Uterus and cervix motion during radiotherapy for cervix cancer
by Gillian Bestwick
Studies have shown that the positional change of the uterus during radiotherapy for cervix cancer can be significant. This investigation quantified the inter-fractional movement of the uterus and cervix in patients with cervical cancer undergoing radiotherapy treatment and assessed the relationship between uterus and cervix positional change and bladder volume.
85 retrospective cone beam computed tomography (CBCT) images from 11 pre-operative cervix cancer patients who had undergone radiotherapy were fused with the planning CT scans. The change in the uterus and cervix positions on the CBCT scans compared to the planning CT scans was quantified. The change in uterine angle and bladder volume were also measured. Changes in uterus position and angle were correlated with bladder volume changes using linear regression.
The largest range of movement was in the superior / inferior direction with a range of 0.02 cm to 3.61 cm. The change in uterine angle was 0o to 23 o. A significant correlation was found between the displacement of all the uterus and uterine angle change with bladder volume change.
Inter-fractional uterus and cervix movement can be substantial and can vary from patient to patient. Despite the use of a full bladder drinking protocol large variations in bladder volumes between fractions can occur and this can impact on the position of the uterus and cervix. This study supported the purchase of an ultrasound scanner which is now used daily to confirm bladder volumes prior to radical cervix radiotherapy.