Lack of significant intraprostatic migration of stranded iodine-125 sources in prostate brachytherapy implants.

PURPOSE

Quantify the migration of iodine-125 RAPIDStrands ("strands") from Day 0 to Day 30 postoperatively in patients treated with prostate brachytherapy.

METHODS AND MATERIALS

Gold fiducial markers were inserted into the prostate before implants to serve as a fixed reference point within the prostate. Study patients underwent CT scans of the pelvis on Day 0 and Day 30 postimplant to image the prostate. In-house MATLAB software reconstructed each strand and determined its location relative to the center of mass of the fiducial markers. The recorded migration was taken to be the difference in these locations between Day 0 and Day 30.

RESULTS

A total of 232 strands containing 1069 sources were implanted in 10 patients. Overall, 84% of strands migrated by less than 5mm in any direction. The collection of strands were displaced a mean distance of +0.22mm laterally (95% confidence interval [CI]: +0.08 to +0.37mm), -0.22mm posteriorly (95% CI: -0.51 to +0.06mm), and +0.41mm superiorly (95% CI: +0.03 to +0.79mm). Strands located in the anterior prostate demonstrated the greatest degree of migration in any direction, moving a mean of +1.55mm superiorly. These strands also moved a mean distance of 0.84mm posteriorly, whereas posteriorly located strands moved by a mean distance of 0.82mm anteriorly, consistent with movement because of the resolution of edema.

CONCLUSIONS

This study did not identify any clinically significant patterns of mean migration of iodine-125 RAPIDStrands from Day 0 to Day 30 postimplant.