Immunohistochemical analysis of tumour regression grade for rectal cancer after neoadjuvant chemoradiotherapy

Aim Tumour regression grade (TRG) as defined by Rödel et al. has been used as an independent prognostic factor for rectal carcinoma after preoperative treatment by chemoradiotherapy (CRT). Determination of TRG 2 and 3, semiquantitatively defined as more or less than 50% tumour regression, respectively, does not appear to correlate with prognosis. The purpose of this study was to find an immunohistochemical pattern to permit improved stratification of intermediate responders defined by disease free (DFS) and overall survival (OS). Method Immunohistochemistry of EGFR (epidermal growth factor receptor), VEGF (vascular endothelial growth factor), CD133 antibody, p53 antibody and Ki67 antibody was evaluated using tissue microarrays (TMA) on post‐treatment surgical specimens from 88 patients. CD133 expression was confirmed in the whole section when available. Results At a median follow‐up of 40 months, TRG was found to be an independent predictor of DFS (P = 0.05) and OS (P = 0.001) but no differences were found between TRG 2 and 3 in terms of DFS (P = 0.74) or OS (P = 0.41). The results of TMA showed an immunohistochemically poor prognostic profile for intermediate responders configured by negativity of CD133 expression. However, when examining CD133 expression in the whole section, there was an intermediate correlation with TMA and the prognostic significance was lost. Conclusion The results did not confirm the value of immunohistochemistry in predicting the prognosis of patients with rectal cancer following neoadjuvant chemoradiotherapy. This questions the accuracy of TMA in detecting CD133 expression in this setting.