Barium Enema and CT Volumetry for Predicting Pathologic Response to Preoperative Chemoradiotherapy in Rectal Cancer Patients

BACKGROUND: Preoperative chemoradiotherapy has been widely used for the prevention of local recurrence of locally advanced rectal cancer, and the effect of chemoradiotherapy is known to be associated with overall survival. OBJECTIVE: We aimed to evaluate the association of the pathologic response grade with tumor recurrence rate after chemoradiotherapy, using radiographic analysis and the Response Evaluation Criteria in Solid Tumors as the parameters. DESIGN: This study was conducted at a single tertiary care institution in Japan. SETTING: This was a retrospective cohort study of patients undergoing preoperative chemoradiotherapy. PATIENTS: A total of 101 low rectal cancer patients receiving preoperative chemoradiotherapy from July 2004 to August 2012 were enrolled. MAIN OUTCOME MEASURES: The tumor reduction rate was measured with the use of traditional Response Evaluation Criteria in Solid Tumors, barium enema, and CT volumetry, and the correlation between the reduction rate and the pathologic response grade was examined. RESULTS: The tumor reduction rate assessed according to Response Evaluation Criteria in Solid Tumors showed no association with the pathologic response grade (p =0.61). In contrast, the radiographic response rate by both barium enema and CT volumetry strongly correlated with the pathologic response grade (p < 0.0001 and p = 0.001). In terms of local tumor recurrence, those diagnosed as high responders by the pathologic response grade, Response Evaluation Criteria in Solid Tumors, barium enema, and CT volumetry had a lower recurrence rate (p =0.03, p =0.03, p =0.0002, and p =0.001). The difference between high responders and low responders was especially prominent by barium enema and CT volumetry. LIMITATIONS: The study is limited by its retrospective nature. CONCLUSIONS: Double-contrast barium enema and CT volumetry were superior to Response Evaluation Criteria in Solid Tumors in evaluating the effect of chemoradiotherapy and predicting the likelihood of tumor recurrence.