Clinical tumour size and nodal status predict pathologic complete response following neoadjuvant chemoradiotherapy for rectal cancer.

PURPOSE: Pathologic complete response (pCR) to neoadjuvant treatment for rectal cancer has been associated with improved local control, reduced distant disease and a survival advantage when compared with non-complete responders. Approximately 10-25 % of patients undergoing neoadjuvant chemoradiotherapy for rectal cancer achieve pCR; however, predictors for its occurrence are inadequately defined. This study aimed to identify clinical and tumour factors that predict pCR in patients receiving neoadjuvant chemoradiotherapy for rectal cancer.
METHODS: Consecutive rectal cancer patients diagnosed and treated in the Auckland region between 1 January 2002 and 1 February 2013 were retrospectively identified. Cases were stratified by the occurrence of pCR or non-pCR. Predictive capacity of several patient, tumour and treatment-related variables were then assessed by univariate and regression analyses.
RESULTS: Two hundred ninety-seven patients received neoadjuvant chemoradiotherapy, of whom 34 (11.4 %) achieved pCR. There were no significant differences in age, gender, ethnicity, BMI, pretreatment clinical T or N stage, tumour distance from the anal verge, tumour differentiation, chemoradiotherapy regimen and time interval to surgery between the pCR and non-pCR groups. Univariate analysis identified pretreatment serum CEA levels, a reduction in pre- to post-treatment serum CEA and smaller tumours as significant correlates of pCR. Logistic regression analysis found smaller tumour size and pretreatment clinical N stage as independent clinical predictors for achieving pCR.
CONCLUSIONS: Smaller tumour size and pretreatment clinical N stage were independent clinical predictors for achieving pCR. Prospective analysis is recommended for more rigorous risk factor assessment.