The role of local excision in rectal cancer after complete response to neoadjuvant treatment

Correlation between pathological response of primary tumour and mesorectal lymph node involvement was prospectively evaluated to assess the role of local excision (LE) in rectal cancer after complete response to neoadjuvant treatment. A series of 272 consecutive rectal cancer, submitted to neoadjuvant radiochemotherapy (RCT) and surgery with total mesorectal excision (TME) were analysed. Tumour downstaging (pT) and tumour regression grade (TRG) together with sex, age, location of the tumour, pre-treatment clinical stage, type of chemoradiation and operation performed entered in an univariate and multivariate analysis. Pathological complete response on primary tumour was found in 56 patients (20.6%). Lymph node metastases were found in 72 patients (26.5%). The rate of positive nodes was 1.8% for pT0 and TRG1 cases, respectively, to go up to 6.3% for pT1 and 24.1% for TRG 2 cases, respectively. At the univariate analysis, factors with a statistically significant correlation with the risk of lymph node metastasis were: clinical pre-treatment N stage (p<0.05), pT stage (p<0.001) and TRG (p<0.001). At the multivariate analysis, the best predictors of pathologic lymph node involvement were pT stage (p = 0.0013 ) and TRG (p = 0.0011). Because LE is an adequate technique to assess the tumour pathological response and nodal involvement in pT0 or TRG1 cases seems extremely infrequent, radical resection is probably not justified after pathological complete response. Prospective randomized trials are necessary to establish if, in these cases, LE can guarantee the same oncologic results offered by the currently adopted protocols of RCT followed by radical resections.