Prognostic value of nodal staging classification and number of examined lymph nodes among patients with ampullary cancer.

BACKGROUND: Metastatic disease in the regional lymph nodes (LNs) is a strong indicator of worse outcomes among patients after curative-intent resection of ampullary cancer (AC). This study aimed to ascertain the threshold number of examined LNs (ELNs) for AC to compare the prognosis accuracy of various nodal classification schemes relative to long-term prognosis.

METHODS: Patients who underwent pancreatoduodenectomy (PD) for AC (2004-2019) were identified using the National Cancer Database. Locally weighted regression scatter plot smoothing (LOWESS) curves were used to ascertain the optimal cut point for ELNs. The accuracy of the American Joint Committee on Cancer N classification, LN ratio, and log odds transformation (LODDS) ratio to stratify patients relative to survival was examined.

RESULTS: Among 8127 patients with AC, 67% were male with a median age of 67 years (IQR, 59-74). Tumors were most frequently classified as T3 (34.9%), followed by T2 (30.6%); T1 (12.9%) and T4 (17.6%) were less common. LN metastasis was identified in 4606 patients (56.7%). Among patients with nodal disease, 37.0% and 19.7% had N1 and N2 disease, respectively. The LOWESS curves identified an inflection cutoff point in the hazard of survival at 20 ELNs. The survival benefit of 20 ELNs was more pronounced among patients without LN metastasis vs patients with N1 disease (median overall survival [OS]: 54.1 months [IQR, 45.9-62.1] in ≥20 ELNs vs 39.0 months [IQR, 35.8-42.2] in <20 ELNs; P < .001) or N2 disease (median OS: 22.5 months [IQR, 18.9-26.2] in ≥20 ELNs vs 25.4 months [IQR, 23.3-27.6] in <20 ELNs; P < .001). When comparing the 4 different N classification schemes, the LODDS classification scheme yielded the highest predictive ability.

CONCLUSIONS: Evaluation of a minimum of 20 LNs was needed to stratify patients with AC relative to the prognosis and to minimize stage migration. The LODDS nodal classification scheme had the highest prognostic accuracy to differentiate survival among patients after PD for AC.