Predicting factors of postoperative relapse in T2-4N0M0 colorectal cancer patients via harvesting a minimum of 12 lymph nodes

The aim of this retrospective study was to determine which clinicopathological factors influenced the incidence of postoperative relapse and overall survival rates after radical resection of T2-4N0M0 colorectal cancer (CRC) patients via harvesting a minimum of 12 lymph nodes. Between January 2001 and June 2006, a total of 342 T2-4N0M0 CRC patients who underwent radical resection were retrospectively analyzed in Kaohsiung Medical University Hospital. Of these 342 patients, 155 were observed by harvesting a minimum of 12 lymph nodes. These 155 patients were followed up intensively, and their outcomes were investigated retrospectively. Of 155 patients, 83 were men (53.5%) and 72 (46.5%) were women. The mean age was 65.5 +/- 11.1 years (range, 24-89 years). The median follow-up period was 49 months (range, 19-80 months). The present data showed invasive depth (P = 0.012), vascular invasion (P < 0.001), and perineural invasion (P = 0.009) as significantly prognostic factors for postoperative 5-year relapse rate by Kaplan-Meier analysis. Likewise, invasive depth (P = 0.013), vascular invasion (P < 0.001), and perineural invasion (P = 0.008) were significant factors for postoperative 5-year survival rate. Meanwhile, using a Cox proportional hazards analysis, depth of tumor invasion (P = 0.026) and vascular invasion (P = 0.001) were the independent predictors for postoperative relapse. Furthermore, the presence of vascular invasion was considerably correlated to the higher postoperative relapse rate and the poorer overall survival rates by survival analyses (P < 0.0001). Besides the conventional depth of tumor invasion, this study highlights the potential for using vascular invasion as a means of identifying a subgroup of T2-4N0M0 CRC patients with adequate lymph node harvest at higher risk who would potential benefit from adjuvant therapy after surgery.