Seed fixity in the prostate/periprostatic region following brachytherapy

Purpose: Although postoperative dosimetric analyses of prostate brachythera py are commonly reported, the Long-term persistence, or fixity, of seeds im planted in the prostate gland and periprostatic region remains unclear, wit h only a few reports regarding the loss or migration of the seeds in the im planted region and none which correlate lung embolization to pelvic seed lo ss. Methods and Materials: The study population consisted of 175 consecutive pa tients implanted with either I-125 (95 patients) or Pd-103 (80 patients) us ing a mean of 136 seeds in a modified uniform loading approach to cover a p lanning volume that was 1.64 times the ultrasound prostate volume. An avera ge of 64% of I-125 seeds were embedded in braided vicryl suture, and these seeds were used on the periphery and extra prostatic regions. Following CT- based dosimetric analysis on day 0, all patients had orthogonal plain films of the pelvis obtained from day 0 to day 502, with an average of 2.3 film pairs per patient. Routine diagnostic PA and lateral chest X rays were obta ined for 156 patients over the same time period. Results: The mean pelvic seed fixity was greater than 98% throughout the ti me covered by this study. The seed fixity rates for I-125 and Pd-103, altho ugh nearly equal, were significantly different up to 60 days post implant. The median I-125 Seed loss per patient was only 1 seed through 180 days whi le for (103)pd, the median seed loss was 2 seeds at 28 and 60 days and 3 se eds at 180 days. The fraction of patients experiencing no seed loss decreas ed from 40% at 28 days to 20% at 180 days for I-125 and from 24% to 7% for (103)pd over the same time interval. Patient and treatment parameters close ly correlated to local seed loss include the number of seeds implanted, the planning volume, and the number of loose seeds, and for I-125, the fractio n of seeds in suture, The fraction of seeds placed outside the gland was no t correlated with seed loss. Of the seeds lost from the pelvis, about 10% w ere found to embolize to the lungs. Among the 156 patients with post-implan t chest X rays, the fraction of patients with pulmonary seed embolization w as 34/156 (21.8%), Of the 20 patients who had post-implant chest X rays obt ained within 14 days of brachytherapy, none had seeds detected in the lungs , while of the 136 patients who had chest X rays obtained greater than 30 d ays following implantation, 25.0% (34 patients) were noted to have seeds vi sualized in the lungs. Conclusions: With a median follow-up of 9 months, I-125 seeds embedded in a vicryl suture or (103)pd seeds can be safely implanted in the prostate and periprostatic tissue with a high probability of prostate bed seed fixity a nd a low incidence of radioactive seed embolization to the lungs. (C) 2000 Elsevier Science Inc.