Surgical indication for and desirable outcomes of conversion surgery in patients with initially unresectable pancreatic ductal adenocarcinoma

Aim of this review is to propose an acceptable surgical indication for conversion surgery in patients with initially unresectable (UR) pancreatic ductal adenocarcinoma (PDAC) by considering desirable outcomes, including resectability, overall survival (OS), and disease‐free survival (DFS). A comprehensive literature search of PubMed was conducted through July 15, 2019. Eligible studies were those reporting on patients with UR‐PDAC who underwent surgery. We excluded case reports with fewer than 10 patients, insufficient descriptions of survival data, and palliative surgery. When patients with UR‐PDAC with no progression after chemo(radiation) therapy were offered surgical exploration, resectability and median survival time (MST) of those who underwent conversion surgery ranged from 20% to 69% (median, 52%) and from 19.5 to 33 months (median, 21.9 months), respectively. When conversion surgery was carried out in patients with expected margin‐negative resection or with clinical response by Response Evaluation Criteria In Solid Tumors (RECIST), resectability and MST ranged from 18% to 27% (median, 20%) and from 21 to 35.3 months (median, 30 months), respectively. Among patients who underwent conversion surgery based on clinical response and decreased CA19‐9 level after multimodal treatment, resectability and MST ranged from 2% to 24% (median, 4.1%) and from 24.1 to 64 months (median, 36 months), respectively. Decreased CA19‐9 level was a predictor of resectability, OS and DFS by multivariate analysis. In conclusion, decision‐making for conversion surgery based on clinical response and decreased CA19‐9 level after multimodal treatment may be appropriate. With regard to desirable outcomes of OS and DFS, conversion surgery may provide improved survival for patients with initial UR‐PDAC.