Histopathological regression grading matches excellently with local and regional spread after neoadjuvant therapy of rectal cancer.

Histopathological regression grading has been shown to predict outcome in chemoradiated rectal cancer. Lymph node spread is still considered the most important single prognostic parameter. Therefore, we investigated the association of regression grading with tumor spread in a single center retrospective cohort. 102 consecutive patients who had undergone neoadjuvant therapy for rectal adenocarcinoma were included. Surgery was performed, including total mesorectal excision. Pathological examination included UICC staging and Dworak's five-tier tumor regression grading. Histological complete response was achieved in 16.7% of cases. Dworak's regression grading and a simplified two tier scheme both correlated excellently with ypT, ypN and UICC stage. However, cases with poor histological response were strongly represented in ypN0. Tumor regression grading is a reliable method for assessment of response to neoadjuvant therapy, but the optimal cut-off for separating good and poor response remains to be established based on clinical outcome.