Prostate gland edema after single-fraction high-dose rate brachytherapy before external beam radiation therapy.
OBJECTIVE
High-dose rate brachytherapy (HDRB) is frequently used as a boost to external beam radiation therapy (EBRT) in prostate cancer patients. With the increasing use of small planning target volume margins in EBRT, prostatic edema induced by HDRB can be a contributing factor to geometric miss when HDRB is performed before or during EBRT. We assessed prostate gland volumetric change after single-fraction HDRB and its impact on definition of treatment volume for EBRT.


METHODS
Thirty-one consecutive patients with intermediate-risk prostate cancer treated with single-fraction HDRB (10 Gy) combined with hypofractionated EBRT were analyzed. A second CT scan was performed 7 days after HDRB, and images were coregistered with the planning CT scan that contained the original clinical target volume (CTV). The post-HDRB prostate CTV volume was compared with the original CTV by a single observer.


RESULTS
All patients presented volumetric variation. In most cases (68%), the prostate increased in volume, whereas it decreased in 32%. The mean prostatic volume was 42.2 cc before HDRB and 43.6 cc after HDRB, representing a mean volume difference of 3.4%, ranging from -14.2% to 23.8% (p=0.756). This difference is the result of mean changes of 0.6mm (-6.1 to 6.6) in the anterior-posterior, 0.5mm (-5.5 to 3.0) in the lateral, and 0.2mm (-5.0 to 5.0) in the superior-inferior axes.


CONCLUSIONS
Although a nonsignificant volumetric change occurs after single-fraction HDRB, individual variations on specific axis could lead to important uncertainties during EBRT.
Division of Radiation Oncology, Department of Oncology, McGill University Health Centre, Montreal, Quebec, Canada. fabio.cury@muhc.mcgill.ca
Fabio L
FL
Cury
Marie
M
Duclos
Armen
A
Aprikian
Horacio
H
Patrocinio
Luis
L
Souhami
D001918:Brachytherapy / Q000009:adverse effects*; D019583:Dose Fractionation, Radiation; D004487:Edema / Q000209:etiology*; D006801:Humans; D008297:Male; D011467:Prostate / Q000528:radiation effects*; D011471:Prostatic Neoplasms / Q000150:complications / Q000532:radiotherapy*; D020266:Radiotherapy, Conformal; D016896:Treatment Outcome