Increased CD133 expression after preoperative chemoradiotherapy in rectal cancers other than mucin-rich tumors.

This study is to characterize the sequential change in CD133 expression after preoperative chemoradiotherapy (CRT) in rectal cancer and its impact on postoperative prognosis. Forty-one patients with rectal cancer who had received CRT before surgery were selected retrospectively. In each case, immunohistochemical analysis was performed to compare CD133 expression in biopsy specimens taken before and after CRT. After CRT, CD133 expression was significantly increased in 14 (34%) patients, mildly increased in 25 (61%), and decreased in 2 (5%). However, no mucin-rich tumors showed high CD133 expression before or after CRT (p < 0.001). Disease-free survival and overall survival were significantly poorer in patients with significantly increased CD133 (p = 0.049 and p = 0.038, respectively). Increased CD133 after CRT is a significant prognostic factor in rectal cancer patients treated with preoperative CRT and surgical resection. CD133 might be an essential cancer stem cell marker.