HIPEC in T4a colon cancer: a defendable treatment to improve oncologic outcome?

Adequate estimation of the potential benefits of 'adjuvant' hyperthermia and intraperitoneal chemotherapy (HIPEC) in T4 patients through assessment of the burden of peritoneal carcinomatosis (PC) in T4 tumors and the risk of PC as the only metastatic site. Analysis of prospectively collected data on patients who underwent surgery for colon cancer (Jan 2004-Jan 2007). About 379 patients (M/F = 204/175) were included, with a median age of 71.8 years (range 35.4-95.0): 39 stage I, 126 stage II, 89 stage III, 116 stage IV disease (+9 with unknown stage). The median follow-up was 34.8months [range 0.0-79.4]. The 3- and 5-year overall survival rates (OS) were 68.4% (95% confidence interval (CI) 63.9%-72.4%) and 60.3% (95%CI 55.6%-64.7%). Relapse analysis was restricted to stages II-III T3 (N = 154) and T4 tumors (N = 19) with complete relapse data, of which 13.2% developed PC. PC has a detrimental effect on OS [HR 6.3 (95%CI: 3.1-13.0, P < 0.0001)]. 50% of T4a and 20% of T4b developed PC. The 1- and 3-year PC percentage was significantly lower for T3 (4.5% and 9.3%) than T4 tumors (15.6% and 36.7%) (P = 0.008). PC was the only metastatic site in 3/15 T3 [proportion 0.20, 95%CI (0.043-0.481)] and 5/8 T4 tumors with PC [proportion 0.625, 95%CI (0.245-0.915)] (P = 0.071). T4a colon tumors have a significantly higher risk of developing PC. Twenty-five percent (5/19) of stages II-III T4 tumors develop PC as the only metastatic site. This could define the possible window of opportunity for adjuvant HIPEC to prevent PC.