Prospective clinical trial of bladder filling and three-dimensional dosimetry in high-dose-rate vaginal cuff brachytherapy.
OBJECTIVE
To investigate the effect of bladder filling on dosimetry and to determine the best bladder dosimetric parameter for vaginal cuff brachytherapy.


METHODS
In this prospective clinical trial, a total of 20 women underwent vaginal cylinder high-dose-rate brachytherapy. The bladder was full for Fraction 2 and empty for Fraction 3. Dose-volume histogram and dose-surface histogram values were generated for the bladder, rectum, and urethra. The midline maximal bladder point (MBP) and the midline maximal rectal point were recorded. Paired t tests, Pearson correlations, and regression analyses were performed.


RESULTS
The volume and surface area of the irradiated bladder were significantly smaller when the bladder was empty than when full. Of the several dose-volume histogram and dose-surface histogram parameters evaluated, the bladder maximal dose received by 2 cm(3) of tissue, volume of bladder receiving >/=50% of the dose, volume of bladder receiving >/=70% of the dose, and surface area of bladder receiving >/=50% of the dose significantly predicted for the difference between the empty vs. full filling state. The volume of bladder receiving >/=70% of the dose and the maximal dose received by 2 cm(3) of tissue correlated significantly with the MBP. Bladder filling did not alter the volume or surface area of the rectum irradiated. However, an empty bladder did result in the nearest point of bowel being significantly closer to the vaginal cylinder than when the bladder was full.


CONCLUSIONS
Patients undergoing vaginal cuff brachytherapy treated with an empty bladder have a lower bladder dose than those treated with a full bladder. The MBP correlated well with the volumetric assessments of bladder dose and provided a noninvasive method for reporting the MBP dose using three-dimensional imaging. The MBP can therefore be used as a surrogate for complex dosimetry in the clinic.
Stewart
Alexandra J
AJ
Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute, and Harvard Medical School, Boston, MA, USA.
Cormack
Robert A
RA
Lee
Hang
H
Xiong
Li
L
Hansen
Jorgen L
JL
O'Farrell
Desmond A
DA
Viswanathan
Akila N
AN
D001918:Brachytherapy / Q000379:methods*; D002986:Clinical Trials as Topic; D005260:Female; D006801:Humans; D010388:Pelvis / Q000000981:diagnostic imaging / Q000528:radiation effects; D011446:Prospective Studies; D012007:Rectum / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000473:pathology; D014057:Tomography, X-Ray Computed; D014521:Urethra / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000473:pathology; D001743:Urinary Bladder / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014621:Vagina