Dosimetric comparison of high-dose-rate brachytherapy and intensity-modulated radiation therapy as a boost to the prostate.
OBJECTIVE
We compared the dose conformity of two radiation modalities: high-dose-rate brachytherapy (HDR BT) and intensity-modulated radiation therapy (IMRT) to deliver a boost to the prostate after external beam radiotherapy (EBRT).


METHODS
Ten successive patients with prostate adenocarcinoma treated with a single 10-Gy HDR BT boost after EBRT were investigated. Four theoretical IMRT plans were computed: (a) 32.85 Gy IMRT and (b) 26 Gy IMRT with CTV-PTV expansions, doses corresponding to the equivalent dose in 2-Gy fractions (EQD2) of one 10-Gy fraction calculated with a prostate alpha/beta ratio of respectively 1.5 and 3 Gy; and (c) 32.85 Gy IMRT and (d) 26 Gy IMRT without CTV-PTV expansions. The dose-volume histogram values converted in EQD2 with an alpha/beta ratio of 3 Gy for the organs at risk were compared.


RESULTS
The HDR BT plan delivered higher mean doses to the PTV compared with IMRT plans. In all, 33% of the rectal volume received a mean dose of 5.32 +/- 0.65 Gy and 20% of bladder volume received 4.61 +/- 1.24 Gy with HDR BT. In comparison, doses delivered with IMRT were respectively 13.4 +/- 1.49 Gy and 10.81 +/- 4 Gy, even if only 26 Gy was prescribed to the PTV with no CTV-PTV expansion (p < 0.0001). The hot spots inside the urethra were greater with HDR BT but acceptable.


CONCLUSIONS
Use of HDR BT produced a more conformal plan for the boost to the prostate than IMRT even without CTV-PTV expansions.
Hermesse
Johanne
J
Department of Radiation Oncology, Liege University Hospital, Liege, Belgium. jhermesse@chu.ulg.ac.be
Biver
Sylvie
S
Jansen
Nicolas
N
Lenaerts
Eric
E
Nickers
Philippe
P
D000465:Algorithms; D001918:Brachytherapy / Q000379:methods*; D006801:Humans; D008297:Male; D009068:Movement; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012007:Rectum / Q000528:radiation effects; D047368:Tumor Burden; D014521:Urethra / Q000528:radiation effects; D001743:Urinary Bladder / Q000528:radiation effects