Randomized trial of high- and low-source strength (125)I prostate seed implants.
OBJECTIVE
A range of (125)I isotope activities is used in permanent prostate implants. In this study, we compared the implant quality and cost in patients randomized to high-source or low-source strength permanent implants.


METHODS
Forty patients were randomized to receive high (0.76 microGy/m(2)/h) or low (0.4 microGy/m(2)/h) seed strength implants. The two treatment arms had a comparable mix of primary and boost patients and underwent implantation by the same team. The postimplant dosimetric evaluation was performed using CT (seed position) and T(2)-weighted MRI (prostate) scans registered using mutual information techniques. The implant quality parameters were assessed by dose indexes (ratio of achieved dose to planned dose) to quantify the relative error tolerance.


RESULTS
The high-source strength implants had better dose coverage as defined by the dose index; a larger percentage of volume receiving 100% of the prescribed dose as determined by CT (V(100)) (96.3% +/- 3.5% vs. 90.4% +/- 5.3%; p <0.002); lower seed cost (2400 US dollar vs. 3840 US dollar average/case); and took less operating room time on average (67 +/- 16 min vs. 85 +/- 20 min; p <0.004). Finally, the differences in the rectal and urethral doses were not statistically significant between the two treatment arms.


CONCLUSIONS
All 40 patients received an excellent implant as indicated by the CT V(100). Unless long-term toxicity differs, high-source strength seed implants improve the probability of excellent implant quality and decrease the average cost of permanent prostate implants.
Narayana
Vrinda
V
Providence Hospital, Southfield, MI 48009, USA. vrinda@umich.edu
Troyer
Sara
S
Evans
Vicki
V
Winfield
Raymond J
RJ
Roberson
Peter L
PL
McLaughlin
Patrick W
PW
D001918:Brachytherapy / Q000191:economics; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008279:Magnetic Resonance Imaging; D008297:Male; D009873:Operating Rooms / Q000191:economics; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D012007:Rectum; D014057:Tomography, X-Ray Computed; D014521:Urethra
D007457:Iodine Radioisotopes