Locally advanced pancreatic adenocarcinoma: reassessment of response with CT after neoadjuvant chemotherapy and radiation therapy.

Purpose: To prospectively evaluate the utility of computed tomography (CT) for determination of tumor response and prediction of resectability after neoadjuvant combined chemotherapy and radiation therapy (CRT) in patients with nonmetastatic locally advanced pancreatic cancer.

Materials And Methods: This study received institutional review board approval, and all participants provided written informed consent. Consecutive patients with cephalic locally advanced pancreatic cancer who underwent surgical exploration and/or resection following neoadjuvant CRT were prospectively enrolled from June 2009 to May 2013. Two radiologists independently analyzed the baseline and post-CRT CT scans for the size, attenuation, and circumferential vascular contacts of the tumor. Associations between the postoperative histologic grade of the tumor response (pTNM) and the clinical, biologic, and CT criteria were assessed by using Spearman correlation coefficients. CT criteria related to the presence of complete (ie, R0) resection were assessed by using logistic regression.

Results: Forty-seven patients were included, 33 with an R0 resection and 14 with positive margins (ie, R1) or no resection. Variables demonstrating a significant correlation with the histologic tumor classification of tumor response were post-CRT carbohydrate antigen 19-9 level (r = 0.46), post-CRT largest tumor axis (r = 0.44), post-CRT sum of the largest and smallest tumor axes (r = 0.46), change in the largest axis (r = -0.31), change in the sum of the largest and smallest axes (r = -0.39), change in superior mesenteric vein (SMV) and/or portal vein (hereafter, SMV/portal vein) contact (r = -0.38), and post-CRT superior mesenteric artery contact (r = 0.34). Partial regression of tumor contact with the SMV/portal vein was associated in all cases with R0 resection (10 of 10 patients, positive predictive value = 100%), and partial regression of tumor contact with any peripancreatic vascular axis was associated with R0 resection in 91% of cases (20 of 22 patients, positive predictive value = 91%). Persistence of SMV/portal vein stenosis after CRT was not predictive of R1 resection.

Conclusion: Partial regression of tumor-vessel contact indicates suitability for surgical exploration, irrespective of the degree of decrease in tumor size or the degree of residual vascular involvement.