Comment on: "Reassessment of the Optimal Number of Examined Lymph Nodes in Pancreatoduodenectomy for Pancreatic Ductal Adenocarcinoma".

Abstract

We read with great interest the article by Malleo et al1 on the reassessment of the optimal examined lymph node (ELN) in pancreatoduodenectomy for pancreatic ductal adenocarcinoma. Malleo et al1 suggested that 28 and 25 ELNs as the optimal and minimal cutpoints, respectively, significantly improved the detection of N2 disease. We highly appreciate the authors for this innovative statistical method and exciting finding. It is of great clinical significance and may aid in survival prediction and clinical decision-making. However, one of the study’s main points needs further discussion. This study by Malleo et al,1 to determine the optimal or minimal ELNs, was conducted in all patients and ignored the effect of T stage on the optimal ELNs. Current studies found that the optimal ELNs for accurate staging was associated with T stage. Hua et al2 confirmed that the optimal ELNs for the adequate staging of pancreatic cancer was related to the T stage and suggested that at least 16, 21, and 23 ELNs should be examined for T1, T2, and T3 pancreatic cancer, respectively. Similar conclusions were reached in studies of colon and thyroid cancers, strongly implying that the higher the T stage of the tumor, the greater the optimal or minimal ELNs required for accurate staging.3,4 By analyzing the data in Table 1, we found that the proportion of patients with N2 increased with advancing T stage: 35.0%, 51.0%, and 54.7% for T1, T2, and T3 patients (P < 0.001), respectively. Marchegiani et al5 also confirmed that larger pancreatic tumors were associated with more positive lymph nodes and higher lymph node ratios (P < 0.05). This strongly indicated that the risk of staging patients with N2 disease was associated with the T stage. In fact, adequate ELN not only improves the accuracy of lymph node staging but also increases the chance of eradicating isolated tumor cells and micrometastases. Specifically, surgeons may need to examine as many lymph nodes as possible to detect N2 disease and enhance the chance of eradicating isolated tumor cells and micro-metastases in T3 patients. Conversely, for T1 patients, examining more lymph nodes seems less important. Currently, precision medicine, which is based on individual diagnosis and treatment, is at the forefront of cancer research. It brings hope for improving the prognosis of pancreatic cancer. Blindly performing extended lymph node dissection does not improve the prognosis of patients with pancreatic cancer. Instead, extended lymphadenectomy is associated with increased morbidity, operating room time, and length of stay.6 With the advances in medical imaging technology, the T stage is easily obtained in preoperative imaging and may provide guidance on the extent of lymph node dissection. Therefore, optimal and minimal ELN based on the T stage can encourage surgeons to develop individualized lymph node dissection protocols rather than a one-size-fits-all approach, which is also consistent with the essence of precision medicine.