Lateral Nodal Features on Restaging Magnetic Resonance Imaging Associated With Lateral Local Recurrence in Low Rectal Cancer After Neoadjuvant Chemoradiotherapy or Radiotherapy

Abstract

IMPORTANCE Previously, it was shown in patients with low rectal cancer that a short-axis (SA) lateral node size of 7 mm or greater on primary magnetic resonance imaging (MRI) resulted in a high lateral local recurrence (LLR) rate after chemoradiotherapy or radiotherapy ([C]RT) with total mesorectal excision (TME) and that this risk was lowered by a lateral lymph node dissection (LLND). The role of restaging MRI after (C)RT with regard to LLR risk and which specific patients might benefit from an LLND is not fully understood.OBJECTIVE To determine the factors on primary and restaging MRI that are associated with LLR in low rectal cancer after (C)RT and to formulate specific guidelines on which patients might benefit from an LLND. DESIGN, SETTING, AND PARTICIPANTSIn this retrospective, multicenter, pooled cohort study, patients who underwent surgery for cT3 or cT4 low rectal cancer with a curative intent from 12 centers in 7 countries from January 2009 to December 2013 were included. All patients' MRIs were rereviewed according to a standardized protocol, with specific attention to lateral nodal features. The original cohort included 1216 patients. For this study, patients who underwent (C)RT and had a restaging MRI were selected, leaving 741 for analyses across 10 institutions, including 651 who underwent (C)RT with TME and 90 who underwent (C)RT with TME and LLND. MAIN OUTCOMES AND MEASURESThe main purpose was to identify the factors on primary and restaging MRI associated with LLR after (C)RT with TME. Whether high-risk patients might benefit in terms of LLR reduction from an LLND was also studied. RESULTSOf the 741 included patients, 480 (64.8%) were male, and the mean (SD) age was 60.4 (12.0) years. An SA lateral node size of 7 mm or greater on primary MRI resulted in a 5-year LLR rate of 17.9% after (C)RT with TME. At 3 years, there were no LLRs in 28 patients (29.2%) with lateral nodes that were 4 mm or less on restaging MRI. Nodes that were 7 mm or greater on primary MRI and greater than 4 mm on restaging MRI in the internal iliac compartment resulted in a 5-year LLR rate of 52.3%, significantly higher compared with nodes in the obturator compartment of that size (9.5%; hazard ratio, 5.8; 95% CI, 1.6-21.3; P = .003). Compared with (C)RT with TME alone, treatment with (C)RT with TME and LLND in these unresponsive internal nodes resulted in a significantly lower LLR rate of 8.7% (hazard ratio, 6.2; 95% CI, 1.4-28.5; P = .007). CONCLUSIONS AND RELEVANCERestaging MRI is important in clinical decision making in lateral nodal disease. In patients with shrinkage of lateral nodes from an SA node size of 7 mm or greater on primary MRI to an SA node size of 4 mm or less on restaging MRI, which occurs in about 30% of cases, LLND can be avoided. However, persistently enlarged nodes in the internal iliac compartment indicate an extremely high risk of LLR, and an LLND lowered LLR in these cases.

Tumor-Infiltrating Immune Cells Act as a Marker for Prognosis in Colorectal Cancer

“…TNM stages were classified according to the American Joint Committee on Cancer guideline (7th Edition) but the detailed TNM categories (namely T, N, M) were lacking. It should be noted that there were two criteria for the category of patients according to their information related to lymph nodes (examined or metastatic) (38–40). Patients from the Second Affiliated Hospital (Wenzhou Medical University) were classified based on the number of examined lymph nodes during surgery.…”

Lateral Lymph Node Metastases in Locally Advanced Low Rectal Cancers May Not Be Treated Effectively With Neoadjuvant (Chemo)Radiotherapy Only

“…We also excluded from the matched cohort patients in whom lateral lymph nodes were selectively removed and all R1 and R2 resections, since independently of the lateral lymph node status, non-radical resections are associated with worse LRFS, DFS and OS and thus would severely influence the long-term oncological outcomes (31, 32). Based on previous publications, a cut-off short-axis size of ≥5 mm for LLN+ was chosen, however, in literature the definition of a LLN+ varies between 5–10 mm for the short-axis, making comparisons challenging (10, 14, 18, 22, 26, 30, 33). Also, we were not able to evaluate the response of the LLN to nCRT as most patients did not undergo a restaging MRI.…”

MRI of rectal cancer—relevant anatomy and staging key points

“…For nodes in the lateral pelvis, mostly size criteria have been tested, with variable cutoffs and variable outcomes [52][53][54][55][56]. According to research by the Lateral Node Study Consortium, in the particular case of cT3/4 low tumours, lateral lymph nodes with a short axis of at least 7 mm on staging MR have a significantly higher risk of lateral recurrence and lateral lymph node dissection in such cases may reduce lateral recurrences significantly [57].…”