Clinical Implication of Perineural and Lymphovascular Invasion in Rectal Cancer Patients Who Underwent Surgery After Preoperative Chemoradiotherapy

BACKGROUND: Lymphovascular and perineural invasion are well-known negative prognostic indicators in rectal cancer, but previous studies on their significance are not consistent. OBJECTIVE: This study assessed the prognostic value of lymphovascular and perineural invasion in rectal cancer patients who received preoperative chemoradiotherapy followed by curative resection. DESIGN: This is a retrospective analysis. SETTING: This study was performed at a tertiary cancer center. PATIENTS: Rectal cancer patients who underwent curative resection after preoperative chemoradiotherapy between January 2000 and December 2010. MAIN OUTCOME MEASURES: The primary outcomes were disease-free survival and overall survival. The survival rates were estimated using Kaplan-Meier analysis, and group comparisons were conducted using a log-rank test. RESULTS: Of the 1156 included patients, 109 (9.4%) presented with lymphovascular invasion and 137 (11.9%) presented with perineural invasion. Lymphovascular and perineural invasion were associated with T and N downstaging after preoperative chemoradiotherapy (p<0.001). In the ypN0 patients, the 5-year disease-free survival rates were 70.8% and 78.5% (p=0.150) for the lymphovascular invasion and absent groups, respectively. In the perineural invasion group, the 5-year disease-free survival rate was 59.0% compared to 80.2% in the absent group (p=0.001). Among the ypN+ patients, the 5-year disease-free survival rates were 36.9% and 44.4% for the lymphovascular invasion and absent groups, respectively (p=0.211). The perineural invasion group had a poorer 5-year disease-free survival rate compared to the absent group (29.7% vs 46.7%; p=0.011). By multivariable analyses, perineural invasion correlated with a poor disease-free survival (HR 1.412, 95% CI 1.082-1.843; p=0.011) and also in ypN0 subgroup analysis (HR 1.717, 95% CI 1.093-2.697; p=0.019). LIMITATIONS: This study was a retrospective study conducted at a single center. CONCLUSIONS: Perineural invasion is a reliable independent predictor of recurrence in rectal cancer patients treated with preoperative chemoradiotherapy. Patients with perineural invasion should be considered for closer surveillance even with ypN0 status.

Automated summary

In rectal cancer patients who underwent preoperative chemoradiotherapy followed by curative resection, perineural invasion is a reliable independent predictor of recurrence. Patients with perineural invasion should be closely monitored even if they have ypN0 status.