Dissecting Tumor Size Underestimation in Pancreatic Cancer: A Comparative Analysis of Preoperative Treatments.

BACKGROUND

Tumor size (TS) in pancreatic ductal adenocarcinoma (PDAC) is one of the most important prognostic factors. However, discrepancies between TS on preoperative images (TSi) and pathological specimens (TSp) have been reported. This study aims to evaluate the factors associated with the differences between TSi and TSp.

PATIENTS AND METHODS

We retrospectively analyzed patients with PDAC who underwent surgery at our institution between January 2010 and November 2023. TS discrepancy (TSD[%]) was defined as ([TSp - TSi]/TSp) × 100. Using logistic regression, we generated a receiver operating characteristic (ROC) curve to define the cutoff for TSi underestimation predicting clinical tumor (T) stage migration. Univariate and multivariate analyses were performed to evaluate predictors of TSi underestimation.

RESULTS

Of the 231 patients, 99 (42%) patients received preoperative chemotherapy. The ROC curve determined a TSD underestimation cutoff of 25.9%. The number of TSp > TSi cases was 185 (80%), and TSi underestimation was present in 117 (51%) patients. T stage migration rates were 76%, 26%, and 50% in clinical stage (c) T1, cT2, cT3, respectively, among the patients with chemotherapy, and 93%, 33%, and 14%, respectively, in those without chemotherapy. Multivariate analyses revealed that independent predictors of TSi underestimation were posterior surface invasion in the patients with preoperative chemotherapy and anterior surface invasion in those without chemotherapy.

CONCLUSIONS

TS was more commonly underestimated than overestimated, and cT1 rarely corresponded to pathological (p)T1. The factors contributing to TSi underestimation differed between patients with and without preoperative chemotherapy. Therefore, these two groups should be considered separately for accurate TSi evaluation.