Predictors of conversion surgery in patients with pancreatic cancer who underwent neoadjuvant or palliative FOLFIRINOX treatment using baseline and follow-up CT

Purpose We aimed to evaluate the predictive factors of conversion surgery in pancreatic adenocarcinoma (PAC) after neoadjuvant or palliative FOLFIRINOX using baseline and follow-up CT. Methods We retrospectively included 189 patients who had undergone more than 4 cycles of FOLFIRINOX. We reviewed baseline CT (B-CT), 1st follow-up CT (1st-CT), and the preoperative or last follow-up CT (L-CT) and determined tumor size changes according to the Response Evaluation Criteria in Solid Tumors (RECIST 1.1). Extra-pancreatic perineural invasion (EPNI) and resectability using NCCN 2019 guideline were evaluated. Subgroup analysis by baseline resectability was performed. Results B-CT included resectable (n = 25, 23.2%), borderline (n = 55, 29.1%), locally advanced (n = 44, 23.3%), and metastatic (n= 65, 34.4%) PAC. Seventy-four patients had undergone surgery (39.2%) with an 83.8% (62/74) RO resection. For operability, resectable status at L-CT (hazard ratio (HR) 65.5; 95% confidence interval (CI)5.0-865; P=0.002), RECIST (partial response) at 1st-CT (HR 3.6; 95% CI1.1-11.7; P = 0.032), and baseline borderline resectability (HR8.6; 95% CI1.6-46.4; P = 0.013) were important predictors. Based on a size reduction cut-off of 22.2%, the area under the receiver operating characteristic (ROC) curve (Az) was 0.761 (sensitivity = 70.3%, specificity = 74.8%). In subgroup analysis, RECIST (partial response) at 1st-CT was a significant predictor of locally advanced PAC (HR 32; 95% CI4.5-227, P 0.001), and the optimal cut-off was 22.2% (Az =0.914; sensitivity =100%, specificity =75%). Baseline tumor size (> 4 cm) (HR 5.6, 95% CI1.3-24.3, P=0.022) and unresectable status at 1st-CT (HR4.8, 95% CI1.1-20.6, P=0.035) were significantly associated with margin-positive resection. Conclusion Both baseline and follow-up CT findings are useful to predict conversion surgery for PAC after FOLFIRINOX.