Nodal involvement in luminal complete response after neoadjuvant treatment for rectal cancer

Background: Pathological complete response (pCR) after neoadjuvant therapy in rectal cancer is correlated with improved survival. There is limited knowledge on the incidence of pCR at a national level with uniform guidelines. The aim of this prospective register-based study was to investigate the incidence and outcome of pCR in relation to neoadjuvant therapy in a national cohort. Method: All patients abdominally operated for rectal cancer between 2007 and 2012 (n = 7885) were selected from The Swedish Colorectal Cancer Register. Twenty-six per cent (n = 2063) had neoadjuvant therapy with either long or short course radiotherapy with >4 weeks delay with the potential to achieve pCR. The primary endpoints were pCR and survival in relation to neoadjuvant therapy. Results: Complete eradication of the luminal tumor, ypTO was found in 161 patients (8%). In 83% of the ypTO the regional lymph nodes were tumor negative (ypTONO), 12% had 1-3 positive lymph nodes (ypTON1) and 4% had more than three positive lymph nodes (ypTON2). There was significantly greater survival with ypTO compared to ypT+ (hazard ratio 0.38 (C.I 0.25-0.58)) and survival was significantly greater in patients with ypTONO compared to ypT0N1-2 (hazard ratio 0.36 (C.I 0.15-0.86)). In ypTO, cT3-4 tumors had the greater risk of node-positivity. The added use of chemotherapy resulted in 10% ypTO compared to 5.1% in the group without chemotherapy (p < 0.00004). Conclusion: Luminal pathological complete response occurred in 8%, 16% of them had tumor positive nodes. The survival benefit of luminal complete response is dependent upon nodal involvement status. (C) 2016 Elsevier Ltd. All rights reserved.