# The Effect of Neoadjuvant Treatment on the Number of Lymph Node Dissection and Prognosis in Locally Advanced Rectal Cancer and Other Factors Affecting Lymph Node Metastasis

## TL;DR

This study examines how neoadjuvant chemoradiotherapy affects lymph node dissection and prognosis in rectal cancer patients, finding that it reduces lymph node count and impacts survival outcomes.

## Contribution

The study identifies factors influencing lymph node count after chemoradiotherapy and their impact on prognosis in rectal cancer.

## Key findings

- Neoadjuvant chemoradiotherapy significantly reduces the number of lymph nodes compared to initial surgery.
- Tumor location, total mesorectal excision, and tumor response to therapy significantly affect lymph node count.
- Metastatic lymph node status and lack of neoadjuvant therapy are associated with poorer overall survival.

## Abstract

Introduction

The current standard treatment for locally advanced rectal cancer is neoadjuvant chemoradiotherapy (CRT), followed by total mesorectal excision. The removal of at least 12 lymph nodes is recommended to accurately stage the disease and predict prognosis, but surgery following neoadjuvant therapy often fails to reach all 12 lymph nodes. This study investigated the changes in lymph node count following chemoradiotherapy and the factors contributing to this change. We also examined the impact of these factors on prognosis.

Materials and methods

A retrospective review was conducted on 250 patients diagnosed with locally advanced rectal cancer between 2012 and 2019. These patients were divided into two groups: those who received neoadjuvant chemoradiotherapy (NACRT) and those who did not. The number of lymph nodes between the two groups and the factors affecting this number were investigated. The distribution of variables was measured using the Kolmogorov-Smirnov test. Cox regression (univariate-multivariate) and Kaplan-Meier regression were used for survival analysis.

Results

Of the patients, 135 received neoadjuvant chemoradiotherapy, and 115 began treatment with initial surgery. The number of lymph nodes was statistically significantly lower in the chemoradiotherapy group (9.5 versus 15.1, p=0.000). Patient comorbidities influenced the initial treatment option and directly affected the number of lymph nodes. Furthermore, tumor location, the use of total mesorectal excision, and the pathological response of the tumor to chemoradiotherapy significantly affected the number of lymph nodes. Multivariate analysis revealed that circumferential resection margin (CRM) negativity was associated with disease-free survival (DFS), while overall survival (OS) was associated with metastatic lymph node status (p=0.01), the lack of neoadjuvant therapy (p=0.00), and impaired total mesorectal excision integrity (p=0.01).

Conclusion

Chemoradiotherapy is the first-line treatment for locally advanced rectal cancer. Chemoradiotherapy reduces the number of lymph nodes. We advocate that pathological tumor response, in addition to lymph node count, should be considered to predict patient prognosis.