Prognostic value of lymph node ratio and extramural vascular invasion on survival for patients undergoing curative colon cancer resection

Clinical Significance of International Union Against Cancer pN Staging and Lymph Node Ratio in Node-Positive Colorectal Cancer after Advanced Lymph Node Dissection

BACKGROUND

Lymph node retrieval in colorectal cancer can be improved by using advanced histopathological techniques like methylene blue-assisted lymph node dissection, which results in a doubling or even tripling of the lymph node count in comparison with conventional lymph node dissection techniques. However, it is not clear whether the established lymph node staging systems are suitable for predicting patients' prognoses under these circumstances.

OBJECTIVE

The aim of this study was to determine whether the current lymph node staging systems are suitable when advanced dissection methods are used.

DESIGN

This is a retrospective cohort study.

SETTING AND PATIENTS

We formed a study group (methylene blue-assisted lymph node dissection) of 293 patients and a control group (conventional lymph node dissection) of 232 patients, each with node-positive cases. Conventional pN staging according to the International Union Against Cancer, seventh edition, and lymph node ratio were applied.

MAIN OUTCOME MEASURES

Overall survival was compared by using the different staging systems in a uni- and multivariable fashion.

RESULTS

The lymph node ratio values were reduced in the advanced methylene blue-assisted lymph node dissection group in comparison with the conventional lymph node dissection group (0.1 vs 0.3, p < 0.001). Although pN staging proved to be reliable, the cutoff values for lymph node ratio staging had to be adapted. The new cutoffs (0.07, 0.15, and 0.34) were prognostic. However, multivariable analysis revealed pN staging and vascular invasion, but not lymph node ratio, as independently prognostic in the methylene blue-assisted lymph node dissection group.

LIMITATIONS

The study group and historical control group are not perfectly balanced because the case number in the stage III subgroup of the control group is small.

CONCLUSIONS

pN staging proved to be a robust prognostic marker in colorectal cancer under the circumstances of improved lymph node harvest. After adaptation of the cutoff values, lymph node ratio is also prognostic but not superior to pN staging.

Complete mesocolic excision and extended (D3) lymphadenectomy for colonic cancer: is it worth that extra effort? A review of the literature

PURPOSE

Recent interest in complete mesocolic excision (CME) with central vascular ligation (CVL) or extended (D3) lymphadenectomy (EL) for curative resection of colon cancer has been driven by published series from experienced practitioners showing excellent survival outcomes and low recurrence rates. In this article, we attempt to clarify the role of CME or EL in modern colorectal surgery.

METHODS

A narrative review of the evidence for CME and EL in the curative treatment of colon cancer.

RESULTS

The principal of CME surgery, similar to total mesorectal excision (TME) for rectal cancer, is the removal of all lymphatic, vascular, and neural tissue in the drainage area of the tumour in a complete mesocolic envelope with intact mesentery, peritoneum and encasing fascia. Extended (D3) lymphadenectomy (EL) is based on similar principles. Sound anatomical and oncological arguments are made to support the principles of removing the tumor contained within an intact mesocolic facial envelope together with an extended lymph node harvest. Excellent oncological outcomes with minimal morbidity and mortality have been reported. This has led to calls for the standardisation of surgery for colon cancer using CME. However, there is conflicting evidence regarding the prognostic benefit of greater lymph node harvests and the evidence for an oncological benefit of CME is limited by methodology flaws and several potential confounding factors.

CONCLUSIONS

Although there is a reasonable anatomical and oncological basis for these techniques, there are no randomised controlled trials from which to draw confident conclusions and there is insufficient consistent high quality evidence to recommend widespread adoption of CME.

A Comprehensive Study of Extramural Venous Invasion in Colorectal Cancer

Colorectal cancer is a common malignancy and a leading cause of cancer related death. Cancer staging following resection is key to determining any adjuvant therapy in those patients with high risk disease. In colorectal cancer, tumour stage and lymph node stage are the main pathological factors which have been considered to influence outcome. Increasing emphasis is now being placed on other factors, especially the presence of extramural venous invasion (EMVI). It is important to understand the relationship of EMVI with other pathological factors and to confirm that in an individual centre that EMVI is being detected at an appropriate rate and is of prognostic significance. This comprehensive study assesses the reporting and prognostic significance of EMVI in a single centre, using prospectively collected data from histopathology reports of a cohort of 2405 patients who underwent surgery for colorectal cancer over a nine year period. Overall, EMVI was reported in 27.9% of colorectal cancer excision specimens. In tumours (n = 1928) that had not received neoadjuvant therapy, the presence of EMVI varied significantly depending on tumour site (χ2 = 12.03, p<0.005), tumour stage (χ2 = 268.188, p<0.001), lymph node stage (χ2 = 294.368, p<0.001) and Dukes' stage (χ2 = 253.753, p<0.001). Multivariate analysis confirmed EMVI as a significant independent prognostic indicator (p<0.001). In conclusion, the presence of EMVI as an independent prognostic indicator is shown and is related to other pathological and prognostic factors. This study emphasises the requirement for the accurate identification of EMVI in colorectal cancer excision specimens and also understanding the relationship of EMVI with other prognostic factors.