[Lymph node metastasis pattern in transverse colon cancer: a single-center data analysis of 336 cases]

Objective: To investigate the status of lymph node metastasis in transverse colon cancer and its association with clinicopathological characteristics and prognosis. Methods: A retrospective cohort study was performed. Clinical data from patients with transverse colon cancer at stages T1-4, N0-2, M0 who were consecutively admitted in the Department of Colorectal Surgery, Fudan University Shanghai Cancer Center from 2010 to 2022 were retrospectively analyzed. Patients were excluded if they had a history of prior tumors, developed a second or subsequent primary malignancy during the follow-up after the current primary transverse colon cancer, or underwent emergency surgery due to complications such as gastrointestinal bleeding or obstruction. The observation indicators included: (1) lymph node metastasis status and its impact on prognosis; (2) lymph node dissection status and the impact of dissection of <12 lymph nodes on prognosis; (3) factors influencing the dissection of <12 lymph nodes. Postoperative follow-up was performed to evaluate tumor recurrence, metastasis, and survival, with a follow-up cutoff date of March, 2025. Chi-squared tests, one-way ANOVA, multivariate logistic regression, the Kaplan-Meier method, and log-rank tests were used to analyze the relevant factors of lymph node dissection and its impact on patient prognosis. Postoperative follow-up was conducted via outpatient visits and telephone interviews to assess tumor recurrence, metastasis, and survival. Results: A total of 336 transverse colon cancer patients were included, including 219 males and 117 females, with a median age of 60 years (range: 24-84 years). There were 212, 83, and 41 patients with stage N0, N1, and N2, respectively. The median number of metastatic lymph nodes in the entire cohort was 0 (range: 0-18), with an overall lymph node metastasis rate of 36.9% (124/336). The metastasis rates of the 1st, 2nd, and 3rd station lymph nodes were 30.4% (102 cases), 19.6% (66 cases), and 2.4% (8 cases), respectively. Within the T1, T2, T3, and T4 stage groups, the 1st, 2nd, and 3rd station lymph node metastasis rates were 3.1% (1/32), 0, and 0 in T1; 14.6% (6/41), 2.4% (1/41), and 0 in T2; 31.6% (54/171), 23.4% (40/171), and 2.3% (4/171) in T3; and 44.6% (41/92), 27.2% (25/92), and 4.3% (4/92) in T4, respectively. There was a statistically significant difference in the total lymph node metastasis rates among different T stages (χ²=36.816, P<0.001). Additionally, statistically significant differences were also observed in the metastasis rates of lymph nodes at Station 1 and Station 2 among different stages (χ²=24.924, P<0.001; χ²=20.338, P<0.001). However, no statistically significant difference was found in the metastasis rate of lymph nodes at station 3 (χ²=3.313, P=0.346). Skip metastasis was observed in 23 patients (6.8%), including 14 cases in T3 stage and 9 cases in T4 stage, with no skip metastasis found in T1 or T2 stages. The median follow-up time was 39 months (95%CI: 36-42). 1-, 3-, and 5-year overall survival (OS) rates were 96.6%, 87.8%, and 85.8%, respectively, and disease-free survival (DFS) rates were 94.7%, 82.6%, and 74.7%, respectively. The 5-year DFS rates in N0, N1, and N2 stages were 85.4%, 66.1%, and 41.3%, respectively (χ²=67.408, P<0.001). Patients with station 1 lymph node metastasis had a significantly lower 5-year DFS than those without metastasis (56.8% vs. 83.0%, χ²=32.348, P<0.001). Similarly, patients with station 2 lymph node metastasis had a significantly lower 5-year DFS than those without (50.2% vs. 81.0%, χ²=28.313, P<0.001). However, no significant difference in 5-year DFS was found between patients with station 3 lymph node metastasis and those without (51.4% vs. 75.1%, χ²=2.759,P=0.097). There was also no significant difference in 5-year DFS between patients with and without skip metastasis (65.0% vs. 75.5%,χ²=0.879, P=0.349). The median number of dissected lymph nodes in the entire cohort was 16 (range: 3-52). Using 12 lymph nodes as the cutoff, 286 patients (85.1%) had ≥12 lymph nodes dissected, and 50 patients (14.9%) had <12. The 5-year DFS in the <12 lymph nodes group was lower than that in the ≥12 group (62.1% vs. 76.6%), but the difference was not statistically significant (χ²=2.863, P=0.091). Univariate analysis showed that age, tumor length, high-moderate differentiation, and T stage were influencing factors for dissecting <12 lymph nodes (all P<0.1). Going further, multivariate logistic regression analysis revealed that age ≥50 years (OR=2.564, 95%CI: 1.085-6.054, P=0.032), high-moderate tumor differentiation (OR=2.582, 95% CI: 1.265-5.271, P=0.009), and T1-2 stage (OR=2.520, 95%CI: 1.177-5.396, P=0.017) were independent risk factors for dissecting <12 lymph nodes (all P<0.05). Conclusions: Lymph node metastasis in transverse colon cancer mainly occurs at the 1st and 2nd stations. Skip metastasis may occur in T3-T4 stages. For T1-2 stage transverse colon cancer, D2 radical resection can be performed, but for cancers in T3 to T4, D3 radical operation should be carried out.