Standardize the surgical technique and clarify the oncologic significance of robotic D3-D4 lymphadenectomy for upper rectum and sigmoid colon cancer with clinically more than N2 lymph node metastasis

Abstract

Background: The territory of D3-D4 lymphadenectomy for upper rectal and sigmoid colon cancer varies, and its oncological efficacy is unclear. This prospective study aimed to standardize the surgical technique of robotic D3-D4 lymphadenectomy and clarify its oncologic significance. Methods: Patients with upper rectal or sigmoid colon cancer with clinically suspected more than N2 lymph node metastasis were prospectively recruited to undergo standardized robotic D3-D4 lymphadenectomy. Immediately postsurgery, the retrieved lymph nodes were mapped to five N3-N4 nodal stations: the inferior mesenteric artery, para-aorta, inferior vena cava, infra-renal vein, and common iliac vessels. Patients were stratified according to their nodal metastasis status to compare their clinicopathological data and overall survival. Univariate and multivariate analyses were performed to determine the relative prognostic significance of the five specific nodal stations. Surgical outcomes and functional recovery of the patients were assessed using the appropriate variables. Results: A total of 104 patients who successfully completed the treatment protocol were assessed. The standardized D3-D4 lymph node dissection harvested sufficient lymph nodes (34.4±7.2) for a precise pathologic staging. Based on histopathological analysis, 28 patients were included in the N3-N4 nodal metastasis-negative group and 33, 34, and nine patients in the single-station, double-station, and triple-station nodal metastasis-positive groups, respectively. Survival analysis indicated no significant difference between the single-station nodal metastasis-positive and N3-N4 nodal metastasis-negative groups in the estimated 5-year survival rate [53.6% (95% CI: 0.3353–0.7000) vs. 71.18% (95% CI: 0.4863–0.8518), P=0.563], whereas patients with double-station or triple-station nodal metastatic disease had poor 5-year survival rates (24.76 and 22.22%), which were comparable to those of AJCC/UICC stage IV disease than those with single-station metastasis-positive disease. Univariate analysis showed that the metastatic status of the five nodal stations was comparable in predicting the overall survival; in contrast, multivariate analysis indicated that common iliac vessels and infra-renal vein were the only two statistically significant predictors (P<0.05) for overall survival. Conclusions: Using a robotic approach, D3-D4 lymph node dissection could be safely performed in a standardized manner to remove the relevant N3-N4 lymphatic basin en bloc, thereby providing significant survival benefits and precise pathological staging for patients. This study encourages further international prospective clinical trials to provide more solid evidence that would facilitate the optimization of surgery and revision of the current treatment guidelines for such a clinical conundrum.