Study of Skip Metastasis to Lateral Lymph Nodes in Low Rectal Cancer

We reviewed the clinical records of 302 patients with low rectal carcinoma to evaluate the effectiveness of lateral lymph node(LLN)dissection in cases of skip metastases to the LLN. Patients were divided into 4 groups according to nodal status: group N(133 cases), no metastasis in both the mesorectum lymph node(MLN)and LLN; groupM(100 cases), metastasis in the MLN and no LLN metastasis; group L(15 cases), which was defined as skip metastasis, with no metastasis in the MLN and LLN metastasis; and group ML(54 cases), node metastases in both the MLN and LLN. LLN metastasis was found in 22.8% of all patients, and skip metastasis was found in 10.1%. The recurrence rate in group L(40.0%, 6 cases)was significantly lower than that in group ML(75.9%, 41 cases)and not different from that in group M(43.0%, 43 cases). The initial recurrence sites in group L were the lung(3 cases)and local recurrence(3 cases). In group L, 20.0% had hematogenous recurrence, which was lower than in group ML. There was no significant difference between group L(5-year survival rate: 57.1%)and group M(71.7%)in terms of prognosis. Multivariate analysis revealed that histology was a risk factor for LLN metastasis in lowrectal cancer without MLN metastasis. The positive predictive value of LLN metastasis based on computed tomography was 43.9%. It was believed that LLN dissection was important, especially for non-differentiated cancer, in consideration of skip metastases to the LLN.