Natural Grasp Intention Recognition Based on Gaze in Human-Robot Interaction.

OBJECTIVE: While neuroscience research has established a link between vision and intention, studies on gaze data features for intention recognition are absent. The majority of existing gaze-based intention recognition approaches are based on deliberate long-term fixation and suffer from insufficient accuracy. In order to address the lack of features and insufficient accuracy in previous studies, the primary objective of this study is to suppress noise from human gaze data and extract useful features for recognizing grasp intention. METHODS: We conduct gaze movement evaluation experiments to investigate the characteristics of gaze motion. The target-attracted gaze movement model (TAGMM) is proposed as a quantitative description of gaze movement based on the findings. A Kalman filter (KF) is used to reduce the noise in the gaze data based on TAGMM. We conduct gaze-based natural grasp intention recognition evaluation experiments to collect the subject's gaze data. Four types of features describing gaze point dispersion ( fvar), gaze point movement ( fgm), head movement ( fhm), and distance from the gaze points to objects ( fdj) are then proposed to recognize the subject's grasp intentions. With the proposed features, we perform intention recognition experiments, employing various classifiers, and the results are compared with different methods. RESULTS: The statistical analysis reveals that the proposed features differ significantly across intentions, offering the possibility of employing these features to recognize grasp intentions. We demonstrated the intention recognition performance utilizing the TAGMM and the proposed features in within-subject and cross-subject experiments. The results indicate that the proposed method can recognize the intention with accuracy improvements of 44.26% (within-subject) and 30.67% (cross-subject) over the fixation-based method. The proposed method also consumes less time (34.87 ms) to recognize the intention than the fixation-based method (about 1 s). CONCLUSION: This work introduces a novel TAGMM for modeling gaze movement and a variety of practical features for recognizing grasp intentions. Experiments confirm the effectiveness of our approach. SIGNIFICANCE: The proposed TAGMM is capable of modeling gaze movements and can be utilized to process gaze data, and the proposed features can reveal the user's intentions. These results contribute to the development of gaze-based human-robot interaction.

Predictive factors for dissection-free sentinel node micrometastases in early oral squamous cell carcinoma.

This sentinel node (SN) biopsy trial aimed to assess its effectiveness in identifying predictive factors of micrometastases and to determine whether elective neck dissection is necessary in oral squamous cell carcinoma. This retrospective study included 55 patients from three previous trials, with positive SNs. The relationship between the sizes of the metastatic focus and metastasis in non-sentinel node (NSN) was investigated. Four of the 55 largest metastatic focus were isolated tumor cells, and the remaining 51 were ranged from 0.2 to 15 mm, with a median of 2.6 mm. The difference of prevalence between 46 negative- and 9 positive-NSN was statistically significant with regard to age, long diameter of primary site and number of cases with regional recurrence. In comparing the size of largest metastatic focus dividing the number of positive SN, with metastaic focus range of < 3.0 mm in one-positive SN group, there were 18 (33%) negative-NSN and no positive-NSN. Regarding prognosis, 3-year overall survival rate of this group (n = 18) and other (n = 37) were 94% and 73% (p = 0.04), and 3-year recurrence free survival rate of this group and other were 94% and 51% (p = 0.03), respectively. Absolutely a further prospective clinical trial would be needed, micrometastases may be defined as solitary SN metastasis with < 3.0 mm of metastatic focus, and approximately 33% of neck dissections could be avoided using these criteria.

A Concurrent Framework for Constrained Inverse Kinematics of Minimally Invasive Surgical Robots.

Minimally invasive surgery has undergone significant advancements in recent years, transforming various surgical procedures by minimizing patient trauma, postoperative pain, and recovery time. However, the use of robotic systems in minimally invasive surgery introduces significant challenges related to the control of the robot's motion and the accuracy of its movements. In particular, the inverse kinematics (IK) problem is critical for robot-assisted minimally invasive surgery (RMIS), where satisfying the remote center of motion (RCM) constraint is essential to prevent tissue damage at the incision point. Several IK strategies have been proposed for RMIS, including classical inverse Jacobian IK and optimization-based approaches. However, these methods have limitations and perform differently depending on the kinematic configuration. To address these challenges, we propose a novel concurrent IK framework that combines the strengths of both approaches and explicitly incorporates RCM constraints and joint limits into the optimization process. In this paper, we present the design and implementation of concurrent inverse kinematics solvers, as well as experimental validation in both simulation and real-world scenarios. Concurrent IK solvers outperform single-method solvers, achieving a 100% solve rate and reducing the IK solving time by up to 85% for an endoscope positioning task and 37% for a tool pose control task. In particular, the combination of an iterative inverse Jacobian method with a hierarchical quadratic programming method showed the highest average solve rate and lowest computation time in real-world experiments. Our results demonstrate that concurrent IK solving provides a novel and effective solution to the constrained IK problem in RMIS applications.

Impact of age for overall survival in head and neck sarcoma.

The purpose to the present study is to research the association between age at surgery and survival outcomes of patients with sarcoma in head and neck. Twenty-six patients with head and neck sarcoma who underwent by surgery from 2003 to 2017 were enrolled in the present observation study. Patients who did not undergo chemotherapy were significantly older age at surgery by Mann-Whitney U test. Fifty-five was the cutoff age that predicted death by receiver operating curve analysis. Shorter survival rates of overall, disease-specific, local recurrence-free and disease-free were associated with older age by log-rank test. Age (≥55 years/<55 years) was correlated with shorter overall survival by multivariate analysis of Cox's proportional hazards model adjusting with chemotherapy (absence/presence). In conclusion, older age predicts worse overall survival in head and neck sarcoma.

Macroscopic and multiple metastases in sentinel lymph node biopsy are respectively associated with poor prognosis in early oral cancer.

BACKGROUND: A multicenter, randomized controlled phase III trial was conducted on sentinel lymph node biopsy (SLNB) and elective neck dissection for T1 (depth of invasion ≥ 4 mm)-T2N0M0 oral cavity squamous cell carcinoma. This study identified factors associated with poor prognosis in patients who underwent SLNB based on a subgroup analysis of this trial. METHODS: We analyzed 418 sentinel lymph nodes (SLNs) from 132 patients who underwent SLNB. The metastatic SLNs were classified into three categories based on size-isolated tumor cells: < 0.2 mm, micrometastasis: ≥ 0.2 mm and < 2 mm, and macrometastasis: ≥ 2 mm. Three groups were formed based on the number of metastatic SLNs: no metastasis, 1 metastatic node, and ≥ 2 metastatic nodes. The size and number of metastatic SLNs on survival were evaluated using Cox proportional hazard models. RESULTS: Patients with macrometastasis and ≥ 2 metastatic SLNs had worse overall survival (OS) and disease-free survival (DFS) after adjustment for potential confounders (HR for OS: macrometastasis, 4.85; 95% CI 1.34-17.60; ≥ 2 metastatic SLN, 3.63; 95% CI 1.02-12.89; HR for DFS: macrometastasis, 2.94; 95% CI 1.16-7.44; ≥ 2 metastatic SLN, 2.97; 95% CI 1.18-7.51). CONCLUSIONS: In patients who underwent SLNB, a poorer prognosis was associated with macrometastasis or having ≥ 2 metastatic SLNs.

Estimation of CO2 Separation Performances through CHA-Type Zeolite Membranes Using Molecular Simulation.

Chabazite (CHA)-type zeolite membranes are a potential material for CO2 separations because of their small pore aperture, large pore volume, and low aluminum content. In this study, the permeation and separation properties were evaluated using a molecular simulation technique with a focus on improving the CO2 separation performance. The adsorption isotherms of CO2 and CH4 on CHA-type zeolite with Si/Al = 18.2 were predicted by grand canonical Monte Carlo, and the diffusivities in zeolite micropores were simulated by molecular dynamics. The CO2 separation performance of the CHA-type zeolite membrane was estimated by a Maxwell-Stefan equation, accounting for mass transfer through the support tube. The results indicated that the permeances of CO2 and CH4 were influenced mainly by the porosity of the support, with the CO2 permeance reduced due to preferential adsorption with increasing pressure drop. In contrast, it was important for estimation of the CH4 permeance to predict the amounts of adsorbed CH4. Using molecular simulation and the Maxwell-Stefan equation is shown to be a useful technique for estimating the permeation properties of zeolite membranes, although some problems such as predicting accurate adsorption terms remain.

Evaluation of FAU-type Zeolite Membrane Stability in Transesterification Reaction Conditions.

The transesterification conversion of methyl ether can be enhanced by the removal of the byproduct methanol using methanol permselective faujasite (FAU-type) zeolite membranes. However, the authors previously observed that the methanol flux during the transesterification reaction was lower than the predicted flux. Therefore, this study investigated the stability of FAU-type zeolite membranes in the presence of organic components associated with the transesterification reaction of methyl hexanoate and 1-hexanol. The stability was defined in terms of changes in methanol permeance and zeolite structure. The effect of reaction components (methanol, 1-hexanol, methyl hexanoate, and hexyl hexanoate) on the FAU-type zeolite structure and the methanol permeation performance of the FAU-type zeolite membranes were evaluated to find the component causing the lower methanol flux. From these results, two esters were found to adsorb strongly on the FAU-type zeolite. The methanol flux of the FAU-type zeolite membrane was examined after vapor exposure of each of the four reaction chemicals at 373 K for 8 h. In the case of methyl hexanoate and hexyl hexanoate vapor exposure, the methanol flux was reduced by about 75% compared to the initial flux of 15 kg m-2 h-1. These results indicated methanol permeation performance was inhibited by the adsorption of esters.

Auditory Feedback for Enhanced Sense of Agency in Shared Control.

There is a growing need for robots that can be remotely controlled to perform tasks of one's own choice. However, the SoA (Sense of Agency: the sense of recognizing that the motion of an observed object is caused by oneself) is reduced because the subject of the robot motion is identified as external due to shared control. To address this issue, we aimed to suppress the decline in SoA by presenting auditory feedback that aims to blur the distinction between self and others. We performed the tracking task in a virtual environment under four different auditory feedback conditions, with varying levels of automation to manipulate the virtual robot gripper. Experimental results showed that the proposed auditory feedback suppressed the decrease in the SoA at a medium level of automation. It is suggested that our proposed auditory feedback could blur the distinction between self and others, and that the operator attributes the subject of the motion of the manipulated object to himself.

Impact of low and high body mass index on predicting therapeutic efficacy and prognosis in patients with metastatic renal cell carcinoma treated with first-line tyrosine kinase inhibitors.

OBJECTIVE: To evaluate the significance of both low and high body mass index (BMI) as a biomarker in first-line tyrosine kinase inhibitors (TKIs) for metastatic renal cell carcinoma (mRCC). METHODS: The oncological outcome of 235 patients with mRCC treated with TKI from 2007 to 2018 was reviewed retrospectively. All patients received first-line TKI as therapy. We analyzed the relationship between BMI (low and high) and disease control rate. The primary outcome was progression free survival and overall survival, and the association between BMI and survival prognosis was evaluated. RESULTS: The median BMI was 22.5 kg/m2 , and 25 patients (10.7%) had a low BMI (<18.5 kg/m2 ), 158 patients (67.2%) had a normal BMI (18.5-25 kg/m2 ), and 52 patients (22.1%) had a high BMI (≥ 25 kg/m2 ). Patients in the low BMI group had a significantly lower disease control rate, whereas patients in the high BMI group had a significantly higher disease control rate (p = 0.002 and p = 0.030, respectively). A log-rank test showed prognosis to be significantly poorer in the low BMI group and to be significantly better in the high BMI group than that in the normal BMI group. Multivariable Cox regression analysis showed that low BMI was an independent indicator of poor prognosis, whereas high BMI was an independent indicator of favorable prognosis. CONCLUSION: We showed the impact of both low and high BMI on predicting therapeutic efficacy and prognosis in mRCC patients treated with TKI.

A Wirelessly Powered 4-Channel Neurostimulator for Reconstructing Walking Trajectory.

A wirelessly powered four-channel neurostimulator was developed for applying selective Functional Electrical Stimulation (FES) to four peripheral nerves to control the ankle and knee joints of a rat. The power of the neurostimulator was wirelessly supplied from a transmitter device, and the four nerves were connected to the receiver device, which controlled the ankle and knee joints in the rat. The receiver device had functions to detect the frequency of the transmitter signal from the transmitter coil. The stimulation site of the nerves was selected according to the frequency of the transmitter signal. The rat toe position was controlled by changing the angles of the ankle and knee joints. The joint angles were controlled by the stimulation current applied to each nerve independently. The stimulation currents were adjusted by the Proportional Integral Differential (PID) and feed-forward control method through a visual feedback control system, and the walking trajectory of a rat's hind leg was reconstructed. This study contributes to controlling the multiple joints of a leg and reconstructing functional motions such as walking using the robotic control technology.

Intelligent Gait Analysis and Evaluation System Based on Cane Robot.

Gait analysis and evaluation are vital for disease diagnosis and rehabilitation. Current gait analysis technologies require wearable devices or high-resolution vision systems within a limited usage space. To facilitate gait analysis and quantitative walking-ability evaluation in daily environments without using wearable devices, a mobile gait analysis and evaluation system is proposed based on a cane robot. Two laser range finders (LRFs) are mounted to obtain the leg motion data. An effective high-dimensional Takagi-Sugeno-Kang (HTSK) fuzzy system, which is suitable for high-dimensional data by solving the saturation problem caused by softmax function in defuzzification, is proposed to recognize the walking states using only the motion data acquired from LRFs. The gait spatial-temporal parameters are then extracted based on the gait cycle segmented by different walking states. Besides, a quantitative walking-ability evaluation index is proposed in terms of the conventional Tinetti scale. The plantar pressure sensing system records the walking states to label training data sets. Experiments were conducted with seven healthy subjects and four patients. Compared with five classical classification algorithms, the proposed method achieves the average accuracy rate of 96.57%, which is improved more than 10%, compared with conventional Takagi-Sugeno-Kang (TSK) fuzzy system. Compared with the gait parameters extracted by the motion capture system OptiTrack, the average errors of step length and gait cycle are only 0.02 m and 1.23 s, respectively. The comparison between the evaluation results of the robot system and the scores given by the physician also validates that the proposed method can effectively evaluate the walking ability.

Development of High-Cell-Density Tissue Method for Compressed Modular Bioactuator.

Bioactuators have been developed in many studies in the recent decade for actuators of micro-biorobots. However, bioactuators have not shown the same power as animal muscles. Centrifugal force was used in this study to increase the cell density of cultured muscle cells that make up the bioactuator. The effect of the centrifugal force on cells in the matrix gel before curing was investigated, and the optimal centrifugal force was identified to be around 450× g. The compressed modular bioactuator (C-MBA) fabricated in this study exhibited 1.71 times higher cell density than the conventional method. In addition, the contractile force per unit cross-sectional area was 1.88 times higher. The proposed method will contribute to new bioactuators with the same power as living muscles in animals.

A Therapeutic Strategy for Lower Motor Neuron Disease and Injury Integrating Neural Stem Cell Transplantation and Functional Electrical Stimulation in a Rat Model.

Promising treatments for upper motor neuron disease are emerging in which motor function is restored by brain-computer interfaces and functional electrical stimulation. At present, such technologies and procedures are not applicable to lower motor neuron disease. We propose a novel therapeutic strategy for lower motor neuron disease and injury integrating neural stem cell transplantation with our new functional electrical stimulation control system. In a rat sciatic nerve transection model, we transplanted embryonic spinal neural stem cells into the distal stump of the peripheral nerve to reinnervate denervated muscle, and subsequently demonstrated that highly responsive limb movement similar to that of a healthy limb could be attained with a wirelessly powered two-channel neurostimulator that we developed. This unique technology, which can reinnervate and precisely move previously denervated muscles that were unresponsive to electrical stimulation, contributes to improving the condition of patients suffering from intractable diseases of paralysis and traumatic injury.

Visual Sensing System to Investigate Self-Propelled Motion and Internal Color of Multiple Aqueous Droplets.

This study proposes a visual sensing system to investigate the self-propelled motions of droplets. In the visual sensing of self-propelled droplets, large field-of-view and high-resolution images are both required to investigate the behaviors of multiple droplets as well as chemical reactions in the droplets. Therefore, we developed a view-expansive microscope system using a color camera head to investigate these chemical reactions; in the system, we implemented an image processing algorithm to detect the behaviors of droplets over a large field of view. We conducted motion tracking and color identification experiments on the self-propelled droplets to verify the effectiveness of the proposed system. The experimental results demonstrate that the proposed system is able to detect the location and color of each self-propelled droplet in a large-area image.

Impact of modified Glasgow prognostic score on predicting prognosis and modification of risk model for patients with metastatic renal cell carcinoma treated with first line tyrosine kinase inhibitor.

INTRODUCTION AND OBJECTIVES: Intermediate risk group of the International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) criteria is thought to consist of patients with different prognoses. This study investigated the impact of a pretreated modified Glasgow prognostic score (mGPS), which is defined on the basis of the pretreated serum albumin and C-reactive protein level, on predicting the prognosis of patients with metastatic renal cell carcinoma (mRCC) and its usefulness for the re-stratification of patients into a more improved risk model. MATERIALS AND METHODS: One hundred ninety-six mRCC patients treated with first-line tyrosine kinase inhibitor (TKI) were retrospectively investigated. All patients were classified into either a high-mGPS or a low-mGPS group on the basis of mGPS score upon starting systemic therapy, the overall survival (OS) and cancer specific survival (CSS) rates in each group were compared. We use decision curve analysis and calculate C-index based on OS and CSS to compare IMDC+mGPS model and IMDC model. RESULTS: The categories of favorable, intermediate, and poor risk groups in the IMDC model were assessed in 32, 113, and 51 cases, respectively. The low- and high-mGPS groups consisted of 149 and 47 cases. The median OS in the high- and low-mGPS groups were 38.4 months and 5.6 months, and their median CSSs were 41.0 months and 5.6 months, respectively (P < 0.0001). Multivariate analysis showed that a high mGPS, multiple metastatic organs, and hypercalcemia were independent predictive factors for a worse OS (P = 0.0260). Next, we divided the intermediate risk group into two subgroups using the mGPS score. The OS and CSS for the high-mGPS subgroup were significantly worse than those for the low-mGPS one (P = 0.0024, median OS: 21.0 months and 33.7 months, P = 0.0007, median CSS: 21.0 months and 39.8 months), and there was no significant difference in OS between the high-mGPS subgroup in the intermediate risk group and poor risk group (P = 0.2250). The value of C-index based on OS at IMDC and IMDC+mGPS model were 0.6771 and 0.6967, and those based on CSS were 0.6850 and 0.7080, respectively. In decision curve analysis to evaluate the clinical net benefit using the IMDC+mGPS model compared to the IMDC model, there was no significant difference between the two groups. CONCLUSION: mGPS is useful for establishing a more improved prognostic model that is able to stratify mRCC patients treated with first-line TKI.

Predictive factors for false negatives following sentinel lymph node biopsy in early oral cavity cancer.

Prophylactic elective neck dissection (ND) with navigation surgery using radioisotope-based sentinel lymph node biopsy (SLNB) is non-inferior to elective ND in terms of survival but has an advantage in postoperative functional disability. We conducted a subgroup analysis to identify predictive factors for false-negative (FN)-SLNB in patients with early oral cavity cancer. This study is a supplementary analysis using the dataset of a previously reported randomized clinical trial on SLN navigation surgery for oral cancers. This study investigated the association of clinical and SLN-related factors with false-negative cases in the SLNB group. From 2011 to 2016, 275 patients were enrolled and randomly assigned to the ND and SLNB study groups, with 134 patients assigned to the SLNB group. In the SLNB group, seven cases with negative SLNs and neck recurrences were judged as FN-SLNBs according to the general definition. The number of detected SLNs with and without adjusting for the propensity score was significantly associated with FNs in the logistic analysis. FN-SLNB was associated with the number of identified SLNs, suggesting the need for careful postoperative monitoring for neck recurrence in patients with one or two identified SLNs after acquiring sufficient experience in the identification technique.

Role of Human Papilloma Virus and Lifestyle Factors in Overall Survival of Patients with Oropharyngeal Squamous Cell Carcinoma.

Background: Patients with human papillomavirus (HPV)-associated oropharyngeal squamous cell carcinoma (OPSCC) have a significantly better treatment response and overall survival (OS) rates than non-HPV-associated OPSCC. Objectives: We conducted the present study to further characterize the interplay between lifestyle risk factors, which are not only HPV status, but also smoking history and alcohol consumption, and the OS to optimize the treatment of patients with OPSCC. Materials and Methods: Between January 2006 and December 2013, 94 patients newly diagnosed with OPSCC were treated with curative intent at Aichi Cancer Center Hospital (Nagoya, Japan). To determine negative prognostic factors associated with the OS, univariate and multivariable Cox regression analyses were performed. Results: Of the 94 OPSCC patients, 53 (56.4%) were positive for HPV. The univariate analysis revealed that T classification, smoking history, alcohol consumption, and HPV status were significant determinants of the OS. In the multivariate analysis, adjusted for the clinical stage, smoking history, alcohol consumption, HPV status, and a smoking history of >10 pack-years was an independent negative prognostic factor for the OS among patients with OPSCC (HR: 10.4, 95 %CI: 1.34-80.6, p < 0.05). Conclusions: Smoking is a very important negative prognostic factor even in cases of HPV-associated OPSCC. The impact of smoking needs to be reaffirmed when deciding on treatment plans and de-escalation trials in OPSCC, even in cases of HPV-associated OPSCC.

Prognostic model of upfront cytoreductive nephrectomy in patients with metastatic renal cell carcinoma treated with immune checkpoint inhibitors and/or targeted agents.

INTRODUCTION AND OBJECTIVES: The aim of this study was to investigate prognostic factors and to establish a prognostic model using them for upfront cytoreductive nephrectomy (CN) in patients with metastatic renal cell carcinoma (mRCC) treated with immune checkpoint inhibitor (ICI) and/or tyrosine kinase inhibitor (TKI). MATERIALS AND METHODS: Two hundred eleven patients who were diagnosed as mRCC at initial diagnosis and were treated with TKI and/or ICI were classified into 2 groups: those undergoing CN (upfront CN group, 117 cases) and those who initially underwent systemic therapy (non-upfront CN group, 94 cases). In the upfront CN group, the patients' background and overall survival (OS) were compared with those in the other two groups, and prognostic factors were analyzed. A prognostic model of the upfront CN group was established. RESULTS: The median of the observation period for the upfront CN group was 25 months. The rates of patients with clear cell histology, with a Karnofsky performance status (KPS) of ≥ 80%, with a single metastatic organ, with a normal pretreated C-reactive protein level, and with an intermediate risk according to the International mRCC Database Consortium (IMDC) model were significantly higher than those in the non-upfront CN group (87.2% and 30.9%, p < 0.0001; 92.3% and 77.7%, p = 0.0025; 41.9% and 24.5%, p = 0.0080; 47.9% and 13.8%, p < 0.0001; 66.7% and 45.7%, p = 0.0023, respectively). The 50% OS in the upfront CN group was 33.1 months, significantly better than that in the non-upfront CN group (11.1 months, p < 0.0001), and these results were consistent regardless of their prognostic risk level. Multivariate analysis showed that multiple metastatic organs and a KPS of < 80% were independent predictive factors for OS (hazard ratio: 1.653 and 2.995, p = 0.0339 and 0.0054, respectively). Using these two parameters to stratify the upfront CN group, the 50% OSs in cases with no risk factors, in those with one factor, and in those with two factors were 43.4 months, 29.1 months, and 7.7 months, respectively (p < 0.0001). CONCLUSION: The upfront CN group was able to be stratified by our prognostic model into three subgroups with different prognoses. This model can provide useful information for making decisions in consideration of upfront CN in patients with mRCC.

Distribution pattern and pathologic analysis of metastatic sentinel and non-sentinel lymph nodes in lymphatic basin dissection for clinical T2/T3 oral cancer with clinical N0 status.

OBJECTIVE: The localization pattern of metastatic sentinel lymph node (SN) and non-SNs and pathologic analysis of metastatic lymph nodes in SN lymphatic basin dissection (SLBD) were investigated in patients with cT2/T3cN0 oral squamous cell carcinoma (OSCC). METHODS: This prospective multicenter trial involved 10 institutions nationwide in Japan. A total of 57 patients were enrolled. The lateral neck was divided into 5 lymphatic basins. The lymphatic basin containing SNs was defined as the SN lymphatic basin. All patients underwent SLBD with backup selective neck dissection (I-III) combined with primary tumor removal. When SNs were found outside of levels I-III, including in the contralateral neck, SLBD was performed by removing the compartments containing SNs separately. SN metastasis was classified as isolated tumor cells (ITCs), micrometastasis, or macrometastasis. ITCs are defined as a lesion no larger than 0.2 mm in largest dimension and are classified as pN0. RESULTS: SN metastasis was observed in 22 cases. All metastatic lymph nodes, including false-negative cases, were detected in the SN lymphatic basin. Isolated tumor cells in the SNs did not affect prognosis, whereas micrometastasis tended to have poor prognosis. After adjusting for other risk factors, a positive SN remained a significant predictor of poor 5-year overall survival in pT2-4 OSCC. CONCLUSION: SLBD for intraoperative SN biopsy is a sufficient therapeutic procedure and is valuable for determining pathologic nodal stage in OSCC. SN positivity was demonstrated to be an independent predictor of poor prognosis in patients with pT2-4 disease undergoing SLBD with backup selective neck dissection (I-III).