The clinical significance of distal spread differs according to the primary tumor location in rectal cancer.

Purpose: Treatment strategies of rectal cancer differ between tumors located above (RS/Ra) and below (Rb) the peritoneal reflection. Based on the extent of distal spread (DS), the Japanese Society for Cancer of Colon and Rectum proposed an optimal distal margin in RS/Ra and Rb tumors. In this study, we investigated the clinical significance of DS between RS/Ra and Rb tumors. Methods: We analyzed 287 stage I–III rectal cancer patients who underwent curative intent resection without preoperative therapy. DS and other pathological factors were evaluated using whole-mount sections. To investigate the clinical significance of DS in RS/Ra and Rb tumors, clinicopathological variables, including DS, were analyzed for the survival outcome according to the tumor group. Results: DS was detected in 20 out of 185 (11%) patients with RS/Ra tumors and 8 out of 102 (8%) patients with Rb tumors. DS was not significantly associated with the overall survival (OS) or relapse-free survival (RFS) in RS/Ra tumors, but was an independent prognostic factor for the OS and RFS in Rb tumors (P = 0.002 and 0.007, respectively). Conclusions: The clinical significance of DS differs between RS/Ra and Rb tumors. DS is associated with a worse survival in Rb tumors, but not in RS/Ra tumors. [ABSTRACT FROM AUTHOR]