2747 - Neoadjuvant chemoradiotherapy with/without lateral lymph node dissection for low rectal cancer: Which patients can benefit?

Background

Guidelines for rectal cancer treatment differ in Japan, Europe, and the United States. Neoadjuvant chemoradiotherapy (CRT) has been used to control lateral lymph nodes (LLNs) in the West. The usefulness of LLN dissection (LLND) has been discussed in Japan, and a randomized study stated the possible advantage of local control. However, it is still unclear whether adding LLND to CRT is beneficial.

Methods

To investigate the effectiveness of LLND on rectal cancer patients who underwent neoadjuvant CRT, we retrospectively collected magnetic resonance images (MRIs) in a cohort of 1500 patients with cStage II/III lower rectal cancer below the peritoneal reflection and centrally reviewed MRIs. We measured short-axis LLN sizes on pre- and post-CRT images and evaluated patients’ prognosis according to LLN size and whether LLND was performed.

Results

MRIs were collected from 752 patients, of whom 189 underwent neoadjuvant CRT. Both pre- and post-CRT MRIs were available in 155 patients, of whom 66 underwent LLND (LLND group) and 89 did not (non-LLND group). The LLND and non-LLND group showed the following differences: positive circumferential resection margin by MRI after CRT: 53.0% vs. 32.6%; positive extramural venous invasion: 36.4% vs. 24.7%; laparoscopic surgery: 39.4% vs. 88.8%; and mean pre-CRT LLN size: 5.2 mm vs. 3.6 mm. Five-year relapse-free survival (5y-RFS) was 73.8% and 66.1% in the LLND and non-LLND groups, respectively (p = 0.38). Two local recurrences occurred in the LLND group. In stratified analysis, 5y-RFS of 40 patients whose LLN size was ≥5 mm in pre-CRT images was 77.8% in the LLND group and 46.2% in the non-LLND group (p = 0.06). On the other hand, 115 patients whose LLN size was <5 mm in pre-CRT images showed almost no difference between the LLND and non-LLND group (5y-RFS: 71.1% vs. 69.5%, p = 0.85).

Conclusions

Our data indicated that adding LLND to CRT may have survival benefits on those who had LLN size of ≥ 5 mm before CRT. Stratification by short-axis LLN size using pre-CRT MRIs may facilitate optimal multidisciplinary treatment strategies for low rectal cancer.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Department of Surgery, Kyoto University Graduate School of Medicine.

Funding

The Japanese Foundation for Research and Promotion of Endoscopy, The Japan Society of Clinical Oncology, and Kondou Kinen Medical Foundation.

Disclosure

All authors have declared no conflicts of interest.