PV QA 1 - Poster Viewing Q&A 1
Purpose/Objective(s): Many adjuvant treatment regimens exist for gastric cancers which include chemotherapy, radiation, or both. It is unclear which regimen has the best benefit. We assess the benefit of adjuvant chemoradiation (CRT) for resectable gastric cancers and prognostic factors associated with adjuvant treatment.
Materials/Methods: We included patients from 2004-2014 with pathologic IIA-IIIC gastric adenocarcinoma, negative margins, and ≥11 lymph nodes removed. Exclusion criteria included a prior cancer diagnosis, neoadjuvant treatment, perioperative treatment, and unknown adjuvant radiation or systemic therapy. Treatments compared include no adjuvant therapy (no Tx), post-operative radiation alone (RT), chemotherapy (CT) alone, or post-operative chemoradiation (CRT). Multivariate Cox regression was used to identify factors associated with improved OS.
Results: We identified a total of 9,233 patients with a median follow-up of 56.57 months (IQR 35.42-80.82) and median survival of 37.3 months (95% CI: 35.6-39.3 months). Most patients were treated with adjuvant CRT (n=2706, 29%), no adjuvant treatment (n=2525, 27%), and adjuvant CT (n=1089, 11%). Adjuvant RT alone was least utilized (n=99, 1%). Adjuvant CRT had a significant OS benefit compared to chemotherapy alone (HR 0.88, 95% CI 0.79-0.97, p=0.01). Other factors associated with improved OS include Asian race (vs. White HR 0.64, 95% CI 0.57-0.71, p<0.001), and early T-stage. Worse OS was associated with age ≥65 (HR 1.59, 95% CI: 1.40-1.80, p<0.001), +LVI (HR: 1.12, 95% CI: 1.01-1.25, p=0.038), and stage III disease (vs. Stage II; pIIIA HR1.71, 95% CI: 1.55-1.90, p<0.001; pIIIB HR 2.36, 95% CI: 2.10-2.65, p<0.001; pIIIC HR 3.18, 95% CI: 2.75-3.67, p<0.001), and higher grade (HR: 1.59, 95% CI: 1.22-2.05, p<0.001). For diffuse histologies (N=530), improved OS was associated with adjuvant CT (vs. no Tx, HR 0.47, p=<0.001), CRT (HR 0.52, p<0.001), and Asian/Pacific Islander race (HR 0.59, 95% CI: 0.40-0.88, p=0.009). Worse OS is associated with stage pIIIB (vs. pII, HR 2.48, 95% CI: 1.46-4.22, p<0.001) and pIIIC (HR 3.18, 95% CI: 1.73-5.59, p<0.001).
Conclusion: Adjuvant treatment for post-op stage II or higher gastric adenocarcinomas with chemoradiation has an OS benefit compared to chemotherapy. Over a quarter of patients do not receive adjuvant treatment and have worse survival. Diffuse histologies also benefit from adjuvant chemotherapy or chemoradiation and Asians/Pacific Islanders have improved survival compared to other races. Further studies are ongoing to identify the best adjuvant regimens.
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