Lymph node metrics following neoadjuvant therapy to refine patient selection for adjuvant chemotherapy in resected pancreatic cancer: A multi-institutional analysis

Background: In patients with localized pancreatic ductal adenocarcinoma (PDAC) undergoing neoadjuvant therapy (NAT) and resection, selection of adjuvant chemotherapy (AC) is typically guided by high-risk features on histopathologic examination. We evaluated the interaction between post-NAT lymph node metrics and AC receipt on survival. Methods: Patients who received NAT followed by pancreatectomy (2010–2020) at seven centers were reviewed. Overall survival (OS) in patients receiving AC or not was stratified by lymph node positivity (LNP) or lymph node ratio (LNR) dichotomized at 0.1. Cox models evaluated the independent association between these nodal metrics, AC receipt, and OS. Results: Of 464 patients undergoing NAT and resection, 264 (57%) received AC. Patients selected for AC were younger (median 63 vs. 67 years; p < 0.001), received shorter duration of NAT (2.8 vs. 3.2 months; p = 0.01), had fewer postoperative complications (Clavien–Dindo grade > 3: 1.2% vs. 11.7%; p < 0.001), and lower rates of pathologic complete response (4% vs. 11%; p = 0.01). The median number of nodes evaluated was similar between cohorts (n = 20 in both; p = 0.9). Post-NAT LNP rates were not different, and median LNR was 0.1, in AC and non-AC cohorts. Both LNP (hazard ratio [HR]: 2.1, p < 0.001) and LNR (0 < LNR ≤ 0.1: HR: 1.98, p = 0.002; LNR > 0.1: HR 2.46, p < 0.001) were independently associated with OS on Cox modeling, although receipt of AC was not associated with improved OS (median 30.6 vs. 29.4 months; p = 0.2). In patients with LNR > 0.1, receipt of AC was associated with significantly longer OS compared to non-AC (24 vs. 20 months, respectively; p = 0.04). Conclusions: LNR following NAT, not simply nodal positivity, may be useful to refine selection of AC in resected PDAC.