Comparable regional therapeutic effects between neoadjuvant chemotherapy and neoadjuvant chemoradiotherapy for locally advanced lower rectal cancer in terms of histopathological analysis.

Neoadjuvant chemoradiotherapy (NACRT) for lower rectal cancer is commonly used in many Western countries. NACRT improves local control, but it may also induce anal dysfunction, postoperative complications, and late effects associated with radiation. Neoadjuvant chemotherapy (NAC) for lower rectal cancer has recently been employed to improve these problems, but the local control effect of NAC when compared with NACRT is controversial. The aim of the present study was to compare the effects of NAC and NACRT using histopathological analysis. The subjects included 16 patients treated with NAC and 10 patients treated with NACRT prior to surgery. Pathological effects on primary lesions and lymph nodes were evaluated based on fibrosis and tumor depth prior to and following preoperative therapy. In the NAC and NACRT groups, the T downgrade rates were 87.5 and 80%, T depth/F depth ratios were 0.61 and 0.73, pathological T downgrade rates were 25 and 40%, pathological complete response rates were 12.5 and 0% for primary lesions and 33.3 and 37.5% for lymph nodes, and the N conversion rates were 80 and 37.5%. There were no significant differences between the groups. These results suggest that the pathological therapeutic effects of NAC were similar to those of NACRT, and NAC may be effective as an alternative therapy to NACRT.