External radiation is associated with limited improvement in overall survival in resected margin-negative stage IIB pancreatic adenocarcinoma.

BACKGROUND: The absolute benefit of adjuvant external beam radiation therapy after a margin-negative resection in early stage pancreatic cancer has not been determined.

METHODS: We queried the National Cancer Data Base for patients with pathologic stage I-II pancreatic adenocarcinoma who underwent operative resection between 2004 and 2012. Multivariate Cox regression adjusted for age, race, comorbidities, facility type, location and volume, type of pancreatectomy, and tumor grade was used to estimate stage-specific survival.

RESULTS: A total of 15,966 patients with stage I-II pancreatic adenocarcinoma underwent upfront operative therapy (no neoadjuvant treatment) and had a margin-negative resection during the study period. A total of 835 (5.2%) patients were pathologic stage IA, 1,539 (9.5%) were stage IB, 3,378 (20.9%) were stage IIA, and 10,214 (63.1%) were stage IIB. Chemoradiation utilization increased with increasing stage (22.8% in stage IA vs 39.6% in stage IIB, P < .01). Chemoradiation was more common at low-volume centers (39.0% vs 31.7% at high-volume centers, P < .01) and with younger age (43.3% of patients <70 years old compared to 25.0% ≥70 years old, P < .01). Treatment at a high-volume center was associated with decreased mortality (hazard ratio 0.80-0.89) across all stages. Age ≥70 years old (hazard ratio 1.18-1.29, P < .01) and higher grade (hazard ratio 1.68-2.69, P < .01) were associated with higher risk of mortality at all stages. Chemoradiation was associated with a benefit in median overall survival over chemotherapy alone for stage IIB disease (21.8 months vs 19.5 months, P < .01). Chemoradiation was not associated with a significant benefit in median overall survival for stage IA, IB, or IIA disease (P > .30).

CONCLUSION: Addition of radiation to adjuvant chemotherapy after margin-negative resection of pancreatic adenocarcinoma is associated with a limited survival benefit in patients with pathologic stage IIB disease and should be weighed against its associated risks in these patient groups.