Current Evidence Does Not Warrant Frozen Section Evaluation for the Presence of Tumor Spread Through Alveolar Spaces

STAS: New explorations and challenges for thoracic surgeons

Spread through air spaces (STAS) represents a relatively novel concept in the pathology of lung cancer, and it specifically refers to the dissemination of tumour cells into the parenchymal air spaces adjacent to the primary tumour. In 2015, the World Health Organization (WHO) classified STAS as a new invasive form of lung adenocarcinoma (LUAD). Many studies investigated the role of STAS and revealed its association with the prognosis of LUAD and its influence on the outcomes of other malignant pulmonary neoplasms. Additionally, the underlying mechanisms and predictive models of STAS have received considerable attention in recent years. This paper provides a comprehensive overview of the research advancements and prospects of STAS by examining it from multiple perspectives.

Prognostic Impact and Clinical Features of Spread through Air Spaces in Operated Lung Cancer: Real-World Analysis

Background and Objectives: Lung cancer is the leading cause of cancer-related deaths. Spread through air spaces (STAS) is an adverse prognostic factor that has become increasingly known in recent years. This study aims to investigate the impact of STAS presence on overall survival (OS) and disease-free survival (DFS) in patients with surgically resected stage IA-IIIA lung cancer and to identify clinicopathological features associated with STAS. Materials and Methods: This research involved 311 lung cancer surgery patients. The relationship between the presence of STAS in the patients' surgical pathology and OS and DFS values was examined. Clinicopathological features associated with the presence of STAS were determined. Results: There were 103 (33%) STAS-positive patients. Adenocarcinoma histological subtype, perineural invasion (PNI), and lymphovascular invasion (LVI) were significantly correlated with being STAS positive. STAS significantly predicted DFS and OS. One-year and five-year DFS rates were significantly lower in the STAS-positive group compared to the STAS-negative group (65% vs. 88%, 29% vs. 62%, respectively, p ≤ 0.001). Similarly, one-year and five-year OS rates were significantly lower in the STAS-positive group compared to the STAS-negative group (92% vs. 94%, 54% vs. 88%, respectively, p ≤ 0.001). In multivariate analysis, STAS was found to be an independent prognostic factor for both DFS and OS (HR: 3.2 (95%CI: 2.1-4.8) and 3.1 (95%CI: 1.7-5.5), p < 0.001 and <0.001, respectively). Conclusions: In our study, STAS was found to be an independent prognostic biomarker in operated stage IA-IIIA lung cancer patients. It may be a beneficial pathological biomarker in predicting the survival of patients and managing their treatments.

Does dual-layer spectral detector CT provide added value in predicting spread through air spaces in lung adenocarcinoma? A preliminary study

OBJECTIVES

To examine the predictive value of dual-layer spectral detector CT (DLCT) for spread through air spaces (STAS) in clinical lung adenocarcinoma.

METHODS

A total of 225 lung adenocarcinoma cases were retrospectively reviewed for demographic, clinical, pathological, traditional CT, and spectral parameters. Multivariable logistic regression analysis was carried out based on three logistic models, including a model using traditional CT features (traditional model), a model using spectral parameters (spectral model), and an integrated model combining traditional CT and spectral parameters (integrated model). Receiver operating characteristic (ROC) curve analysis and decision curve analysis (DCA) were performed to assess these models.

RESULTS

Univariable analysis showed significant differences between the STAS and non-STAS groups in traditional CT features, including nodule density (p < 0.001), pleural indentation types (p = 0.006), air-bronchogram sign (p = 0.031), the presence of spiculation (p < 0.001), long-axis diameter of the entire nodule (LD) (p < 0.001), and consolidation/tumor ratio (CTR) (p < 0.001). Multivariable analysis revealed that LD > 20 mm (odds ratio [OR] = 2.271, p = 0.025) and CTR (OR = 24.208, p < 0.001) were independent predictors in the traditional model, while electronic density (ED) in the venous phase was an independent predictor in the spectral (OR = 1.062, p < 0.001) and integrated (OR = 1.055, p < 0.001) models. The area under the curve (AUC) for the integrated model (0.84) was the highest (spectral model, 0.83; traditional model, 0.80), and the difference between the integrated and traditional models was statistically significant (p = 0.015). DCA showed that the integrated model had superior clinical value versus the traditional model.

CONCLUSIONS

DLCT has added value for STAS prediction in lung adenocarcinoma.

CLINICAL RELEVANCE STATEMENT

Spectral CT has added value for spread through air spaces prediction in lung adenocarcinoma so may impact treatment planning in the future.

KEY POINTS

• Electronic density may be a potential spectral index for predicting spread through air spaces in lung adenocarcinoma. • A combination of spectral and traditional CT features enhances the performance of traditional CT for predicting spread through air spaces.

Preoperative nomogram for predicting spread through air spaces in clinical-stage IA non-small cell lung cancer using 18F-fluorodeoxyglucose positron emission tomography/computed tomography

PURPOSE

This study aims to assess the predictive value of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) radiological features and the maximum standardized uptake value (SUVmax) in determining the presence of spread through air spaces (STAS) in clinical-stage IA non-small cell lung cancer (NSCLC).

METHODS

A retrospective analysis was conducted on 180 cases of NSCLC with postoperative pathological assessment of STAS status, spanning from September 2019 to September 2023. Of these, 116 cases from hospital one comprised the training set, while 64 cases from hospital two formed the testing set. The clinical information, tumor SUVmax, and 13 related CT features were analyzed. Subgroup analysis was carried out based on tumor density type. In the training set, univariable and multivariable logistic regression analyses were employed to identify the most significant variables. A multivariable logistic regression model was constructed and the corresponding nomogram was developed to predict STAS in NSCLC, and its diagnostic efficacy was evaluated in the testing set.

RESULTS

SUVmax, consolidation-to-tumor ratio (CTR), and lobulation sign emerged as the best combination of variables for predicting STAS in NSCLC. Among these, SUVmax and CTR were identified as independent predictors for STAS prediction. The constructed prediction model demonstrated area under the curve (AUC) values of 0.796 and 0.821 in the training and testing sets, respectively. Subgroup analysis revealed a 2.69 times higher STAS-positive rate in solid nodules compared to part-solid nodules. SUVmax was an independent predictor for predicting STAS in solid nodular NSCLC, while CTR and an emphysema background were independent predictors for STAS in part-solid nodular NSCLC.

CONCLUSION

Our nomogram based on preoperative 18F-FDG PET/CT radiological features and SUVmax effectively predicts STAS status in clinical-stage IA NSCLC. Furthermore, our study highlights that metabolic parameters and CT variables associated with STAS differ between solid and part-solid nodular NSCLC.

CT-Based Deep-Learning Model for Spread-Through-Air-Spaces Prediction in Ground Glass-Predominant Lung Adenocarcinoma

BACKGROUND

Sublobar resection is strongly associated with poor prognosis in early-stage lung adenocarcinoma, with the presence of tumor spread through air spaces (STAS). Thus, preoperative prediction of STAS is important for surgical planning. This study aimed to develop a STAS deep-learning (STAS-DL) prediction model in lung adenocarcinoma with tumor smaller than 3 cm and a consolidation-to-tumor (C/T) ratio less than 0.5.

METHODS

The study retrospectively enrolled of 581 patients from two institutions between 2015 and 2019. The STAS-DL model was developed to extract the feature of solid components through solid components gated (SCG) for predicting STAS. The STAS-DL model was assessed with external validation in the testing sets and compared with the deep-learning model without SCG (STAS-DLwoSCG), the radiomics-based model, the C/T ratio, and five thoracic surgeons. The performance of the models was evaluated using area under the curve (AUC), accuracy and standardized net benefit of the decision curve analysis.

RESULTS

The study evaluated 458 patients (institute 1) in the training set and 123 patients (institute 2) in the testing set. The proposed STAS-DL yielded the best performance compared with the other methods in the testing set, with an AUC of 0.82 and an accuracy of 74%, outperformed the STAS-DLwoSCG with an accuracy of 70%, and was superior to the physicians with an AUC of 0.68. Moreover, STAS-DL achieved the highest standardized net benefit compared with the other methods.

CONCLUSION

The proposed STAS-DL model has great potential for the preoperative prediction of STAS and may support decision-making for surgical planning in early-stage, ground glass-predominant lung adenocarcinoma.

Computed Tomography Radiomics for Preoperative Prediction of Spread Through Air Spaces in the Early Stage of Surgically Resected Lung Adenocarcinomas

PURPOSE

To assess the added value of radiomics models from preoperative chest CT in predicting the presence of spread through air spaces (STAS) in the early stage of surgically resected lung adenocarcinomas using multiple validation datasets.

MATERIALS AND METHODS

This retrospective study included 550 early-stage surgically resected lung adenocarcinomas in 521 patients, classified into training, test, internal validation, and temporal validation sets (n=211, 90, 91, and 158, respectively). Radiomics features were extracted from the segmented tumors on preoperative chest CT, and a radiomics score (Rad-score) was calculated to predict the presence of STAS. Diagnostic performance of the conventional model and the combined model, based on a combination of conventional and radiomics features, for the diagnosis of the presence of STAS were compared using the area under the curve (AUC) of the receiver operating characteristic curve.

RESULTS

Rad-score was significantly higher in the STAS-positive group compared to the STAS-negative group in the training, test, internal, and temporal validation sets. The performance of the combined model was significantly higher than that of the conventional model in the training set {AUC: 0.784 [95% confidence interval (CI): 0.722-0.846] vs. AUC: 0.815 (95% CI: 0.759-0.872), p=0.042}. In the temporal validation set, the combined model showed a significantly higher AUC than that of the conventional model (p=0.001). The combined model showed a higher AUC than the conventional model in the test and internal validation sets, albeit with no statistical significance.

CONCLUSION

A quantitative CT radiomics model can assist in the non-invasive prediction of the presence of STAS in the early stage of lung adenocarcinomas.

Development and validation of a clinic-radiological model to predict tumor spread through air spaces in stage I lung adenocarcinoma

OBJECTIVES

Tumor spread through air spaces (STAS) is associated with poor prognosis and impacts surgical options. We aimed to develop a user-friendly model based on 2-[18F] FDG PET/CT to predict STAS in stage I lung adenocarcinoma (LAC).

MATERIALS AND METHODS

A total of 466 stage I LAC patients who underwent 2-[18F] FDG PET/CT examination and resection surgery were retrospectively enrolled. They were split into a training cohort (n = 232, 20.3% STAS-positive), a validation cohort (n = 122, 27.0% STAS-positive), and a test cohort (n = 112, 29.5% STAS-positive) according to chronological order. Some commonly used clinical data, visualized CT features, and SUVmax were analyzed to identify independent predictors of STAS. A prediction model was built using the independent predictors and validated using the three chronologically separated cohorts. Model performance was assessed using ROC curves and calculations of AUC.

RESULTS

The differences in age (P = 0.009), lesion density subtype (P < 0.001), spiculation sign (P < 0.001), bronchus truncation sign (P = 0.001), and SUVmax (P < 0.001) between the positive and negative groups were statistically significant. Age ≥ 56 years [OR(95%CI):3.310(1.150-9.530), P = 0.027], lesion density subtype (P = 0.004) and SUVmax ≥ 2.5 g/ml [OR(95%CI):3.268(1.021-1.356), P = 0.005] were the independent factors predicting STAS. Logistic regression was used to build the A-D-S (Age-Density-SUVmax) prediction model, and the AUCs were 0.808, 0.786 and 0.806 in the training, validation, and test cohorts, respectively.

CONCLUSIONS

STAS was more likely to occur in older patients, in solid lesions and higher SUVmax in stage I LAC. The PET/CT-based A-D-S prediction model is easy to use and has a high level of reliability in diagnosing.

Updates on lung adenocarcinoma: invasive size, grading and STAS

Advancements in the classification of lung adenocarcinoma have resulted in significant changes in pathological reporting. The eighth edition of the tumour-node-metastasis (TNM) staging guidelines calls for the use of invasive size in staging in place of total tumour size. This shift improves prognostic stratification and requires a more nuanced approach to tumour measurements in challenging situations. Similarly, the adoption of new grading criteria based on the predominant and highest-grade pattern proposed by the International Association for the Study of Lung Cancer (IASLC) shows improved prognostication, and therefore clinical utility, relative to previous grading systems. Spread through airspaces (STAS) is a form of tumour invasion involving tumour cells spreading through the airspaces, which has been highly researched in recent years. This review discusses updates in pathological T staging, adenocarcinoma grading and STAS and illustrates the utility and limitations of current concepts in lung adenocarcinoma.

The value of frozen section diagnosis of tumor spread through air spaces in small-sized (≤ 2 cm) non-small cell lung cancer

BACKGROUND

The current accuracy of frozen section diagnosis of tumor spread through air spaces (STAS) in non-small cell lung cancer (NSCLC) is poor. However, the accuracy and prognostic value of STAS assessment on frozen sections in small-sized NSCLC (diameter ≤ 2 cm) is unknown.

METHODS

Three hundred fifty-two patients with clinical stage I NSCLC (≤ 2 cm) were included, of which the paraffin sections and frozen sections were reviewed. The accuracy of STAS diagnosis in frozen sections was assessed using paraffin sections as the gold standard. The relationship between STAS on frozen sections and prognosis was assessed by the Kaplan-Meier method and log-rank tests.

RESULTS

STAS on frozen sections in 58 of 352 patients could not be evaluated. In the other 294 patients, 36.39% (107/294) was STAS-positive on paraffin sections and 29.59% (87/294) on frozen sections. The accuracy of frozen section diagnosis of STAS was 74.14% (218/294), sensitivity was 55.14% (59/107), specificity was 85.02% (159/187) and agreement was moderate (K = 0.418). In subgroup analysis, the Kappa values for frozen section diagnosis of STAS in the consolidation-to-tumor ratio (CTR) ≤ 0.5 group and CTR > 0.5 group were 0.368, 0.415, respectively. In survival analysis, STAS-positive frozen sections were associated with worse recurrence-free survival in the CTR > 0.5 group (P < 0.05).

CONCLUSIONS

The moderate accuracy and prognostic significance of frozen section diagnosis of STAS in clinical stage I NSCLC (≤ 2 cm in diameter; CTR > 0.5) suggests that frozen section assessment of STAS can be applied to the treatment strategy of small-sized NSCLC with CTR > 0.5.

Segmentectomy Provides Comparable Outcomes to Lobectomy for Stage IA Non-small Cell Lung Cancer with Spread through Air Spaces

This study aimed to compare the recurrence-free survival (RFS) and overall survival (OS) among wedge resection (non-anatomical resection), segmentectomy and lobectomy for pathological stage IA non-small cell lung cancer (NSCLC) with spread through air spaces (STAS). Patients underwent surgical treatment for pathological stage IA NSCLC between January 1, 2005, and March 31, 2016, at our hospital. Surgical procedures were classified as lobectomy, segmentectomy, and wedge resection. Among the 555 analyzed cases, STAS was observed in 148 patients (26.7%). STAS was correlated with worse RFS (P < 0.001) and OS (P < 0.001) and was an independent poor prognostic factor for RFS (hazard ratio: 2.37, P < 0.001) and OS (hazard ratio: 2.02, P < 0.001) in the multivariate analysis. In patients with STAS, the RFS and OS in the segmentectomy group were comparable to those in the lobectomy group. However, the RFS and OS in the wedge resection group were significantly lower than those in the lobectomy group (RFS, P < 0.001; OS, P = 0.001). Wedge resection was an independent prognostic factor for poor RFS (hazard ratio [HR] = 3.87; 95% confidence interval [CI] = 1.84 - 8.12, P < 0.001), and poor OS (hazard ratio [HR] = 3.39; 95% confidence interval [CI] = 1.33 - 8.76, P = 0.011) in the multivariate analysis. Segmentectomy is an adequate operation for patients with stage IA NSCLC with or without STAS. However, wedge resection is associated with a higher risk of recurrence in this patient population.

Prognostic impact of spread through air spaces in lung adenocarcinoma

OBJECTIVE

Spread through air spaces (STAS) is a pattern of invasion present in some adenocarcinomas (ADC). The goal of this study was to assess the impact of STAS in patients treated with different types of surgical resections and on the clinical outcome in patients with ADC of different diameters and with different degrees of nodal involvement.

METHODS

A total of 109 patients were reviewed. Complete surgical resection with systematic nodal dissection was achieved in all patients. The median follow-up was 65 months (3-90 months).

RESULTS

STAS was observed in 70 cases (64.2%); 13 patients (18.5%) had lymph node involvement (N1 and N2). Overall survival and progression-free survival were higher in patients without STAS (P = 0.042; P = 0.027). The presence of STAS in tumours ≤2 cm was a predictor of worse progression-free survival following sublobar resection compared to major resections (P = 0.011). Sublobar resection of N0 STAS-positive tumours was associated with worse long-term survival compared to a major resection (P = 0.04). Statistical analyses showed that age >70 years and recurrence were independent variables for survival; smoking pack-years >20, sublobar resection and nodal involvement were independent variables for recurrence; and smoking pack-years >20 were independent variables for a history of cancer and pleural invasion for local recurrence.

CONCLUSIONS

STAS seems to play a role in long-term survival, particularly for patients with N0 and tumours smaller than 2 cm. Further studies are necessary to validate this hypothesis.

An individual nomogram can reliably predict tumor spread through air spaces in non-small-cell lung cancer

Background

Tumor spread through air spaces (STAS) has been shown to adversely affect the prognosis of lung cancer. The correlation between clinicopathological and genetic features and STAS remains unclear.

Method

We retrospectively reviewed 3075 NSCLC patients between2017-2019. We evaluated the relationship between STAS and patients’ clinicopathological and molecular features. The chi-square test was performed to compare categorical variables. Univariate analysis and multivariate logistic regression analysis were performed to investigate the association of clinical factors with STAS. A nomogram was formulated to predict the presence of STAS.

Results

STAS was identified in 617 of 3075 patients (20.07%). STAS was significantly related to sex (p < 0.001), smoking (p < 0.001), CEA (p < 0.001), differentiation (p < 0.001), histopathological type (p < 0.001), lymphatic vessel invasion (p < 0.001), pleural invasion (p < 0.001), T stage (p < 0.001), N stage (p < 0.001), M stage (p < 0.001), and TNM stage (p < 0.001). STAS was frequently found in tumors with wild-type EGFR (p < 0.001), KRAS mutations (p < 0.001), ALK rearrangements (p < 0.001) or ROS1 rearrangements (p < 0.001). For programmed death-1 (PD-1)/programmed death ligand-1 (PD-L1), STAS was associated with PD-L1 expression level in tumor cells (p < 0.001) or stromal cells (p < 0.001), while PD-1 only in stromal cells (p < 0.001). Multivariable analyses demonstrated significant correlations between STAS and CEA level (p < 0.001), pathological grade (p < 0.001), lymphatic vessel invasion (p < 0.001), pleural invasion (p = 0.001), and TNM stage (p = 0.002). A nomogram was formulated based on the results of the multivariable analysis.

Conclusions

Tumor STAS was associated with several invasive clinicopathological features. A nomogram was established to predict the presence of STAS in patients with NSCLC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-02002-1.

Oral Cancer Screening by Artificial Intelligence-Oriented Interpretation of Optical Coherence Tomography Images

Early diagnosis of oral cancer is critical to improve the survival rate of patients. The current strategies for screening of patients for oral premalignant and malignant lesions unfortunately miss a significant number of involved patients. Optical coherence tomography (OCT) is an optical imaging modality that has been widely investigated in the field of oncology for identification of cancerous entities. Since the interpretation of OCT images requires professional training and OCT images contain information that cannot be inferred visually, artificial intelligence (AI) with trained algorithms has the ability to quantify visually undetectable variations, thus overcoming the barriers that have postponed the involvement of OCT in the process of screening of oral neoplastic lesions. This literature review aimed to highlight the features of precancerous and cancerous oral lesions on OCT images and specify how AI can assist in screening and diagnosis of such pathologies.

Pretreatment prediction of tumour spread through air spaces in clinical stage I non-small cell lung cancer

OBJECTIVES

To construct a nomogram prediction model for tumour spread through air spaces (STAS) in clinical stage I non-small cell lung cancer (NSCLC) and discuss its potential application value.

METHODS

380 patients with clinical stage I NSCLC in Tianjin Chest Hospital were collected as the training cohort and 285 patients in Fujian Provincial Hospital were collected as the validation cohort. Univariable and multivariable logistic regression analyses were performed to determine independent factors for STAS in the training cohort. Based on the results of the multivariable analysis, the nomogram prediction model of STAS was constructed by R software.

RESULTS

The incidence of STAS in the training cohort was 39.2%. STAS was associated with worse overall survival and recurrence-free survival (P<0.01). Univariable analysis showed that maximum tumour diameter (Tdmax), consolidation-to-tumour ratio (CTR), spiculation, vacuole and carcinoembryonic antigen were associated with STAS (P<0.05). Multivariable analysis showed that Tdmax, CTR, spiculation sign, and vacuole were independent risk factors for STAS (P<0.05). Based on this, the nomogram prediction model of STAS in clinical stage I NSCLC was constructed and internally validated by bootstrap. The Hosmer-Lemeshow test showed a χ2 value of 7.218 (P=0.513). The area under the ROC curve (AUC) and C-index were 0.724 (95% CI: 0.673-0.775). The external validation conducted on validation cohort produced an AUC of 0.759 (95% CI: 0.703-0.816).

CONCLUSIONS

The constructed nomogram prediction model of STAS in clinical stage I NSCLC has good calibration and can potentially be applied to guide treatment selection.

Assessment of the feasibility of frozen sections for the detection of spread through air spaces (STAS) in pulmonary adenocarcinoma

Spread through air spaces (STAS) is reportedly associated with worse prognosis in sublobar resections of lung adenocarcinoma. Recently, it was proposed that STAS detected on frozen sections can be an indication for lobectomy instead of sublobar resection. We undertook this study to evaluate the reliability of STAS assessment on frozen sections compared to permanent sections, as well as the associations among STAS, tumor grade, and recurrence-free survival (RFS) after sublobar resection. A total of 163 stage I lung adenocarcinoma resections with frozen sections were identified retrospectively. For each case, and for frozen and permanent sections separately, the presence or absence of STAS, as well as the tumor grade, were recorded. Compared to permanent sections, STAS detection on frozen sections had low sensitivity (55%), low positive predictive value (48%), and fair agreement (K = 0.34), whereas there was higher specificity (80%) and negative predictive value (85%). Accuracy was 74%. Tumor grade assessment on frozen sections showed higher sensitivity (77%), positive predictive value (90%), agreement (K = 0.72), specificity (94%), and accuracy (87%), and the same negative predictive value (85%). High-grade histology on frozen sections was associated with shorter RFS (p = 0.02), whereas STAS on frozen sections was not (p = 0.47). Our results suggest that the intraoperative detection of STAS has low sensitivity and positive predictive value. False-positive results may lead to overtreatment of patients with lung cancer. The determination of tumor grade on frozen sections offers better sensitivity and specificity, plus it is associated with RFS, whereas STAS on frozen sections is not. Further study is needed to explore the utility of assessing tumor grade on frozen sections.

Preoperative CT-based peritumoral and tumoral radiomic features prediction for tumor spread through air spaces in clinical stage I lung adenocarcinoma

OBJECTIVES

This study aims to develop and evaluate preoperative CT-based peritumoral and tumoral radiomic features to predict tumor spread through air space (STAS) status in clinical stage I lung adenocarcinoma (LUAD).

MATERIALS AND METHODS

From June 2018 to December 2019, a retrospective diagnostic investigation was done. Patients with pathologically confirmed STAS status (N = 256) were eventually enrolled. The development cohort consisted of 191 patients (74.6%) chosen randomly in a 7:3 ratio, whereas the validation group consisted of 65 patients (25.4%). The performance of models was assessed using receiver operating characteristic analysis, accuracy, sensitivity, specificity, negative predictive values, and positive predictive values.

RESULTS

The STAS positive status was found in 85 (33.2%) of the 256 patients (female: 53.2%; median [IQR] age: 62.0, [53.0-79.0] years), while the STAS negative status was found in 171 patients (66.8%) (female:50.6%; median [IQR] age: 62.0, [53.0-87.0] years). The combined TRS and PRS-15 mm model had an AUC of 0.854 (95% CI, 0.799-0.909) in the development cohort and 0.870 (95% CI, 0.781-0.958) in the validation cohort, indicating that the tumor radiomic signature (TRS) model and different peritumoral radiomic signature (PRS) models were used to build the optimal gross radiomic signature (GRS) model. The radiomic nomogram achieves superior discriminatory performance than GRS and clinical and radiological signatures (CRS), with an AUC of 0.871 (95% CI, 0.820-0.922) in the development cohort and AUC of 0.869 (95% CI, 0.776-0.961) in the validation cohort. Based on the Akaike information criterion (AIC) and decision curve analysis (DCA), the radiomic nomogram provided greater clinical predictive capacity than clinical or any radiomic signatures alone.

CONCLUSION

In conclusion, we discovered that peritumoral characteristics were substantially related to STAS status. This study revealed the unit of radiomic signature and clinical signatures may have a better performance in STAS status.

Spread through air spaces positivity and extent of resection in patients with Stage I non-small cell lung cancer: A contemporary review

The concept of spread through air spaces is a type of cancer spread that is unique to lung and may be established as a criterion for invasion. It is a potential risk factor for recurrence and poor prognosis in patients with early-stage non-small cell lung cancer. This review provides a contemporary overview on recent data in this field and aim to help surgeons to decide the extent of resection according to patients" spread through air spaces status.

Spread Through Air Spaces (STAS) in Non-Small Cell Lung Carcinoma: Evidence Supportive of an In Vivo Phenomenon

Tumor spread through air spaces (STAS) is associated with locoregional recurrence in patients undergoing limited resection (LR) for non-small cell lung carcinoma (NSCLC). We hypothesized that the observation of STAS in both the initial LR specimen and the additional resection specimen from the same patient, processed using different knives, would provide evidence that STAS is an in vivo phenomenon contributing to locoregional recurrence. We retrospectively identified patients with NSCLC (9 adenocarcinoma, 1 squamous cell carcinoma) who underwent LR, had STAS in the LR specimen, and underwent additional resection (lobectomy or LR). The LR and additional resection specimens from each patient were processed at different times using different tissue-processing knives. All specimens were analyzed for STAS. All 10 patients underwent LR with negative margins (R0). All additional resection specimens had STAS: 8 patients had STAS clusters in their completion lobectomy specimens, and 2 had STAS in their additional LR specimens. In 2 patients, STAS was found in the completion lobectomy specimen only after extensive sampling (>10 sections) from the staple line adjacent to the initial LR. The presence of STAS in both the LR and the additional resection specimen processed using different knives supports the concept that STAS is an in vivo phenomenon, rather than an artifact from tissue processing. This observation indicates that occult STAS tumor cells can be present in the lung tissue of the remaining unresected lobe after LR and supports the concept that STAS is a contributing factor for locoregional recurrence following LR.

Aerogenous Metastasis and Spread Through the Air Spaces - Distinct Entities or Spectrum of the Same Process?

Clinicopathological and imaging studies indicate that metastatic spread of cancer cells through the airways may occur in primary lung cancer. The term aerogenous metastasis was been proposed years before the concept of spread through the airspaces (STAS) was introduced in the current World Health Organization classification. The pathogenesis of STAS has not been fully elucidated. The current definition of STAS is controversial and limited to early stage adenocarcinomas. In this article, existing knowledge on the pathogenesis, histology, imaging findings, and clinical and prognostic significance of these 2 entities is presented.

Radiomic values from high-grade subtypes to predict spread through air spaces in lung adenocarcinoma

BACKGROUND

We aimed to establish a radiomic prediction model for tumor spread through air spaces (STAS) in lung adenocarcinoma using radiomic values from high-grade subtypes (solid and micropapillary).

METHODS

We retrospectively reviewed 327 patients with lung adenocarcinoma from two institutes (Cohort 1: 227 patients; Cohort 2: 100 patients) between March 2017 and March 2019. STAS was identified in 113 (34.6%) patients. A high-grade likelihood prediction model was constructed based on a historical cohort of 82 patients with "near-pure" pathological subtype. The STAS prediction model based on the patch-wise mechanism identified the high-grade likelihood area for each voxel within the internal border of the tumor. STAS presence was indirectly predicted by a volume percentage threshold of the high-grade likelihood area. Performance was evaluated by receiver operating curve analysis with 10-repetition, 3-fold cross-validation in Cohort 1, and was individually tested in Cohort 2.

RESULTS

Overall, 227 patients (STAS-positive: 77 [33.9%]) were enrolled for cross-validation (Cohort 1) while 100 (STAS-positive: 36 [36.0%]) underwent individual testing (Cohort 2). The gray level co-occurrence matrix (variance) and histogram (75^th percentile) features were selected to construct the high-grade likelihood prediction model, which was used as the STAS prediction model. The proposed model achieved good performance in Cohort 1 with an area under the curve, sensitivity, and specificity, of 81.44%, 86.75%, and 62.60%, respectively, and correspondingly, in Cohort 2, they were 83.16%, 83.33%, and 63.90%, respectively.

CONCLUSIONS

The proposed computed tomography-based radiomic prediction model could help guide preoperative prediction of STAS in early-stage lung adenocarcinoma and relevant surgeries.

Radiomics-based prediction for tumour spread through air spaces in stage I lung adenocarcinoma using machine learning

OBJECTIVES

As evidence has proven that sublobar resection is oncologically contraindicated by tumour spread through air spaces (STAS), its preoperative recognition is vital in customizing surgical strategies. We aimed to assess the value of radiomics in predicting STAS in stage I lung adenocarcinoma.

METHODS

We retrospectively reviewed the patients with stage I lung adenocarcinoma, who accepted curative resection in our institution between January 2011 and December 2013. Using 'PyRadiomics' package, 88 radiomics features were extracted from computed tomography (CT) images and a prediction model was consequently constructed using Naïve Bayes machine-learning approach. The accuracy of the model was assessed through receiver operating curve analysis, and the performance of the model was validated both internally and externally.

RESULTS

A total of 233 patients were included as the training cohort with 69 (29.6%) patients being STAS (+). Patients with STAS had worse recurrence-free survival and overall survival (P < 0.001). After feature extraction, 5 most contributing radiomics features were selected out to develop a Naïve Bayes model. In the internal validation, the model exhibited good performance with an area under the curve value of 0.63 (0.55-0.71). External validation was conducted on a test cohort with 112 patients and produced an area under the curve value of 0.69.

CONCLUSIONS

CT-based radiomics is valuable in preoperatively predicting STAS in stage I lung adenocarcinoma, which may aid surgeons in determining the optimal surgical approach.

Integration of clinicopathological and mutational data offers insight into lung cancer with tumor spread through air spaces

Background

Tumor spread through air spaces (STAS) was defined as a unique tumor invasion pattern in adenocarcinoma (ADC) by The World Health Organization Classification of Lung Tumors in 2015. Since then, STAS had been shown to be associated with local recurrence and poor survival results, as the typical signature and potential mechanisms of STAS remained unclear. Our objectives were to comprehensively demonstrate the clinicopathological and genetic signatures in STAS-positive lung cancer patients.

Methods

The clinicopathological and gene alteration characteristics of 878 STAS-positive lung cancer patients were presented. Associations between parameters were evaluated using the Chi-square test, Fisher’s exact test, and logistic regression. The capture-based targeted next generation sequencing (NGS) with a platform of 68 lung cancer-related genes was conducted in 139 cases, and the mutational spectrum was summarized.

Results

STAS was identified in 391 female and 481 male patients, of which ADC accounted for the majority of cases (92.6%). The concomitant solid or micropapillary subtype was observed in 92.12% patients with ADC. Poorly differentiated histological subtypes were more frequent and negatively correlated with tumor size in smaller tumor cases (P=0.036, Pearson’s R=−0.075). Furthermore, in the subgroup of nodules within 3 cm, the distribution of the solid and micropapillary subtypes were significantly frequent in lymph node-positive patients (P<0.001). Tumor protein p53 (TP53) alterations were more frequent in smoking patients (27.6%, P=0.007), human epidermal growth factor receptor 2 (HER2) alterations were more common in female (10.8%, P=0.025), while Kirsten rat sarcoma viral oncogene (KRAS) (20.3%, P=0.024) and TP53 (45.9%, P=0.003) were more prevalent in males.

Conclusions

Poorly differentiated histological subtypes likely played a crucial role in promoting the invasiveness of STAS, especially in small tumor-size cases. Epidermal growth factor receptor (EGFR), TP53, KARS, anaplastic lymphoma kinase (ALK), and ROS proto-oncogene 1 (ROS1) were the five most frequent alterations in STAS-positive ADC.

Current status and perspectives of spread through air spaces in lung cancer

According to the World Health Organization classification of 2015, spread through air spaces (STAS) is a newly recognized pattern of invasion in lung adenocarcinoma. Many researchers have reported that STAS is recognized in all histological subtypes, and there is a strong association between STAS and prognosis in lung cancer. However, there are several technical issues associated with STAS, such as distinction between the actual in vivo phenomenon and an artifact, difficulty in assessing STAS in frozen specimens, and establishing the relationship between morphological and molecular properties of STAS. This review focuses on the current state of knowledge and the outlook of the STAS phenomenon from the perspective of surgeons, pathologists, and radiologists.

Accuracy and Reproducibility of Intraoperative Assessment on Tumor Spread Through Air Spaces in Stage 1 Lung Adenocarcinomas

INTRODUCTION

Tumor spread through air spaces (STAS) is associated with worse prognosis in early-stage lung adenocarcinomas, particularly in sublobar resection. Intraoperative consultation for STAS has been advocated to guide surgical management. However, data on accuracy and reproducibility of intraoperative assessment of STAS remain limited. We evaluated diagnostic yield, interobserver agreement (IOA), and intraobserver agreement (ITA) for STAS detection on frozen section (FS).

METHODS

A panel of three pathologists evaluated stage 1 lung adenocarcinomas (n = 100) for the presence or absence of STAS and artifacts as reference. Five pulmonary pathologists independently reviewed all cases in two rounds, detecting STAS and artifacts in FS and the corresponding FS permanent and non-FS permanent, with a consensus conference between rounds.

RESULTS

The FS had low sensitivity (44%), high specificity (91%), relatively high accuracy (71%), and overall area under the receiver operating characteristic curve of 0.67 for detecting STAS. The average ITA was moderate for both STAS (κ_mean: 0.598) and artifact (κ_mean: 0.402) detection on FS. IOA was moderate for STAS (κ_round-1: 0.453; κ_round-2: 0.506) and fair for artifact (κ_round-1: 0.300; κ_round-2: 0.204) detection on FS. IOA for STAS improved in FS permanent and non-FS permanent, whereas ITA was similar across section types. On multivariable logistic regression, the only significant predictor of diagnostic discordance was the presence of artifacts.

CONCLUSIONS

FS is highly specific but not sensitive for STAS detection in stage 1 lung adenocarcinomas. IOA on STAS is moderate in FS and improved only marginally after a consensus conference, raising concerns regarding global implementation of intraoperative assessment of STAS and warranting more precise criteria for STAS and artifacts.

Could tumor spread through air spaces benefit from adjuvant chemotherapy in stage I lung adenocarcinoma? A multi-institutional study

Background:

The benefit of adjuvant chemotherapy (ACT) remains unknown for patients with stage I lung adenocarcinoma (ADC) with spread through air spaces (STAS). This study investigated the effect of adjuvant chemotherapy in stage I ADC/STAS-positive patients.

Methods:

A total of 3346 patients with stage I ADC from five institutions in China were identified from 2009 to 2013, of whom 1082 were diagnosed with STAS (32.3%). By using the Kaplan–Meier method and Cox proportional hazard regression model, we explored the impact of STAS on prognosis, and determined if the use of adjuvant chemotherapy was associated with improved outcomes in patients with stage I ADC/STAS-positive. A validation cohort was also included in this study.

Results:

Patients with stage I ADC/STAS-positive in the primary cohort had unfavorable overall survival (OS) and disease-free survival (DFS). A multivariate Cox regression model confirmed the survival disadvantages of STAS in patients with stage I ADC [OS: hazards ratio (HR) = 1.877, 95% confidence interval (CI): 1.579–2.231; p < 0.001; DFS: HR = 1.895, 95% CI: 1.614–2.225; p < 0.001]. Lobectomy was associated with better OS and DFS than sublobar resection (SR) in both stage IA and IB ADC/STAS-positive. Similar results were observed in the validation cohort. For patients with stage IB ADC/STAS-positive, ACT was revealed as an independent factor for favorable survival (OS: HR = 0.604, 95% CI: 0.397–0.919; p = 0.018; DFS: HR = 0.565, 95% CI: 0.372–0.858; p = 0.007). However, among patients with stage IA ADC/STAS-positive, ACT was associated with improved outcomes only for those undergoing SR (OS: HR = 0.787, 95% CI: 0.359–0.949; p = 0.034; DFS: HR = 0.703, 95% CI: 0.330–0.904; p = 0.029).

Conclusion:

The presence of STAS was correlated with poor prognosis in patients with stage I ADC. Our study suggested that ACT might be considered for patients with stage IB ADC/STAS-positive and those with stage IA ADC/STAS-positive who underwent SR.

Segmentectomy vs Lobectomy for Clinical Stage IA Lung Adenocarcinoma With Spread Through Air Spaces

BACKGROUND

This study aimed to investigate the prognosis after segmentectomy as compared with lobectomy for small-sized lung adenocarcinoma with spread through air spaces (STAS).

METHODS

This retrospective study included 609 patients who underwent lobectomy or segmentectomy with lymph node dissection for clinical stage IA lung adenocarcinoma between April 2011 and March 2020 at Hiroshima University Hospital. Patient characteristics and prognosis after segmentectomy and lobectomy were investigated.

RESULTS

STAS was detected in 293 patients (48.1%). The recurrence-free survival (RFS) rate was significantly worse with STAS-positive adenocarcinoma than with STAS-negative adenocarcinoma both in patients who underwent lobectomy (5-year RFS, 68.2% vs 90.2%; P < .001) and in patients who underwent segmentectomy (5-year RFS, 81.3% vs 93.0%; P = .003). Among the patients with STAS, there was no significant difference in RFS between patients who underwent lobectomy (5-year RFS, 68.2%) and those who underwent segmentectomy (5-year RFS, 81.3%; P = .225). In a multivariable analysis using propensity score to adjust clinical patient characteristics, segmentectomy was not found to be an independent prognostic factor of RFS (hazard ratio 0.732, P = .326) among patients with STAS. Among the patients with STAS, only 1 patient (1%) with insufficient resection margin (0.5 mm) had local recurrence and 1 patient (1%) with invasive mucinous adenocarcinoma had recurrence in preserved lobe after segmentectomy.

CONCLUSIONS

Spread through air spaces was a poor prognostic factor in patients with clinical stage IA lung adenocarcinoma. Prognosis after segmentectomy was comparable with that of lobectomy in lung adenocarcinoma with STAS without increasing locoregional recurrence.

Solid Nodule Appearance as a Predictor of Tumor Spread Through Air Spaces in Patients with Lung Adenocarcinoma: A Propensity Score Matching Study

OBJECTIVE

Spread through air spaces (STAS) has been reported to be an invasive histological pattern with poor prognosis in lung cancer; however, little is known about its intrinsic risk factors. This work analyzed the correlation between pathological and radiological features and STAS in resected lung adenocarcinomas.

PATIENTS AND METHODS

We retrospectively reviewed 1821 consecutive surgically treated patients with histologically diagnosed lung adenocarcinoma (174 positive for STAS and 1647 negative for STAS) from December 2017 to November 2018 at our institution. Propensity score matching identified 170 well-balanced pairs of patients. The correlations between pathological and radiological features and the presence of STAS were analyzed.

RESULTS

Before propensity matching, the incidence rate of STAS was 9.6% in all patients. In matched cohorts, multivariate analysis showed that the presence of STAS was significantly correlated with pure solid nodules (SNs) (p = 0.001) and solid/micropapillary patterns (SMPs) (p = 0.002). The odds ratio for STAS in SN-positive and SMP-positive adenocarcinoma against that in SN-negative and SMP-negative adenocarcinoma was 10.922 (95% confidence interval, 5.826-20.475; p < 0.001). Tumor differentiation, visceral pleural invasion (VPI), lymphovascular invasion (LVI), invasive adenocarcinoma, and non-lepidic subtype were significantly associated with STAS in the univariate analysis (p < 0.05); however, the differences failed to reach a significant level in the multivariate analysis.

CONCLUSION

We found that STAS was significantly correlated with several invasive clinicopathological patterns. The presence of SNs and SMPs were revealed as independent predictors for STAS, which could offer clinicians clues to identify STAS-positive adenocarcinoma.

Novel imprint cytological classification is correlated with tumor spread through air spaces in lung adenocarcinoma

OBJECTIVES

Spread through air spaces (STAS) is a risk factor for local recurrence after sublobar resection in lung cancer patients. We recently proposed the novel Nakayama-Higashiyama imprint cytological classification (N-H classification) based on small-sized lung adenocarcinoma surgical specimens, which correlated with histological patterns and nodal involvement. This study aimed to evaluate the correlation between STAS and the N-H classification and to validate the N-H classification as an intraoperative predictor of the presence of STAS.

MATERIALS AND METHODS

We retrospectively analyzed 164 intraoperative imprint cytologies and their paired histologic specimens from patients undergoing surgical resection for lung adenocarcinoma in our institute in 2017-2019. Using the NH classification, imprint cytological findings were classified into 5 groups (Groups I to V) based on cell cluster shape, cell and nucleus size, and the existence of necrosis. We examined the characteristics of imprint cytology and STAS in the resected tissues and analyzed the relationship between them.

RESULTS

Tumor STAS was observed in 29 (17.7 %) cases. The presence of STAS was significantly associated with the NH classification (P < 0.0001). STAS was present in 6 of 57 cases (10.5 %) in NH classification Group II, 11 of 42 cases (26.2 %) in Group III, and 12 of 28 cases (42.9 %) in Group IV/V; STAS was not observed in any case in Group I. Logistic regression analysis revealed that tumors with a ground glass opacity rate of <50 % on computed tomography (P = 0.00867) and Groups III-V of the NH classification (P = 0.00201) were significant independent predictors for STAS.

CONCLUSION

Intraoperative imprint cytology with the N-H classification for lung adenocarcinoma is well correlated with the STAS status of the tumor and might have applications as an intraoperative predictive marker of STAS. This classification may be useful for intraoperative detection of STAS and in the decision-making process for the surgical procedure.

Updates on spread through air spaces (STAS) in lung cancer

Air space invasion of tumours, particularly spread through air spaces (STAS), is a relatively recent concept that has been identified as a novel mechanism of invasion. It has predominantly been described in lung adenocarcinoma, although it may be seen in other primary lung malignancies as well. STAS in lung cancer has been reported to have numerous associations with poor survival. The objective of this article was to review the concept of air space invasion, update findings regarding its clinical impact, and discuss controversies in the field. With this aim, we performed a PubMed search of the English-language literature. STAS has been introduced as a novel mechanism of invasion that is important for pathologists to recognise. There is a compelling body of evidence associating the presence of STAS with lower survival and suggesting that STAS is an independent prognostic factor, regardless of the stage of tumour. The standard of care for lung adenocarcinomas with STAS irrespective of size of tumour and nodal metastasis may be lobectomy rather than sublobar resection, owing to the risk of locoregional recurrence. Emerging data suggest that more work should be performed to improve consensus on and identification of STAS, including at frozen section.

Significance of tumor spread through air spaces (STAS) in lung cancer from the pathologist perspective

Airspace invasion in lung cancer has been known over the last 30 years, but it was only recently that WHO 2015 formally recognized it as a mechanism of invasion with the terminology of tumor spread through air spaces (STAS). Multiple studies have shown the association of STAS with lower survival and suggest that STAS is an independent prognostic factor across lung adenocarcinoma of all stages and in other histologic subtypes of lung cancer as well. Consequently, STAS is designated as an exclusion criterion of adenocarcinoma in situ and minimally invasive adenocarcinoma; thus, the presence of STAS impacts the diagnosis and staging of lung adenocarcinoma. Further, wedge resection and segmentectomy have been increasingly applied for small node negative tumors and the presence of STAS in those specimens may indicate the requirement of completion lobectomy. Given these significant clinical implications, we, pathologists, need to recognize and appropriately report STAS (possibly including at the time of intraoperative consultation). However, emerging data suggests that more work should be done to improve consensus and identification of STAS, including at frozen section. In this review, the evolution of our understanding of airspace invasion over the past decade, the clinical significance of STAS, and controversies and practical issues associated with the diagnosis of STAS are discussed.

The role of spread through air spaces (STAS) in lung adenocarcinoma prognosis and therapeutic decision making

Spread through air spaces (STAS) was included as a novel pattern of invasion in lung adenocarcinoma by the World Health Organization in 2015. Since then, multiple studies have investigated the association of STAS with clinicopathological and molecular features and its implication in the prognosis of early stage lung cancer patients undergoing different surgery types. The aim of this comprehensive review is to present current data on the role of STAS and its perspective in lung adenocarcinoma management.

Spread Through Air Spaces (STAS) in Lung Cancer: A Multiple-Perspective and Update Review

BACKGROUND

Spread through air spaces (STAS) is a spreading phenomenon of lung cancers, which is defined as tumor cells within air spaces in the lung parenchyma beyond the edge of the main tumor. To date, several articles have reviewed the studies concerning the significance of STAS; however, most articles focused on the prognosis without summarizing the significance of STAS on other aspects. In this review, we comprehensively summarized the current literature related to STAS, so as to explore the clinical significance of STAS from multiple perspectives.

MAIN BODY

This section provided a comprehensive overview of the significance of STAS from multiple perspectives and summarized current controversies and challenges in the diagnosis and clinical application.

CONCLUSION

STAS is a conspicuous spreading phenomenon of lung cancers indicating worse prognosis; nevertheless, the treatment strategy for patients with STAS remains to be discussed. Further studies are needed to elaborate whether a STAS-positive patient who underwent limited resection needs a second operation or postoperative adjuvant treatment. Meanwhile, the internal mechanism of STAS formation is largely undiscovered. Whether the capability of detachment-migration-reattachment in STAS tumor cells is achieved at the time of primary tumorigenesis or in the progress of tumor development needs to be studied, and the related signal pathways or genetic alterations need to be explored. With this information, it may be possible to improve the prognosis of patients with STAS-positive lung cancers.

An effective inflation treatment for frozen section diagnosis of small-sized lesions of the lung

Background

The accuracy of intraoperative pathological diagnosis of small-sized pulmonary nodules including ground-glass opacity (GGO) is important for the surgeon to choose a suitable surgical procedure. Diagnosis of the small-sized lesions of the lung by frozen section (FS) is very difficult for the pathologist because of limited FS technology. Here we tested an effective inflation treatment for FS to improve the diagnostic accuracy of small-sized lung lesions.

Methods

The lung specimens were derived from 113 patients who underwent the surgery at Shanghai Chest Hospital in 2018–2019. The specimens were randomly divided into two groups—uninflated or inflated with diluted embedding medium (Tissue-Tek OCT; Sakura Finetek-USA, CA). The qualities of the FSs were compared with that of corresponding permanent paraffin sections. The FS diagnoses were compared with the final pathologic diagnoses of corresponding permanent sections.

Results

Our results showed that the quality of FS of lung tissue was excellent after inflation with diluted embedding medium (1:1). The total consistency between diagnosis of inflated FS and final pathological diagnosis was 85.7%. In control group, however, the consistency was only 70.2%. When the lesions were less than 1cm, the consistency between diagnosis of inflated FS and final pathological diagnosis was 90.3%, compared to 64.9% consistency in uninflated group (P=0.014, <0.05). When the lesions’ computed tomography (CT) measurement threshold ≤−350 HU, the consistency between diagnosis of inflated FS and final pathological diagnosis was 88% compared to 73.2% consistency in uninflated group (P=0.071, >0.05). Accuracy, sensitivity and specificity were observed about 90% for adenocarcinoma in situ (AIS), whereas it is drop to more than 80% for minimally invasive adenocarcinoma (MIA) in inflated FS.

Conclusions

Inflation with diluted embedding medium (1:1) could make lung tissue expand well during FS. By using this method, small-sized lesions (especially less than 1 cm) could be correctly diagnosed to enable adequate surgical procedure, and evaluation of which can be easily based on the intraoperative pathological diagnosis. The small lesions especially AIS could be readily identified on FS. Therefore, this method improves the diagnostic accuracy of FSs for small-sized lung lesions, and has important practical consequences for further therapy.

Preoperative bronchial cytology for the assessment of tumor spread through air spaces in lung adenocarcinoma resection specimens

BACKGROUND

Tumor spread through air spaces (STAS), a significant prognostic indicator, has been described recently as a pattern of invasion in pulmonary carcinomas. However, questions remain regarding preoperative identification of STAS and whether it represents an in vivo phenomenon versus an ex vivo artifact.

METHODS

We retrospectively reviewed 67 paired preoperative bronchoalveolar lavage (BAL) or bronchial washing (BW) cytology specimens with the subsequent lung adenocarcinoma surgical resection specimen to determine whether preoperative cytology could predict STAS. Other clinical, radiologic, and pathologic features of the resected lesions were also correlated with preoperative bronchial cytology results.

RESULTS

Positive bronchial cytology was observed in 28 cases (41.8%), 24 of which had STAS (85.7%); however, negative BAL/BW cytology was observed in 39 cases (58.2%), 29 of which had STAS (74.4%) (x²  = 1.27, P = .26, not significant). High-STAS burden was observed in 44 cases (83.0%), 21 (47.7%) with negative BAL/BW and 23 (52.3%) with positive BAL/BW. Low-STAS burden was observed in 9 cases (17.0%), 8 (88.9%) with negative BAL/BW and only 1 (11.1%) with positive BAL/BW (x²  = 5.11, P = .024, significant). For tumors with STAS, a statistically significant difference was identified in the maximal STAS distance from the main tumor edge between BAL/BW-positive and BAL/BW-negative groups (P = .007). Of the remaining clinicopathologic and radiologic features, only visceral pleural invasion was significantly associated with BAL/BW positivity.

CONCLUSION

Presurgical bronchial cytology alone cannot adequately predict tumor STAS; however, it may provide useful information regarding the extent and overall burden of STAS on the subsequent resection specimen.

Advances In Research Of Spreading Through Air Spaces And The Effects On The Prognosis Of Lung Cancer

The concept of spread through air spaces (STAS) has been described as a new form of invasion in the lung in the 2015 WHO classification of Lung Tumors, namely invasion through alveolar spaces. STAS is a prognostic factor independent of growth pattern and tumor stage, and it is also an independent risk factor for unfavorable prognosis of stage I lung adenocarcinoma (ADC) and stage I lung squamous cell carcinoma (SCC). The pathological characteristics are different between ADC and SCC. STAS is not reported as routine, so setting a unified pathological reading standard, and hunting for STAS as a regular reading process is urgently advocated. We write this review to investigate the research progress of STAS and its effects on the prognosis of lung cancer.

Pathology in the era of "Personalized Medicine": The need to learn how to integrate multivariate immunohistochemical and "omics" data with clinicopathologic information in a clinically relevant way"

"Personalized medicine" has been proposed as a new paradigm for patient care that, based on the integration of genomics and other "omics" data with clinical and other multidisciplinary information, promises early disease detection, improved outcomes and reduced side effects to therapies. Pathologists have become important participants in this new approach as the guardians of tissues and experts in the performance of molecular and other laboratory tests. Large amounts of new laboratory data in multiple neoplasms and other entities are being reported but there has been limited discussion about how best to evaluate the clinical significance of this information and how to integrate it into currently available diagnostic and therapeutic modalities. This article introduces a variety of epistemological problems presented by the "personalized medicine" paradigm and briefly discusses various topics that will be evaluated in further detail in future articles of this new series on Evidence-Based Pathology.

Challenges for real-time intraoperative diagnosis of high risk histology in lung adenocarcinoma: A necessity for sublobar resection

Recently, the incidence of small, peripheral lung adenocarcinoma has been increasing as lung cancer screening with radiologic examination is more widely performed. Tumor size is one of the determinants of the prognostic outcome in clinically node-negative lung adenocarcinoma. Sublobar resection has been proposed as one of the minimally invasive surgical options for small-sized adenocarcinomas. Despite the lack of robust clinical trial evidence, sublobar resection has become more popular, especially in developed countries where less extensive surgery may be of benefit in a population where the age of the elderly is growing. However, high risk histologic features such as micropapillary subtype and tumor spread through air space (STAS) have been associated with a significantly higher risk of local recurrence after sublobar resection, but not after lobectomy. Surgical decision-making based on frozen section diagnosis of high risk histologic features may be useful to prevent local control failure after sublobar resection. At the present time, there is little evidence to demonstrate the diagnostic accuracy of identifying high risk histologic features on frozen section. One study has so far demonstrated that diagnostic accuracy of identifying STAS is higher than that of identifying the micropapillary subtype. Additionally, the presence of STAS has been found to be more strongly associated with local recurrence in patients who had undergone sublobar resection. Although further investigation is required for validation of this finding, STAS diagnosis on frozen section may shed further light on intraoperative surgical decision-making during sublobar resection. To this end, we review the recently published data on the intraoperative identification of high risk features.

Tumor Spread Through Air Spaces in Non-Small Cell Lung Cancer: A Systematic Review and Meta-Analysis

BACKGROUND

A series of studies have assessed the clinicopathological features and prognostic impact of spread through air spaces (STAS) in non-small cell lung cancer (NSCLC) bringing conflicting findings so far. We performed a systematic review and meta-analysis to synthesize the available evidence regarding to the prognostic value of STAS in NSCLCs.

METHODS

Studies were identified by searching databases including PubMed, EMBASE, Web of Science, and Cochrane Library up to August 2018 without language restrictions. Results of these searches were filtered according to a set of eligibility criteria and analyzed in line with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines.

RESULTS

A total of 3,754 patients from 14 studies were selected for the present study. The pooled results suggested that presence of STAS was associated with worse recurrence-free survival (hazard ratio [HR], 1.975; 95% confidence interval [CI], 1.691 to 2.307; p < 0.001) and overall survival (HR, 1.75; 95% CI, 1.375 to 2.227; p < 0.001) in NSCLCs. Subgroup analysis by histology type indicated the presence of STAS was significantly associated with inferior recurrence-free survival in resected lung adenocarcinoma (n = 7; HR, 2.288; 95% CI, 1.843 to 2.840; I² = 7.80%), lung squamous cell carcinoma (n = 3; HR, 1.622; 95% CI, 1.279 to 2.056; I² = 0%), and lung pleomorphic carcinoma (n = 1; HR, 4.76; 95% CI, 1.168 to 19.398). Additionally, a number of clinicopathological characteristics indicating STAS in NSCLCs are summarized.

CONCLUSIONS

Our study indicates that tumor STAS was a potentially significant prognostic predictor for surgical patients with NSCLCs. The prognostic impact of STAS present in the resection margin remains undetermined. Further large-scale prospective studies are warranted to confirm the prognostic significance of STAS in patients with NSCLCs.

CT Manifestations of Tumor Spread Through Airspaces in Pulmonary Adenocarcinomas Presenting as Subsolid Nodules

PURPOSE

The aim of this study was to identify potential computed tomography manifestations of pulmonary adenocarcinomas presenting as subsolid nodules and associated with the histologic evidence of spread of tumor through air spaces (STAS).

MATERIALS AND METHODS

From a radiologic-pathologic repository of resected pulmonary adenocarcinomas including 203 subsolid nodules, 40 STAS-positive nodules were randomly selected and matched to 40 STAS-negative nodules. Total average diameter, as well as average and long-axis diameters of the solid component, was measured. The proportion of solid component diameter to total average diameter was calculated. Measurements and proportions between STAS-positive and STAS-negative nodules were compared with paired samples t test, χ test, or the Fisher exact test.

RESULTS

The total average diameter in STAS-positive nodules was significantly larger than in STAS-negative nodules (P=0.024). The average and long-axis diameters of the solid component of STAS-positive nodules were significantly larger than that of STAS-negative nodules (P=0.001 and 0.003). The proportion of solid component to total average diameter was significantly larger in STAS-positive than in STAS-negative nodules (P=0.041). At a threshold of ≥10 mm for the average and the solid component long-axis diameters, significantly more nodules were STAS-positive than STAS-negative (P=0.015 and 0.001).

CONCLUSIONS

Total average diameter, average and long-axis diameters of the solid component, and a high proportion of solid component diameter compared with total average diameter are computed tomography manifestations of subsolid pulmonary adenocarcinomas with STAS. These findings could serve as an in-vivo tool for the likelihood estimation of STAS, and consequently influence management of subsolid adenocarcinomas.

Lobectomy Is Associated with Better Outcomes than Sublobar Resection in Spread through Air Spaces (STAS)-Positive T1 Lung Adenocarcinoma: A Propensity Score-Matched Analysis

INTRODUCTION

Spread through air spaces (STAS) is a form of invasion wherein tumor cells extend beyond the tumor edge within the lung parenchyma. In lung adenocarcinoma (ADC), we investigated the (1) association between STAS and procedure-specific outcomes (sublobar resection and lobectomy), (2) effect of surgical margin-to-tumor diameter ratio in STAS-positive patients, and (3) potential utility of frozen sections (FSs) for detecting STAS intraoperatively.

METHODS

We investigated 1497 patients who underwent lobectomy (n = 970) or sublobar resection (n = 527) for T1N0M0 lung ADC after propensity score matching. Outcomes were analyzed by using a competing risks approach. The effect of margin-to-tumor ratio on recurrence pattern (locoregional and distant) was investigated in patients who underwent sublobar resection. Five pathologists evaluated the feasibility of intraoperatively identifying STAS by using FSs (sensitivity, specificity, and interrater reliability).

RESULTS

On multivariable analysis after propensity score matching (349 pairs/procedure), sublobar resection was significantly associated with recurrence (subhazard ratio = 2.84 [p < 0.001]) and lung cancer-specific death (subhazard ratio = 2.63 [p = 0.021]) in patients with STAS but not in those without STAS. Patients with STAS who underwent sublobar resection had a higher risk of locoregional recurrence regardless of margin-to-tumor ratio (for a margin-to-tumor ratio of ≥1 versus <1, the 5-year cumulative incidence of recurrence rates were 16% and 25%, respectively); among patients without STAS, locoregional recurrences occurred in patients with margin-to-tumor ratio lower than 1 (a 5-year cumulative incidence of recurrence rate of 7%). The sensitivity and specificity for detecting STAS by use of FSs were 71% and 92%, with substantial interrater reliability (Gwet's AC1, 0.67).

CONCLUSIONS

In patients with T1 lung ADC with STAS, lobectomy was associated with better outcomes than sublobar resection was. Pathologists can recognize STAS on FSs.

Spread Through Air Spaces (STAS): A New Pathologic Morphology in Lung Cancer

In 2015, the World Health Organization classification of lung cancer proposed the concept of spread through air spaces (STAS) as a new pattern of invasion in lung adenocarcinoma. The definition of STAS included one or more pathologic micropapillary clusters, solid nests or single cells beyond the edge of the tumor into air spaces in the surrounding lung parenchyma, and separation from the main tumor other than tumor islands. The roles of STAS has been investigated in many studies. The results indicated that STAS is associated with key clinical variables and the prognosis of patients both in lung adenocarcinoma, lung squamous cell carcinoma, small-cell lung cancer, and lung pleomorphic carcinoma. This mini review will be focused on the developments and perspectives of STAS in lung cancer.