The radiological morphology of mesopancreas: A new variable to predict a positive vascular margin after pancreatoduodenectomy for pancreatic ductal adenocarcinoma?

Abstract

615 Background: The most frequently invaded surgical margins on pancreatoduodenectomy (PD) specimens of pancreatic ductal adenocarcinoma (PDAC) are vascular margins, especially the superior mesenteric artery (SMA), also called mesopancreatic margin. Considering embryology, it may be hypothesized that PDAC cells tend to infiltrate the retroperitoneum through the contents of mesopancreas, justifying the frequent SMA positive margin. Because the radiological aspect of mesopancreas has been poorly studied, the aim of this original research was to assess the mesopancreatic infiltration on diagnostic imaging, corroborate with the corresponding margin pathology and evaluate the impact on survival in PDAC patients who underwent PD. Methods: From 2015 to 2021, all patients who underwent PD for PDAC with curative intent were reviewed, excluding patients lost to follow-up, who died postoperatively or within the first year for non-oncological reason, and those with unavailable preoperative imaging. Surgical margins of pathological specimens were reassessed. Blinded reviewing of preoperative radiographic images was conducted. According to qualitative assessment, the mesopancreas tissue was defined as normal fat (NF), fat stranding (FS) or solid infiltration (SI). Results: 133 patients were included in the study, including 51 (38%) who received neoadjuvant therapy. The tumor location was into the head or the uncinate process in 54% and 46%, respectively. At diagnosis, PDAC were classified as resectable (51%), borderline resectable (28%) and locally advanced (9%) according to the NCCN classification. FS or SI in the mesopancreas was present in 45 (34%) and 18 (14%) patients, respectively. Tumor size on imaging, tumor location, chronic obstructive pancreatitis, vascular contacts and NCCN resectability status were predictive factors of mesopancreas infiltration (p<0.001). Median overall and disease-free survivals were significantly lower in case of SI compared to NF and FS in the mesopancreas. When comparing patients with mesopancreatic FS at diagnosis who received neoadjuvant therapy (n=20) to those who underwent upfront surgery (n=25), no significant impact was observed in survivals. R0 resection was obtained in 36%; in all patients with R1 resection, a vascular margin was involved. Tumor size at pathology, SMA margin and resection status were factors that were significantly influenced by the radiological infiltration of the mesopancreas. Conclusions: The SI of mesopancreas on diagnostic imaging was associated with a poor prognosis, but not FS, in patients who underwent PD for PDAC. SMA margin and resection status were correlated with the radiological texture of the mesopancreas, which suggests to further explore underlying mechanisms related to tumoral invasion of vascular margin and mesopancreas.