Long-term complications with prostate implants: iodine-125 vs. palladium-103.
The linear quadratic model predicts that the normal tissue biologically effective dose (BED) will be lower with palladium-103 (Pd-103) vs. iodine-125 (I-125) for the currently prescribed minimum tumor doses (MTD) used for I-125 (160 Gy) and Pd-103 (115 Gy) prostate cancer brachytherapy. The predicted BEDs for I-125 and Pd-103 suggest that the long-term complication rates should be lower with Pd-103 vs. I-125 in clinical practice. A review of 123 early stage T1c and T2 prostate cancer patients implanted at Yale University with I-125 (82 patients) or Pd-103 (41 patients) reveals a significantly lower overall complication rate with Pd-103 (0%) vs. I-125 (13%). Most important, the grade III-IV complication rate for Pd-103 was 0% vs. 6% for I-125. The 3-year actuarial probability of remaining free of a long-term complication was 100% for Pd-103 vs. 82% for I-125 (P<0.01). A review of the literature for 992 patients implanted with I-125 vs. 540 patients implanted with Pd-103 shows a consistently higher complication rate for I-125 vs. Pd-103. Assuming that the MTD for Pd-103 may be increased to produce an equivalent late-reacting normal tissue BED to that for I-125, then the radiobiology model predicts the log10 cell kill for Pd-103 implant will be greater than that of an I-125 implant for all tumor doubling times (high-grade tumors and low-grade tumors). The implications of these findings are discussed in terms of future research directions for prostate implants.
Peschel
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Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06520-8040, USA. richard.peschel@yale.edu
Chen
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Roberts
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Nath
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D000206:Actuarial Analysis; D001918:Brachytherapy / Q000009:adverse effects*; D016923:Cell Death; D005500:Follow-Up Studies; D005544:Forecasting; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage / Q000009:adverse effects*; D008137:Longitudinal Studies; D008297:Male; D008954:Models, Biological; D009367:Neoplasm Staging; D010165:Palladium / Q000008:administration & dosage / Q000009:adverse effects*; D011336:Probability; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011868:Radioisotopes / Q000008:administration & dosage / Q000009:adverse effects*; D019275:Radiopharmaceuticals / Q000008:administration & dosage / Q000009:adverse effects*; D011879:Radiotherapy Dosage; D012062:Relative Biological Effectiveness; D012189:Retrospective Studies; D016896:Treatment Outcome
D007457:Iodine Radioisotopes; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D010165:Palladium