CD8+ tumor-infiltrating lymphocyte infiltration prediction with radiomic signature in locally advanced rectal cancer.
123 Background: Despite increasing use of cancer immunotherapies, no biomarker relevant to anti-tumor immunity has been developed in rectal cancer. The present study aims to develop a radiomic signature to predict the infiltration of CD8+ tumor-infiltrating lymphocytes (TILs). Methods: In total, 131 patients undergoing neoadjuvant chemoradiotherapy (CRT) from 2005 to 2012 were analyzed. The study included pre-CRT dataset A ( n = 113; n = 75 and 38 for training and validation) and post-CRT datasets B ( n = 32; predominance of tumor) and C ( n = 20; pure fibrosis). To build the radiomic signature, 38 features selected from pre-CRT T2-weighted MRI scans were incorporated into the least absolute shrinkage and selection operator method. Results: Higher CD8+ TIL infiltration was associated with better overall and progression-free survival ( P = 0.01 and 0.03, respectively). In pre-CRT dataset A, the area under the receiver operating characteristic curve values of radiomic score for predicting CD8+ TILs were 0.760 and 0.729 for training and validation subsets, respectively. A significant correlation was observed between the radiomic signature and CD8+ TIL density in the post-CRT dataset B (Pearson’s R = ‒0.372, P = 0.036), whereas no association was found within the dataset C accounting for pure fibrosis after CRT (Pearson’s R = ‒0.069, P = 0.77). Conclusions: We established the MRI-derived radiomic signature for predicting CD8+ TIL infiltration in the contemporary treatment era of rectal cancer. The noninvasive characterization of tumor immune status would provide insights into the role of radiomic-pathology modeling to predict the local immune phenotypes.