To identify independent factors of sphincter preserving surgery, and to evaluated whether preoperative chemoradiotherapy (CRT) improves the sphincter preservation rate for lower rectal cancers.

A total of 541 consecutive patients who underwent curative surgery for locally advanced rectal cancer (cT3-4Nx or cTxN+ ) within 6 cm of the anal verge with or without neoadjuvant CRT in Department of Colorectal Surgery, Union Hospital, Fujian Medical University between September 2000 and September 2013 were reviewed. Of these, 333 patients underwent surgery alone (Non-CRT group) and 208 patients also received preoperative chemoradiotherapy (CRT group). Clinical data were retrospectively reviewed to determine the factors influencing sphincter preservation, and to evaluate sphincter preservation rate according to tumor height over 1-cm intervals. The categorical variables were compared using χ² test and Fisher exact test. Continuous variables were compared using t test. Logistic regression was used to identify factors influencing sphincter preservation. A receiver operating characteristic (ROC) curve was constructed, and Youden's index was calculated to evaluate the predictive abilities of factors.

Multivariate analysis indicated that the independent factors influencing sphincter preservation were tumor height (OR=5.867, 95% CI: 4.155 to 8.285, P=0.000), pathological T stage (OR=0.688, 95% CI: 0.462 to 1.025, P=0.066), CRT (OR=2.088, 95% CI: 0.971 to 4.492, P=0.060) and histopathological type (OR=0.288, 95% CI: 0.136 to 0.611, P=0.001). The results of ROC analysis showed that the cut-off points for factors affecting sphincter preservation were as follows: (1) tumor height prior to CRT higher than 4.5 cm, (2) not mucinous or signet ring adenocarcinoma, (3) pathological T stage higher than T3, (4) had received preoperative CRT. In an analysis according to tumor height, the sphincter preservation rate was higher in CRT group only when tumor was located in 3.0 to 3.9 cm and 4.0 to 4.9 cm from the annal verge (3.0 to 3.9 cm, 59.4% vs. 2.8%, χ²=26.138, P=0.000; 4.0 to 4.9 cm, 76.9% vs. 37.9%, χ²=10.563, P=0.001).

There is a large increased rate of sphincter preservation when patients meet the following conditions: (1) tumor height prior to CRT higher than 4.5 cm, (2) not mucinous or signet ring adenocarcinoma, (3)pathological T stage higher than T3, (4) had received preoperative CRT. Only when tumors are between 3 and 5 cm from the anal verge, CRT could increase the rate of anal sphincter preservation.

Rectal neoplasms; Anal canal; Antineoplastic combined chemotherapy protocols