Td-dMRI for early predicting pCR to neoadjuvant short-course radiotherapy followed by camrelizumab and chemotherapy in LARC

Motivation: pCR assessment for immunotherapy is challenging for radiologists. Goal(s): To investigate the feasibility of time-dependent diffusion MRI (td-dMRI) in early predicting pathological complete response (pCR) to neoadjuvant short-course radiotherapy followed by camrelizumab and chemotherapy in locally advanced rectal cancer (LARC). Approach: td-dMRI data were fitted with a two-compartment model to estimate cell diameter (d), intracellular volume fraction (fin), cellularity, extracellular diffusivities (Dex). Histogram of the microstructural parameters of td-dMRI were calculated. ROC curves were generated to evaluate the power of prediction for pCR. Results: For predicting pCR, the post-D17Hz-ske and post-dske were finally entered into the prediction model, with the AUC of 0.947. Impact: Time-dependent diffusion MRI has potential in characterizing changes of cellular tissue microstructures after short-course radiotherapy and then predicting pCR to neoadjuvant treatment including immunotherapy, which may promote the clinical application of immunotherapy in LARC.