Neglected lymph nodal metastases in patients with renal cancer: when to extend the anatomical template of lymph node dissection during nephrectomy

Background The role of lymph node dissection (LND) in patients with renal cell carcinoma (RCC) is still controversial. However, detecting lymph node invasion (LNI) is key due to prognostic implications and to identify patients who might benefit from adjuvant therapies such as adjuvant pembrolizumab. Materials and methods Out of 796 patients, 261 (33%) received eLND, of whom 62 (8%) for suspicious lymph node (LN) metastases at preoperative staging (cN1). eLND was divided in 3 anatomical areas: (1) hilar, (2) side-specific (pre-/para-aortic or pre-/para-caval) and (3) inter-aorto-caval nodes. Overall maximum LN diameter was measured by a dedicated radiologist for each patient. Multivariable logistic regression models (MVA) were tested for the effect of maximum LN diameter in predicting the presence of nodal metastases outside the anatomical area of cN1. Results LNI was confirmed in 50% of cN1, whilst only 13 out of 199 cN0 patients were pN1 at final histology (6.5%; p < 0.001). In a per-patient analysis, of 62 cN1 patients, 24% vs. 18% vs. 8% harboured pN1 disease only inside vs. in-outside vs. only outside the suspicious anatomical field of cN1 at preoperative CT/MRI scan. At MVA, increasing diameter of suspicious LNs was independently associated with risk of finding positive LNs outside the suspicious anatomical field (OR 1.05, 95%CI 1.02–1.11; p = 0.02). Conclusions Roughly 50% of cN1 patients undergoing eLND will harbour LN metastases, also outside the suspicious radiological area, and maximum LNs diameter at preoperative imaging correlates with such risk. Thus, an eLND might be justified in patients with large suspicious LN metastases, to better stage this patient population and to improve postoperative treatment management.