Prognostic significance of mesenteric tumor nodules in patients with stage III colorectal cancer

Abstract

3566 Background: Tumor nodules are occasionally found in adjacent mesentery of colorectal cancer specimens, but their prognostic significance is unclear. According to the TNM staging system, mesenteric nodules are classified as part of T or N categories, but clinically they are regarded to reflect a worse prognosis, more like M1. We investigated the clinical significance of mesenteric tumor nodules. Methods: We reviewed 786 patients with stage III colorectal cancer referred between 1995 and 1999. We standardized TNM staging by assigning N status based on number of definite lymph nodes. Mesenteric nodules were considered separately and not assigned to T or N categories. Survival analyses were performed. Results: Mesenteric tumor nodules were found in 116 patients (14.8%); 48 with colon cancer (41.4%) and 68 rectal cancer (58.6%). Mean age at surgery was 62.8±1.0 yrs (SE), and the male: female ratio was 1.2. All tumors were adenocarcinomas with an average size of 4.3±0.1 cm, and the majority were moderately differentiated. Resection margins were clear except in 7 cases. With respect to high risk features, 6 cases (5.2%) had bowel perforation, 12 (10.3%) obstructive symptoms, 41 (35.3%) lymphovascular invasion, and 11 (9.5%) were T4 lesions. Adjuvant chemotherapy was given to 84.8% of colon cancer patients. Two (2.9%) rectal cancer patients received neoadjuvant chemo-radiation, and 63 (92.6%) received adjuvant therapy; chemotherapy, radiation or both. In the cohort with mesenteric nodules, the median time to progression was 23.1 months; the median 5-yr disease free survival was 35%; and the median overall survival (OS) was 47.9 months, with 44% OS at 5 yrs. After TNM standardization, 19 (16.4%) patients were down-staged to either stage I or II, and their 5-yr OS was 60% (SEER Stage II 5 yr survival 82.5%). In the remaining cohort-patients with stage III disease after standardization, the 5-yr OS was 40% (SEER 5yr survival Stage IIIc 44.3%; Stage IV 8.1%). Conclusions: In comparison to SEER survival data, the presence of mesenteric nodules appears to worsen prognosis of any T/N0 disease to that of overall stage III disease. Patients with mesenteric nodules in the setting of any T/N1+ disease had prognosis similar to that of stage IIIC disease, but their prognosis was better than M1 disease. No significant financial relationships to disclose.