Lymph node yield in the pathological staging of resected nonmetastatic colon cancer: the more the better?

Introduction: Guidelines recommend regional lymphadenectomy with a lymph node yield (LNY) of at least 12 lymph nodes (LN) for adequate colon cancer (CC) staging. LNY ≥22LN may improve survival, especially in right-sided CC [Lee et al., Surg Oncol, 27(3), 2018]. This multicentric retrospective cohort study evaluated the impact of LNY and tumor laterality on CC staging and survival. Materials and methods: Patients with stage I-III CC that underwent surgery from 2012 to 2018 were grouped according to LNY: <22 and ≥ 22. Primary outcomes were LN positivity (N+ rate) and disease-free survival (DFS). Overall survival (OS) was the secondary outcome. Exploratory analyses were performed for laterality and stage. Results: We included 795 patients (417 < 22LN, 378 ≥ 22LN); 53% had left-sided CC and 29%/37%/38% had stage I/II/III tumors. There was no association between LNY ≥22LN and N+ rate after adjustment for grade, T stage, lymphovascular invasion (LVI) and perineural invasion; a trend for a higher N+ rate in left-sided CC was identified (interaction p = 0.033). With a median follow-up of 63.6 months for DFS and 73.2 months for OS, 254 patients (31.9%) relapsed and 207 (26.0%) died. In multivariate analysis adjusted for age, ASA score, laparoscopic approach, T/N stage, mucinous histology, LVI and adjuvant chemotherapy, LNY ≥22LN was significantly associated with both DFS (HR 0.75, p = 0.031) and OS (HR 0.71, p = 0.025). Restricted cubic spline analysis showed a more significant benefit for right-sided CC. Conclusion: LNY ≥22LN was associated with longer DFS and OS in patients with operable CC, especially for right-sided CC.