Role of lymph node ratio in selection of adjuvant treatment (chemotherapy vs. chemoradiation) in patients with resected gastric cancer.

Background Recent randomized controlled trials have failed to show a survival difference between adjuvant chemotherapy (CT) and adjuvant chemoradiotherapy (CRT) in patients with resected gastric cancer (GC). However, a subset of patients with lymph node (LN) positive disease may still benefit from CRT. Additional evidence is needed to help guide physicians in identifying patients in whom CRT should be considered. Our objective was then to compare survival outcomes based on lymph node ratio (LNR) (ratio of metastatic to harvested LNs) for patients with gastric and gastroesophageal junction (GEJ) adenocarcinoma treated with surgery and either CT or CRT. Methods This retrospective population-based study used California Cancer Registry (CCR) data from 2004 to 2013. It included 1,493 patients diagnosed with stage IB-III gastric/GEJ adenocarcinoma and treated with CT or CRT following total or partial gastrectomy. Overall survival (OS) was the primary outcome and GC-specific survival was secondary. Mortality hazards ratios (HR) for these outcomes were computed using propensity score weighted Cox regression models, stratified by LNR strata categories as 0%, 1-9%, 10-25% and >25%. Results Out of 1,493 patients that met inclusion criteria, 462 were treated with CT while 1,031 received CRT. Median follow-up for all subjects was 76 months and median survival was 54 months for CRT and 35 for the CT cohort, P<0.001. Compared to CT, CRT was associated with improved survival among patients with LNR of 10-25% [HR =0.62 (95% CI, 0.46-0.83)] and >25% [HR =0.67 (95% CI, 0.56-0.80)]. Similar findings were observed for GC-specific survival and for analyses limited to patients that had at least 15 LNs evaluated. Conclusions LNR appears to be a simple and readily available measure that could be used in treatment planning for resected GC. CRT offers significant survival advantage over CT among patients with high LN disease burden (LNR of ≥10%).