Rectal cancer lateral lymph nodes: multicentre study of the impact of obturator and internal iliac nodes on oncological outcomes

Abstract

Background In patients with rectal cancer, enlarged lateral lymph nodes (LLNs) result in increased lateral local recurrence (LLR) and lower cancer-specific survival (CSS) rates, which can be improved with (chemo)radiotherapy ((C)RT) and LLN dissection (LLND). This study investigated whether different LLN locations affect oncological outcomes. Methods Patients with low cT3–4 rectal cancer without synchronous distant metastases were included in this multicentre retrospective cohort study. All MRI was re-evaluated, with special attention to LLN involvement and response. Results More advanced cT and cN category were associated with the occurrence of enlarged obturator nodes. Multivariable analyses showed that a node in the internal iliac compartment with a short-axis (SA) size of at least 7 mm on baseline MRI and over 4 mm after (C)RT was predictive of LLR, compared with a post-(C)RT SA of 4 mm or less (hazard ratio (HR) 5.74, 95 per cent c.i. 2.98 to 11.05 vs HR 1.40, 0.19 to 10.20; P < 0.001). Obturator LLNs with a SA larger than 6 mm after (C)RT were associated with a higher 5-year distant metastasis rate and lowered CSS in patients who did not undergo LLND. The survival difference was not present after LLND. Multivariable analyses found that only cT category (HR 2.22, 1.07 to 4.64; P = 0.033) and margin involvement (HR 2.95, 1.18 to 7.37; P = 0.021) independently predicted the development of metastatic disease. Conclusion Internal iliac LLN enlargement is associated with an increased LLR rate, whereas obturator nodes are associated with more advanced disease with increased distant metastasis and reduced CSS rates. LLND improves local control in persistent internal iliac nodes, and might have a role in controlling systemic spread in persistent obturator nodes. Members of the Lateral Node Study Consortium are co-authors of this study and are listed under the heading Collaborators.

Management of Clinically Involved Lateral Lymph Node Metastasis in Locally Advanced Rectal Cancer: A Radiation Dose Escalation Study

“…However, the response rate in the nCRT-boost subgroup was 72.9%, meaning that more patients would avoid LLND. Especially, in line with the studies from the Lateral Node Study Consortium, patients with obturator nodes metastasis achieved a much higher response rate and a lower recurrence rate than those with internal iliac nodes metastasis (30). Significantly, compared with the nCRT subgroup, the rates of enteritis and dermatitis in the nCRT-boost subgroup were similar.…”

From “East vs West” towards international multidisciplinary collaboration: An appraisal of lateral lymph nodes in rectal cancer

“…Unlike mesorectal lymph nodes where size is just one of many factors associated with its malignancy, 39,41 LLR risks have been significantly associated with the size (SA) of an LLN 11,26,42,43 . Primarily enlarged LLNs (>10 mm) have LLR rates reaching 40% 16–18 and increase even further when remaining persistently enlarged after neoadjuvant treatment 8–10,26,43,44 . Ogura et al 9 found in a retrospective, international cohort of 1216 patients with re‐evaluation of all MRIs, that patients with LLNs measuring ≥7 mm on the primary MRI resulted in an LLR rate of 19.5% after 5 y.…”

“…The evidence currently available demonstrates clinical implications related to the size and/or anatomical location of an LLN 8–13 . Sufficient awareness of LLNs and knowledge of their consequences is therefore necessary.…”

“…The lateral compartments, which contain LLNs, are located between the bony pelvis and pelvic muscles laterally and the rectum with its mesorectum and mesorectal fascia medially. Various visual anatomical atlases exist 8 , 10 depicting individual lateral compartments. The internal iliac compartment (see Figure 1 ) contains lymphatic tissue located medially of the lateral border of the internal iliac artery.…”

“… 1 LLNs surround the internal iliac and obturator vessels and are not standardly removed during total mesorectal excision (TME) rectal surgery. 6 , 7 , 8 , 9 , 10 , 11 …”