Prognostic influence of histopathological regression patterns in rectal adenocarcinoma receiving neoadjuvant therapy

BACKGROUND: Neoadjuvant chemoradiation therapy (CRT) is an important management strategy in rectal carcinoma. Different systems grading response have shown varying prognostic influence. METHODS: To analyze the prognostic influence of pathological response in a series of 183 patients with rectal carcinoma receiving neoadjuvant therapy. To determine the prognostic significance of the histopathological patterns of response. RESULTS: A total of 183 patients from two hospitals. The concordance rate between pathologists was good. In total, 18% of the patients showed grade 0 (complete response), 31.7% grade 1, 19.2% grade 2 and 31.1% grade 3 regression. T down-staging was found in 51.9% of the cases. 46 patients recurred and 18 died of disease (median follow-up time: 39 months). We found a statistically significant association between pathological response and pT stage and down-staging. Inflammatory reaction in the tumor bed was significantly associated to regression and prognosis. Cox's multivariate analysis of survival revealed that down-staging and presence of mucin pools in the tumor bed behaved as significant predictors of recurrence and regression grade and mucin pools as significant predictors of survival. CONCLUSIONS: Pathological response is an important surrogate marker of prognosis in some large series, but results are varying. There are many systems to grade regression and this makes it difficult to compare the results by different groups. It is important to report the specific pattern of response, for some of them may have prognostic relevance. We feel there is an urgent need to develop standarized protocols and employ a universal regression scheme if we intend to use this factor to guide therapy.