Prostate brachytherapy: comparison of dose distribution with different 125I source designs.
OBJECTIVE
To evaluate the interchangeability of various commercially available iodine 125 ((125)I) sources and to assess the dosimetric effect of a change in source.


METHODS
A modified peripherally loading prostate brachytherapy plan to deliver 145 Gy was devised by using a model (125)I source, which until recently was the only available (125)I source. A dose-volume histogram was generated. By using the available radial dose functions and anisotropy distributions for eight other currently commercially available sources, the same implant placement was planned and dose-volume histogram distributions tabulated. This exercise was performed for 15-, 45-, and 60-cm(3) glands. No implants were placed, and no physical radiation measurements were made. Dose calculations were theoretic: They were generated by using a widely available treatment planning system.


RESULTS
There was little difference in dose distribution to the volume receiving 100% of the prescribed dose (<6%); only one source showed a difference greater than 2%. Large differences, up to -40% to +60%, were seen in the volume of tissue encompassed within internal high-dose regions receiving 150% or 200% of the prescribed dose. These findings held true, irrespective of gland size, within a clinically relevant range (15-60 cm(3)) and for a uniformly loaded radionuclide distribution.


CONCLUSIONS
Reviewing only peripheral dose at or near the prescription dose of 145 Gy revealed little difference in doses for various source designs. Marked differences in high-dose regions were seen and may affect the dose received by internal sites. Effects of these changes on cure and/or complications remain speculative.
Beyer
D C
DC
Arizona Oncology Services, 8994 E Desert Cove Ave, Suite 100, Scottsdale, AZ 85260, USA. dbeyer@azoncology.com
Puente
F
F
Rogers
K L
KL
Gurgoze
E M
EM
D001918:Brachytherapy; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted
D007457:Iodine Radioisotopes