Lymph Node Metastasis in Extraperitoneal Rectal Cancer After Neoadjuvant Therapy: An Unsolved Problem?

Abstract

Background/aim: Thanks to the promising benefits obtained in terms of quality of life, there has been growing interest in organ-sparing approaches after neoadjuvant chemoradiotherapy (nCRT) in patients with locally advanced rectal cancer, mainly represented by transanal local excision and watch-and-wait. The main mandatory criterion is complete lymph nodal response (pN0). However, considering the reduced specificity of current radiological means in identifying one-to-one correspondence between clinical and pathological staging, the problem of underestimating lymph nodal involvement remains unsolved. The aim of this study was to identify the true percentage of patients eligible for conservative surgery and possible predictive factors.

Patients and methods: Data for 59 patients with rectal cancer treated with nCRT followed by total mesorectal excision were analyzed. Patients with metastatic tumors and tumors treated with up-front surgery were excluded. Our primary endpoint was the pathological lymph nodal response rate after neoadjuvant chemoradiotherapy. The secondary endpoint was to identify predictive factors for lymph nodal response.

Results: The percentage of patients with pN0 was 62.71%, while in 37.28%, an organ-sparing approach would have not been oncologically correct. Parameters associated with pN0 were lower tumor size (T0-T2) (p=0.013) and lower grading (<G3) (p=0.06). Parameters associated with poorer disease-free survival were pN+ (p=0.019), higher lymph node ratio (p=0.001), and higher stage (p=0.038).

Conclusion: Organ-sparing approaches may be a promising option in patients with extraperitoneal rectal cancerthat respond to nCRT. Nevertheless, it is essential to consider the limit of lymph node metastases to ensure oncological safety and, especially in cases with advanced tumors, total mesorectal excision should be the approach of choice.

Keywords: Rectal cancer; clinical complete response; complete pathological response; lymph node metastasis; neoadjuvant chemoradiotherapy; organ-sparing surgery; watch and wait.