external - beam radiation therapy ( ebrt ) with intracavitary high - dose - rate ( hdr ) brachytherapy is the standard treatment modality for advanced cervical cancer .
although long - term survival rates in patients with cervical cancer treated with definitive radiotherapy ( rt ) have improved considerably in recent years , the incidence of late gastrointestinal complications has also increased .
the rectum is a major organ at risk during treatment planning because of its close proximity to the pelvic organs and relative immobility ; radiation proctitis has been reported in 5% to 11% of patients treated for gynecological cancer .
sigmoid complications such as obstructive sigmoiditis and perforation are rarely reported , although some previous studies have estimated they occur in 0.6 - 6.4% of cases .
herein we report two uncommon cases of radiation sigmoiditis mimicking sigmoid colon cancer after ebrt with intracavitary hdr brachytherapy for uterine cervical cancer with dosimetric consideration .
we also discuss the importance of radiation dose to the sigmoid colon in three - dimensional image - based brachytherapy .
a 79-year - old woman received definitive rt for international federation of gynecology and obstetrics ( figo ) stage iiib cervical cancer .
ebrt was performed at a total dose of 50.4 gy in 1.8 gy fractions for five days each week using a 15-mv photon .
intracavitary hdr brachytherapy ( microselectron - hdr ) of 24 gy in six fractions was conducted twice each week using a tandem and colpostat . following the completion of rt , the cervical cancer completely disappeared .
after one year , the patient returned to the hospital complaining of intermittent rectal bleeding .
a barium study revealed a 3-cm - long severe narrowing of the sigmoid wall , which was suspicious for sigmoid colon cancer ( fig .
sigmoidoscopy revealed luminal narrowing with a friable hyperemic nodular mucosal change 15 cm from the anal verge ( fig .
a 58-year - old woman received definitive rt with concurrent chemotherapy for figo stage iiia cervical cancer .
ebrt was performed at a total dose of 50.4 gy in 1.8 gy fractions for five days each week using a 15-mv photon .
intracavitary hdr brachytherapy ( microselectron - hdr ) of 24 gy in six fractions was conducted twice each week using a tandem and colpostat .
six cycles of weekly cisplatin ( 30 mg / m ) were given during rt .
after five years , the patient visited our emergency department with complaints of poor oral intake , lower abdominal pain and no stool passage over ten days .
sigmoidoscopy revealed an approximately 5-cm - long section of diffuse luminal narrowing in the sigmoid colon and hyperemic mucosal nodularities with mucosal edema ( fig .
a computed tomography ( ct ) scan also revealed thickening of the wall of the rectosigmoid colon probably caused by radiation or inflammation ; however no evidence of any cancer recurrence was found ( fig .
she has been managed conservatively with laxatives and has been clinically followed with improved symptoms .
we estimated an irradiated dose of brachytherapy of 518.7 to 642.3 cgy at the sigmoid colon point , which was 29.5% to 60.5% higher than prescribed dose at point a per fraction .
a 79-year - old woman received definitive rt for international federation of gynecology and obstetrics ( figo ) stage iiib cervical cancer .
ebrt was performed at a total dose of 50.4 gy in 1.8 gy fractions for five days each week using a 15-mv photon .
intracavitary hdr brachytherapy ( microselectron - hdr ) of 24 gy in six fractions was conducted twice each week using a tandem and colpostat . following the completion of rt , the cervical cancer completely disappeared .
after one year , the patient returned to the hospital complaining of intermittent rectal bleeding .
a barium study revealed a 3-cm - long severe narrowing of the sigmoid wall , which was suspicious for sigmoid colon cancer ( fig .
sigmoidoscopy revealed luminal narrowing with a friable hyperemic nodular mucosal change 15 cm from the anal verge ( fig .
a 58-year - old woman received definitive rt with concurrent chemotherapy for figo stage iiia cervical cancer .
ebrt was performed at a total dose of 50.4 gy in 1.8 gy fractions for five days each week using a 15-mv photon .
intracavitary hdr brachytherapy ( microselectron - hdr ) of 24 gy in six fractions was conducted twice each week using a tandem and colpostat .
six cycles of weekly cisplatin ( 30 mg / m ) were given during rt .
after five years , the patient visited our emergency department with complaints of poor oral intake , lower abdominal pain and no stool passage over ten days .
sigmoidoscopy revealed an approximately 5-cm - long section of diffuse luminal narrowing in the sigmoid colon and hyperemic mucosal nodularities with mucosal edema ( fig .
a computed tomography ( ct ) scan also revealed thickening of the wall of the rectosigmoid colon probably caused by radiation or inflammation ; however no evidence of any cancer recurrence was found ( fig .
she has been managed conservatively with laxatives and has been clinically followed with improved symptoms .
we estimated an irradiated dose of brachytherapy of 518.7 to 642.3 cgy at the sigmoid colon point , which was 29.5% to 60.5% higher than prescribed dose at point a per fraction .
acute and late gi complications are a major concern during and after rt . radiation sigmoiditis is not well - known compared to other gi complications such as proctitis and enteritis because it has been rarely reported .
galland and spencer . reported 23 cases of sigmoid complications among 80 cases of radiation colitis induced by pelvic rt .
ramirez et al .   reported that a total of 35 patients developed sigmoid perforation among over 5,000 patients who were treated with rt for stage ib - iiib cervical cancer . in this report
the sigmoiditis occurred one year after rt completion for one patient and five years after rt completion for the other patient .
both cases showed obstructive symptoms , which make clinicians suspicious of sigmoid colon cancer or recurrent cancer . during the follow - up of cancer patients who received rt previously , clinicians need to keep the possibility of rt complications in mind .
holloway et al .   reported that the sigmoid - to - tandem distance is significantly related to sigmoid dose using 3d imaging techniques .
concordantly , the simulation films of case 1 showed close proximity between the sigmoid colon and the tandem , which suggests the possibility of a high sigmoid dose during brachytherapy ( fig .
the estimated dose at the sigmoid colon point during brachytherapy was 518.7 to 642.3 cgy , which was 29.5% to 60.5% higher than prescribed dose at point a ( 400 cgy ) per fraction .
the international commission on radiation units ( icru ) 38 did not describe this hot spot in the sigmoid colon .
the rectal and bladder reference dose points are only standard for reporting normal tissue doses with brachytherapy .
indeed , these points are based on plain films and two - dimensional ( 2d ) brachytherapy planning .
as ebrt is moving from conventional to conformal planning , the incorporation of three - dimensional ( 3d ) sectional imaging such as ct and mri into brachytherapy planning is under active investigation .
recently , there has been a proposal to establish image - guided intracavitary brachytherapy guidelines for cervical carcinoma . in the group european
de curietherapies and european society for therapeutic radiology and oncology ( gec - estro ) recommendations , the rectum and bladder , as well as the sigmoid colon , are highlighted as organs at risk .
many studies have reported a sigmoid dose in 3d image - based planning for the treatment of cervical carcinoma with hdr brachytherapy .
kim et al .   reported that the sigmoid dose was higher than the rectal dose in 8 of 13 ( 61% ) patients and its volume was discontinuously located as multiple " hot spots " in 9 of 13 ( 69% ) patients on dosimetric analysis of 3d image - based planning of intracavitary brachytherapy for cervical cancer .
currently at our institution , 3d image - based brachytherapy is implemented to decrease the radiation dose to organs at risk , including the sigmoid colon ( fig .
3 ) . 3d image - based brachytherapy planning can be helpful , especially for patients who have risk factors .
patients who have a history of abdominal surgery , pelvic inflammatory disease , or diverticulosis are at a greater risk of developing radiation - induced gi complications because such conditions may create adhesions to the uterus , which prevent the loops of the bowel from moving during rt . in conclusion ,
radiation sigmoiditis is characterized by obstructive symptoms and its radiological findings can mimic sigmoid colon cancer .
radiation oncologists should acknowledge the sigmoid colon as well as rectum and bladder as organs at risk .
3d image - based brachytherapy could be an optimal modality to reduce the radiation - toxicity associated with treatment for uterine cervical cancer .
 external - beam radiation therapy with intracavitary high - dose - rate brachytherapy is the standard treatment modality for advanced cervical cancer ; however , late gastrointestinal complications are a major concern after radiotherapy . 
 while radiation proctitis is a well - known side effect and radiation oncologists make an effort to reduce it , the sigmoid colon is often neglected as an organ at risk . 
 herein , we report two cases of radiation sigmoiditis mimicking sigmoid colon cancer after external - beam radiation therapy with intracavitary high - dose - rate brachytherapy for uterine cervical cancer with dosimetric consideration . 
INTRODUCTION
CASE REPORTS
1. Case 1
2. Case 2
3. Dosimetric analysis
DISCUSSION