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

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.

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.

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.

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.