Abstract
Our study aimed to investigate whether radiomics on MRI sequences can differentiate responder (R) and non-responder (NR) patients based on the tumour regression grade (TRG) assigned after surgical resection in locally advanced rectal cancer (LARC) treated with neoadjuvant chemoradiotherapy (nCRT). Eighty-five patients undergoing primary staging with MRI were retrospectively evaluated, and 40 patients were finally selected. The ROIs were manually outlined in the tumour site on T2w sequences in the oblique-axial plane. Based on the TRG, patients were grouped as having either a complete or a partial response (TRG = (0,1), n = 15). NR patients had a minimal or poor nCRT response (TRG = (2,3), n = 25). Eighty-four local first-order radiomic features (RFs) were extracted from tumour ROIs. Only single RFs were investigated. Each feature was selected using univariate analysis guided by a one-tailed Wilcoxon rank-sum. ROC curve analysis was performed, using AUC computation and the Youden index (YI) for sensitivity and specificity. The RF measuring the heterogeneity of local skewness of T2w values from tumour ROIs differentiated Rs and NRs with a p-value ≈ 10−5; AUC = 0.90 (95%CI, 0.73–0.96); and YI = 0.68, corresponding to 80% sensitivity and 88% specificity. In conclusion, higher heterogeneity in skewness maps of the baseline tumour correlated with a greater benefit from nCRT.
Highlights
Colorectal cancer is the third most common cancer and the second leading cause of oncologic-related mortality in the world [1]
Accurate imaging of the tumour and lymph nodes using high-quality MRI is essential in determining the local staging of rectal cancer, which is a critical marker when deciding whether to perform neoadjuvant chemoradiotherapy (nCRT) [6]
Recent evidence has suggested that 15–27% of patients will achieve a pathological complete response to nCRT before surgery, suggesting that a “wait and watch” approach could be the best choice for these patients, thereby avoiding surgical complications
Summary
Colorectal cancer is the third most common cancer and the second leading cause of oncologic-related mortality in the world [1]. It is more common among men than women, the incidence is rapidly increasing in the female population, and is 3–4 times more common in developed than in developing countries [2]. Accurate imaging of the tumour and lymph nodes using high-quality MRI is essential in determining the local staging of rectal cancer, which is a critical marker when deciding whether to perform nCRT [6]. The percentage of patients who do not achieve tumour regression after nCRT, defined as non-responder (NR) patients, is reported to be between 7 and 30% [7,8]
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