Influence of neoadjuvant chemoradiotherapy on the anal sphincter: ultrastructural damage may be critical.
BACKGROUND
Neoadjuvant chemoradiotherapy (nCRT) in addition to the curative surgery has been the first of treatment for local advanced rectal cancer because of its benefits in local recurrence and sphincter-saving. However, its side effects on anorectal function have been recognized. The histopathological changes on internal anal sphincter (IAS) have been reported, but ultrastructure changes of external anal sphincter (EAS) are unknown. The aim of this study is to detect the alterations on the gross morphology of IAS and ultrastructure of EAS after nCRT.


METHODS
We collected 34 anal canal specimens of patients undergoing abdominoperineal resection (APR) prospectively. The length and thickness of IAS were measured with vernier caliper. The EAS was dissected for observation with transmission electron microscope (TEM).


RESULTS
Ten patients received nCRT (nCRT group) before surgery and 24 underwent APR directly (control group). The length and thickness of IAS in nCRT group were 22.68 ± 3.56 and 5.39 ± 0.74 mm, respectively. These parameters were 21.28 ± 3.62 and 5.35 ± 1.12 mm in control group, respectively. There were no significant differences in the length and thickness of IAS between the two groups (P>0.05). In nCRT group, the sarcomere and myofibril were arranged disorderly and parts of them that were filled with collagenous fiber, triads, and mitochondria were destroyed severely and the glycogenosome also distributed disorderly. Such alterations of EAS did not occur in control group.


CONCLUSIONS
The nCRT cannot change the gross morphology of IAS, while it induces serious damages to the ultrastructures of EAS which may adversely affect the anorectal function.
Department of Colorectal Surgery, Changhai Hospital, Changhai Road 168#, Shanghai, China.
Xiaoming
X
Zhu
Department of Colorectal Surgery, Changhai Hospital, Changhai Road 168#, Shanghai, China.
Zheng
Z
Lou
Department of Colorectal Surgery, Changhai Hospital, Changhai Road 168#, Shanghai, China.
Haifeng
H
Gong
Department of Colorectal Surgery, Changhai Hospital, Changhai Road 168#, Shanghai, China.
Ronggui
R
Meng
Department of Colorectal Surgery, Changhai Hospital, Changhai Road 168#, Shanghai, China.
Liqiang
L
Hao
Department of Colorectal Surgery, Changhai Hospital, Changhai Road 168#, Shanghai, China. weizhang2000cn@163.com.
Wei
W
Zhang
D001003:Anal Canal / Q000187:drug effects / Q000528:radiation effects* / Q000648:ultrastructure*; D059248:Chemoradiotherapy / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy / Q000009:adverse effects*
Anal sphincter; Neoadjuvant chemoradiotherapy; Rectal cancer; Ultrastructure