Robust temporal adiabatic passage with perfect frequency conversion between detuned acoustic cavities.

For classical waves, phase matching is vital for enabling efficient energy transfer in many scenarios, such as waveguide coupling and nonlinear optical frequency conversion. Here, we propose a temporal quasi-phase matching method and realize robust and complete acoustical energy transfer between arbitrarily detuned cavities. In a set of three cavities, A, B, and C, the time-varying coupling is established between adjacent elements. Analogy to the concept of stimulated Raman adiabatic passage, amplitudes of the two couplings are modulated as time-delayed Gaussian functions, and the couplings' signs are periodically flipped to eliminate temporal phase mismatching. As a result, robust and complete acoustic energy transfer from A to C is achieved. The non-reciprocal frequency conversion properties of our design are demonstrated. Our research takes a pivotal step towards expanding wave steering through time-dependent modulations and is promising to extend the frequency conversion based on state evolution in various linear Hermitian systems to nonlinear and non-Hermitian regimes.

A second wave of topological phenomena in photonics and acoustics.

Light and sound are the most ubiquitous forms of waves, associated with a variety of phenomena and physical effects such as rainbows and echoes. Light and sound, both categorized as classical waves, have lately been brought into unexpected connections with exotic topological phases of matter. We are currently witnessing the onset of a second wave of active research into this topic. The past decade has been marked by fundamental advances comprising two-dimensional quantum Hall insulators and quantum spin and valley Hall insulators, whose topological properties are characterized using linear band topology. Here, going beyond these conventional topological systems, we focus on the latest frontiers, including non-Hermitian, nonlinear and non-Abelian topology as well as topological defects, for which the characterization of the topological features goes beyond the standard band-topology language. In addition to an overview of the current state of the art, we also survey future research directions for valuable applications.

Role of Lower Esophageal Squamous Cell Carcinoma Margin Location on Abdominal Lymph Node Metastasis Risk.

BACKGROUND: Different sites of esophageal cancer are accompanied by different regional lymph node metastasis (LNM) risks. We aimed to investigate the impact of a lower tumor margin on abdominal LNM risk. METHODS: We enrolled patients who underwent esophagectomy for esophageal squamous carcinoma (ESCC) from 2014 to 2017 in West China Hospital. Overall survival (OS) analysis was performed. We measured the distance between the lower tumor margin and esophagogastric junction (LED) with upper gastrointestinal contrast-enhanced X-ray (UGCXR). Multivariate logistic regression analysis and propensity score matching (PSM) were performed to explore the relationship between LED and the risk of abdominal LNM. Abdominal LNM risk in ESCC was stratified based on the location of the lower tumor margin. A model predicting abdominal LNM risk was constructed and presented with a nomogram. RESULTS: The included patients had an abdominal LNM rate of 48.29%. In multivariate logistic regression analysis, LED was identified as a risk factor for abdominal LNM. Subgroup analysis of middle ESCC showed that patients with an LED less than 10 cm had a significantly higher rate of abdominal LNM than those with an LED greater than 10 cm. The abdominal LNM rate in middle ESCC patients with an LED less than 10 cm was 32.2%, while it was 35.1% in lower ESCC patients whose lower tumor margin did not invade the esophagogastric junction (EGJ), which was comparable after PSM. CONCLUSIONS: LED could help surgeons evaluate the risk of abdominal LNM preoperatively and better guide dissection of abdominal lymph nodes according to risk level.

Experimental Realization of Weyl Exceptional Rings in a Synthetic Three-Dimensional Non-Hermitian Phononic Crystal.

Weyl points-topological monopoles of quantized Berry flux-are predicted to spread to Weyl exceptional rings in the presence of non-Hermiticity. Here, we use a one-dimensional Aubry-Andre-Harper model to construct a Weyl semimetal in a three-dimensional parameter space comprising one reciprocal dimension and two synthetic dimensions. The inclusion of non-Hermiticity in the form of gain and loss produces a synthetic Weyl exceptional ring (SWER). The topology of the SWER is characterized by both its topological charge and non-Hermitian winding numbers. We experimentally observe the SWER and synthetic Fermi arc in a one-dimensional phononic crystal with the non-Hermiticity introduced by active acoustic components. Our findings pave the way for studying the high-dimensional non-Hermitian topological physics in acoustics.

Risk Factors and a Nomogram for Prediction of Refractory Pudendal Neuralgia: A Retrospective Multivariate Analysis Study.

BACKGROUND: Pudendal neuralgia (PN) is one of the most common forms of genital pain. About 4% or higher of patients suffering from chronic pain. OBJECTIVES: The aim of this study was to evaluate the risk factors for prediction of refractory PN (RPN). STUDY DESIGN: A retrospective multivariate analysis study. SETTING: This retrospective analysis included 112 patients with PN who received the pudendal nerve block treatment at the Pain Department of General Hospital of People's Liberation Army. METHODS: Univariate and multivariable logistic regression analyses were used for covariates selection. A nomogram was developed to estimate nonresponse to the pudendal nerve block. RESULTS: The median age of patients and duration of patients were 48.0 and 1.25 years, respectively. Among 112 patients, there were 64 good responders to the pudendal nerve block for neuropathic pain and 48 nonresponders. Multivariate analysis of 112 patients with PN demonstrated high self-rating depression scale scores (> 32) (odds ratio [OR], 95% confidence interval [CI]: 0.11, 0.01-0.77), damage to more than 2 terminal branches (OR, 95% CI: 0.22, 0.07-0.71), sensory deficit at S2-S4 on the dermatome map (OR, 95% CI: 0.22, 0.05-0.90), and duration of pain (> 4 years) (OR, 95% CI: 0.10, 0.03-0.42) were significant prognostic factors for nonresponse to the pudendal nerve block. LIMITATIONS: There are information biases for retrospective analysis, thus making it more difficult to come up with definitive conclusions. Large-scale randomized clinical trials are warranted to evaluate the risk factors for prediction of RPN. CONCLUSIONS: A longer duration of pain was correlated with a worse prognosis of the neurological disease. Patients with depression were prone to nonresponse to the pudendal nerve block treatment. Pain involved in more than 2 terminal branches and small fibers, affected at S2-S4 dermatome map, were considered to poor prognosis.

Sacral Nerve Stimulation in Patients With Refractory Pudendal Neuralgia.

BACKGROUND: Pudendal neuralgia (PN) is one of the most common forms of genital pain. Only 42.2% of PN patients respond to the first-line treatment. Novel neuromodulation techniques in the treatment of refractory PN patients are urgently required. OBJECTIVES: The aim of this study was to evaluate the treatment effects and adverse events of sacral nerve stimulation (SNS) for patients with refractory PN. STUDY DESIGN: A prospective nonrandomized study. SETTING: This prospective analysis included 33 patients who received the phase II surgical implantation. METHODS: A total of 55 eligible PN patients were recruited for SNS treatment after informed consent, and 33 of 55 patients with a minimum 50% improvement were candidates for surgical implantation. Visual Analog Scale (VAS) scores, Self-rating Anxiety and Depression Scale, Quality of life score (SF-36), and sleep monitoring indicators before and after surgery were used to assess the effects of SNS on patients with refractory PN. RESULTS: Thirty-three patients were included in the final analysis, involving 24 women and 9 men with a mean age of 49.5 years (26-70 years). There was a favorable decrease in pain severity (VAS scores) from 7.1 ± 1.1 at baseline to 6.1 ± 1.0 on postoperative day 1, and 2.8 ± 0.7 at 1 week, 1.7 ± 0.5 at 1 month, 1.1 ± 0.7 at 6 months, and 1.0 ± 0.6 at 12 months after surgery, respectively (P < 0.05). The mean score of each section of SF-36 after SNS was significantly higher than that at baseline (P < 0.05). Total sleep time and sleep time in each period were significantly prolonged after SNS implantation compared with that before surgery (6 months vs Pre, total: 5.32 ± 1.49 hours vs 3.66 ± 1.19 hours, deep: 2.52 ± 0.63 hours vs 1.36 ± 0.43 hours, light: 1.78 ± 0.42 hours vs 0.99 ± 0.30 hours, rapid eye movement: 1.41 ± 0.29 hours vs 0.89 ± 0.27 hours, P < 0.05). No serious device complications were reported during the follow-up period. LIMITATIONS: Large-scale randomized clinical trials are warranted to evaluate the risk factors for prediction of refractory PN. CONCLUSIONS: These data imply that SNS can have beneficial effects on patients with refractory PN.

Observation of Degenerate Zero-Energy Topological States at Disclinations in an Acoustic Lattice.

Building upon the bulk-boundary correspondence in topological phases of matter, disclinations have recently been harnessed to trap fractionally quantized density of states (DOS) in classical wave systems. While these fractional DOS have associated states localized to the disclination's core, such states are not protected from deconfinement due to the breaking of chiral symmetry, generally leading to resonances which, even in principle, have finite lifetimes and suboptimal confinement. Here, we devise and experimentally validate in acoustic lattices a paradigm by which topological states bind to disclinations without a fractional DOS but which preserve chiral symmetry. The preservation of chiral symmetry pins the states at the midgap, resulting in their protected maximal confinement. The integer DOS at the defect results in twofold degenerate states that, due to symmetry constraints, do not gap out. Our study provides a fresh perspective about the interplay between symmetry protection in topological phases and topological defects, with possible applications in classical and quantum systems alike.

A New Risk Factor for Cervical Anastomotic Leakage-Role of The Relative Gastric Length in the Surgical Treatment of Esophageal Cancer.

BACKGROUND: Blood supply is especially weak near the gastric fundus. Making the anastomosis in this area would increase the risk of anastomotic leakage (AL). In cervical anastomosis, the gastric conduit needs to travel through the thorax. Therefore, the relative length between the stomach and the thorax is an essential factor in deciding if the poorly supplied area could be removed. This study was to explore if a small relative gastric length was a risk of cervical AL. If all other conditions are equal, could intrathoracic anastomosis be a better choice? METHODS: Patients who underwent esophagectomy with a preoperative barium swallow in West China Hospital between 2014 and 2017 were included. The length of the greater curvature and the thorax were obtained from the barium esophagogram. The ratio between the length of the greater curvature and the thorax was the relative gastric length calculated from the greater curvature (RGL-G). RESULTS: A total of 782 patients were enrolled in the final analysis. The cervical AL group had a significantly higher ratio of patients with an RGL-G less than 1.3 (26.7% vs. 8.9%, p = 0.003). The multivariate logistic regression proved that RGL-G less than 1.3 was a risk factor for cervical anastomotic leakage (p = 0.012). Correspondingly, RGL-G less than 1.3 was not a risk factor (6.3% vs. 14.3%, p = 0.289) in the intrathoracic anastomosis group. CONCLUSIONS: RGL-G less than 1.3 was a new risk factor for cervical AL, but it would not be a problem for intrathoracic anastomosis.

Synthetic Three-Dimensional Z×Z_{2} Topological Insulator in an Elastic Metacrystal.

We report a three-dimensional (3D) topological insulator (TI) formed by stacking identical layers of Chern insulators in a hybrid real-synthetic space. By introducing staggered interlayer hopping that respects mirror symmetry, the bulk bands possess an additional Z_{2} topological invariant along the stacking dimension, which, together with the nontrivial Chern numbers, endows the system with a Z×Z_{2} topology. A 4-tuple topological index characterizes the system's bulk bands. Consequently, two distinct types of topological surface modes (TSMs) are found localized on different surfaces. Type-I TSMs are gapless and are protected by Chern numbers, whereas type-II gapped TSMs are protected by Z_{2} bulk polarization in the stacking direction. Remarkably, each type-II TSM band is also topologically nontrivial, giving rise to second-order topological hinge modes (THMs). Both types of TSMs and the THMs are experimentally observed in an elastic metacrystal.

Pretreatment-assisted robot intrathoracic layered anastomosis: our exploration in Ivor-Lewis esophagectomy.

BACKGROUND: Minimal invasive Ivor-Lewis esophagectomy (MIIVE) with intrathoracic esophago-gastric anastomosis (EGA) is still under exploration and the preferred technique for intrathoracic anastomosis has not been established. METHODS: We retrospectively reviewed 43 consecutive patients who underwent MIIVE using the series technique called pretreatment-assisted robot intrathoracic layered anastomosis (PRILA), performed by a single surgeon between September 2018 and December 2020. The operative outcomes were analyzed. RESULTS: The mean total operation time had been reduced from 446.38±54.775 minutes (range, 354-552) in the first year to 347.70±60.420 minutes (range, 249-450) later. There were no conversions to thoracotomy. All the patients achieved R0 resection. No patient suffered from anastomotic leakage. There was no 30-day mortality. The median length of postoperative stay was 10.0 days. CONCLUSIONS: PRILA further visualizes and streamlines the process of minimal invasive intrathoracic EGA, thus ensuring the precise anastomosis. It could be considered as a feasible alternative for intrathoracic EGA in MIILE.

Exosome circCMTM3 promotes angiogenesis and tumorigenesis of hepatocellular carcinoma through miR-3619-5p/SOX9.

AIM: As one of the most common and lethal carcinomas, hepatocellular carcinoma (HCC) is a global health concern and affects millions of people worldwide. Current treatments for HCC are very limited due to its unclear pathogenesis. Here, we aim to further investigate the role of circCMTM3/microRNA (miR)-3619-5p in HCC. METHODS: Human blood samples were collected from HCC patients and healthy people. Quantitative reverse transcription-polymerase chain reaction and western blot analysis were undertaken to measure levels of circCMTM3, miR-3619-5p, SOX9, and exosome markers. The MTT, colony formation, and Transwell assays were used to examine the viability, migration, and invasion of human umbilical vein endothelial cells (HUVECs), respectively. Tube formation assay was used to assess angiogenesis. Dual luciferase assay was used to validate circCMTM3/miR-3619-5p and miR-3619-5p/SOX9 interactions. A nude mouse xenograft model was used to test the role of circCMTM3 in HCC in vivo. RESULTS: Levels of circCMTM3 in exosomes from HCC patients and cells were elevated. Knockdown of circCMTM3 greatly decreased viability, migration, and invasion of HUVECs, as well as angiogenesis. CircCMTM3 acted as a miR-3619-5p sponge and miR-3619-5p inhibitor reversed the effects of si-circCMTM3 on angiogenesis. MiR-3619-5p directly targeted SOX9 and modulated angiogenesis through SOX9. Furthermore, knockdown of circCMTM3 suppressed angiogenesis and HCC tumor growth in vivo. CONCLUSION: The exosome circCMTM3/miR-3619-5p/SOX9 axis from HCC cells promotes angiogenesis and thus contributes to HCC tumorigenesis.

Safety profile of preoperative administration of low-molecular-weight heparin on minimally invasive lung cancer surgery: a randomized controlled trial.

BACKGROUND: Venous thromboembolism remains a common but preventable complication for cancerous lung surgical patients. Current guidelines recommend thromboprophylaxis for lung patients at high risk of thrombosis, while a consensus about specific administration time is not reached. This study was designed to investigate the safety profile of preoperative administration of low-molecular-weight-heparin (LMWH) for lung cancer patients. METHODS: From July 2017 to June 2018, patients prepared to undergo lung cancer surgery were randomly divided into the preoperative LMWH-administration group (PRL) for 4000 IU per day and the postoperative LMWH-administration group (POL) with same dosage, all the patients received thromboprophylaxis until discharge. Baseline characteristics including demographics and preoperative coagulation parameters were analyzed, while the endpoints included postoperative coagulation parameters, postoperative drainage data, hematologic data, intraoperative bleeding volume and reoperation rate. RESULTS: A total of 246 patients were collected in this RCT, 34 patients were excluded according to exclusion criterion, 101 patients were assigned to PRL group and 111 patients belonged to POL group for analysis finally. The baseline characteristic and preoperative coagulation parameters were all comparable except the PRL group cost more operation time (p = 0.008) and preoperative administration duration was significantly longer (p < 0.001). The endpoints including postoperative day 1 coagulation parameters, mean and total drainage volume, drainage duration, intraoperative bleeding volume and reoperation rate were all similar between the two groups. Moreover, coagulation parameters for postoperative day 3 between the two groups demonstrated no difference. CONCLUSION: Preoperative administration of low-molecular-weight-heparin demonstrated safety and feasibility for lung cancer patients intended to receive minimally invasive surgery. TRIAL REGISTRATION: ChiCTR2000040547 ( www.chictr.org.cn ), 2020/12/1, retrospectively registered.

From McKeown to Ivor Lewis, the learning curve for thoracic lymphadenectomy over the first 100 robotic esophagectomy cases: a retrospective study.

BACKGROUND: Lymphadenectomy is an essential but challenging part of the surgical treatment for esophageal cancer. However, the previously reported learning curve for robotic esophagectomy primarily focused on only one surgical approach (McKeown or Ivor Lewis). However, both approaches must be mastered by a mature robotic surgical team to deal with different clinical conditions and satisfy patients' needs. This study aimed to show how an experienced esophageal surgical team became proficient in both McKeown and Ivor Lewis robotic esophagectomy. METHODS: A retrospective review of the first 100 cases of robot-assisted minimally invasive esophagectomy (RAMIE) by a single surgical team was performed. The cumulative sum (CUSUM) analysis was used to distinguish the change point during the learning course. A subgroup analysis was performed according to a surgical approach (McKeown or Ivor Lewis) to determine the effect of experience from one surgical approach on learning the other RAMIE technique. RESULTS: According to the tendency of the CUSUM plot, the learning curve was divided into four phases. The subgroup analysis indicated the decline of the CUSUM plot in the 3rd phase originated from the start of the Ivor Lewis approach. The attending surgeon took 23 cases to achieve a significant improvement in the number of harvested thoracic lymph nodes using the McKeown approach. Regardless of the acquired experience of McKeown RAMIE, it took another 18 cases for the surgical team to achieve significant improvement in harvesting thoracic lymph nodes using the Ivor Lewis approach. CONCLUSIONS: Twenty-three cases were needed for an experienced surgical team to improve thoracic lymphadenectomy results using McKeown RAMIE. There was another learning phase during the transition from McKeown to Ivor Lewis esophagectomy. Importantly, the acquired experience from performing McKeown RAMIE could shorten how long it takes to learn Ivor Lewis RAMIE.

Is the routine placement of a feeding jejunostomy during esophagectomy worthwhile?-a systematic review and meta-analysis.

BACKGROUND: Malnutrition dramatically increases the risk of postoperative complications and delays patient recovery. Therefore, a feeding jejunostomy tube (FJT) is routinely placed during esophagectomy to maintain the postoperative nutrition supply. However, recently published studies have questioned the need of a FJT in every esophageal cancer patient. Because most patients can resume oral intake shortly after surgery, the nutrition-providing function of a FJT becomes much less critical. In contrast, FJT-related complications could be severe. METHODS: Relevant publications were found out by systemic searching of four medical databases (PubMed, EMBASE, Medline, and Cochrane Center Register of Controlled Trials). By reading the titles and the abstracts, potentially relevant studies were screened from the search results. The incidence of postoperative complications and FJT-related complications were calculated and compared to evaluate the efficacy of a FJT. RESULTS: Eighteen studies were included in the meta-analysis. The no-FJT group had a similar or even lower incidence of postoperative complications [anastomotic leakage (AL), pulmonary complications, and wound infections] compared with the FJT group. Ileus and FJT site infections were the most common FJT-related complications. The incidence of ileus was approximately 6% (95% CI: 3-12%), and over 63% of the patients with an ileus required re-operation to relieve the obstruction. The pooled mean rate of FJT site infections was 7% (95% CI: 6-9%). Approximately 7% of patients had dysfunction (obstruction or dislocation) of the jejunostomy tube (95% CI: 3-14%). CONCLUSIONS: The non-selective placement of a FJT during esophagectomy provides few benefits to the patients and may even increase the risk of postoperative complications. Therefore, an intraoperative FJT should be selectively prescribed, but not routinely in the surgical treatment of esophageal cancer.

Is immunonutrition superior to standard enteral nutrition in reducing postoperative complications in patients undergoing esophagectomy? A meta-analysis of randomized controlled trials.

PURPOSE: Perioperative enteral nutrition supports are recommended in esophagus cancer patients. Immunonutrition contains immuno-enhancing nutrients in addition to standard formula. These new nutrients are thought to be efficacious in reducing inflammatory response and improving postoperative immune response and they have been proved to be better than standard enteral nutrition in reducing postoperative complications in gastric cancer. However, if it would lead to a better clinical outcome in patients undergoing esophagectomy remains controversial. METHODS: A systematic literature search was performed in the online database of PubMed, Medline, EMBASE and Cochrane Library. The relevant studies were screened out of the results by reading titles and abstracts. Then, we read the full-texts to finally confirm the studies included in this meta-analysis. RESULTS: Six randomized controlled trials having enrolled 638 patients were included in the final analysis. The pooled analysis didn't show statistically significant difference between immunonutrition group and standard nutrition group in reducing postoperative complications. CONCLUSIONS: The postoperative complications are comparable between immunonutrition and the standard enteral nutrition in patients undergoing esophagectomy, but its value in severe malnutrition patients is undetermined, whereas the high tolerance and other advantages brought by the immunonutrition should not be overlooked and need to be further proved.

Long Noncoding RNA DUXAP8 Promotes Pancreatic Carcinoma Cell Migration and Invasion Via Pathway by miR-448/WTAP/Fak Signaling Axis.

OBJECTIVES: Pancreatic carcinoma (PC) has become the fourth leading cause of cancer deaths. Long noncoding RNA DUXAP8 has also been reported to play a regulatory role in PC progression. However, its molecular mechanism in PC is not fully elucidated. METHODS: Quantitative real-time polymerase chain reaction was used to detect the levels of DUXAP8, microRNA (miR)-448, Wilms tumor 1-associating protein (WTAP), focal adhesion kinase (Fak), and matrix metallopeptidase 2/9. Western blotting was carried out to detect matrix metallopeptidase 2/9, WTAP, Fak, and p-Fak. The interaction between DUXAP8 and miR-448 as well as WTAP and miR-448 was validated by bioinformatics and dual-luciferase reporter assays. Transwell assay was used to analyze cell invasion and migration. 3-[4,5-Dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay was used to analyze cell proliferation. RESULTS: DUXAP8 was upregulated, whereas miR-448 was downregulated in PC tissue and cells. Meanwhile, DUXAP8 knockdown or miR-448 overexpression inhibited migration, invasion, and proliferation of PC cells. DUXAP8 directly targeted miR-448, and miR-448 directly bound to WTAP. Downregulation of miR-448 reversed the inhibition of migration and invasion of PC cells by DUXAP8 knockdown. CONCLUSIONS: DUXAP8 sponges miR-448 to modulate migration, invasion, and proliferation of PC cells, indicating a novel mechanistic role of DUXAP8 in the regulation of PC progression.

Landau-Zener Transition in the Dynamic Transfer of Acoustic Topological States.

Topological notions in physics often emerge from adiabatic evolution of states. It not only leads to fundamental insight of topological protection but also provides an important approach for the study of higher-dimensional topological phases. In this work, we first demonstrate the transfer of topological boundary states (TBSs) across the bulk to the opposite boundary in an acoustic waveguide system. By exploring the finite-size induced minigap between two TBS bands, we unveil the quantitative condition for the breakdown of adiabaticity in the system by demonstrating the Landau-Zener transition with both theory and experiments. Our results not only serve as a foundation of future studies of dynamic state transfer but also inspire applications leveraging nonadiabatic transitions as a new degree of freedom.

Role of nodal skip metastasis in patients with mid-thoracic oesophageal squamous cell carcinoma: a propensity score matching study.

OBJECTIVES: Nodal skip metastasis (NSM) is a common phenomenon in mid-thoracic oesophageal squamous cell carcinoma (MT-OSCC); however, the prognostic implications of NSM in patients with MT-OSCC remain unclear. METHODS: This retrospective study enrolled 300 patients with MT-OSCC who underwent radical oesophagectomy and who had pathologically confirmed lymph node metastasis from January 2014 to December 2016. The patients were divided into 2 groups according to the presence or absence of NSM. Propensity score matching was applied to minimize patient selection bias. The impact of NSM on overall survival (OS) was assessed by Kaplan-Meier and multiple Cox proportional hazards analyses. The median follow-up time was 57 months. RESULTS: The NSM rate in the entire cohort was 22.0% (66/300). Pathological N (pN) stage (P < 0.001) and sex (P = 0.001) were identified as significant independent risk factors for NSM. NSM was more frequent in pN1 compared with pN2 patients (87.9% vs 12.1%, P < 0.001) and no NSM was found in pN3. NSM(+) patients had better prognoses than NSM(-) patients (Kaplan-Meier; 3-year OS, 62.1% vs 34.1%, P < 0.001). Propensity score matching produced 51 matched pairs, and the 3-year OS was still better in the NSM(+) compared with the NSM(-) group (66.7% vs 40.0%, P = 0.025). Multivariable Cox analysis confirmed NSM(+) as an independent factor favouring OS in patients with MT-OSCC. CONCLUSIONS: NSM usually occurs at pN1 stage in patients with MT-OSCC, and is associated with a favourable prognosis.