Prognostic implications of MRI-detected lateral nodal disease and extramural vascular invasion in rectal cancer

Background: Lateral nodal disease in rectal cancer remains a subject of debate and is treated differently in the East and theWest. The predictive value of lateral lymph node and MRI-detected extramural vascular invasion (mrEMVI) features on oncological outcomes was assessed in this study.

Methods: In this retrospective cohort study, data on patients with cT3-4 rectal cancer within 8cm from the anal verge were considered over a 5-year period (2009-2013). Lateral lymph node size, malignant features and mrEMVI features were evaluated and related to oncological outcomes.

Results: In total, 192 patients were studied, of whom 30 (15.6 per cent) underwent short-course radiotherapy and 145 (75.5 per cent) received chemoradiotherapy. A lateral lymph node short-axis size of 10mm or more was associated with a significantly higher 5-year lateral/presacral local recurrence rate of 37 per cent, compared with 7.7 per cent in nodes smaller than 10mm (P = 0.041). Enlarged nodes did not result in a higher 5-year rate of distant metastasis (23 per cent versus 27.7 per cent in nodes smaller than 10mm; P = 0.563). However, mrEMVI positivity was related to more metastatic disease (5-year rate 43 versus 26.3 per cent in the mrEMVI-negative group; P = 0.014), but not with increased lateral/presacral recurrence. mrEMVI occurred in 46.6 per cent of patients with nodes smaller than 10mm, compared with 29 per cent in patients with nodes of 10mm or larger (P = 0.267).

Conclusion: Although lateral nodal disease is more a local problem, mrEMVI mainly predicts distant recurrence. The results of this study showed an unacceptably high local recurrence rate in patients with a short axis of 10mm or more, despite neoadjuvant (chemo) radiotherapy.