Table 1 Definition of anatomical boundaries of high risk clinical target volume (HR-CTV) according to clinical stage

IB

At superior level of the ovoid.

If uterine body involvement does not exist, upper limit of uterine cervix is cranial margin of HR-CTV for IB disease. As the surrogate structure of upper limit of uterine cervix, recognize the level at which uterine vessels first abut cervical tissue or to point at which uterine volume expands and uterine cavity appears. Add 8 mm around tandem superiorly to cover conical cervical apex.

If direct uterine body involvement exists, measure the distance between fundus of the uterus and most cranial part of the tumor on MRI taken within one week before first brachytherapy. Subtract this distance from total length of the uterus and contour HR-CTV from the external os of the uterus until this subtracted length.

Width of HR-CTV is equal to that of uterine cervix.

-

IIA

Modify contour inferiorly to cover most inferior extent of vaginal extension using information derived from pelvic examination and MRI as a reference.

If uterine body involvement does not exist, upper limit of uterine cervix is cranial margin of HR-CTV for IB disease. As the surrogate structure of upper limit of uterine cervix, recognize the level at which uterine vessels first abut cervical tissue or to point at which uterine volume expands and uterine cavity appears. Add 8 mm around tandem superiorly to cover conical cervical apex.

If direct uterine body involvement exists, measure the distance between fundus of the uterus and most cranial part of the tumor on MRI taken within one week before first brachytherapy. Subtract this distance from total length of the uterus and contour HR-CTV from the external os of the uterus until this subtracted length.

Width of HR-CTV is equal to that of uterine cervix.

-

IIB

If vaginal extension does not exists, contour until the superior level of the ovoid.

If vaginal extension exists, modify contour inferiorly to cover most inferior extent of vaginal extension using information derived from pelvic examination and MRI as a reference.

If uterine body involvement does not exist, upper limit of uterine cervix is cranial margin of HR-CTV for IB disease. As the surrogate structure of upper limit of uterine cervix, recognize the level at which uterine vessels first abut cervical tissue or to point at which uterine volume expands and uterine cavity appears. Add 8 mm around tandem superiorly to cover conical cervical apex.

If direct uterine body involvement exists, measure the distance between fundus of the uterus and most cranial part of the tumor on MRI taken within one week before first brachytherapy. Subtract this distance from total length of the uterus and contour HR-CTV from the external os of the uterus until this subtracted length.

Measure the width of tumor by the physical examination and/or trans-rectal ultrasonography (TRUS) and based on this length determine the width of HR-CTV on CT image.

Determine the width of HR-CTV according to information of MRI taken before brachytherapy. If parametrial invasion is evident on CT image, rely on CT information.

Caudal margin of parametrial invasion is set at superior level of the ovoid. Cranial margin of parametrial invasion is set at the cranial margin of cervix.

Contour HR-CTV posteriorly if uterosacral ligament invasion exists which is confirmed by pelvic examination, CT, or MRI.

IIIA

Contour HR-CTV so that the lowest extent of vaginal disease is adequately covered. Urethral meatus can be used as a anatomical landmark to compare CT, MRI, and physical examination.

If uterine body involvement does not exist, upper limit of uterine cervix is cranial margin of HR-CTV for IB disease. As the surrogate structure of upper limit of uterine cervix, recognize the level at which uterine vessels first abut cervical tissue or to point at which uterine volume expands and uterine cavity appears. Add 8 mm around tandem superiorly to cover conical cervical apex.

If direct uterine body involvement exists, measure the distance between fundus of the uterus and most cranial part of the tumor on MRI taken within one week before first brachytherapy. Subtract this distance from total length of the uterus and contour HR-CTV from the external os of the uterus until this subtracted length.

If no parametrial involvement exists, contour until lateral edge of the uterine cervix.

If parametrial involvement exists, refer to the description in IIB.

Contour HR-CTV posteriorly if uterosacral ligament invasion exists which is confirmed by pelvic examination, CT, or MRI.

IIIB

If vaginal extension does not exists, contour until the superior level of the ovoid.

If invasion to upper 2/3 of vagina exists, refer to the description in IIA.

If invasion to lower 1/3 to vagina exists, refer to the description in IIIA.

If uterine body involvement does not exist, upper limit of uterine cervix is cranial margin of HR-CTV for IB disease. As the surrogate structure of upper limit of uterine cervix, recognize the level at which uterine vessels first abut cervical tissue or to point at which uterine volume expands and uterine cavity appears. Add 8 mm around tandem superiorly to cover conical cervical apex.

If direct uterine body involvement exists, measure the distance between fundus of the uterus and most cranial part of the tumor on MRI taken within one week before first brachytherapy. Subtract this distance from total length of the uterus and contour HR-CTV from the external os of the uterus until this subtracted length.

If parametrial involvement extends until pelvic wall, extend the lateral margin until pelvic wall such as inner margin of the obturator muscle or pelvic bone.

If no parametrial involvement exists on contralateral side, refer to the description in IB.

If parametrial involvement in contralateral side does not extend to pelvic wall, refer to the description in IIB.

Contour HR-CTV posteriorly if uterosacral ligament invasion exists which is confirmed by pelvic examination, CT, or MRI. If fixation of uterosacral ligament exists, extend HR-CTV to the sacral bone.