Prognostic Impact of pT Stage and Peritoneal Invasion in Locally Advanced Colon Cancer

BACKGROUND: TNM stage has been identified as an independent variable for local recurrence and survival after colon cancer resection. It is still unclear whether peritoneal invasion (pT4a) is a risk factor for adverse oncologic outcome or whether these patients have better results compared with contiguous organs infiltration (pT4b), independent from nodal status (pN). OBJECTIVE: The purpose of this study was to analyze whether peritoneal invasion is an independent risk factor for worse oncologic outcome after curative colon cancer resection. DESIGN: This was a retrospective analysis with multivariate regression of a prospective database, according to Strengthening the Reporting of Observational Studies in Epidemiology Statement. SETTINGS: The study was conducted in a specialized colorectal unit of a tertiary hospital. PATIENTS: A consecutive series of pT3-pT4a-pT4b patients with colon cancer who underwent curative surgery (1993-2010) were included, and patients with metastasis were excluded. MAIN OUTCOME MEASURES: A multivariate Cox regression analysis was performed to assess independent risk factors for 5-year local recurrence, peritoneal carcinomatosis-like recurrence, disease-free survival, and cancer-specific survival. RESULTS: A total of 1010 patients were analyzed (79.3% pT3, 9.9% pT4a, and 10.8% pT4b). At diagnosis, 22.0% had obstructive symptoms, and 10.5% had bowel perforation. A total of 72.2% of the surgeries were elective, and in 15.6% en bloc resection of contiguous organs was performed. Median follow-up was 62 months (38-100 mo). For the whole group, 5-year actuarial rates were 8.8% for local recurrence, 2.5% for peritoneal carcinomatosis, 75.5% for disease-free survival, and 81.8% for cancer-specific survival. At multivariate analysis, pT4a stage was an independent risk factor for local recurrence (p = 0.002; HR = 3.1), peritoneal carcinomatosis (p = 0.02; HR = 4.9), worse disease-free survival (p = 0.002; HR = 1.9), and cancer-specific survival (p = 0.001; HR = 2.2). When considering only the 566 patients with ≥12 nodes identified, T stage was still associated with higher local recurrence (p = 0.04) and carcinomatosis rate (p = 0.04), as well as worse disease-free (p = 0.009) and cancer-specific survival (p = 0.014). LIMITATIONS: This was a retrospective, single-center study. CONCLUSIONS: pT4a stage is an independent risk factor for worse oncologic outcome after curative colon cancer resection compared with pT3 and pT4b stages. The current pT4a-pT4b classification should be reconsidered. Of note, even in pT4a patients, 5-year carcinomatosis rate does not exceed 6%. See Video Abstract at http://links.lww.com/DCR/A926.