Introduction
Information about the distribution characteristics and prognostic significance of lateral lymph nodes (LLNs) on primary computed tomography (CT) scan in rectal cancer patients is lacking.
Aims & Methods
Between January 2013 and December 2016, patients with pathologically-proved rectal cancer and pretreatment abdominal enhanced CT in our department were screened. We firstly redivided LLNs into 7 categories based on their locations. Then, the number and distribution of all measurable LLNs and the characteristics of the largest LLN in each lateral compartment were recorded. Furthermore, we investigated the long-term outcomes in patients with different LLNs characteristics and LLN risk scoring.
Results
A total of 572 patients were enrolled in this study. About 80% of patients had measurable LLNs. Most patients developed measurable LLNs in the obturator cranial compartment and a total of 231 (40.38%) patients and 281 (49.13%) patients had left and right obturator cranial LNs, respectively. The proportion of patients with left and right distal internal iliac LNs was 8.57% and 16.61%, respectively, and patients with left and right extended distal internal iliac LNs was 6.64% and 8.22%, respectively. We found the largest LLN short-axis diameter with 3-5 mm and 5-7 mm accounted for the most in every single compartment. The proportion of patients with the largest LLN short-axis diameter with 3-5 mm and 5-7 mm in the left obturator cranial compartment was 64.5% and 16%, respectively, and in the right obturator cranial compartment was 55.2% and 24.9%, respectively. In the whole cohort, there were 20 (4.4%) patients with >10 mm LLN, 52 (11.3%) patients with 7-10 mm LLN, 158 (34.4%) patients with 5-7 mm LLN, 206 (44.9%) patients with 3-5 mm LLN, 23 (5.0%) patients with 0-3 mm LLN. LLNs in the left proximal internal iliac compartment and the left distal internal iliac compartment had the largest short-axis diameter (5.42 ± 2.94) and long-axis diameter (8.47 ± 11.34), respectively. LLNs in the left obturator caudal compartment had both the shortest short-axis (3.85 ± 2.18) and long-axis diameter (5.47 ± 2.99), respectively. Lateral local recurrence (LLR) was observed in 20 patients, which accounted for 83.3% of the local recurrence (LR). Patients with LLN short-axis diameter > 10 mm had the worst 5-year OS (18.5%), which was comparable with that in patients with simultaneous distant metastasis (SDM, 8.5%). With regard to local recurrence-free survival (LRFS) and lateral local recurrence-free survival (LLRFS), patients with LLN short-axis diameter > 10 mm had the worst 5-year LRFS (35.7%) and LLRFS (35.7%). We used the largest LLN characteristics on CT scan to stratify the risk of LLNM (considering short-axis diameter, morphology, border and appearance). Patients with LLN risk scoring ≥ 2 had a worse prognosis than those with LLN risk scoring < 2, while better than those with SDM.
Conclusion
Our study comprehensively descripted the distribution characteristics and prognostic significance of LLNs. Our results confirmed that LLR is the main locoregional recurrence pattern. In addition, most rectal cancer patients have measurable LLNs. However, these patients with enlarged LLNs still have a significant better prognosis than patients with distant metastasis, which indicated the potential value of locoregional treatment for enlarged LLNs. Well-designed studies with larger sample size are required to prove our results.
References
1. Kim TH, Jeong SY, Choi DH, et al. Lateral lymph node metastasis is a major cause of locoregional recurrence in rectal cancer treated with preoperative chemoradiotherapy and curative resection. Ann Surg Oncol. 2008;15(3):729-737.
2. Ogura A, Konishi T, Cunningham C, et al. Neoadjuvant (Chemo)radiotherapy With Total Mesorectal Excision Only Is Not Sufficient to Prevent Lateral Local Recurrence in Enlarged Nodes: Results of the Multicenter Lateral Node Study of Patients With Low cT3/4 Rectal Cancer. J Clin Oncol. 2019;37(1):33-43.
3. Sammour T, Chang GJ. Lateral pelvic lymph node dissection and radiation treatment for rectal cancer: Mutually exclusive or mutually beneficial?. Ann Gastroenterol Surg. 2018;2(5):348-350.
4. Ogura A, Konishi T, Beets GL, et al. Lateral Nodal Features on Restaging Magnetic Resonance Imaging Associated With Lateral Local Recurrence in Low Rectal Cancer After Neoadjuvant Chemoradiotherapy or Radiotherapy. JAMA Surg. 2019;154(9):e192172.
5. Kroon HM, Dudi-Venkata NN, Bedrikovetski S, et al. Malignant Features in Pretreatment Metastatic Lateral Lymph Nodes in Locally Advanced Low Rectal Cancer Predict Distant Metastases. Ann Surg Oncol. 2022;29(2):1194-1203.
