Impact of deep muscle invasion on nodal status and survival in patients with pT2 esophageal squamous cancer.

BACKGROUND: Whether T2 esophageal squamous cell carcinoma should be subclassified remains controversial. We aimed to investigate the impact of the depth of muscularis propria invasion on nodal status and survival outcomes. METHODS: We identified patients with pT2 esophageal squamous cell carcinoma who underwent primary surgery from January 2009 to June 2017. Clinical data were extracted from prospectively maintained databases. Tumor muscularis propria invasion was stratified into superficial or deep. Binary logistic regression was used to determine risk factors for lymph node metastases. The impact of the depth of muscularis propria invasion on survival was investigated using Kaplan‒Meier analysis and a Cox proportional hazard regression model. RESULTS: A total of 750 patients from three institutes were investigated. The depth of muscularis propria invasion (odds ratio [OR]: 3.95, 95% confidence interval [CI]: 2.46-6.35; p < 0.001) was correlated with lymph node metastases using logistic regression. T substage (hazard ratio [HR]: 1.37, 95% CI: 1.05-1.79; p < 0.001) and N status (HR: 1.51, 95% CI: 1.05-2.17; p < 0.001) were independent risk factors in multivariate Cox regression analysis. The deep muscle invasion was associated with worse overall survival (HR: 1.52, 95% CI: 1.19-1.94; p = 0.001) than superficial, specifically in T2N0 patients (HR: 1.38, 95% CI: 1.08-1.94; p = 0.035). CONCLUSIONS: We found that deep muscle invasion was associated with significantly worse outcomes and recommended the substaging of pT2 esophageal squamous cell carcinoma in routine pathological examination.

Increased resected lymph node stations improved survival of esophageal squamous cell carcinoma.

BACKGROUND: Neoadjuvant chemoradiotherapy (nCRT) and surgery have been recommended as the standard treatments for locally advanced esophageal squamous cell carcinoma (ESCC). In addition, nodal metastases decreased in frequency and changed in distribution after neoadjuvant therapy. This study aimed to examine the optimal strategy for lymph node dissection (LND) in patients with ESCC who underwent nCRT. METHODS: The hazard ratios (HRs) for overall survival (OS) and disease-free survival (DFS) were calculated using the Cox proportional hazard model. To determine the minimal number of LNDs (n-LNS) or least station of LNDs (e-LNS), the Chow test was used. RESULTS: In total, 333 patients were included. The estimated cut-off values for e-LNS and n-LNS were 9 and 15, respectively. A higher number of e-LNS was significantly associated with improved OS (HR: 0.90; 95% CI 0.84-0.97, P = 0.0075) and DFS (HR: 0.012; 95% CI: 0.84-0.98, P = 0.0074). The e-LNS was a significant prognostic factor in multivariate analyses. The local recurrence rate of 23.1% in high e-LNS is much lower than the results of low e-LNS (13.3%). Comparable morbidity was found in both the e-LNS and n-LND subgroups. CONCLUSION: This cohort study revealed an association between the extent of LND and overall survival, suggesting the therapeutic value of extended lymphadenectomy during esophagectomy. Therefore, more lymph node stations being sampled leads to higher survival rates among patients who receive nCRT, and standard lymphadenectomy of at least 9 stations is strongly recommended.

Vitamin D receptor induces oxidative stress to promote esophageal squamous cell carcinoma proliferation via the p53 signaling pathway.

Background: Esophageal squamous cell carcinoma (ESCC) is a common pathological esophageal cancer with poor prognosis. Vitamin D deficiency reportedly occurs in ESCC patients, and this is related to single nucleotide polymorphism of vitamin D receptor (VDR). Objective: We investigated the effect of VDR on ESCC proliferation, invasion, and metastasis and its potential mechanism. Methods: ESCC and normal tissues were collected from 20 ESCC patients. The ESCC tissue microarray contained 116 pairs of ESCC and normal tissues and 73 single ESCC tissues. VDR expression and its clinicopathological role were determined by real-time quantitative polymerase chain reaction, Western blot, and immunohistochemistry staining. sh-VDR and VDR overexpression were used to validate the effect of VDR on ESCC cell phenotype, and tandem mass tag-based quantitative proteomics and bioinformatics methods identified differential VDR-related proteins. The downstream pathway and regulatory effect were analyzed using ingenuity pathway analysis (IPA). Differentially expressed proteins were verified through parallel reaction monitoring and Western blot. In vivo imaging visualized subcutaneous tumor growth following tail vein injection of VDR-deficient ESCC cells. Results: High VDR expression was observed in ESCC tissues and cells. Gender, T stage, and TNM stage were related to VDR expression, which was the independent prognostic factor related to ESCC. VDR downregulation repressed ESCC cell proliferation, invasion, and migration in vitro and subcutaneous tumor growth and lung metastases in vivo. The cell phenotype changes were reversed upon VDR upregulation, and differential proteins were mainly enriched in the p53 signaling pathway. TP53 cooperated with ABCG2, APOE, FTH1, GCLM, GPX1, HMOX1, JUN, PRDX5, and SOD2 and may activate apoptosis and inhibit oxidative stress, cell metastasis, and proliferation. TP53 was upregulated after VDR knockdown, and TP53 downregulation reversed VDR knockdown-induced cell phenotype changes. Conclusions: VDR may inhibit p53 signaling pathway activation and induce ESCC proliferation, invasion, and metastasis by activating oxidative stress.

Will synchronous esophageal and lung resection increase the incidence of anastomotic leaks? A multicenter retrospective study.

BACKGROUND: Reports on combined resection for synchronous lung lesions and esophageal cancer (CRLE) cases are rare and mostly individual cases. Furthermore, the feasibility of CRLE has always been a controversial topic. In the current study, the authors retrospectively analyzed the feasibility of CRLE and established an individualized prediction model for esophageal anastomotic leaks after CRLE by performing a multicenter retrospective study. METHODS: Patients who underwent esophagectomy between January 2009 and June 2021 were extracted from a four-center prospectively maintained database, and those with CRLE at the same setting were matched in a 1:2 propensity score-matched (PSM) ratio to esophagectomy alone (EA) patients. A nomogram was then established based on the variables involved in multivariate logistic regression analysis. Internal validation of the nomogram was conducted utilizing Bootstrap resampling. Decision and clinical impact curve analysis were computed to assess the practical clinical utility of the nomogram. A prognosis analysis for CRLE and EA patients by Kaplan-Meier curves was conducted. RESULTS: Of the 7152 esophagectomies, 216 cases of CRLE were eligible, and 1:2 ratio propensity score-matched EA patients were matched. The incidence of anastomotic leaks following CRLE increased significantly ( P =0.035). The results of the multivariate analysis indicated the leaks varied according to the type of lung resection (anatomic>wedge resection, P =0.016) and site of resected lobe (upper>middle/low lobe; P =0.027), and a nomogram was established to predict the occurrence of leaks accurately (area under the curve=0.786). Although no statistically significant difference in overall survival (OS) was observed in the CRLE group ( P =0.070), a trend toward lower survival rates was noted. Further analysis revealed that combined upper lobe anatomic resection was significantly associated with reduced OS ( P =0.027). CONCLUSION: Our study confirms that CRLE is feasible but comes with a significantly increased risk of anastomotic leaks and a concerning trend of reduced survival, particularly when upper lobe anatomic resections are performed. These findings highlight the need for careful patient selection and surgical planning when considering CRLE.

Impact of Skeletal Muscle Loss and Sarcopenia on Outcomes of Locally Advanced Esophageal Cancer during Neoadjuvant Chemoradiation.

BACKGROUND: The impact of changes in skeletal muscle and sarcopenia on outcomes during neoadjuvant chemoradiotherapy (NACR) for patients with esophageal cancer remains controversial. PATIENTS AND METHODS: We retrospectively analyzed the data of patients with locally advanced esophageal squamous cell cancer who received NACR followed by esophagectomy between June 2013 and December 2021. The images at third lumbar vertebra were analyzed to measure the cross-sectional area and calculate skeletal muscle index (SMI) before and after NACR. SMI less than 52.4 cm2/m2 for men and less than 38.5 cm2/m2 for women were defined as sarcopenia. The nonlinearity of the effect of percent changes in SMI (ΔSMI%) to survival outcomes was assessed by restricted cubic splines. RESULTS: Overall, data of 367 patients were analyzed. The survival outcomes between sarcopenia and non-sarcopenia groups had no significant differences before NACR. However, patients in post-NACR sarcopenia group showed poor overall survival (OS) benefit (P = 0.016) and poor disease-free survival (DFS) (P = 0.043). Severe postoperative complication rates were 11.9% in post-NACR sarcopenia group and 5.0% in post-NACR non-sarcopenia group (P = 0.019). There was a significant non-linear relationship between ΔSMI% and survival outcomes (P < 0.05 for non-linear). On the multivariable analysis of OS, ΔSMI% > 12% was the independent prognostic factor (HR 1.76, 95% CI 1.03-2.99, P = 0.039) and significant difference was also found on DFS analysis (P = 0.025). CONCLUSIONS: Patients with post-neoadjuvant chemoradiotherapy sarcopenia have worse survival and adverse short-term outcomes. Moreover, greater loss in SMI is associated with increased risks of death and disease progression during neoadjuvant chemoradiotherapy, with maximum impact noted with SMI loss greater than 12%.

Mendelian randomization analysis of atopic dermatitis and esophageal cancer in East Asian and European populations.

Background: Emerging observational studies showed an association between atopic dermatitis (AD) and gastrointestinal cancers. However, it remains unclear whether this association is causal, particularly in the case of cancers like esophageal cancer, which exhibit ancestral genetic traits. Methods: To assess the potential causal relationship between AD and esophageal cancer across diverse ancestral backgrounds, we conducted a 2-sample Mendelian randomization study. Independent genetic instruments for AD from the FinnGen consortium (N case = 7024 and N control = 198 740), BioBank Japan (N case = 2385 and N control = 209 651) and Early Genetics and Lifecourse Epidemiology (EAGLE) eczema consortium (N case = 18 900 and N control = 84 166, without the 23andMe study) were used to investigate the association with esophageal cancer in the UK Biobank study (N case = 740 and N control = 372 016) and BioBank Japan esophageal cancer sample (N case = 1300 and N control = 197 045). Results: When esophageal cancer extracted from East Asian ancestry was used as a outcome factor, AD data extracted from BioBank Japan (OR = 0.90, 95% CI: 0.83-0.98), FinnGen consortium (OR = 0.86, 95% CI: 0.77-0.96), and EAGLE consortium (OR = 0.92, 95% CI: 0.81-1.06) were negatively associated with esophageal cancer susceptibility. However, AD as a whole did not show an association with esophageal cancer from European ancestry. Conclusion: This study provides support for a causal relationship between AD and esophageal cancer in East Asian populations but not between AD and esophageal cancer from European ancestry. The specific associations between esophageal cancer and AD appear to exhibit significant disparities between the East Asian and European regions.

Targeting PIM kinases in cancer therapy: An update on pharmacological small-molecule inhibitors.

PIM kinases, a serine/threonine kinase family with three isoforms, has been well-known to participate in multiple physiological processes by phosphorylating various downstream targets. Accumulating evidence has recently unveiled that aberrant upregulation of PIM kinases (PIM1, PIM2, and PIM3) are closely associated with tumor cell proliferation, migration, survival, and even resistance. Inhibiting or silencing of PIM kinases has been reported have remarkable antitumor effects, such as anti-proliferation, pro-apoptosis and resensitivity, indicating the therapeutic potential of PIM kinases as potential druggable targets in many types of human cancers. More recently, several pharmacological small-molecule inhibitors have been preclinically and clinically evaluated and showed their therapeutic potential; however, none of them has been approved for clinical application so far. Thus, in this perspective, we focus on summarizing the oncogenic roles of PIM kinases, key signaling network, and pharmacological small-molecule inhibitors, which will provide a new clue on discovering more candidate antitumor drugs targeting PIM kinases in the future.

A novel tumor staging system incorporating cN status for stratifying early stage esophageal squamous cell carcinoma patients after trimodal therapy.

BACKGROUNDS: The aim of this study is to investigate the prognostic value of cN status for early stage esophageal squamous cell carcinoma (ESCC) patients after neoadjuvant chemoradiotherapy (nCRT) and construct a new staging model for individual survival prediction. METHODS: Patients with ESCC who underwent nCRT and esophagectomy were included in this study. Both the Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC) were meticulously ascertained to assess the cogency of each oncological staging system. A discernible abatement in the values of AIC and BIC signifies a model endowed with enhanced predictive prowess and exemplary veracity. RESULTS: A new staging model was established based on ypTNM stage and cN status by precisely stratifying ypI ESCC patients. The novel ypTNM-cN staging demonstrated superior overall survival trend alignment over the AJCC 8th ypTNM staging, with a notably lower AIC of 3143.014 versus 3149.950. This superiority was supported by a BIC of 3146.605 against 3153.541. In the context of disease-free survival outcomes, the emergent ypTNM-cN staging, with an AIC value registering at 3196.057 and a BIC value at 3199.648, distinctively eclipsed the AJCC 8th ypTNM staging, which documented values of 3203.853 and 3207.444, respectively. CONCLUSION: We constructed a new staging system based on ypTNM stage and cN status to precisely stratify the patients with ypI stage. Our new ypTNM-cN staging system provides new insights for classifying stage ypI ESCC and shows reliable classification efficacy for all ESCC patients after nCRT and surgery.

Self-Assembled Acid-Responsive Nanosystem for Synergistic Anti-Angiogenic/Photothermal/Ferroptosis Therapy against Esophageal Cancer.

Esophageal cancer (EC) treatment via anti-angiogenic therapy faces challenges due to non-cytotoxicity and non-specific biodistribution of the anti-angiogenic agents. Hence, the quest for a synergistic treatment modality and a targeted delivery approach to effectively address EC has become imperative. In this study, an acid-responsive release nanosystem (Bev-IR820@FeIII TA) that involves the conjugation of bevacizumab, an anti-angiogenic monoclonal antibody, with TA and Fe3+ to form a metal-phenolic network, followed by loading with the near-infrared photothermal agent (IR820) to achieve combinational therapy, is designed. The construction of Bev-IR820@FeIII TA can be realized through a facile self-assembly process. The Bev-IR820@FeIII TA exhibits tumor-targeting capabilities and synergistic therapeutic effects, encompassing anti-angiogenic therapy, photothermal therapy (PTT), and ferroptosis therapy (FT). Bev-IR820@FeIII TA exhibits remarkable proficiency in delivering drugs to EC tissue through its pH-responsive release properties. Consequently, bevacizumab exerts its therapeutic effects by obstructing tumor angiogenesis, thereby impeding tumor growth. Meanwhile, PTT facilitates localized thermal ablation at the tumor site, directly eradicating EC cells. FT synergistically collaborates with PTT, giving rise to the formation of a reactive oxygen species (ROS) storm, subsequently culminating in the demise of EC cells. In summary, this amalgamated treatment modality carries substantial promise for synergistically impeding EC progression and showcases auspicious prospects for future EC treatment.

Causal relationship between lung diseases and risk of esophageal cancer: insights from Mendelian randomization.

BACKGROUND: An increasing number of cohort studies have indicated a correlation between lung diseases and esophageal cancer, but the exact causal relationship has not been definitively established. Therefore, the objective of this study is to assess the causal relationship between lung diseases and esophageal cancer. METHODS: Single-nucleotide polymorphisms (SNPs) related to lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), lung cancer, and idiopathic pulmonary fibrosis (IPF), along with outcomes data on esophageal cancer, were extracted from public genome-wide association studies (GWAS). A two-sample Mendelian randomization (MR) analysis was then performed using publicly available GWAS data to investigate the potential causal relationship. The effect estimates were primarily calculated using the fixed-effects inverse-variance-weighted method. RESULTS: Totally, 81 SNPs related to asthma among 218,792 participants in GWAS. Based on the primary causal effects model using MR analyses with the inverse variance weighted (IVW) method, asthma was demonstrated a significantly related to the risk of esophageal cancer (OR 1.0006; 95% CI 1.0003-1.0010, p = 0.001), while COPD (OR 1.0306; 95% CI 0.9504-1.1176, p = 0.466), lung cancer (OR 1.0003, 95% CI 0.9998-1.0008, p = 0.305), as well as IPF (OR 0.9999, 95% CI 0.9998-1.0000, p = 0.147), showed no significant correlation with esophageal cancer. CONCLUSIONS: The two-sample MR analysis conducted in this study revealed a positive causal relationship between asthma and esophageal cancer. In contrast, esophageal cancer demonstrated no significant correlation with COPD, lung cancer, or IPF. Further large-sample prospective studies are needed to validate these findings and to provide appropriate recommendations regarding esophageal cancer screening among patients with asthma.

Pararespiratory and paradigestive lymph node metastases in esophageal squamous cell carcinoma: predicting survival and refining the N staging system.

BACKGROUND: The site of lymph node metastasis (LNM) may affect the prognosis of patients with esophageal squamous cell carcinoma (ESCC). To investigate the prognoses of pararespiratory and paradigestive LNM and to propose a novel N (nN) staging system that integrates both the LNM site and count. METHODS: This study was a multicenter, large-sample, retrospective cohort study that included ESCC patients with LNM between January 2014 and December 2019 from three Chinese institutes. Patients were set into training (two institutes) and external validation (one institute) cohorts. The primary outcomes were survival differences in LNM site and the development of novel nodal staging system. The overall survival (OS) of patients with pararespiratory LNM only (Group A), paradigestive LNM only (Group B), and both sites (Group C) was evaluated by Kaplan-Meier. Cox proportional hazards models were used to identify the independent prognostic factors. An nN staging system considering both the LNM site and count was developed and evaluated by the area under the receiver operating characteristic curve (AUC). RESULTS: In total, 1313 patients were included and split into training (n = 1033) and external validation (n = 280) cohorts. There were 342 (26.0%), 568 (43.3%) and 403 (30.7%) patients in groups A, B and C, respectively. The OS of patients with pararespiratory and patients with paradigestive LNM presented significant differences in the training and validation cohorts (P < 0.050). In the training cohort, LNM site was an independent prognostic factor (hazard ratio: 1.58, 95% confidence intervals: 1.41-1.77, P < 0.001). The nN staging definition: nN1 (1-2 positive pararespiratory/paradigestive LNs), nN2 (3-6 pararespiratory LNs or 1 pararespiratory with 1paradigestive LN), nN3 (3-6 LNs with ≥ 1 paradigestive LN), nN4 (≥ 7 LNs). Subsets of patients with different nN stages showed significant differences in OS (P < 0.050). The prognostic model of the nN staging system presented higher performance in the training and validation cohorts at 3-year OS (AUC, 0.725 and 0.751, respectively) and 5-year OS (AUC, 0.740 and 0.793, respectively) than the current N staging systems. CONCLUSIONS: Compared to pararespiratory LNM, the presence of paradigestive LNM is associated with worse OS. The nN staging system revealed superior prognostic ability than current N staging systems.

Efficacy and safety of PD-1/PD-L1 inhibitor combined with chemotherapy versus chemotherapy alone in the treatment of advanced gastric or gastroesophageal junction adenocarcinoma: a systematic review and meta-analysis.

Background: There is increasing evidence that immunotherapy (programmed cell death-1 (PD-1) inhibitor) combined with chemotherapy is superior to chemotherapy alone in neoadjuvant therapy for patients with previously untreated, unresectable advanced, or metastatic esophageal adenocarcinoma (EAC)/gastric/gastroesophageal junction adenocarcinoma (GEA). However, the results of recent studies have been contradictory. Therefore, the aim of this article is to evaluate the efficacy and safety of PD-1 inhibitors combined with chemotherapy in neoadjuvant therapy through meta-analysis. Method: We comprehensively reviewed the literature and clinical randomized controlled trials (RCTs) by February 2022 by searching Medical Subject Headings (MeSH) and keywords such as "esophageal adenocarcinoma" or "immunotherapy" in several databases, including the Embase, Cochrane, PubMed, and ClinicalTrials.gov websites. Two authors independently selected studies, extracted data, and assessed the risk of bias and quality of evidence by using standardized Cochrane Methods procedures. The primary outcomes were 1-year overall survival (OS) and 1-year progression-free survival (PFS), estimated by calculating the 95% confidence interval (CI) for the combined odds ratio (OR) and hazard ratio (HR). Secondary outcomes estimated using OR were disease objective response rate (DORR) and incidence of adverse events. Results: Four RCTs with a total of 3,013 patients researching the efficacy of immunotherapy plus chemotherapy versus chemotherapy alone on gastrointestinal cancer were included in this meta-analysis. The results showed that immune checkpoint inhibitor plus chemotherapy treatment was associated with an increased risk of PFS (HR = 0.76 [95% CI: 0.70-0.83]; p < 0.001), OS (HR = 0.81 [95% CI: 0.74-0.89]; p < 0.001), and DORR (relative ratio (RR) = 1.31 [95% CI: 1.19-1.44]; p < 0.0001) when compared with chemotherapy alone in advanced, unresectable, and metastatic EAC/GEA. However, immunotherapy combined with chemotherapy increased the incidence of adverse reactions such as alanine aminotransferase elevation (OR = 1.55 [95% CI: 1.17-2.07]; p = 0.003) and palmar-plantar erythrodysesthesia (PPE) syndrome (OR = 1.30 [95% CI: 1.05-1.63]; p = 0.02). Nausea (OR = 1.24 [95% CI: 1.07-1.44]; p = 0.005) and white blood cell count decreased (OR = 1.40 [95% CI: 1.13-1.73]; p = 0.002), and so on. Fortunately, toxicities were within acceptable limits. Meanwhile, for patients with a combined positive score (CPS) ≥1, compared with chemotherapy alone, immunotherapy combined with chemotherapy had a better overall survival rate (HR = 0.81 [95% CI: 0.73-0.90]; p = 0.0001). Conclusion: Our study shows that immunotherapy plus chemotherapy has an obvious benefit for patients with previously untreated, unresectable advanced, or metastatic EAC/GEA when compared with chemotherapy alone. However, a high risk of adverse reactions may occur during immunotherapy plus chemotherapy, and more studies focusing on the treatment strategies of untreated, unresectable advanced, or metastatic EAC/GEA are warranted. Systematic review registration: www.crd.york.ac.uk, identifier CRD42022319434.

MTHFD1L confers a poor prognosis and malignant phenotype in esophageal squamous cell carcinoma by activating the ERK5 signaling pathway.

MTHFD1L, a key enzyme of folate metabolism, is seldom reported in cancer. In this study, we investigate the role of MTHFD1L in the tumorigenicity of esophageal squamous cell carcinoma (ESCC). ESCC tissue microarrays (TMAs) containing 177 samples from 109 patients were utilized to evaluate whether MTHFD1L expression, determined using immunohistochemical analysis, is a prognostic indicator for ESCC patients. The function of MTHFD1L in the migration and invasion of ESCC cells was studied with wound healing, Transwell, and three-dimensional spheroid invasion assays in vitro and a lung metastasis mouse model in vivo. The mRNA microarrays and Ingenuity pathway analysis (IPA) were used to explore the downstream of MTHFD1L. Elevated expression of MTHFD1L in ESCC tissues was significantly associated with poor differentiation and prognosis. These phenotypic assays revealed that MTHFD1L significantly promote the viability and metastasis of ESCC cell in vivo and in vitro. Further detailed analyses of the molecular mechanism demonstrated that the ESCC progression driven by MTHFD1L was through up-regulation ERK5 signaling pathways. These findings reveal that MTHFD1L is positively associated with the aggressive phenotype of ESCC by activating ERK5 signaling pathways, suggesting that MTHFD1L is a new biomarker and a potential molecular therapeutic target for ESCC.

Research progress of traditional Chinese medicine as sensitizer in reversing chemoresistance of colorectal cancer.

In recent years, the incidences and mortalities from colorectal cancer (CRC) have been increasing; therefore, there is an urgent need to discover newer drugs that enhance drug sensitivity and reverse drug tolerance in CRC treatment. With this view, the current study focuses on understanding the mechanism of CRC chemoresistance to the drug as well as exploring the potential of different traditional Chinese medicine (TCM) in restoring the sensitivity of CRC to chemotherapeutic drugs. Moreover, the mechanism involved in restoring sensitivity, such as by acting on the target of traditional chemical drugs, assisting drug activation, increasing intracellular accumulation of anticancer drugs, improving tumor microenvironment, relieving immunosuppression, and erasing reversible modification like methylation, have been thoroughly discussed. Furthermore, the effect of TCM along with anticancer drugs in reducing toxicity, increasing efficiency, mediating new ways of cell death, and effectively blocking the drug resistance mechanism has been studied. We aimed to explore the potential of TCM as a sensitizer of anti-CRC drugs for the development of a new natural, less-toxic, and highly effective sensitizer to CRC chemoresistance.