Comparative effectiveness of adjuvant chemoradiotherapy after gastrectomy among older patients with gastric adenocarcinoma: a SEER-Medicare study

Abstract

Background: Since the INT-0116 trial reported a survival advantage, postoperative chemoradiotherapy (CRT) has been a care standard for US patients in whom gastric adenocarcinoma has been diagnosed. We sought to estimate the association between treatment and survival among the older US Medicare population.

Methods: This is a retrospective cohort study of Medicare beneficiaries aged 65-79 years with stage IB-III gastric adenocarcinoma diagnosed between 2002 and 2009 in a Surveillance, Epidemiology, and End Results region. Patients were categorized on the basis of treatment: (1) gastrectomy only and (2) gastrectomy plus adjuvant CRT. We examined factors associated with receipt of adjuvant CRT, including stage at diagnosis, comorbidity, and tumor subtype. Overall survival was measured from 90 days after gastrectomy until death or the censoring date of December 31, 2010.

Results: Of the 1519 patients who underwent gastrectomy, 41.7% received adjuvant CRT. Factors associated with adjuvant CRT included age younger than 75 years at cancer diagnosis and stage II or stage III cancer. The median overall survival from the time of gastrectomy was 25.1 months (interquartile range 43.7 months) for gastrectomy only and 26.9 months (interquartile range 40.9 months) for adjuvant CRT. Multivariable and propensity-score-stratified models demonstrated a survival benefit associated with adjuvant CRT [hazard ratio (HR) 0.58; 95% confidence interval (CI) 0.50-0.67], although the magnitude was greater for stage II tumors (HR 0.50; 95% CI 0.39-0.61) and stage III tumors (HR 0.58; 95% CI 0.45-0.73) than for stage IB tumors (HR 1.02; 95% CI 0.71-1.45).

Conclusions: Adjuvant CRT, in conjunction with gastrectomy, was associated with a survival benefit among older patients with stage II or stage III tumors.

Keywords: Adjuvant chemoradiotherapy; Comparative effectiveness research; Gastric cancer; SEER–Medicare.

Figure 1. Study Cohort

*Exclusions were sequential. †Based on landmark analysis that determined more than 80% of individuals received adjuvant chemoradiotherapy within 90 days of gastrectomy. ‡No adjuvant therapy within 3 months post-gastrectomy.

Figure 2. Kaplan-Meier Survival Curves Illustrating the Survival of Medicare Beneficiaries Diagnosed with Gastric Adenocarcinoma According to Treatment Regimen

(a) All patients, (b) Patients with stage IB disease, (c) Patients with stage II disease, and (d) Patients with stage III disease. *Number of individuals at risk at 12, 36 and 60 months masked to comply with SEER-Medicare policy for groups <11.