A new radiomics approach combining the tumor and peri-tumor regions to predict lymph node metastasis and prognosis in gastric cancer

Abstract

Objective: The development of non-invasive methods for evaluating lymph node metastasis (LNM) preoperatively in gastric cancer (GC) is necessary. In this study, we developed a new radiomics model combining features from the tumor and peri-tumor regions for predicting LNM and prognoses.

Methods: This was a retrospective observational study. In this study, two cohorts of patients with GC treated in Zhongshan Hospital Fudan University (Shanghai, China) were included. In total, 193 patients were assigned to the internal training/validation cohort; another 98 patients were assigned to the independent testing cohort. The radiomics features were extracted from venous phase computerized tomography (CT) images. The radiomics model was constructed and the output was defined as the radiomics score (RS). The performance of the RS and CT-defined N status (ctN) for predicting LNM was compared using the area under the curve (AUC). The 5-year overall survival and progression-free survival were compared between different subgroups using Kaplan-Meier curves.

Results: In both cohorts, the RS was significantly higher in the LNM-positive group than that in the LNM-negative group (all P < 0.001). The radiomics model combining features from the tumor and peri-tumor regions achieved the highest AUC in predicting LNM (AUC, 0.779 and 0.724, respectively), which performed better than the radiomics model based only on the tumor region and ctN (AUC, 0.717, 0.622 and 0.710, 0.603, respectively). The differences in 5-year overall survival and progression-free survival between high-risk and low-risk groups were significant (both P < 0.001).

Conclusions: The radiomics model combining features from the tumor and peri-tumor regions could effectively predict the LNM in GC. Risk stratification based on the RS was capable of distinguishing patients with poor prognoses.

Keywords: gastric cancer; lymph node metastasis; prognosis; radiomics.

Figure 1.

A flow diagram of the patient inclusion and exclusion process. CT, computerized tomography; GIST, gastrointestinal stromal tumor.

Figure 2.

Examples of manually sketching the region of interest at a certain venous phase CT slice. The tumor lesion was delineated as the yellow region (C1) and the 5-mm peri-tumor tissue was delineated as the red region (C2). (A) A 77-year-old man with gastric body cancer in the internal training/validation cohort, stratified as a high-risk patient with a RS (C1+C2) value of 2.03. No lymph node metastasis was found by post-operative pathological examinations. The post-operative survival time was 12 months. (B) A 57-year-old man with gastric body cancer in the internal training/validation cohort, stratified into the low-risk group with a RS (C1+C2) value of 0.05. Pathological examinations confirmed the occurrence of lymph node metastasis. The survival time was >5 years. (C) A 73-year-old man with gastric cardia cancer in the independent testing cohort stratified as a low-risk patient with a RS (C1+C2) value of 1.17. No lymph node metastasis was found by pathological examinations. No disease progression was found during the follow-up period. (D) A 63-year-old woman with gastric body cancer in the independent testing cohort, stratified into the high-risk group with an RS (C1+C2) value of 4.10. The CT images showed enlarged lymph nodes around the tumor. The pathological examinations showed the occurrence of lymph node metastasis. This patient developed disease progression a week after surgery. RS (C1), radiomics score (C1); RS (C1+C2), radiomics score (C1+C2).

Figure 3.

Comparisons among the ROC curves of RS (C1), RS (C1+C2), and ctN for predicting lymph node metastasis. (A) The ROC curves of three characteristics in the internal training/validation cohort. (B) The ROC curves of three characteristics in the independent testing cohort. ROC, receiver operator characteristic curve; RS (C1), radiomics score (C1); RS (C1+C2), radiomics score (C1+C2); ctN, CT-defined N status.

Figure 4.

Kaplan–Meier curves for 5-year overall survival and progression-free survival in different risk groups stratified according to the radiomics score. (A) The 5-year overall survival in the internal training/validation cohort. (B) The progression-free survival of the patients in the independent testing cohort. RS, radiomics score.