Inverse automated treatment planning with and without individual optimization in interstitial permanent prostate brachytherapy with high- and low-activity 125I.
OBJECTIVE
To determine whether dose distribution achieved with treatment plans using high- and low-activity (125)I implants differs.


METHODS
Based on intraoperative transrectal ultrasound scans of 71 patients, inverse automated treatment plans (IATP) were performed with 15.5-kBq (0.42-mCi) and 25.2-kBq (0.68-mCi) (125)I implants using a commercial 3-D planning system (Variseed). A prescription dose of 145 Gy in 98% of the prostate volume (V100), a maximum dose to the urethra of 250 Gy (D1), and a maximum dose to 10% of the anterior rectal wall of 145 Gy (D10) were required. The plans were manually corrected, if necessary.


RESULTS
In the IATP, a better dose coverage of the prostate was found for high-activity seeds (V100 of 98% vs 84%). The prostate dose values increased with the prostate volume. After manual optimization, the differences were only marginal with a prostate V100 of 99% for both activities, a urethra D1 of 247 Gy and 239 Gy, and a rectum D10 of 135 Gy and 124 Gy for high- and low-activity seeds. Low-activity seeds required more sources (66 vs 47) and needles (24 vs 17; all numbers are median values).


CONCLUSIONS
Concerning the prostate dose coverage, high-activity seeds are superior in the IATP. After manual adjustment, the dose values for the prostate and the organs at risk are similar. Considering a supposedly decreased toxicity and a shorter implantation time for a lower number of seeds, we recommend high-activity seeds for experienced teams.
Pinkawa
Michael
M
Department of Radiotherapy, University Hospital, RWTH Aachen, Germany. Michael.Pinkawa@post.rwth-aachen.de
Maurer
Uwe
U
Mulhern
Andrew
A
Gagel
Bernd
B
Block
Thomas
T
Borchers
Holger
H
Grieger
Johannes
J
Henkel
Thomas
T
Eble
Michael
M
D001918:Brachytherapy / Q000379:methods*; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D011467:Prostate / Q000033:anatomy & histology; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012044:Regression Analysis; D014463:Ultrasonography; D014521:Urethra / Q000528:radiation effects
D007457:Iodine Radioisotopes