Baseline radiomics features in metastatic colorectal cancer: Correlation with metastatic site and clinical-pathological characteristics

Radiomics is an emerging field of research based on the extraction of a large amount of features from biomedical images and on computed analysis algorithms of tumour architecture. Few data regarding metastatic colorectal cancer (mCRC) are available. In particular, no correlation of baseline radiomics features (RF) both with metastatic (m) sites and clinical-pathological characteristics has been investigated so far. Baseline chest-abdomen CT scans of mCRC patients (pts) were retrospectively analysed. RF were extracted from regions of interest (ROI) delineated on CT scan from each m site, including primary tumor, when on-site. The association of specific F and disease site (liver, lung, nodes, peritoneum and on-site primary tumor) was investigated. Sites similarity was assessed with Principal Component Analysis, an unsupervised learning technique to identify patterns and clusters. Then RFs were tested individually for correlation with clinical-pathological covariates of interest (gender, CEA level, synchronous disease, RAS/BRAF status, mucinous histology, grading, number of m site, primary tumor site). Wilcoxon-Mann-Whitney test was used for this purpose (significance level set at 0.05). After RF extraction from the different ROIs, the dataset was composed of 433 observations of 236 variables. Observations referred to the number (N) of pts = 89 and the N of ROIs = 18. RF classes were divided in statistical F (grey-level histogram) (N of F=10); morphological F (N=14); texture F GLCM (grey level co-occurrence matrix) (N=100); texture F GLRLM (grey level run length matrix) (N=66); texture F GLSZM (grey level size zone matrix) (N=32). Regarding the association of RF with m sites, an homogenous distribution with liver, nodes, peritoneum and primary tumor was detected, while lung metastases showed a different pattern for all the RF classes. A significant correlation of specific RF with clinical-pathologic characteristics was shown, in particular with gender, CEA level, synchronous disease, mucinous histology, RAS/BRAF status. Despite its retrospective nature and the limited number of pts, this is the first experience demonstrating I) a different pattern of RF for lung m versus a homogeneous RF distribution for the other m sites; and II) a significant association of specific RF with few clinical-pathologic characteristics. Our results, if confirmed in a prospective validation set, may represent a hypothesis generator regarding the different behaviour of lung metastases and a possible R signature able to identify different prognostic subgroups of pts.