based on the TCGA Head and Neck Squamous Cell Carcinoma (HNSCC) cohort in order to correlate patients' survival with TIGIT and CD274 (encoding for PD-L1) gene expression levels. (3) Results: Database analysis revealed a beneficial outcome in OAS for tumor patients with high intraepithelial CD3-TIGIT-expression (n = 327). Hereby, OAS was 53.9 months vs. 30.1 months for patients with lower TIGIT gene expression levels (p = 0.033). In our retrospective OSCC-TMA cohort, elevated TIGIT levels on CD3+ cells correlated significantly with improved OAS (p = 0.025) as well as distant RFS (p = 0.026). (4) Conclusions: This study introduces TIGIT as a novel prognostic factor in OSCC, indicating the improved outcome of OSCC patients relative to their increased TIGIT expression. TIGIT might provide therapeutic implications for future immunotherapy in advanced-stage OSCC patients.

Influence of Radiotherapy on Ossification of Vascularized Osseous Reconstruction of the Jaw: A Radiological Retrospective Cohort Study Based on Panoramic Radiographs.

Background: The aim of this study was to evaluate the impact of irradiation and time of irradiation on the ossification of jaws reconstructed with free bone grafts. Methods: In total, 100 reconstructions of the jaw were retrospectively evaluated for ossification between bone segments by two raters based on postoperative panoramic radiographs (immediate postOP, approximately 6, 12 and 24 months follow-up). Three subgroups were divided according to the time of irradiation: preoperative radiation therapy (n = 41), postoperative radiation therapy (n = 26) and patients without any radiation therapy (n = 33) as the control group. Ossification time and influencing factors were documented. Results: The fastest ossification with a median of 304 ± 37 days was observed (p < 0.001) in the nonirradiated control group. No significant difference (p = 0.087) in ossification was found between the pre- (447 ± 136 days) and postoperative (510 ± 112 days) radiation groups. Ossification between two graft segments (336 ± 38 days) showed significantly (p < 0.001) faster ossification than between the original and grafted bone (448 ± 85 days). Moreover, closer initial contact between the segments resulted in faster ossification (p < 0.001). When analyzing cofactors, tobacco consumption was the only negative factor aggravating ossification (p = 0.006). Conclusion: Head and neck radiation corresponded with the impaired and prolonged ossification of jaw reconstructions with free bone grafts. There was no difference in ossification if radiotherapy was performed before or after reconstructive surgery. A close bony contact was particularly important for ossification between the original and grafted bone.

Loss of MMP-27 Predicts Mandibular Bone Invasion in Oral Squamous Cell Carcinoma.

Invasion of the mandibular bone is frequent in oral squamous cell carcinoma (OSCC), which often results in extensive ablative and reconstructive procedures for the patient. The purpose of this single-center, retrospective study was to identify and evaluate potential biomarkers and risk factors for bone invasion in OSCC. Initially, in silico gene expression analysis was performed for different HNSCC tumor T-stages to find factors associated with invasive (T4a) tumor growth. Afterwards, the protein expression of bone-metabolizing MMP-27, TNFRSF11B (Osteoprotegerin, OPG), and TNFSF11 (RANKL) was investigated via Tissue Microarrays (TMAs) for their impact on mandibular bone invasion. TMAs were assembled from the bone-tumor interface of primary OSCCs of the floor of the mouth and gingiva from 119 patients. Sixty-four carcinomas with patho-histological jaw invasion (pT4a) were compared to 55 carcinomas growing along the mandible without invasion (pT2, pT3). Tissue samples were additionally evaluated for patterns of invasion using the WPOI grading system. Statistical analysis of in silico data revealed decreased MMP-27 mRNA expression to be strongly associated with the pT4a-stage in OSCC, indicating invasive tumor growth with infiltration of adjacent anatomical structures. Our own clinico-pathological data on OSCCs presented a significant decrease of MMP-27 in tumors invading the nearby mandible (pT4a), compared to pT2 and pT3 tumors without bone invasion. Loss of MMP27 evolved as the strongest predictor of mandibular bone invasion in binary logistic regression analysis. To our knowledge, this is the first study investigating the role of MMP-27 expression in OSCC and demonstrating the importance of the loss of MMP-27 in mandibular bone invasion.

The Emerging Role of Small Extracellular Vesicles in Inflammatory Airway Diseases.

Extracellular vesicles (EVs) are produced and released by all cells and are present in all body fluids. They exist in a variety of sizes, however, small extracellular vesicles (sEVs), the EV subset with a size range from 30 to 150 nm, are of current interest. By transporting a complex cargo that includes genetic material, proteins, lipids, and signaling molecules, sEVs can alter the state of recipient cells. The role of sEVs in mediating inflammatory processes and responses of the immune system is well-documented, and adds another layer of complexity to our understanding of frequent diseases, including chronic rhinosinusitis (CRS), asthma, chronic obstructive pulmonary disease (COPD), and upper airway infections. In these diseases, two aspects of sEV biology are of particular interest: (1) sEVs might be involved in the etiopathogenesis of inflammatory airway diseases, and might emerge as attractive therapeutic targets, and (2) sEVs might be of diagnostic or prognostic relevance. The purpose of this review is to outline the biological functions of sEVs and their capacity to both augment and attenuate inflammation and immune response in the context of pathogen invasion, CRS, asthma, and COPD.

PD-L1 Influences Cell Spreading, Migration and Invasion in Head and Neck Cancer Cells.

The programmed cell death protein-1 (PD-1)/programmed cell death ligand-1 (PD-L1) axis blockade has been implemented in advanced-stage tumor therapy for various entities, including head and neck squamous cell carcinoma (HNSCC). Despite a promising tumor response in a subgroup of HNSCC patients, the majority suffer from disease progression. PD-L1 is known to influence several intrinsic mechanisms in cancer cells, such as proliferation, apoptosis, migration and invasion. Here, we modulated PD-L1 expression in three HNSCC cell lines with differential intrinsic PD-L1 expression. In addition to an alteration in the epithelial-to-mesenchymal transition (EMT) marker expression, we observed PD-L1-dependent cell spreading, migration and invasion in a spheroid spreading assay on four different coatings (poly-L-lysine, collagen type I, fibronectin and Matrigel®) and a chemotactic transwell migration/invasion assay. Furthermore, the overexpression of PD-L1 led to increased gene expression and small interfering ribonucleic acid (siRNA) knockdown and decreased gene expression of Rho-GTPases and related proteins in a RT2 Profiler™ PCR Array. Rac1 and Rho-GTPase pulldown assays revealed a change in the activation state concordantly with PD-L1 expression. In summary, our results suggest a major role for PD-L1 in favoring cell motility, including cell spreading, migration and invasion. This is presumably caused by altered N-cadherin expression and changes in the activation states of small Rho-GTPases Rho and Rac1.

Buparlisib modulates PD-L1 expression in head and neck squamous cell carcinoma cell lines.

High expression of the immune checkpoint receptor PD-L1 is associated with worse patient outcome in a variety of human cancers, including head and neck squamous cell carcinoma (HNSCC). Binding of PD-L1 with its partner PD-1 generates an inhibitory signal that dampens the immune system. Immunotherapy, that is blocking the PD-1/PD-L1 checkpoint, has proven to be an effective tool in cancer therapy. However, not all patients are able to benefit from this immune checkpoint inhibition. Therefore, evidence is growing of intrinsic PD-L1 signaling in cancer cells. For example, intrinsic PD-L1 expression was associated with PI3K/Akt/mTOR signaling, which is part of diverse oncogenic processes including cell proliferation, growth and survival. In this study we demonstrate the effects of PI3K/Akt/mTOR pathway inhibition by buparlisib on PD-L1 expression in HNSCC cell lines. After buparlisib treatment for 72 h, PD-L1 was downregulated in total cell lysates of HNSCC cells. Moreover, flow cytometry revealed a downregulation of PD-L1 membrane expression. Interestingly, the buparlisib mediated effects on PD-L1 expression were reduced by additional irradiation. In PD-L1 overexpressing cells, the buparlisib induced inhibition of proliferation was neutralized. In summary, our findings imply that blocking the PI3K/Akt/mTOR pathway could be a good additional therapy for patients who show poor response to immune checkpoint therapy.

Infiltrating immune cells are associated with radiosensitivity and favorable survival in head and neck cancer treated with definitive radiotherapy.

OBJECTIVES: The aim of this study was to investigate the influence of CD4+, CD8+ and Forkhead box protein 3 (FoxP3+) tumor-infiltrating lymphocytes, as well as CD1a+ tumor-infiltrating dendritic cells on the radiosensitivity and survival of primarily chemoirradiated advanced head and neck squamous cell carcinomas. STUDY DESIGN: Immunohistochemical staining for CD4, CD8, FoxP3 and CD1a was performed in 82 primarily chemoirradiated head and neck squamous cell carcinomas. Associations with clinicopathologic data, programmed cell death protein-1 (PD-1), programmed cell death ligand-1 (PD-L1), p16, radiation response, and survival were examined. RESULTS: High CD4 expression was associated with complete response after radiation (P = .006) and high CD1a expression (P = .024). High CD8+ tumor-infiltrating lymphocyte counts were associated with absence of tumor relapse (P = .032) and better disease-free survival (P = .051). Strong overall T-cell infiltration was found more often in tumors with high-grade differentiation (P = .004), complete response after radiation (P = .022), and better overall survival and disease-specific survival (each P = .052). Tumors with high FoxP3+ T regulatory (Treg) infiltration more often showed high-grade tumor differentiation (P = .017), advanced patient age (P = .02), high PD-1 (P = .007), high CD4 (P = .002), and high CD8 expression (P = .002), as well as better disease-free survival (P = .019). CONCLUSIONS: T-cell activation (high CD4, CD8 and FoxP3 expression) is associated with radio response and favorable survival in advanced head and neck cancer treated with definitive chemoradiation.

Predictive value of FHIT, p27, and pERK1/ERK2 in salivary gland carcinomas: a retrospective study.

OBJECTIVES: The aim of this study was to investigate the predictive value of the biomarkers FHIT, p27, and pERK1/ERK2 in salivary gland carcinomas. MATERIAL AND METHODS: Immunohistochemical staining of FHIT, p27, and pERK1/ERK2 of 265 patients with salivary gland carcinomas was conducted, and associations with clinico-histopathological data, overall survival, and disease-specific survival were examined. RESULTS: Expression of FHIT (quick score 98.7 vs. 206.4) and p27 (QS 187.3 vs. 244.8) was significantly lower in carcinomas compared to non-tumor control tissue. Loss of FHIT frequently occurred in ACC (55.2%), SDC (68.2%), and SCC (100%). In the totality of tumors, loss of FHIT expression was found in 46.7% (106/227) and was significantly associated with advanced T stage and UICC stage, high-grade histology, loss of p27, PI3K, and survivin. FHIT positivity went along with significantly better overall and disease-specific survival. Negativity of p27 occurred in 28.7% (70/244) of tumors, particularly in SDC (54.4%) and SCC (50%). In the totality of tumors, p27 was associated with advanced patient age, high-grade histology, PI3K, survivin as well as better overall and disease-specific survival (p < 0.05). Positive pERK1/ERK2 expression correlated with positive survivin expression but did not affect overall survival in the totality of tumors. In mucoepidermoid carcinomas, pERK1/ERK2 expression was associated with low-grade malignancy, positive nuclear survivin, and better disease-specific survival. CONCLUSIONS: Loss of FHIT and p27 characterizes aggressive tumor growth and unfavorable prognosis in salivary gland cancer. CLINICAL RELEVANCE: The results may help to stratify patient-specific therapies according to individual tumor characteristics.

Biological predictors of radiosensitivity in head and neck squamous cell carcinoma.

OBJECTIVES: The aim of this study is to investigate the influence of prognostic biomarkers on radiosensitivity and survival of advanced head and neck squamous cell carcinomas treated by primary (chemo)radiation. MATERIAL AND METHODS: The clinicopathological data and immunohistochemical staining of p16, c-Met, survivin, PD-1, and PD-L1 of 82 primarily (chemo)irradiated patients with head and neck squamous cell carcinoma were analyzed. Associations with local and locoregional radiation response, overall survival (OS), disease-free (DFS), and disease-specific survival (DSS) were assessed. RESULTS: Complete tumor response was associated with increased patient age (p = 0.007), N0-status (p = 0.022), M0-status (p = 0.007), and p16-positivity (p = 0.022). High PD-L1 was associated with M0-status (p = 0.026) and indicated tumor response to irradiation (p = 0.057); survivin expression showed higher rates of response failure (p = 0.073). Low PD-1 was associated with increased T-stage (p = 0.029) and local recurrence (p = 0.014). High PD-1 was strongly correlated with PD-L1-positive tumor infiltrating lymphocytes (p < 0.001). Low PD-L1 showed a significant correlation with high c-Met expression (p = 0.01). Significant predictors for unfavorable univariate survival were incomplete tumor response (DSS, p < 0.001), single radiotherapy (DSS, p = 0.002), M1-status (DSS, p < 0.001), decreased radiation dose (DSS, p = 0.014), high survivin (DSS, p = 0.045), and high c-Met (OS, p < 0.05). Survivin and c-Met also showed prognostic significance in multivariate survival analysis. CONCLUSIONS: P16 and PD-L1 indicate radiosensitivity, whereas survivin and c-Met implicate radioresistance in primarily (chemo)irradiated head and neck squamous cell carcinomas. The role of the PD-1/PD-L1 immune checkpoints in radiation response and survival merits further investigation. CLINICAL RELEVANCE: The findings may improve patient-specific therapy according to individual tumor characteristics.