Seed displacements after permanent brachytherapy for prostate cancer in dependence on the prostate level.
OBJECTIVE
To evaluate seed displacements after permanent prostate brachytherapy considering different prostate levels.


METHODS
In 61 patients, postimplant CT scans were performed 1 day and 1 month after an implant with stranded seeds. Seed and prostate surface displacements were determined relative to pelvic bones. Four groups of seed locations were selected: seeds at the base (n = 305; B), at the apex (n = 305; A), close to the urethra (n = 306; U), and close to the rectal wall (n = 204; R). The length of two strands (always containing four seeds) per patient was measured in all CT scans and compared.


RESULTS
The largest inferior seed displacements were found at the base: mean 5.3 mm (B), 2.2 mm (A), 2.7 mm (U), 3.3 mm (R; p < 0.001). Posterior displacements predominated both at the base and the central region: mean 2.2 mm (B), 2.0 mm (U), 0.8 mm (A), -0.6 mm (R; p < 0.001). With a decreasing edema between day 1 and 30 (mean prostate volume of 51 cm(3) vs. 41 cm(3); p < 0.001), a mean caudal prostate base displacement of 3.9 mm was found, whereas the mean inward displacement ranged from 1.2 to 1.6 mm at the remaining borders (lateral, anterior, posterior, apical). The analysis of the strand lengths revealed an implant compression between day 1 and 30 (mean 1.7 mm; p < 0.001).


CONCLUSIONS
The largest prostate tissue and seed displacements were observed at the prostate base, associated with an implant compression. Predominantly inferior and posterior displacements implicate consequential smaller preplanning margins at the apex and the posterior prostate.
Pinkawa
Michael
M
Department of Radiotherapy, RWTH Aachen, Aachen, Germany. mpinkawa@ukaachen.de
Gagel
Bernd
B
Asadpour
Branka
B
Piroth
Marc D
MD
Klotz
Jens
J
Borchers
Holger
H
Jakse
Gerhard
G
Eble
Michael J
MJ
D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use; D001918:Brachytherapy / Q000009:adverse effects / Q000379:methods*; D003131:Combined Modality Therapy; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D020360:Neoadjuvant Therapy; D009929:Organ Size; D011467:Prostate / Q000000981:diagnostic imaging / Q000528:radiation effects; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000532:radiotherapy*; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012007:Rectum / Q000000981:diagnostic imaging / Q000528:radiation effects*; D014057:Tomography, X-Ray Computed; D014521:Urethra / Q000000981:diagnostic imaging / Q000528:radiation effects*
D018931:Antineoplastic Agents, Hormonal; D007457:Iodine Radioisotopes