Adjuvant Chemotherapy With or Without Radiotherapy for Resected Pancreatic Cancer After Multiagent Neoadjuvant Chemotherapy

Background: Adjuvant therapy is associated with improved pancreatic cancer survival after neoadjuvant chemotherapy and surgery. However, whether adjuvant treatment should include radiotherapy is unclear in this setting.

Methods: This study queried the National Cancer Database for pancreatic adenocarcinoma patients who underwent curative resection after multiagent neoadjuvant chemotherapy between 2010 and 2019 and received adjuvant treatment. Adjuvant chemotherapy plus radiotherapy (external beam, 45-50.4 gray) was compared with adjuvant chemotherapy alone. Uni- and multivariable Cox regression was used to assess survival associations. Analyses were repeated in a propensity score-matched subgroup.

Results: Of 1983 patients who received adjuvant treatment after multiagent neoadjuvant chemotherapy and resection, 1502 (75.7%) received adjuvant chemotherapy alone and 481 (24.3%) received concomitant adjuvant radiotherapy (chemoradiotherapy). The patients treated with adjuvant chemoradiotherapy were younger, were treated at non-academic facilities more often, and had higher rates of lymph node metastasis (ypN1-2), positive resection margins (R1), and lymphovascular invasion (LVI+). The median survival was shorter for the chemoradiotherapy-treated patients according to the unadjusted analysis (26.8 vs 33.2 months; p = 0.0017). After adjustment for confounders, chemoradiotherapy was associated with better outcomes in the multivariable model (hazard ratio [HR], 0.75; 95% confidence interval [CI], 0.61-0.93; p = 0.008). The association between chemoradiotherapy and improved outcomes was stronger for the patients with grade III tumors (HR, 0.53; 95% CI, 0.37-0.74) or LVI+ tumors (HR, 0.58; 95% CI, 0.44-0.75). In a subgroup of 396 propensity-matched patients, chemoradiotherapy was associated with a survival benefit only for the patients with LVI+ or grade III tumors.

Conclusion: After multiagent neoadjuvant chemotherapy and resection for pancreatic cancer, additional adjuvant chemoradiotherapy versus adjuvant chemotherapy alone is associated with improved survival for patients with LVI+ or grade III tumors.