Outcomes after PD-103 versus I-125 for low dose rate prostate brachytherapy monotherapy: An international, multi-institutional study

Radiother Oncol. 2023 Jun:183:109599. doi: 10.1016/j.radonc.2023.109599. Epub 2023 Mar 7.


Background and purpose: Pd-103 and I-125 are commonly used in low dose rate (LDR) brachytherapy for prostate cancer. Comparisons of outcomes by isotope type are limited, but Pd-103 has distinct radiobiologic advantages over I-125 despite its lesser availability outside the United States. We evaluated oncologic outcomes after Pd-103 vs I-125 LDR monotherapy for prostate cancer.

Materials and methods: We retrospectively analyzed databases at 8 institutions for men who received definitive LDR monotherapy with Pd-103 (n = 1,597) or I-125 (n = 7,504) for prostate cancer. Freedom from clinical failure (FFCF) and freedom from biochemical failure (FFBF) stratified by isotope were analyzed by Kaplan-Meier univariate and Cox multivariate analyses. Biochemical cure rates (prostate-specific antigen level ≤ 0.2 ng/mL between 3.5 and 4.5 years of follow-up) by isotype were calculated for men with at least 3.5 years of follow-up and compared by univariate and multivariate logistic regression.

Results: Compared with I-125, Pd-103 led to higher 7-year rates of FFBF (96.2% vs 87.6%, P < 0.001) and FFCF (96.5% vs 94.3%, P < 0.001). This difference held after multivariate adjustment for baseline factors (FFBF hazard ratio [HR] = 0.31, FFCF HR = 0.49, both P < 0.001). Pd-103 was also associated with higher cure rates on univariate (odds ratio [OR] = 5.9, P < 0.001) and multivariate (OR = 6.0, P < 0.001) analyses. Results retained significance in sensitivity analyses of data from the 4 institutions that used both isotopes (n = 2,971).

Conclusions: Pd-103 monotherapy was associated with higher FFBF, FFCF, and biochemical cure rates, and suggests that Pd-103 LDR may lead to improved oncologic outcomes compared with I-125.

Keywords: Brachytherapy; I-125; Low dose rate; Pd-103; Prostate Cancer.

Publication types

  • Multicenter Study
  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural

MeSH terms

  • Brachytherapy* / methods
  • Follow-Up Studies
  • Humans
  • Iodine Radioisotopes / therapeutic use
  • Male
  • Palladium / therapeutic use
  • Prostate
  • Prostate-Specific Antigen
  • Prostatic Neoplasms* / drug therapy
  • Prostatic Neoplasms* / radiotherapy
  • Radiotherapy Dosage
  • Retrospective Studies


  • Palladium-103
  • Iodine-125
  • Iodine Radioisotopes
  • Palladium
  • Prostate-Specific Antigen