Background: Change in tumor size at CT is insufficient for reliable assessment of treatment response after neoadjuvant chemotherapy and radiation therapy (CRT) and shows poor correlation with histologic grading of response. Purpose: To investigate the use of perfusion CT to predict the response of pancreatic ductal adenocarcinoma (PDA) to CRT. Materials and Methods: Between June 2016 and May 2018, study participants with biopsy-proven PDA were prospectively recruited to undergo perfusion CT before and after planned CRT. Blood flow (BF), blood volume (BV), and permeability-surface area product (PSP) were quantified from CT images. Participants were categorized into responders and nonresponders according to therapy response. The Mann-Whitney test was used to compare the baseline perfusion values between responders and nonresponders, and the Wilcoxon matched-pairs signed rank test was used to compare perfusion values before and after CRT. Results: The final cohort of 21 participants (median age, 68 years; interquartile range [IQR], 65-72 years; eight men) underwent dynamic perfusion (dual-source) CT before neoadjuvant CRT. All participants underwent pancreatectomy. Eighteen participants underwent post-CRT perfusion CT. Baseline BF was higher in responders (n = 10) than in nonresponders (n = 11) (median, 44 [IQR, 39-56] vs 28 [IQR, 16-52] mL/100 g/min; P = .04), while BV and PSP were similar between groups (median BV, 4.3 [IQR, 3.5-6.9] vs 2.0 [IQR, 1.6-6.5] mL/100 g, P = .15; median PSP, 25 [IQR, 21-30] vs 20 [IQR, 10-34] mL/100 g/min, P = .31). Response Evaluation Criteria in Solid Tumors (RECIST) and carbohydrate antigen (CA) 19-9 showed no correlation with perfusion parameters (eg, RECIST and BF: R = 0.05, P = .84, 95% confidence interval [CI]: 20.40, 0.48; CA 19-9 and BF: R = 0.06, P = .78, 95% CI: 20.39, 0.49) or histopathologic response (r = 0.16, P = .47, 95% CI: 20.3, 0.57 and r = 0.09, P = .71, 95% CI: 20.37, 0.51, respectively). For responders, perfusion parameters increased after CRT (eg, median BF, 54 [IQR, 42-73] vs 43 [IQR, 28-53] mL/100 g/min; P = .04). The perfusion change in nonresponders was not significant (median BF, 43 [IQR, 28-53] vs 33 [IQR, 16-52] mL/100 g/min; P = .06). Conclusion: Perfusion CT may be useful in helping predict the histopathologic response to therapy in pancreatic ductal adenocarcinoma.
