Combination of differentiation and T stage can predict unresponsiveness to neoadjuvant therapy for rectal cancer.

Aim The study aimed to identify the factors predictive for extreme unresponsiveness to neoadjuvant therapy for rectal cancer. Method Ninety-six patients with rectal cancer received neoadjuvant therapy (41 were treated with radiotherapy and 55 with chemoradiotherapy) before surgery. Tumour response, downstaging, pathological complete response (pCR) and disease-free survival were evaluated. Results Tumour response, downstaging and pCR occurred in 70 (72.9%), 47 (49.0%) and 14 (14.6%) patients, respectively. Univariate analyses showed that a large tumour size, T4 stage, elevated serum tumour markers, poor differentiation, radiotherapy alone and mucinous tumour were indicators of poor tumour response and/or downstaging. On multivariate analysis, chemoradiotherapy was found to be predictive for tumour response and downstaging, whereas mucinous type and T4 stage negatively affected tumour response. No variable was found to be associated with pCR, but poor differentiation and T4 stage together predicted extreme unresponsiveness with a high specificity and a high positive predictive value. Very poor disease-free survival was also observed in patients simultaneously carrying these phenotypes. Conclusion Neoadjuvant chemoradiotherapy is superior to radiotherapy alone in producing a response of rectal cancer. Unresponsiveness was most likely to occur in patients with poor differentiation and T4 disease. [ABSTRACT FROM AUTHOR]