In this study, we developed and validated a tumour-derived radiomics model based on chest CT images for pre-surgical prediction of STAS profiles in lung adenocarcinoma. We incorporated a deep learning approach while fusing clinical data with radiomics data. The predictive performance of the model is excellent compared with general regression models, which can help thoracic surgeons to select the most suitable treatment for patients before surgery.
Spread through air spaces (STAS) is an aggressive behavior of tumors. This aggressive behavior was first identified in lung adenocarcinoma. In subsequent studies, STAS was also found in squamous cell carcinoma and endocrine-related tumors [11–13]. The occurrence of STAS is thought to be associated with advanced age, male patients, serum carcinoembryonic antigen levels and larger tumor size [14]. Several studies have confirmed that the occurrence of STAS is closely associated with poor prognosis in lung cancer patients. This observation has been made in samples of lung adenocarcinoma with different stages [15–16]. STAS is an independent prognostic factor for both recurrence-free survival (RFS) and overall survival (OS). If we can predict in advance whether STAS will occur or not, this benefits the patient's long-term prognosis and survival.
Eguchi T et al. found that in patients with lung adenocarcinoma who developed STAS, undergoing lobectomy had a better outcome than sublobar resection [17]. Therefore, accurate preoperative prediction of STAS status is important for the selection of surgical options for lung cancer patients. Avoiding some STAS lung cancer patients with small tumor sizes will face higher recurrence and metastasis after undergoing local lung resection. With the preoperative prediction of the model, high-risk STAS patients should directly choose lobectomy to replace the currently common clinical practice of wedge resection of the lesion followed by waiting for intraoperative frozen pathology results. It has been shown that the sensitivity of frozen pathological sections to detect the occurrence of STAS is only 59%-86% [18]. This reduces the probability of intracavitary tumor dissemination on the one hand. On the other hand, it also shortens the operation time and reduces the injury of unnecessary anaesthetic drugs and prolonged tracheal intubation.
It has been shown that the diameter of the tumor and the diameter and percentage of the solid component correlate with the development of STAS [19]. Tumor demarcation, pleural retroflexion and tumor contribution have also been used to assess VPI [20–22]. Qi L et al. concluded that the AUC = 0.76 in the model applying consolidation tumor ratio (CTR) to predict STAS [23]. This result is similar to the AUC of the imaging histology-only model in our study. There are previous studies that included preoperative 18F-FDG PET/CT findings [24]. However, due to the high cost of PET/CT, most patients with CT manifestations of small pulmonary nodules do not choose to undergo PET/CT in the first instance. Radiomics has also been applied to predict STAS [25, 26]. Chen D applied imaging histological features for prediction in stage I lung adenocarcinoma and obtained good performance [27]. Currently there are fewer studies on deep learning applied to predict STAS.DL shows great promise in predicting invasiveness of lung cancer and shows good model efficacy in predicting infiltration-non-infiltration scenarios as well as lymph node metastasis. Junli T applies a 3D convolutional neural network model to predict STAS in non-small cell lung cancer, with efficacy better than the general base model [28]. However, the identification and screening of single imaging features is not an easy task even for highly qualified radiology staff.
However, there are still some limitations of this study: 1. The retrospective nature of this study may have some selection bias. 2. This is a single-centre study with a relatively small sample size, and further large studies are needed in the future. External validation was constructed to build a better model to predict STAS.