Background and aims: Pathologic complete remission (CR) of rectal cancer after neoadjuvant chemoradiation therapy (CRT) is generally confirmed by routine hematoxylin and eosin (H&E) staining. The aim of this study was to identify residual rectal cancer cells in primary lesions of patients with pathologic CR by immunohistochemical staining for cytokeratin.
Patients and methods: The medical records of 358 rectal cancer patients who underwent neoadjuvant CRT prior to radical surgery between October 2002 and August 2007 were reviewed. The authors stained sections of resected specimens of 58 patients (15.9%; 42 males; mean age 54 years) who achieved pathologic CR (as determined originally by H&E staining) with H&E and performed immunohistochemistry (IHC) using monoclonal anti-cytokeratin antibody. These stained sections were reviewed for residual rectal cancer cells by a pathologist.
Results: Of the 58 patients that achieved CR by initial pathologic examinations, eight (13.8%) were found to contain tumor by cytokeratin IHC. H&E staining revealed that six of these were positive for cancer cells, but the remaining two were negative for residual rectal cancer cells.
Conclusion: Through better identification of residual rectal cancer cells, cytokeratin IHC offers a means of improving staging accuracy and thus provides useful information for prognosis and treatment decisions for patients with rectal cancer who had a clinical CR after CRT.