Adjuvant therapy is associated with improved survival in pT1N1 gastric cancer in a heterogeneous western patient population.

Abstract

36 Background: Two recent South Korean studies showed adjuvant therapy (AT) was not associated with improved survival in pT1N1 gastric adenocarcinoma (GAC). We aimed to establish the prognostic utility of lymph node status, determine the pattern of use of AT, and compare survival stratified by type of AT in pT1N1 GAC in a Western patient population. Methods: We identified patients with pT1N0 and pT1N1 GAC using the National Cancer Database from 2004 to 2012. Clinicopathologic variables, treatment regimens, and overall survival (OS) were compared. Results: We compared 4,516 (86.6%) pT1N0 to 696 (13.4%) pT1N1 patients. pT1N1 tumors were larger (median size 2.5 vs. 1.8 cm, p < 0.001), more often poorly differentiated (56.2% vs. 39.6%, p < 0.001), and had higher median retrieved lymph nodes (RLN) (14 vs. 12, p < 0.001) compared to pT1N0. pT1N1 was associated with worse median OS (6.9 years vs. 9.9 years for pT1N0, p < 0.001). pN1 was independently associated with worse OS (HR 2.17 95% CI 1.84-2.56). Increased RLN was associated with improved OS (HR 0.73, 95% CI 0.65-0.83). Among pT1N1 patients, 330 (47.4%) had observation (OBS), 77 (11.1%) received adjuvant chemotherapy (ACT), 68 (9.8%) received adjuvant radiation therapy (ART), and 221 (31.8%) received adjuvant chemoradiation therapy (ACRT). ACT and ACRT were independently associated with improved OS (HR 0.37, 95% CI 0.22-0.65 and HR 0.40, 95% CI 0.28-0.57). Conclusions: pN1 was associated with worse survival and RLN ≥ 15 was associated with improved survival in pT1 GAC. ACT and ACRT were independently associated with improved survival in pT1N1 gastric cancer suggesting a valuable role in Western patients.