Clinical implications of radiologic criteria and prognostic factors for lateral lymph node metastasis in low rectal cancer

Gyung Mo Son

doi:10.3393/ac.2025.01480.0211

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Editorial Colorectal cancer Clinical implications of radiologic criteria and prognostic factors for lateral lymph node metastasis in low rectal cancer: Gyung Mo Son; Annals of Coloproctology 2025;41(6):489-490.
DOI: https://doi.org/10.3393/ac.2025.01480.0211
Published online: December 31, 2025

Department of Surgery, Pusan National University Yangsan Hospital, Pusan National University School of Medicine, Busan, Korea

Correspondence to: Gyung Mo Son, MD, PhD, FACS Department of Surgery, Pusan National University Yangsan Hospital, Pusan National University School of Medicine, 20 Geumo-ro, Mulgeum-eup, Yangsan 50612, Korea Email: skm1711@pusan.ac.kr

• Received: December 2, 2025 • Accepted: December 8, 2025

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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The optimal management of locally advanced low rectal cancer (LALRC) remains one of the most debated issues in colorectal oncology, particularly regarding the appropriate use of lateral lymph node dissection (LLND) [1]. Substantial differences persist between Eastern and Western treatment strategies: in Japan, total mesorectal excision (TME) with bilateral LLND—without neoadjuvant therapy—has been recommended, whereas most Western guidelines favor neoadjuvant chemoradiotherapy followed by TME alone, reserving LLND for highly selected cases [2]. Against this contrasting background, Ohno et al. [3] provide valuable insights by examining the true incidence, radiologic predictors, and prognostic implications of pathological lateral lymph node metastasis (pLLNM) in a uniformly treated cohort of LALRC patients who underwent LLND without preoperative therapy.

The retrospective analysis included 163 patients with pathological stage II–III LALRC treated between 2014 and 2023. Radiologic LLNM (clinical LLNM, cLLNM) was defined as a short-axis diameter ≥6 mm on magnetic resonance imaging (MRI). Among the cohort, 27 patients (16.6%) were diagnosed with pLLNM, a rate comparable to previously reported Japanese data [4]. Notably, 66.7% of patients with radiologically enlarged LLNs had confirmed metastasis, whereas only 3.8% of radiologically negative patients harbored occult metastasis. These findings highlight the usefulness of simple MRI-based size criteria for excluding LLNM and for avoiding unnecessary LLND in low-risk patients [5]. However, despite undergoing bilateral LLND, patients with pLLNM experienced significantly poorer oncologic outcomes. pLLNM was identified as an independent predictor of 3-year relapse-free survival, and lateral pelvic recurrence occurred more frequently in this subgroup. These observations underscore the aggressive tumor biology associated with true lateral pelvic nodal metastasis and suggest that LLND alone may be inadequate for patients with clinically suspicious LLNs [6].

The study also underscores the prognostic importance of MRI-detected extramural vascular invasion (mrEMVI), which was present in approximately 30% of the cohort. mrEMVI independently predicted inferior relapse-free, local recurrence–free, and distant recurrence–free survival. These findings are consistent with prior evidence indicating that EMVI contributes to hematogenous dissemination, circumferential resection margin involvement, and pelvic sidewall spread. Importantly, patients with mrEMVI positivity demonstrated poor outcomes even in the absence of cLLNM, suggesting that intensification of multimodal therapy may be warranted for this subgroup [7].

In addition, tumor distance ≤5 cm from the anal verge and poor histological differentiation were independently associated with worse long-term outcomes. By contrast, postoperative chemotherapy did not significantly improve survival, likely reflecting the limitations of adjuvant therapy adherence and the emerging advantages of total neoadjuvant therapy demonstrated in recent trials [8, 9].

Taken together, several clinically meaningful conclusions can be drawn from this study. First, radiologic LLN short-axis diameter ≥6 mm is a reliable predictor of metastasis and provides an excellent negative predictive value, supporting the omission of LLND in radiologically node-negative patients. Second, patients with radiologically suspicious LLNs appear to constitute a high-risk subgroup in whom LLND alone may be insufficient; prior evidence suggests that combining neoadjuvant chemoradiotherapy with LLND may yield superior oncologic outcomes. Third, mrEMVI is a robust independent prognostic marker, indicating that even cLLNM-negative but mrEMVI-positive patients may benefit from more intensive neoadjuvant or systemic therapy rather than surgery alone.

The study has several limitations, including its retrospective design, single-center setting, and relatively short follow-up in a subset of patients. In addition, detailed MRI morphologic characteristics, such as nodal irregularity or mixed signal intensity, and pathological EMVI confirmation were not evaluated. Nevertheless, the findings provide meaningful real-world validation of simple MRI-based criteria and reinforce the importance of individualized treatment algorithms for patients with LALRC.

In conclusion, the study demonstrates that the established radiologic criterion of LLN short-axis diameter ≥6 mm is a strong and clinically relevant predictor of pLLNM, with excellent value in excluding metastasis. pLLNM and mrEMVI are key prognostic variables that should inform treatment intensification. These results support the selective, risk-adapted application of LLND and highlight the need for further research to optimize multimodal treatment strategies for patients with radiologically suspicious LLNs or mrEMVI-positive disease [10].

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Conflict of interest

Gyung Mo Son is the deputy editor of this journal. No other potential conflict of interest relevant to this article was reported.

Funding

This study was supported by a 2025 research grant from Pusan National University Yangsan Hospital.

REFERENCES

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