Cervix regression and motion during the course of external beam chemoradiation for cervical cancer.
OBJECTIVE
To evaluate the magnitude of cervix regression and motion during external beam chemoradiation for cervical cancer.


METHODS
Sixteen patients with cervical cancer underwent computed tomography scanning before, weekly during, and after conventional chemoradiation. Cervix volumes were calculated to determine the extent of cervix regression. Changes in the center of mass and perimeter of the cervix between scans were used to determine the magnitude of cervix motion. Maximum cervix position changes were calculated for each patient, and mean maximum changes were calculated for the group.


RESULTS
Mean cervical volumes before and after 45 Gy of external beam irradiation were 97.0 and 31.9 cc, respectively; mean volume reduction was 62.3%. Mean maximum changes in the center of mass of the cervix were 2.1, 1.6, and 0.82 cm in the superior-inferior, anterior-posterior, and right-left lateral dimensions, respectively. Mean maximum changes in the perimeter of the cervix were 2.3 and 1.3 cm in the superior and inferior, 1.7 and 1.8 cm in the anterior and posterior, and 0.76 and 0.94 cm in the right and left lateral directions, respectively.


CONCLUSIONS
Cervix regression and internal organ motion contribute to marked interfraction variations in the intrapelvic position of the cervical target in patients receiving chemoradiation for cervical cancer. Failure to take these variations into account during the application of highly conformal external beam radiation techniques poses a theoretical risk of underdosing the target or overdosing adjacent critical structures.
Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX, USA.
Beth M
BM
Beadle
Anuja
A
Jhingran
Mohammad
M
Salehpour
Marianne
M
Sam
Revathy B
RB
Iyer
Patricia J
PJ
Eifel
D000970:Antineoplastic Agents / Q000008:administration & dosage; D002584:Cervix Uteri / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000528:radiation effects; D002945:Cisplatin / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D009068:Movement; D011859:Radiography; D020266:Radiotherapy, Conformal / Q000379:methods*; D016896:Treatment Outcome; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging* / Q000628:therapy*
D000970:Antineoplastic Agents; D002945:Cisplatin