Unexpected Para-aortic Lymph Node Metastasis in Pancreatic Ductal Adenocarcinoma: a Contraindication to Resection?

Background: Margin-negative resection is the only cure for pancreatic cancer. However, para-aortic lymph node metastasis is considered a contraindication to curative resection in pancreatic cancer. To determine if there are long-term survival differences according to the presence or absence of para-aortic lymph node metastasis in patients undergoing pancreatectomy, we evaluated oncologic outcomes in resected pancreatic cancer with unexpected para-aortic lymph node metastasis confirmed on intraoperative frozen section biopsy. Methods: We retrospectively investigated 362 patients with pathologically confirmed pancreatic ductal adenocarcinoma who underwent pancreatectomy between 1996 and 2016. Results: Patients with a metastatic para-aortic lymph node had the poorest median disease-specific survival [hazard ratio 14, 95% confidence interval 10-19]. However, after chemotherapy, patients with a metastatic para-aortic lymph node had a much higher disease-specific survival rate (para-aortic lymph node+/postoperative chemotherapy- versus para-aortic lymph node+/postoperative chemotherapy+, P = 0.0003, adjusted P = 0.0015). Patients with a metastatic para-aortic lymph node who underwent postoperative chemotherapy had a similar survival benefit to patients with metastatic regional lymph node without para-aortic lymph node metastasis, regardless of postoperative chemotherapy (para-aortic lymph node+/postoperative chemotherapy+ versus regional lymph node+/postoperative chemotherapy-, P = 0.3047, adjusted P > 0.9999; para-aortic lymph node+/postoperative chemotherapy+ versus regional lymph node+/postoperative chemotherapy+, P = 0.0905, adjusted P = 0.4525). Conclusions: Unexpected para-aortic lymph node metastasis on frozen section biopsy may no longer be a contraindication to curative resection in "resectable" pancreatic ductal adenocarcinoma, as long as postoperative adjuvant chemotherapy can be administered.restrictio