Indications for Lateral Pelvic Lymph Node Dissection Based on Magnetic Resonance Imaging Before and After Preoperative Chemoradiotherapy in Patients with Advanced Low-Rectal Cancer.

BACKGROUND

We assessed the magnetic resonance imaging (MRI) findings of lateral pelvic lymph node (LPLN) metastasis in patients with advanced low-rectal cancer treated with preoperative chemoradiotherapy (CRT) and LPLN dissection (LPLD) for clinically suspected LPLN metastasis. Our aim was to identify the optimal indications for LPLD.

METHODS

The study population consisted of 77 patients with advanced low-rectal cancer who underwent LPLD for clinically suspicious LPLN metastasis after preoperative CRT. MRI findings before/after CRT, clinical factors, and LPLN metastasis were evaluated.

RESULTS

LPLN metastasis was confirmed in 31 patients (40.3 %). Metastasis was significantly higher in patients with LPLNs with a short-axis diameter ≥8 mm than in patients with LPLNs with a short-axis diameter <8 mm before CRT (75 vs. 20 %, P < 0.0001). LPLN metastasis was also significantly higher in patients with LPLNs with a short-axis diameter >5 mm than in patients with LPLNs with a short-axis diameter ≤5 mm after CRT (75 vs. 20 %, P < 0.0001). Multivariate analysis showed the independent association of female sex [P = 0.0192; odds ratio (OR) 5.616; 95 % confidence interval (CI) 1.315-28.942], pre-CRT short-axis diameter of the LPLN ≥8 mm (P = 0.0047; OR 9.188; 95 % CI 1.948-54.366), and CRT without induction systemic chemotherapy (P = 0.0285; OR 9.235; 95 % CI 1.241-106.947) with LPLN metastasis.

CONCLUSIONS

MRI before CRT is useful to predict LPLN metastasis and to determine the indications for LPLD.