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

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.

All patients abdominally operated for rectal cancer between 2007 and 2012 (n = 7885) were selected from The Swedish Colo-rectal 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.

Complete eradication of the luminal tumor, ypT0 was found in 161 patients (8%). In 83% of the ypT0 the regional lymph nodes were tumor negative (ypT0N0), 12% had 1-3 positive lymph nodes (ypT0N1) and 4% had more than three positive lymph nodes (ypT0N2). There was significantly greater survival with ypT0 compared to ypT+ (hazard ratio 0.38 (C.I 0.25-0.58)) and survival was significantly greater in patients with ypT0N0 compared to ypT0N1-2 (hazard ratio 0.36 (C.I 0.15-0.86)). In ypT0, cT3-4 tumors had the greater risk of node-positivity. The added use of chemotherapy resulted in 10% ypT0 compared to 5.1% in the group without chemotherapy (p < 0.00004).

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.