Adjuvant chemotherapy versus observation following neoadjuvant therapy and surgery for resectable stage I-II pancreatic cancer.

Abstract

Background: Neoadjuvant therapy (NT), either with systemic treatment alone or in combination with radiation, is often utilized in the management of pancreatic adenocarcinoma to increase the likelihood of margin-negative resection. Following NT and resection, additional adjuvant chemotherapy (AC) can be considered for select patients and has been shown to improve overall survival (OS). This National Cancer Data Base (NCDB) analysis was performed to evaluate the outcomes of AC versus observation for resected pancreatic adenocarcinoma treated with NT.

Methods: The NCDB was queried for primary stage I-II cT1-3N0-1M0 resected pancreatic adenocarcinoma treated with NT (2004-2015). Baseline patient, tumor, and treatment characteristics were extracted. The primary endpoint was OS. With a 6-month conditional landmark, Kaplan-Meier analysis, multivariable Cox proportional hazards method, 1:1 propensity score matching were used to analyze the data.

Results: A total of 1737 eligible patients were identified, of which 1247 underwent postoperative observation compared to 490 with AC. The overall median follow-up was 34.7 months. The addition of AC showed improved survival on the multivariate analysis (HR 0.78, p<0.001). Of 490 propensity-matched pairs, all variables were well balanced, including age (p=0.61), Charlson-Deyo comorbidity score (p=0.80), ypT stage (p=0.93), ypN stage (p=0.83), surgical margin (p=0.83), duration of postoperative inpatient admission (p=0.96), and 30-day unplanned readmission after resection (p=0.34). AC remained statistically significant for improved OS, with median OS of 26.3 months vs 22.3 months and 2-year OS of 63.9% vs 52.9% for the observation cohort (p<0.001). Treatment interaction analysis showed OS benefit of AC for patients with smaller tumors (HR 0.67, p<0.001 for <3.1 cm vs HR 0.93, p=0.48 for ≥3.1 cm).

Conclusion: Using propensity score matched analysis, our findings suggest a survival benefit for adjuvant chemotherapy compared to observation following NT and surgery for resectable pancreatic adenocarcinoma, especially in patients with smaller tumors. Prospective studies are needed to identify subset of patients that would benefit from adjuvant chemotherapy.