Efficacy and safety of molecularly targeted agents and immune checkpoint inhibitors for unresectable or recurrent/metastatic oral cancer in Japan.

Background/purpose: For unresectable recurrent/metastatic head and neck cancer, pembrolizumab alone or pembrolizumab combined with cisplatin and 5-fluorouracil is the first-line therapy, depending on the PD-L1 combined positive score (CPS). However, this is based on clinical studies of head and neck cancer, and few similar studies have been conducted on oral cancer alone. This study aimed to investigate the current status of pharmacotherapy for unresectable, recurrent, or metastatic oral cancer. Materials and methods: Patients with unresectable or recurrent/metastatic oral cancer who received cetuximab, nivolumab, or pembrolizumab as first-line treatment were reviewed. Overall survival (OS), progression-free survival (PFS), PFS 2 (PFS2), overall response rate (ORR), disease control rate (DCR), and immune-related adverse events were obtained from medical records. Results: A total of 155 patients were enrolled from six hospitals. The ORR in the nivolumab, pembrolizumab, and cetuximab groups was 17.2 %, 4.2 %, and 21.6 %, respectively, and the DCR was 37.9 %, 41.7 %, and 58.8 %, respectively. Median OS in nivolumab, pembrolizumab, and cetuximab groups was 10.3, 9.5, and 11.1 months, respectively. No significant differences were observed in survival among the three groups. The small number of cases and the retrospective nature of the study precluded the determination of the more effective first-line treatment among the three drugs. Conclusion: The current statuses of nivolumab, pembrolizumab, and cetuximab in unresectable recurrent metastatic oral cancer was reported.

Prognostic value of a mandibular canal staging system for primary lesions in patients with lower gingival squamous cell carcinoma: a multicenter, retrospective study.

BACKGROUND: The Union for International Cancer Control and American Joint Committee on Cancer tumor staging system is used globally for treatment planning. As it may be insufficient for tumor staging of lower gingival carcinomas, we proposed the mandibular canal tumor staging system. In this study, we aimed to compare the two systems for such tumor staging and to identify prognostic markers. METHODS: This multicenter, retrospective study included patients with lower gingival squamous cell carcinoma who underwent radical surgery during 2001-2018. We compared survival rates (Kaplan-Meier estimator) and patient stratification according to the two systems. RESULTS: The proposed system yielded more balanced patient stratification than the existing system. Progression in the tumor grade according to the proposed system was associated with a poorer prognosis. The 5-year overall and disease-specific survival rates for the entire cohort were 74.9% and 81.8%, respectively. Independent factors affecting overall survival were tumor stage according to the proposed system, excision margins, and number of positive nodes, whereas those affecting disease-specific survival were excision margins and number of positive nodes. CONCLUSIONS: Subsite-specific tumor classification should be used for patients with oral cancer, and our results suggest that mandibular canal tumor classification may be effective for patients with lower gingival carcinoma.

Comparison of the 8th edition of TNM staging of oral cancer with the 7th edition and its prognostic significance using clinical depth of invasion and extranodal extension.

OBJECTIVES: The 8th edition of the International Union Against Cancer Control/American Joint Committee on Cancer Staging System introduced depth of invasion (DOI) and extranodal extension (ENE) into the staging of oral cavity cancer. We evaluated the prognostic ability of this new staging system compared with the 7th edition using clinical DOI (cDOI) and clinical ENE (cENE). MATERIALS AND METHODS: We retrospectively reviewed and restaged 2,118 patients with oral squamous cell carcinoma treated between 2001 and 2018 using cDOI and cENE. Overall and disease-specific survival were used as endpoints to compare the prognostic outcomes of the 7th and 8th editions using Harrell's concordance index (C-index). RESULTS: In total, 305 (14.4 %) cases were upstaged in the T category, 85 (4.0 %) cases were upstaged in the N category, and 280 (13.2 %) cases were upstaged in the overall TNM stage. The introduction of the cDOI increased the C-index and hazard ratio (HR) for each T category. The introduction of cENE increased the N3b category of 85 cases, bringing the total to 94 cases, thereby widening the differences between each N category. In the 8th edition, the C-index and HR for overall TNM stage increased, and the discrimination between stage groups improved. CONCLUSIONS: The 8th edition of the TNM clinical staging system using cDOI and cENE predominantly identified patients with a high mortality rate, thus improving the ability to discriminate and prognosticate oral cancer.

Volume-based 18F-fluorodeoxyglucose positron emission tomography/computed tomography parameters correlate with delayed neck metastasis in clinical early-stage oral squamous cell carcinoma.

OBJECTIVE: There is no known preoperative marker that can effectively predict the risk of delayed neck metastasis (DNM), which is an important factor that determines the prognosis of early-stage oral cancer. In this study, we examined whether 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET)/computed tomography (CT) uptake parameters of primary cancer can predict the risk of DNM in early-stage oral squamous cell carcinoma (OSCC). METHODS: Data from patients with stage I-II OSCC who underwent surgical resection of the primary tumor without elective neck dissection between January 2009 and December 2016 were retrospectively reviewed. Patient characteristics, histopathological factors, and PET/CT parameters (maximum standardized uptake value [SUVmax], metabolic tumor volume [MTV], and total lesion glycolysis [TLG]) were evaluated for their association with DNM. DNM rates were calculated, and the parameters that were statistically significant in the univariate analysis were used as explanatory variables. Independent factors associated with DNM were identified using multivariate analysis. For all statistical analyses, p-values < 0.05 were considered statistically significant. RESULTS: Data from 71 patients were analyzed in the study. The overall DNM rate among all patients was 21.8%. The univariate analysis showed that the T classification, depth of invasion, pattern of invasion, lymphovascular invasion, SUVmax, MTV, and TLG were significant predictors of DNM. However, the multivariate analysis revealed that only the depth of invasion, MTV, and TLG were independent predictors of DNM. CONCLUSION: This study suggests that, in addition to conventional predictors, volume-based PET parameters are useful predictors of DNM in those with early-stage OSCC.

Multicenter retrospective study of the prognosis and the effect of postoperative adjuvant therapy in Japanese oral squamous cell carcinoma patients with close margin.

BACKGROUND: The purpose of this retrospective study was to investigate the prognosis of patients with oral cavity cancer with positive margin (PM) or close margin (CM) divided into pN- and pN+ groups. METHODS: The evaluated endpoints were local control and disease-specific survival (DSS) rates. RESULTS: Higher T classification, lymphovascular space invasion (LVSI), and older age were significant risk factors for DSS in the pN- groups. On the other hand, extranodal extension, multiple lymph node metastases, and LVSI were significant risk factors for DSS in the pN+ groups. Among the CM pN+ patients, no significant differences in the 3-year DSS were observed between the only surgery (51.9%) and adjuvant groups (53.2%). CONCLUSIONS: Higher T classification and LVSI are high-risk features more than PM or CM in the pN- groups for DSS. However, further prospective studies are needed to demonstrate the usefulness of adjuvant treatment in patients with PM or CM.

The Impact of Pretreatment Low Body Mass Index on Cause-Specific Mortality in Patients with Squamous Cell Carcinoma of the Oral Cavity.

The association between the pretreatment body mass index (BMI) and oral squamous cell carcinoma (SCC) outcomes is controversial. We aimed to examine the association between BMI and cause-specific mortality due to cancer of the oral cavity and patterns of failure that correlate with increased mortality. We enrolled 2,023 East Asian patients in this multicenter cohort study. We used the cumulative incidence competing risks method and the Fine-Gray model to analyze factors associated with cause-specific mortality, local recurrence, regional metastasis, and distant metastasis as first events. The median follow-up period was 62 mo. The 5-year cause-specific mortality for patients with underweight was 25.7%, which was significantly higher than that for patients with normal weight (12.7%, P < 0.0001). The multivariate model revealed that underweight was an independent risk factor for cause-specific mortality and regional metastasis (P < 0.05). Moreover, patients with underweight displayed a 51% and 55% increased risk of cause-specific mortality and regional metastasis, respectively, compared with their normal weight counterparts. Local recurrence was not associated with the BMI categories; however, the incidence of distant metastasis inversely decreased with BMI value. In summary, being underweight at diagnosis should be considered a high-risk mortality factor for oral SCC.

A Multicenter Study on the Effect of Margin Distance on Survival and Local Control in Stage 1-2 Squamous Cell Carcinoma of the Tongue.

BACKGROUND: Pathological close margins are considered a significant factor for local recurrence in patients with oral cancer. However, the oral cavity has complicated anatomical features, and the appropriate margin distance for each site is unknown. This multicenter, retrospective study aimed to determine the appropriate resection margin for early tongue cancer and investigate the need for additional treatment for close margins and stump dysplasia. PATIENTS AND METHODS: In total, 564 patients from ten hospitals were enrolled in this study. Sex, age, performance status, T stage, tumor length diameter, depth of invasion, elective neck dissection, iodine staining, horizontal margin distance, vertical margin distance, pathological differentiation, invasion pattern, lymphatic invasion, perineural invasion, dysplasia in the resection edge, additional treatment for close margins, local recurrence, neck metastasis, distant metastasis, and outcomes were investigated. RESULTS: Receiver operating characteristic analysis for local recurrence revealed cut-off values of 3.3 mm for horizontal distance and 3.1 mm for vertical distance. Patients with close horizontal or vertical margins showed significantly higher local recurrence rates, but these were not associated with overall or disease-specific survival. Furthermore, there was no effect of additional treatment in patients with dysplasia at the surgical margin. CONCLUSION: For early tongue cancer, a horizontal margin of 3.3 mm was defined as a close margin. Close margins were significantly correlated with local recurrence but did not affect survival. In the future, we would like to examine the concept of "quality margins," including the surrounding anatomical features.

Multicenter retrospective study of nivolumab for recurrent/metastatic oral squamous cell carcinoma.

OBJECTIVES: Immunotherapy with nivolumab for patients with recurrent/metastatic oral squamous cell carcinoma has not been evaluated. Here, we aimed to examine the efficacy, safety, and prognostic factors of nivolumab in these patients. MATERIALS AND METHODS: This multicenter retrospective observational study involved patients who received nivolumab between April 2017 and June 2019. The patient characteristics were evaluated for association with progression-free and overall survival. Progression-free and overall survival rates were calculated; parameters that were significant in the univariate analysis were used as explanatory variables. Independent factors for progression-free and overall survival were identified using multivariate analysis. RESULTS: Totally, 143 patients were included. The overall response and disease control rates were 27.3% and 46.2%, respectively. The median, 1- and 2-year progression-free survival rates were 2.7 months, 25.4%, and 19.2%, respectively; those for overall survival were 11.2 months, 47.3%, and 33.6%, respectively. The independent factors affecting progression-free survival were performance status and immune-related adverse event occurrence, whereas those affecting overall survival were performance status, target disease, and number of previous lines of systemic cancer therapy. Eight patients reported grade ≥3 immune-related adverse events. CONCLUSION: Nivolumab was effective for recurrent/metastatic oral squamous cell carcinoma treatment and was well tolerated by patients.

Examination of Suprahyoid Muscle Resection and Other Factors Affecting Swallowing Function in Patients With Advanced Oral Cancer After Surgical Resection and Reconstruction.

Dysphagia is one of the most common adverse effects associated with oral cancer therapy and could greatly impair postoperative quality of life. The objective of this study was to analyze postoperative swallowing outcomes and factors influencing postoperative swallowing function in patients with advanced oral cancer who underwent primary reconstruction after surgical resection to identify patients at risk of experiencing severe dysphagia after immediate reconstruction of surgical defects, and to determine an ideal approach to provide appropriate perioperative interventions. The swallowing status was evaluated at 4 week postoperatively using the Functional Oral Intake Scale. We also analyzed the effects of patient, tumor, surgical, and other factors on postoperative swallowing function. The study included 67 patients. At 4 weeks postoperatively, 11 patients showed reduced swallowing function, whereas 56 patients showed good swallowing function. The number of resected suprahyoid muscles (odds ratio, 1.55; 95% confidence interval, 1.03-2.32; P=0.035) was an independent factor influencing postoperative swallowing function. Thus, among patients who underwent radical resection of oral cancer with primary reconstruction, those with extensive resection of the suprahyoid muscles were at higher risk of developing postoperative dysphagia. These findings are expected to facilitate increased vigilance for dysphagia, better counseling, and appropriate rehabilitation interventions.

Protocol for a multicentre, prospective observational study of elective neck dissection for clinically node-negative oral tongue squamous cell carcinoma (END-TC study).

INTRODUCTION: In early-stage oral tongue squamous cell carcinoma (OTSCC), elective neck dissection (END) is recommended when occult lymph node metastasis is suspected; however, there is no unanimous consensus on the risks and benefits of END in such cases. The management of clinically node-negative (cN0) OTSCC remains controversial. This study, therefore, aimed to evaluate the efficacy of END and its impact on the quality of life (QoL) of patients with cN0 OTSCC. METHODS AND ANALYSIS: This is a prospective, multicentre, nonrandomised observational study. The choice of whether to perform END at the same time as resection of the primary tumour is based on institutional policy and patient preference. The primary endpoint of this study is 3-year overall survival. The secondary endpoints are 3-year disease-specific survival, 3-year relapse-free survival and the impact on patient QoL. Propensity score-matching analysis will be performed to reduce selection bias. ETHICS AND DISSEMINATION: This study was approved by the Clinical Research Review Board of the Nagasaki University. The protocol of this study was registered at the University Hospital Medical Information Network Clinical Trials Registry. The datasets generated during the current study will be available from the corresponding author on reasonable request. The results will be disseminated internationally, through scientific and professional conferences and in peer-reviewed medical journals. TRIAL REGISTRATION NUMBER: UMIN000027875.

Treatment and Prognosis of Oral Cancer Patients with Confirmed Contralateral Neck Metastasis: A Multicenter Retrospective Analysis.

The prognosis of oral cancer that has metastasized to the contralateral cervical lymph nodes is poor, although the appropriate treatment method has not been established because of its rarity. A multicenter retrospective study on the treatment and prognosis of pN2c oral cancer patients was conducted. We investigated the treatment and prognosis of 62 pN2c patients out of 388 pN+ patients with oral squamous cell carcinomas. Statistical analysis was performed on the various factors with overall survival (OS) and disease specific survival (DSS). In multivariate cox regression analysis, advanced T stage was significantly correlated with poor OS (p = 0.011) and DSS (p = 0.023) of patients with pN2c neck. In pN2c patients, OS, DSS, and neck control was not different between those undergoing ipsilateral neck dissection initially and those undergoing bilateral neck dissection. Thus, contralateral elective neck dissection is not recommended. The most important risk factor for prognosis in pN2c oral cancer patients is advanced T stage. No evidence was found to recommend contralateral elective neck dissection in clinically N1/2b patients. Therefore, the indication for contralateral elective neck dissection in N1/2b patients should be carefully determined in consideration of individual conditions.

Oral melanoma: a multicenter study of 69 patients from Japan.

OBJECTIVES: The purpose of this multicenter retrospective study was to investigate the demographic characteristics and treatment outcomes of patients with mucosal malignant melanoma (MM) of the oral cavity. MATERIALS AND METHODS: This was a multicenter study involving 8 Japanese universities. The medical records of 69 patients who were diagnosed with primary oral MM between January 2000 and December 2020 were retrospectively analyzed. Overall survival (OS) and prognostic factors for OS were analyzed statistically. RESULTS: There were 40 (58.0%) males and 29 (42.0%) females, and their mean (range) age was 69.8 ± 14.6 (22-96) years old. The most common primary site was the palate (30 patients, 43.5%). Stage IVA was the most common disease stage (36 patients, 52.2%). Radical therapy was performed in 55 patients (79.7%). The 2-year and 5-year OS rates of the 69 patients were 64.6% and 42.5%, respectively. The 2-year and 5-year OS rates of the stage III patients were 85.9% and 72.5%, respectively, and those of the stage IVA patients were 56.3% and 26.0%, respectively. The 1-year OS rate of the stage IVB/IVC patients was 26.7%. The 2-year and 5-year OS rates of the radical therapy group were 74.1% and 50.5%, respectively, whereas the 2-year OS rate of the non-radical therapy group was 26.0%. An advanced T classification was the only identified prognostic factor for OS (hazard ratio: 6.312, 95% confidence interval: 1.133-38.522, p < 0.05). CONCLUSIONS: Early detection and radical treatment are essential for improving the prognosis of oral MM patients. CLINICAL RELEVANCE: Early detection and adequate radical therapy leads to the better prognosis of oral MM patients.

A Case of Synovial Chondromatosis of Temporomandibular Joint with Numerous Loose Bodies.

Here, we report a case of synovial chondromatosis of the temporomandibular joint (TMJ) with numerous loose bodies. A 56-year-old woman was examined in the oral surgery department for trismus and pain in the left TMJ when opening the mouth. Imaging indicated TMJ synovial chondromatosis, and the patient was referred to our department for further examination. Her facial features were symmetrical, and no occlusal abnormalities were found. The maximum mouth opening was 30 mm, and movement of the left mandibular condyle was restricted and accompanied by pain and joint sounds. Panoramic radiography showed deformation of the left mandibular condyle and radiopaque lesions surrounding it. Computed tomography showed numerous small granules around the left mandibular condyle, some of which were calcified. Magnetic resonance imaging showed anterior disc displacement without reduction in the left TMJ and hypointense lesions on T2-weighted images. Bone scintigraphy showed an accumulation in the area of the left TMJ. Based on the diagnosis of the left TMJ synovial chondromatosis, the lesions were removed, and plastic surgery on the mandibular condyle was performed under general anesthesia. We removed 386 white loose bodies. Histopathologically, the loose bodies were consistent with synovial chondromatosis lesions. The postoperative course was uneventful, with no recurrence or TMJ dysfunction approximately 5 years after the surgery, indicating that open surgery is the best course of intervention in such cases.

Multicenter Retrospective Study of Weekly Cetuximab Plus Paclitaxel for Recurrent or Metastatic Oral Squamous Cell Carcinoma.

BACKGROUND/AIM: This study was conducted to compare the efficacy and safety of the weekly cetuximab plus paclitaxel (wCmab-PTX) regimen with those of the EXTREME regimen in patients with recurrent or metastatic oral squamous cell carcinoma (R/M OSCC). PATIENTS AND METHODS: This multicenter retrospective study involved a chart review of the clinical records of R/M OSCC patients treated with wCmab-PTX in each institution between January 2013 and December 2017. Data were collected, and the efficacy, safety, and treatment outcomes were analyzed. RESULTS: The best overall response and disease control rates were 48.4% and 61.3%, respectively. The median PFS and OS were 6 and 13 months, respectively. There was no significant difference in prognosis with or without previous platinum administration. The grade 3-4 adverse events were leukopenia (16.1%), followed by acne-like rash (12.9%), and neutropenia (9.7%). All adverse events, excluding more than grade 3 infusion reactions, were tolerable and manageable. CONCLUSION: wCmab-PTX may be considered as a treatment option for R/M patients with OSCC that is refractory to platinum-based chemotherapy, or progressive disease after receiving chemotherapy.

Study of Treatment Methods for Surrounding Soft Tissues of Implants Following Mandibular Reconstructions with Fibula-Free Flaps.

In maxillofacial reconstruction implant treatment, unsatisfactory soft tissue treatment of the area around the implant may lead to inflammation. As a result, appropriate soft tissue treatment is critical. To the best of our knowledge, there are no studies that compare the different tissue treatment methods available. Hence, in this study, we compare three soft tissue treatment methods around implants after mandibular reconstruction is achieved with a fibula-free flap. Out of 33 patients who underwent mandible reconstruction using fibula-free flaps between 2006 and 2015, 5 were selected for this study. A total of 17 implants were used for treatment by the final prosthetics of the five patients. Three soft tissue treatment methods with free gingival graft (FGG) were evaluated, namely, installing a splint in a modified abutment to protect the wounded area during a palatal mucosa transplant (method 1), installing a splint or dentures to a locator abutment (method 2), and the use of screw-in fixed dentures (method 3). The method that could guarantee the widest keratinized mucosa was the screw-in fixed denture method. The results of our study indicated that employing screw-in fixed dentures for FGG may be a useful soft tissue treatment for mandible reconstruction implants.

Clinical significance of the G8 screening tool in elderly patients with oral squamous cell carcinoma.

OBJECTIVES: The present study investigated the clinical significance of the G8 screening tool in elderly oral squamous cell carcinoma (OSCC) patients using a multicenter analysis. MATERIALS AND METHODS: The medical records of 438 primary OSCC patients aged 75 years and older were retrospectively reviewed. To examine the clinical significance of the G8 screening tool in elderly OSCC patients, self-reliance (SR) rates and prognostic factors were statistically analyzed. RESULTS: The mean score of the G8 screening tool was 10.9 ± 2.93. The SR cut-off value of the G8 score was 9.5 in a receiver operating characteristic curve analysis. Five-year overall survival rates were 40.1% in patients with a G8 score < 9.5 and 58.4% in those with a G8 score ≥ 9.5 (p < 0.01). Five-year cancer-specific rates were 34.3% in patients with a G8 score < 9.5 and 55.7% in those with a G8 score ≥ 9.5 (p < 0.01). Five-year SR rates were 40.7% in patients with a G8 score < 9.5 and 55.3% in those with a G8 score ≥ 9.5 (p < 0.05). A multivariate analysis identified an advanced age (≥ 80 vs < 80; HR, 1.437; 95%CI, 1.181-1.843; p < 0.01), poorer ECOG-PS (2-4 vs 0-1; HR, 1.560; 95%CI, 1.14-2.106; p < 0.01), and standard treatment (non-standard therapy vs standard therapy; HR, 0.598; 95%CI, 0.405-0.910; p < 0.05) as significant independent prognostic factors for SR. A lower G8 score was associated with poorer SR (≥ 9.5 vs < 9.5; HR, 0.765; 95%CI, 0.575-1.034; p = 0.081). CONCLUSION: The clinical significance of the G8 score for elderly OSCC patients was demonstrated and its combination with ECOG-PS may be useful for assessing their prognoses.

Relationship Between EGFR Expression in Oral Cancer Cell Lines and Cetuximab Antibody-dependent Cell-mediated Cytotoxicity.

BACKGROUND/AIM: Cetuximab treatment targets the epidermal growth factor receptor (EGFR) overexpressed in oral cancer. This study aimed to investigate the anti-tumour activity of cetuximab against oral cancer cell lines with respect to antibody-dependent cell-mediated cytotoxicity (ADCC), and determine the correlation between ADCC and EGFR expression. MATERIALS AND METHODS: EGFR expression in oral cancer cells was measured by quantitative flow cytometric analysis and immunohistochemistry. ADCC activity was measured by 4-h calcein release assays. RESULTS: Cetuximab-mediated ADCC against oral cancer cells was detectable at a concentration of 0.1 µg/ml. A high correlation was observed between the number of EGFR molecules on the surface of oral cancer cells and ADCC (correlation coefficient: 0.847; p=0.032). CONCLUSION: ADCC is an important mechanism underlying the therapeutic effect of cetuximab, and EGFR expression in tumour cells might serve as a predictive marker to evaluate the effect of cetuximab treatment.

Multicenter retrospective study of the prognosis and treatment outcomes of Japanese oral squamous cell carcinoma patients with level IV/V metastasis.

BACKGROUND: The purpose of this study was to retrospectively describe the characteristics and outcomes of patients with oral squamous cell carcinoma and level IV/V metastasis and to compare patients who underwent no postoperative therapy with those who underwent postoperative radiotherapy (RT) and concomitant chemoradiotherapy (CCRT). METHODS: We evaluated 669 patients. Clinicopathological data, postoperative therapy, and clinical course were investigated. RESULTS: Sixty-one patients (9.1%) developed level IV/V metastasis. The 3-year cumulative overall survival rates of patients with and without level IV/V metastasis were 47.3% and 64.3%, respectively. Tongue tumors, pN2 or N3 classification, and moderate or poor differentiation were significantly associated with the development of level IV/V metastasis. The surgery+RT/CCRT group was associated with better 3-year cumulative disease-specific survival and overall survival rates than the surgery only group. CONCLUSION: Adjuvant therapy (RT alone or CCRT) after surgery is recommended for patients with level IV/V metastasis.

A Multicenter Retrospective Study of Elective Neck Dissection for T1-2N0M0 Tongue Squamous Cell Carcinoma: Analysis Using Propensity Score-Matching.

BACKGROUND: This multicenter retrospective study aimed to determine whether elective neck dissection (END) can be performed for T1-2N0M0 tongue cancer. METHODS: Patients with T1-2N0M0 tongue squamous cell carcinoma who received treatment between January 2000 and December 2012 were enrolled at 14 multicenter study sites. The 5-year overall survival (OS) and 5-year disease-specific survival (DSS) were compared between the propensity score-matched END and observation (OBS) groups. RESULTS: The results showed that the OS rates among the 1234 enrolled patients were 85.5% in the END group and 90.2% in the OBS group (P = 0.182). The DSS rates were 87.0% in the END group and 94.3% in the OBS group (P = 0.003). Among the matched patients, the OS rates were 87.1% in the END group and 76.2% in the OBS group (P = 0.0051), and the respective DSS rates were 89.2% and 82.2% (P = 0.0335). CONCLUSION: This study showed that END is beneficial for T1-2N0M0 tongue cancer. However, END should be performed for patients with a tumor depth of 4-5 mm or more, which is the depth associated with a high rate of lymph node metastasis. The use of END should be carefully considered for both elderly and young patients.