The clinical significance of a pathologically positive lymph node at the circumferential resection margin in rectal cancer.

BACKGROUND This study aimed to determine if the nature of circumferential resection margin (CRM) involvement, either by tumour or lymph nodes, had an impact upon local recurrence and survival in rectal cancer. METHODS A retrospective analysis of a prospectively collected database was performed. Consecutive patients with stage I-III rectal cancer having curative surgery were included. All specimens were analysed by a single histopathologist. Statistical analysis was performed using chi-squared test and Kaplan-Meier. RESULTS Of 265 patients, 29 (11%) had a positive CRM. Compared to patients with a negative CRM, a positive margin due to tumour was associated with a higher 5-year cumulative incidence of local recurrence (43.7% versus 8.8%, p = 0.001) and distant metastases (62% versus 13.6%, p = 0.001) with poorer 5-year cancer-specific survival (32% versus 87.8%, p = 0.001). Although patients with margin positivity due to lymph nodes had a higher rate of distant metastases (41.3% versus 13.6%, p = 0.004) and poorer 5-year cancer-specific survival (59.3% versus 87.8%, p = 0.038), the rate of local recurrence was comparable to that of patients with negative margins (8.3% versus 8.8%, p = 0.694). CONCLUSIONS Our findings suggest that the nature of CRM involvement may be important in determining prognosis in rectal cancer. Local recurrence is higher only when there is tumour present at the margin. Lymph node involvement of the margin confers similar risk of local recurrence to patients with CRM-negative, node-positive disease. These results need further evaluation in multicentre, prospective studies