Prediction of tumor regression grade and identification of prognostic factors using CT and biological features in patients with pancreatic cancer who underwent surgery after neoadjuvant therapy

Background Radiological response of pancreatic ductal adenocarcinoma (PDAC) to neoadjuvant chemoradiation therapy (CRT) is challenging to assess. Purpose To evaluate whether computed tomography (CT) and biological features can predict tumor regression grade (TRG), recurrence-free survival (RFS), and overall survival (OS) of patients who undergo surgery after CRT for PDAC. Material and Methods This retrospective study included 125 patients who underwent surgery after CRT for non-metastatic PDAC between January 2013 and March 2021. Two board-certified radiologists independently reviewed initial and post-CRT CT images and assessed the primary tumor extent and regional lymph node metastasis. Another board-certified radiologist quantitatively assessed the primary tumor on pre- and post-CRT diffusion-weighted and positron emission tomography images. Logistic regression and Cox regression analyses were performed to identify predictors of TRG 0/1, RFS, and OS. Results In total, 44 (35.2%) patients had a TRG of 0/1. The normalized post-CRT carbohydrate antigen (CA) 19–9 level (<37 IU) (odds ratio [OR] = 3.69; P = 0.024) and adjacent organ invasion on post-CRT CT images (OR = 0.24; P = 0.042) were independent predictors of TRG 0/1. During follow-up (mean = 33.6 months), 68 (54.4%) patients experienced tumor recurrence and 65 (52.0%) died. The normalized post-CRT CA 19-9 level (<37 IU) (hazard ratio [HR] = 0.51; P = 0.028) was a significant predictor of RFS, and size change (%) after CRT (HR = 0.24; P = 0.044) was an independent predictor of OS. Conclusion The normalized post-CRT CA 19-9 level and adjacent organ invasion on post-CRT CT images predicted TRG. The normalized post-CRT CA 19-9 level was associated with RFS, whereas size change was an independent predictor of OS.