Prediction of mesorectal nodal metastases after chemoradiation for rectal cancer: results of a randomised trial. Implication for subsequent local excision *

Abstract Background and purpose For patients with rectal cancer treated with full thickness local excision the risk of mesorectal nodal metastases has to be very low. The aim was to assess this risk after preoperative radiotherapy in relation to pathological T-category. Patients and methods Three hundred sixteen patients with resectable cT3-4 low rectal carcinoma were randomised to receive either preoperative 5×5 Gy irradiation with subsequent surgery performed within 7 days or chemoradiation (50.4, 1.8 Gy per fraction plus bolus 5-fluorouracil and leucovorin) followed by surgery after 4–6 weeks. The pathological reports of patients who fulfilled entry criteria and had preoperative irradiation followed by transabdominal surgery were analysed. Results Significant downstaging of primary tumour ( P P =0.007) was observed after chemoradiation in comparison with short-course irradiation. In chemoradiation group, for patients with complete pathological response and for ypT1 category, the rate of nodal metastases was low — 5% (95% confidence interval [CI] 0–14%) and 8% (95% CI 0–24%), respectively. The rate of ypN-positive disease in chemoradiation group was similar to that recorded in short-course irradiation group for ypT2 category 26% (95% CI 14–38%) vs. 28% (95% CI 16–40%), P =0.83 and for ypT3-4 category 55% (95% CI 41–69%) vs. 64% (95% CI 54–74%), respectively, P =0.37. For ypT2 category after chemoradiation, the rate of nodal disease remained high even in subgroup with low residual cancer cells density (20%, 95% CI 4–36%). Conclusions For patients with tumours downstaged by chemoradiation to ypT0 and ypT1 full thickness local excision may be considered as an acceptable approach, because the risk of mesorectal lymph nodes metastases is low. The selection criteria for preoperative radio(chemo)therapy and local excision are discussed.