Prophylactic para-aortic lymph node dissection after neoadjuvant chemotherapy for gastric cancer with bulky lymph node metastasis.

Abstract

344 Background: Neoadjuvant chemotherapy (NAC) followed by D2 gastrectomy with para-aortic lymph node dissection (PAND) is the standard treatment for gastric cancer with extensive lymph node metastasis (ELM) in Japan. ELM includes bulky lymph node metastasis along the celiac artery and its branches (Bulky N2) and metastasis of para-aortic lymph nodes (PAN). However, the benefit of PAND for gastric cancer with Bulky N2 but without PAN involvement is unclear. The aim of this study was to evaluate the efficacy of prophylactic PAND after NAC for this subgroup of patients. Methods: We retrospectively reviewed 21 patients who underwent NAC followed by curative (R0) gastrectomy for Bulky N2 (+) but PAN (-) gastric cancer from 2008 to 2019. Bulky lymph node was defined as one lymph nodes ≥ 3cm or two adjacent lymph nodes ≥ 1.5cm each. PAN metastasis included no. 16a2/16b1 lymph node metastasis. PAND was defined as systematic lymph node dissection of PAN. Patients were divided into two groups: a D2+PAND group (11 patients) and a D2 group (10 patients). We compared the clinicopathological features, recurrence patterns, and survival outcomes between the two groups. Results: The most common NAC regimen was S-1+cisplatin (12 patients: 57%), and other regimens in D2+PAND group included docetaxel+S-1+cisplatin or oxaliplatin. The D2+PAND group had longer operation time (p=0.006), and tended toward more undifferentiated histological type (p=0.063), better pathological response (p=0.086), and higher rate of adjuvant chemotherapy (p=0.090) than the D2 group. The ypStage was similar between the two groups. Pathological PAN metastasis was detected in two patients (18%) in D2+PAND group. Recurrence occurred in seven (70%) patients in D2 group and three (27%) patients in D2+PAND group, and lymph node recurrence was observed in four (40%), and one (10%) patients, respectively. The D2+PAND group had significantly better overall survival, recurrence-free survival, and disease-specific survival than the D2 group (p=0.008, 0.008, and 0.020, respectively). Conclusions: Prophylactic PAND after NAC may reduce recurrence risk for locally advanced gastric cancer with Bulky N2 but without PAN involvement.