The impact of early tumor shrinkage on conversion surgery and the survival in patients with unresectable locally advanced pancreatic cancer

Purposes: Owing to recent advances in induction chemo(radio)therapy, patients with unresectable locally advanced pancreatic ductal adenocarcinoma (UR-LA PDAC) are sometimes indicated for conversion surgery (CS). However, the predictors for proceeding to CS are unclear. We investigated the predictive factors for CS, especially at the early stage of induction therapy, and evaluated the impact of CS on the survival. Methods: We analyzed 49 UR-LA PDAC patients retrospectively and investigated the predictive factors for proceeding to CS, including early tumor shrinkage (ETS). ETS in this study was defined as shrinkage of tumors by ≥ 15% at 8–12 weeks after the induction of treatment. Results: CS was performed in 21 patients (43%). In a multivariate logistic regression analysis, ETS was an independent predictive factor for successfully proceeding to CS (P = 0.046). The median overall survival (OS) was not reached in the CS group but was 17.2 months in the non-CS group (P < 0.0001). A multivariate analysis by the Cox proportional hazard model identified CS as the only significant independent determinant of the OS (hazard ratio: 0.26, 95% confidence interval: 0.07–0.94, P = 0.004). Conclusions: ETS by induction therapy is a significant predictor of proceeding to CS among patients with UR-LA PDAC. CS was the only independent prognostic factor for this population.