Benefit of Adjuvant Chemoradiotherapy for Gastric Adenocarcinoma: A SEER Population Analysis.

Background: Despite results of the Intergroup 0116 (INT-0116) study showing an overall survival benefit of adjuvant chemoradiotherapy in gastric adenocarcinoma, its use in the United States remains controversial. The Surveillance Epidemiology of End Results (SEER) database was used to compare cause-specific survival outcomes in resected gastric adenocarcinoma with various adjuvant therapies and patterns of care.

Methods: Individual data from 1988 to 2008 were selected for patients with resected, nonmetastatic gastric adenocarcinoma. These patients were stratified by stage (American Joint Committee on Cancer [AJCC], 6th edition), as well as treatment modalities (surgery alone, S; surgery followed by radiotherapy, SR; surgery with chemotherapy, SC; surgery followed by radiotherapy with chemotherapy, SRC; and radiotherapy followed by surgery with chemotherapy, RSC). Overall 21,472 patients (8335 stages IA and 1B; 5944 stage II, 4594 stage III, and 2599 stage IV) were included in this study.

Results: The median age of the cohort was 66 years, with 63.0% male and 66.4% white. The median number of lymph nodes examined was 17.6. Median survival by stage was 96 months for stage I, 30 months for stage II, 20 months for stage III, and 14 months for stage IV. Using the SRC group as the reference group, for stage I patients, S had the most favorable cause-specific survival (hazard ratio [HR], 0.67; confidence interval, [CI] 0.60-0.76). For patients with stage II, III, or IV, those treated with SRC had the best outcome compared with the other treatment modalities. After 1999, the number of patients treated with surgery alone decreased by at least 14%, whereas the number treated with SRC increased by approximately 12%.

Conclusions: This large SEER database analysis showed that stage I patients benefited most from surgery alone, whereas those at more advanced stages benefited most from adjuvant radiotherapy with chemotherapy. This result is consistent with INT-0116 for gastric adenocarcinoma in support of trimodality therapy and is reflected by the increased fraction of patients receiving chemotherapy and adjuvant radiation.