Outcomes after PD-103 versus I-125 for Low Dose Rate Prostate Brachytherapy Monotherapy: An International, Multi-Institutional Study.

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.

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.

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).

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.

Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology. 2023 Mar 06 [Epub ahead of print]

Chad Tang, Jeremiah Sanders, Howard Thames, David M Swanson, Juanita M Crook, Teresa Bruno, Pierre Blanchard, Jay Ciezki, Mira Keyes, Daniel Song, Tanmay Singh, Gregory Merrick, Richard Stock, Francis J Sullivan, Henry Mok, Jeremy Millar, Steven J Frank

The University of Texas MD Anderson Cancer Center, Houston, TX, USA. Electronic address: ., The University of Texas MD Anderson Cancer Center, Houston, TX, USA., BC Cancer, University of British Columbia, Canada., Institut Gustave Roussy, Paris, France., Cleveland Clinic, Cleveland, OH, USA., Johns Hopkins University, Baltimore, MD, USA., Urologic Research Institute, Wheeling, WV, USA., Mt Sinai School of Medicine, NY, NY, USA., Galway Clinic, Galway, Ireland; and., Alfred Health, Melbourne, Australia.