No downstaging after short-term preoperative radiotherapy in rectal cancer patients

Abstract

Purpose: In retrospective studies, total mesorectal excision (TME) surgery has been demonstrated to result in a reduction in the number of local recurrences of rectal cancer. Reports on improved local control after preoperative, hypofractionated radiotherapy have led to the introduction of a randomized multicenter trial to evaluate the effect of TME surgery with and without preoperative radiotherapy. Treatment with preoperative radiotherapy might have an effect on the pathologic characteristics that determine staging of rectal cancer. We investigated the occurrence of downstaging in rectal cancer patients treated with and without preoperative radiotherapy.

Patients and methods: We analyzed the differences in tumor size, number of examined lymph nodes, tumor-node-metastasis stage, and histopathologic features in 1,321 patients entered onto a randomized trial. The trial compared preoperative radiotherapy (5 x 5 Gy) followed by TME surgery with TME surgery alone. Patients who had an interval of more than 10 days between the start of radiotherapy and surgery were excluded from analysis.

Results: Differences were observed in tumor size (P <.001) and total number of examined lymph nodes (P <.001). No difference in tumor or node classification was detected. The irradiated group demonstrated more poorly differentiated tumors as well as more mucinous tumors.

Conclusion: In rectal cancer patients, short-term, preoperative radiotherapy with 5 x 5 Gy does not lead to downstaging if the interval between the start of radiotherapy and surgery does not exceed 10 days.