Spread through air spaces in lung cancer patients is a risk factor for pulmonary metastasis after surgery

Diagnostic performance of radiomics analysis for pulmonary cancer airway spread: a systematic review and meta-analysis

PURPOSE

Spread through air spaces (STAS) is a unique metastatic pattern of pulmonary cancer closely associated with patient prognosis. This study evaluates the application of radiomics in the diagnosis of pulmonary cancer STAS through meta-analysis and explores its clinical significance and potential limitations.

METHODS

We systematically searched the PubMed, Embase, and Cochrane Central Register of Controlled Trials databases for relevant studies between inception and April 1, 2024. The main evaluation indicators included sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and area under the curve (AUC). A total of 18 studies, covering 6,642 lung cancer cases, were included in the systematic review.

RESULTS

In the development cohort, the sensitivity of radiomics for diagnosing STAS was 0.80 [95% confidence interval (CI): 0.75-0.84; P < 0.001; I2: 72.8%], and the specificity was 0.79 (95% CI: 0.71-0.85; P < 0.001; I2: 93.4%). In the validation cohort, the sensitivity was 0.81 (95% CI: 0.75-0.86; P < 0.001; I2: 45.8%), and the specificity was 0.74 (95% CI: 0.68-0.80; P < 0.001; I2: 65.0%). The summary AUC for both cohorts was 0.85 (95% CI: 0.82-0.88). Deeks' funnel plot analysis showed no significant publication bias in either cohort (P values: 0.963 and 0.106, respectively).

CONCLUSION

Radiomics analysis demonstrates important clinical significance in the diagnosis of pulmonary cancer STAS, with promising sensitivity and specificity results in both development and validation cohorts.

CLINICAL SIGNIFICANCE

While radiomics analysis offers valuable diagnostic insights for STAS in pulmonary cancer, its limitations must be carefully considered. Future research should focus on addressing these limitations and further exploring the application prospects of radiomics in lung cancer diagnosis and treatment.

Benefit of adjuvant chemotherapy for resected stage I lung cancer with spread through air spaces: a systematic review and meta-analysis

BACKGROUND

Spread through air spaces (STAS) has been proved to be an independent risk factor for poor prognosis in patients with stage I lung cancer. Evidence regarding the application of adjuvant chemotherapy (ACT) in STAS-positive patients with stage I lung cancer remains insufficient. This study aims to elucidate the significance and indication of ACT in patients with stage I lung cancer with STAS.

METHODS

Three major electronic databases were searched to identify relevant studies published up to June 26, 2024. Subsequently, the retrieved studies were screened according to predetermined inclusion and exclusion criteria. Hazard ratio (HR) and corresponding 95 % confidence interval (CI) were computed, and sensitivity analysis was performed to evaluate the sources of heterogeneity.

RESULTS

Five studies involving 2899 patients were included in the meta-analysis. ACT could effectively prolong disease-free survival (DFS; HR 0.69 [95 % CI 0.48-0.99]; P = 0.044) and overall survival (OS; HR 0.61 [95 % CI 0.47-0.79]; P < 0.001) in patients with stage I lung cancer with STAS. Even patients who have undergone lobectomy could benefit from ACT (DFS; HR 0.61 [95 % CI 0.45-0.82]; P = 0.001| OS; HR 0.60 [95 % CI 0.42-0.85]; P = 0.005). Moreover, ACT significantly extended DFS in STAS-positive stage IB cases (HR 0.55, 95 % CI 0.38-0.79; P = 0.001), rather than stage IA cases (HR 0.72, 95 %CI 0.42-1.25; P = 0.246).

CONCLUSION

ACT might be recommended to STAS-positive stage IB lung cancer patients, even if they have undergone radical lobectomy. Randomized controlled trials (RCTs), however, are required to confirm these findings.

Dynamic change of polarity in spread through air spaces of pulmonary malignancies

Spread through air spaces (STAS) is a histological finding of lung tumours where tumour cells exist within the air space of the lung parenchyma beyond the margin of the main tumour. Although STAS is an important prognostic factor, the pathobiology of STAS remains unclear. Here, we investigated the mechanism of STAS by analysing the relationship between STAS and polarity switching in vivo and in vitro. Histopathological analysis revealed that apical membranes were observed outside the STAS lesions around colorectal cancer (CRC) lung metastases and lung adenocarcinomas. When apical-out CRC organoids were administered intratracheally to mice, the organoids had greater metastatic potential than did single cells. To investigate the pathobiology of STAS, we established an in vitro model of STAS in which CRC or lung cancer organoids were co-cultured with 2D-cultured mouse airway epithelial organoids (2D-MAOs). Adhesion of cancer organoids to 2D-MAOs was much less than to type I collagen or endothelial cells, suggesting a protective role of the airway epithelium against adhesion. Loss of the apical membrane of CRC organoids at the contact surface with 2D-MAOs after adhesion was responsible for establishing adhesion. When airway epithelium was stimulated by transforming growth factor beta 1 (TGF-β1), adhesion of CRC organoids was enhanced. Among TGF-β1-induced genes in airway epithelium, follistatin-like protein 1 (FSTL1) increased CRC organoid adhesion by promoting loss of the apical membrane. These results suggested that TGF-β1-induced FSTL1 may promote metastatic progression of STAS by altering the polarity status. Elucidating the mechanism of STAS could contribute to the improvement of survival in patients with pulmonary malignancies associated with STAS. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Pro: "Is Spread Through Air Spaces an In Vivo Phenomenon or an Inducible Artifact?"

In this PRO-CON debate, you will read very different perspectives about a simple question regarding an observation under the microscope: What is the significance of tumor cells in the air spaces of the lung parenchyma beyond the tumor edge of a resected lung cancer? An important underlying question is whether this entire PRO-CON debate is a mere academic exercise or whether spread through air spaces (STAS), as currently defined, describes a clinically useful phenomenon. The journey of STAS began with a complete paradigm shift to reverse the thinking that all air space tumor cells beyond the edge of lung cancers are an artifact. This led to a new concept where STAS could be separated from artifacts with a definition that has proven to be clinically useful. As with any major change in thinking, it is understandable that there would be some disagreement with this paradigm shift. Nevertheless, after a decade since it was described, many pathologists and clinicians around the world have found STAS to provide important information about the behavior of lung cancer. Numerous PRO-STAS articles supporting the usefulness of STAS have been published with clinical data on many thousands of patients from numerous institutions all over the world. In contrast, for the CON-STAS articles, widespread international representation and data are limited. It is now difficult to ignore the numerous reports and is reasonable to consider how to use the presence of STAS in clinical decisions. Hopefully, this PRO-CON debate will further stimulate clinical and scientific investigations aimed at a better understanding of STAS.

Significance of Spread Through Air Spaces and Vascular Invasion in Early-stage Adenocarcinoma Survival: A Comprehensive Clinicopathologic Study of 427 Patients for Precision Management

Spread through air spaces (STAS) is a novel invasive pattern of lung cancer associated with poor prognosis in non-small cell cancer (NSCLC). We aimed to investigate the incidence of STAS in a surgical series of adenocarcinomas (ADCs) resected in our thoracic surgery unit and to identify the association of STAS with other clinicopathological characteristics. We retrospectively enrolled patients with stage cT1a-cT2b who underwent resection between 2016 and 2022. For each case, a comprehensive pathologic report was accessible which included histotype, mitoses, pleural invasion, fibrosis, tumor infiltrating lymphocytes, necrosis, inflammation, vascular and perineural invasion, as well as STAS. PD-L1 expression was also investigated. A total of 427 patients with ADCs underwent surgery. Regarding overall survival (OS), no significant difference was observed between the STAS positive (STAS+) and STAS negative (STAS-) groups ( P =0.44). However, vascular invasion (VI) was associated with a poorer survival probability ( P =0.018). STAS+/VI+ patients had tendentially worse survival compared with STAS+/VI- ( P =0.089). ADCs with pathologic evidence of immune system (IS) activation (TILs>10% and PD-L1≥1) demonstrated significantly increased OS compared with ADCs with no IS and VI. In terms of recurrence rate, no statistical differences were found between the STAS+ and STAS- samples ( P =0.2). VI was also linked to a significantly elevated risk of recurrence ( P =0.0048). Our study suggests that in resected early-stage ADCs, STAS+ does not seem to influence recurrence or mortality. VI was instead an adverse pathologic prognostic factor for both survival and recurrence, whereas IS seemed to be protective.

Lung adenocarcinoma presenting with intrapulmonary metastases through air spaces concomitant with silicosis: a case report and literature review

Herein, we reported a rare case of bilateral intrapulmonary metastases spread through air spaces (STAS) and silicosis to advance understanding and knowledge of this disease. A middle-aged man was diagnosed with a left upper lung nodule with bilateral silicosis by preoperative imaging. Local pleural indentation and extensive metastases spread in the visceral pleura were observed during the operation. Pathological examination showed multiple metastases of lung adenocarcinoma, and STAS positive. Genetic testing indicated EGFR mutation, and ektinib was administered. STAS can promote lung cancer, leading to multiple pulmonary metastases, and silicosis can contribute to the carcinogenesis of lung cancer. This case provided valuable clinical lessons. More studies are warranted to elucidate the role and underlying mechanism of silicosis and STAS in the development of lung cancer. More accurate imaging methods and radiographic criteria should be formulated for different diffuse nodules and STAS grades, and the exploration of optimal therapeutic regimens to treat these concomitant patients is urgently needed to improve diagnostic rates and formulate more optimal therapies.

Prognostic significance of limited resection in pathologic stage I lung adenocarcinoma with spread through air spaces

Background

Tumor spread through air spaces (STAS) is now recognized as tumor invasion. However, the association between STAS and procedure-specific outcomes (limited resection and lobectomy) in patients with pathologic stage I lung adenocarcinoma (ADC) is still under investigation.

Methods

To investigate whether limited resection predicts poorer survival in such patients, we retrospectively analyzed the clinicopathologic features of a large cohort of 1,566 patients with stage I ADC from 2017 to 2020 and classified them according to STAS status and surgical method. Kaplan-Meier, Cox hazard proportional regression, and propensity score matching (PSM) were adopted for prognostic evaluation.

Results

STAS-positive patients had worse recurrence-free survival (RFS) (P<0.001). There was no significant difference in RFS and overall survival (OS) between limited resection and lobectomy, neither for the STAS-negative nor STAS-positive group before matching. After matching, limited resection was found to achieve comparable RFS to lobectomy in STAS-positive patients with pathologic I, IA, or IB stage tumor, (P=0.816, P=0.576, P=0.281, respectively), but worse OS in stage I and stage IB patients (P=0.029, P=0.010, respectively). Furthermore, in multivariable analysis, limited resection was not an independent prognostic factor of RFS or OS. Instead, the high-grade histological subtype was the only independent prognostic factor for RFS (P=0.001). In the subgroup analysis, adjuvant chemotherapy (ACT) did not improve the outcomes of stage IB STAS-positive patients.

Conclusions

Limited resection was associated with worse survival than lobectomy in stage I STAS-positive patients, but not in stage IA STAS-positive patients.

Retrospective analysis of the prognostic implications of tumor spread through air spaces in lung adenocarcinoma patients treated with surgery

Background

Tumor spread through air spaces (STAS) in lung adenocarcinoma is a novel mechanism of invasion. STAS has been proposed as an independent predictor of poor prognosis. The aim of this study was to evaluate the correlations between STAS status and other clinicopathologic variables and to assess the prognostic implications of STAS and the distance from the edge of the tumor to the farthest STAS in patients with resected lung adenocarcinoma.

Material and methods

This is a single-institution retrospective observational study. We included all patients with resected lung adenocarcinoma from January 2017 to December 2018 at La Paz University Hospital. The cut-off for the distance from the edge of the tumor to the farthest STAS was 1.5 mm and was assessed by the area under the receiver operating characteristic curve.

Results

A total of 73 patients were included. STAS was found in 52 patients (71.2%). Histological grade 3 (P = 0.035) and absence of lepidic pattern (P = 0.022) were independently associated with the presence of STAS. The median recurrence-free survival (RFS) was 48.06 months [95% confidence interval (CI) 33.58 months to not reached]. STAS-positive patients had shorter median RFS [39.23 months (95% CI 29.34-49.12 months)] than STAS-negative patients (not reached) (P = 0.04). STAS-positive patients with a distance from the edge of the tumor to the farthest STAS ≥1.5 mm had an even shorter median RFS [37.63 months (95% CI 28.14-47.11 months)]. For every 1 mm increase in distance, the risk of mortality increased by 1.26 times (P = 0.04).

Conclusions

Histological grade 3 and absence of lepidic pattern were independently associated with the presence of STAS. STAS was associated with a higher risk of recurrence. The distance from the edge of the tumor to the farthest STAS also had an impact on overall survival.

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Lung adenocarcinoma patients with STAS had higher risk of recurrence.

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Patients with STAS and a distance from the edge of the tumor to the farthest STAS ≥1.5 mm had an even shorter RFS.

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The distance from the edge of the tumor to the farthest STAS also had an impact on overall survival.

Impact of preoperative biopsy on tumor spread through air spaces in stage I non-small cell lung cancer: a propensity score-matched study

Background

Percutaneous needle biopsy (PNB) and bronchoscopic biopsy (BB) are widely used in the preoperative diagnosis of pulmonary nodules, but whether PNB or BB may cause tumor spread through air spaces (STAS) has not been reported.

Methods

433 postoperative patients with pathological stage I non-small cell lung cancer (NSCLC) from January 2015 to December 2018 at our hospital were enrolled and divided into PNB group (n = 40), BB group (n = 48) and non-biopsy group (n = 345). The PNB and BB groups were matched using propensity score matched (PSM) separately from the non-biopsy group, after which the effects of PNB and BB on STAS, recurrence-free survival (RFS) and overall survival (OS) were assessed.

Results

After PSM for 9 confounding factors (gender, age, smoking history, tumor site, scope of surgery, pathology type, stage, maximum tumor diameter and postoperative treatment), 38 cases in the PNB group were successfully matched with 38 cases in the non-biopsy group and 28 cases in the BB group were successfully matched with 28 cases in the non-biopsy group. After PSM, there was no significant difference in the incidence of STAS between the PNB and non-biopsy groups (42.1% vs. 34.2%, P > 0.05) and between the BB and non-biopsy groups (42.9% vs. 46.4%, P > 0.05). The results after PSM showed no significant effect of both PNB and BB on RFS and OS after radical surgery (P > 0.05).

Conclusion

Preoperative biopsy in patients with stage I NSCLC has not been shown to increase the occurrence of STAS, nor postoperative recurrence and death.

Clinicopathological Impact of the Spread through Air Space in Non-Small Cell Lung Cancer: A Meta-Analysis

This study aimed to elucidate the clinicopathological significance of spread through air space (STAS) in non-small cell lung cancer (NSCLC) through a meta-analysis. Using 47 eligible studies, we obtained the estimated rates of STAS in various histological subtypes of NSCLC and compared the clinicopathological characteristics and prognosis between NSCLC with and without STAS. The estimated STAS rate was 0.368 (95% confidence interval [CI], 0.336–0.0.401) in patients with NSCLC. Furthermore, the STAS rates for squamous cell carcinoma and adenocarcinoma were 0.338 (95% CI, 0.273–0.411) and 0.374 (95% CI, 0.340–0.409), respectively. Among the histological subtypes of adenocarcinoma, micropapillary-predominant tumors had the highest rate of STAS (0.719; 95% CI, 0.652–0.778). The STAS rates of solid- and papillary-predominant adenocarcinoma were 0.567 (95% CI, 0.478–0.652) and 0.446 (95% CI, 0.392–0.501), respectively. NSCLCs with STAS showed a higher visceral pleural, venous, and lymphatic invasion than those without STAS. In addition, anaplastic lymphoma kinase mutations and ROS1 rearrangements were significantly more frequent in NSCLCs with STAS than in those without STAS. The presence of STAS was significantly correlated with worse overall and recurrence-free survival (hazard ratio, 2.119; 95% CI, 1.811–2.480 and 2.372; 95% CI, 2.018–2.788, respectively). Taken together, the presence of STAS is useful in predicting the clinicopathological significance and prognosis of patients with NSCLC.

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.

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.

Meta-analysis of Lobectomy and Sublobar Resection for Stage I Non-small Cell Lung Cancer With Spread Through Air Spaces

Surgery is the preferred treatment for early-stage non-small cell lung cancer (NSCLC). Numerous studies have shown that spread through air spaces (STAS) can predict the survival of patients with stage I NSCLC. However, for stage I NSCLC, it is not known whether sublobar resection or lobectomy should be performed if STAS is present. In the present study, we compared the survival outcomes of patients with STAS who underwent lobectomy versus those who underwent sublobar resection. A search was performed on the PubMed, Cochrane Library and EMBASE on March 6, 2021 to identify relevant studies. Predetermined criteria were utilized to screen studies. A meta-analysis was performed using hazard ratio (HR). In total, 13 studies involving 5947 patients were included in the meta-analysis. It was found that STAS was significantly correlated with worse RFS (HR = 2.58, 95% CI: 2.16-3.07) and OS (HR = 2.41, 95% CI: 1.97-2.95) in patients with stage I NSCLC. Lobectomy resulted in a longer RFS (HR = 2.59, 95% CI: 1.99-3.37) and OS (HR = 2.78, 95% CI: 1.92-4.02) than sublobar resection in stage I NSCLC patients with STAS. STAS is an independent prognostic factor in NSCLC. Lobectomy may be more effective for stage I NSCLC patients who underwent sublobar resection previously if STAS is present.

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.

Spread through air spaces (STAS) in invasive mucinous adenocarcinoma of the lung: Incidence, prognostic impact, and prediction based on clinicoradiologic factors

Background

Spread through air spaces (STAS) has recently been demonstrated to exhibit a negative impact on lung adenocarcinoma prognosis. However, most of these studies investigated STAS in nonmucinous adenocarcinoma. Here, we investigated the incidence of STAS in invasive mucinous adenocarcinoma (IMA) of the lung and evaluated whether tumor STAS was a risk factor of disease recurrence in IMA. We also examined clinicoradiologic factors in patients with IMA harboring STAS.

Methods

We reviewed pathologic specimens and imaging characteristics of primary tumors from 132 consecutive patients who underwent surgical resection for IMA to evaluate STAS. Patients with and without STAS were compared with respect to clinical characteristics as well as computed tomography (CT) imaging using logistic regression. The relationships between all variables including STAS and survival were analyzed.

Results

Among a total of 132 patients, full pathologic specimens were available for 119 patients, and STAS was observed in 86 (72.3%). IMA patients with STAS were significantly associated with older age, presence of lobulated and spiculated margins on CT scan (P = 0.009, P = 0.006, and P = 0.027). In multivariate analysis for overall survival (OS), STAS was a borderline independent poor prognostic predictor (P = 0.028). Older age, history of smoking, higher T stage, presence of lymph node metastasis, and consolidative morphologic type remained independent predictors for OS.

Conclusions

STAS was associated with reduced OS and was a borderline independent poor prognostic factor in IMA. IMA with STAS was associated with older age and presence of lobulated and spiculated margins on CT scan.

Key points

Significant findings of the study

Compared with other subtypes, IMA shows a higher incidence of STAS, which is an independent poor prognostic predictor even in IMA. Lobulated and spiculated margins on CT are associated with STAS.

What this study adds

Considering that STAS can carry the potential for aerogenous metastasis, predicting STAS using preoperative surrogate CT imaging is desirable to avoid limited resection.

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.

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.